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  • 1. Adamo, A.
    et al.
    Östlin, G.
    Zackrisson, E.
    Papaderos, P.
    Bergvall, Nils
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Rich, R. M.
    Micheva, G.
    Star cluster formation and evolution in Mrk 930: properties of a metal-poor starburst2011In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 415, no 3, p. 2388-2406Article in journal (Refereed)
    Abstract [en]

    We present the analysis of the large population of star clusters in the blue compact galaxy (BCG) Mrk 930. The study has been conducted by means of a photometric analysis of multiband data obtained with the Hubble Space Telescope (HST). We have reconstructed the spectral energy distributions of the star clusters and estimated the age, mass and extinction for a representative sample. Similar to previous studies of star clusters in BCGs, we observe a very young cluster population with 70 per cent of the systems formed less than 10 Myr ago. In Mrk 930, the peak in the star cluster age distribution at 4 Myr is corroborated by the presence of Wolf-Rayet spectral features, and by the observed optical and infrared (IR) line ratios [OIII]/H beta and [Ne III]/[Ne II]. The recovered extinction in these very young clusters shows large variations, with a decrease at older ages. It is likely that our analysis is limited to the optically brightest objects (i.e. systems only partially embedded in their natal cocoons; the deeply embedded clusters being undetected). We map the extinction across the galaxy using low-resolution spectra and the H alpha-to-H beta ratio, as obtained from ground-based narrow band imaging. These results are compared with the extinction distribution recovered from the clusters. We find that the mean optical extinction derived in the starburst regions is close to the averaged value observed in the clusters [more than 80 per cent of the systems have E(B - V) <= 0.2mag], but locally, do not trace the more extinguished clusters. Previous HST studies of BCGs have revealed a population of young and extremely red super star clusters. We detect a considerable fraction of clusters affected by a red excess also in Mrk 930. The nature of the red excess, which turns up at near-IR wavelengths (I band and longwards), remains unknown. We compare the cluster formation history and the star formation history, the latter derived from the fit of spectral population synthesis models to the spectra. We find a general agreement between the two independently estimated quantities. Using the cluster properties, we perform a study of the host environmental properties. We find that the cluster formation efficiency (the fraction of star formation happening in clusters) is significantly higher, suggesting a key role of the environment for the formation of these massive objects.

  • 2.
    Agarwal, Bhaskar
    et al.
    Yale Univ, Dept Astron, 52 Hillhouse Ave,Steinbach Hall, New Haven, CT 06511 USA..
    Johnson, Jarrett L.
    Los Alamos Natl Lab, Theoret Div X, Los Alamos, NM 87545 USA..
    Zackrisson, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Labbe, Ivo
    Leiden Univ, Leiden Observ, NL-2300 RA Leiden, Netherlands..
    van den Bosch, Frank C.
    Yale Univ, Dept Astron, 52 Hillhouse Ave,Steinbach Hall, New Haven, CT 06511 USA..
    Natarajan, Priyamvada
    Yale Univ, Dept Astron, 52 Hillhouse Ave,Steinbach Hall, New Haven, CT 06511 USA..
    Khochfar, Sadegh
    Univ Edinburgh, Inst Astron, Royal Observ, Edinburgh EH9 3HJ, Midlothian, Scotland..
    Detecting direct collapse black holes: making the case for CR72016In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 460, no 4, p. 4003-4010Article in journal (Refereed)
    Abstract [en]

    We propose that one of the sources in the recently detected system CR7 by Sobral et al. through spectrophotometric measurements at z=6.6 harbours a direct collapse black hole (DCBH). We argue that the LW radiation field required for direct collapse in source A is provided by sources B and C.By tracing the LW production history and star formation rate over cosmic time for the halo hosting CR7 in a ACDM universe, we demonstrate that a DCBH could have formed at z similar to 20. The spectrum of source A is well fit by nebular emission from primordial gas around a BH with MBH similar to 4.4x10(6)M(circle dot) accreting at a 40 per cent of the Eddington rate, which strongly supports our interpretation of the data. Combining these lines of evidence, we argue that CR7 might well be the first DCBH candidate.

  • 3.
    Agarwal, Bhaskar
    et al.
    Heidelberg Univ, Inst Theoret Phys, Zentrum Astron, Albert Ueberle Str 2, D-69120 Heidelberg, Germany..
    Regan, John
    Heidelberg Univ, Inst Theoret Phys, Zentrum Astron, Albert Ueberle Str 2, D-69120 Heidelberg, Germany.;Dublin City Univ, Sch Math Sci, Ctr Astrophys & Relat, Dublin D09 Y5N0, Ireland..
    Klessen, Ralf S.
    Heidelberg Univ, Inst Theoret Phys, Zentrum Astron, Albert Ueberle Str 2, D-69120 Heidelberg, Germany..
    Downes, Turlough P.
    Dublin City Univ, Sch Math Sci, Ctr Astrophys & Relat, Dublin D09 Y5N0, Ireland..
    Zackrisson, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala Univ, Dept Phys & Astron, Box 515, SE-75120 Uppsala, Sweden..
    An analytic resolution to the competition between Lyman-Werner radiation and metal winds in direct collapse black hole hosts2017In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 470, no 4, p. 4034-4038Article in journal (Refereed)
    Abstract [en]

    A near pristine atomic cooling halo close to a star forming galaxy offers a natural pathway for forming massive direct collapse black hole (DCBH) seeds, which could be the progenitors of the z > 6 redshift quasars. The close proximity of the haloes enables a sufficient Lyman-Werner flux to effectively dissociate H-2 in the core of the atomic cooling halo. A mild background may also be required to delay star formation in the atomic cooling halo, often attributed to distant background galaxies. In this paper, we investigate the impact of metal pollution from both the background galaxies and the close star forming galaxy under extremely unfavourable conditions such as instantaneous metal mixing. We find that within the time window of DCBH formation, the level of pollution never exceeds the critical threshold (Z(cr) similar to 1 x 10(-5) Z(circle dot)) and attains a maximum metallicity of Z similar to 2 x 10(- 6) Z(circle dot). As the system evolves, the metallicity eventually exceeds the critical threshold, long after the DCBH has formed.

  • 4.
    Agarwal, Jessica
    et al.
    Max Planck Inst Sonnensyst Forsch, Justus Von Liebig Weg 3, D-37077 Gottingen, Germany..
    A'Hearn, M. F.
    Univ Maryland, Dept Astron, College Pk, MD 20742 USA..
    Vincent, J. -B
    Guettler, C.
    Max Planck Inst Sonnensyst Forsch, Justus Von Liebig Weg 3, D-37077 Gottingen, Germany..
    Hoefner, S.
    Max Planck Inst Sonnensyst Forsch, Justus Von Liebig Weg 3, D-37077 Gottingen, Germany..
    Sierks, H.
    Max Planck Inst Sonnensyst Forsch, Justus Von Liebig Weg 3, D-37077 Gottingen, Germany..
    Tubiana, C.
    Max Planck Inst Sonnensyst Forsch, Justus Von Liebig Weg 3, D-37077 Gottingen, Germany..
    Barbieri, C.
    Univ Padua, Dept Phys & Astron G Galilei, Vic Osservat 3, I-35122 Padua, Italy..
    Lamy, P. L.
    Aix Marseille Univ, Lab Astrophys Marseille, CNRS, UMR 7326, 38 Rue Frederic Joliot Curie, F-13388 Marseille 13, France..
    Rodrigo, R.
    CSIC, Ctr Astrobiol, INTA, European Space Agcy,ESAC, POB 78, E-28691 Madrid, Spain.;Int Space Sci Inst, Hallerstr 6, CH-3012 Bern, Switzerland..
    Koschny, D.
    European Space Agcy, Res & Sci Support Dept, NL-2201 Noordwijk, Netherlands..
    Rickman, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics. PAS Space Res Ctr, Poland..
    Barucci, M. A.
    Univ Paris Diderot, UPMC Univ Paris 06, CNRS, LESIA,Observ Paris, 5 Pl J Janssen, F-92195 Meudon, France..
    Bertaux, J. -L
    Bertini, I.
    Univ Padua, Ctr Ateneo Studi Attivita Spaziali Giuseppe Colom, Via Venezia 15, I-35131 Padua, Italy..
    Boudreault, S.
    Max Planck Inst Sonnensyst Forsch, Justus Von Liebig Weg 3, D-37077 Gottingen, Germany..
    Cremonese, G.
    INAF Osservat Astron Padova, Vicolo Osservat 5, I-35122 Padua, Italy..
    Da Deppo, V.
    CNR IFN UOS Padova LUXOR, Via Trasea 7, I-35131 Padua, Italy..
    Davidsson, B.
    Jet Prop Lab, M-S 183-301,4800 Oak Grove Dr, Pasadena, CA 91109 USA..
    Debei, S.
    Univ Padua, Dept Ind Engn, Via Venezia 1, I-35131 Padua, Italy..
    De Cecco, M.
    Univ Trento, Via Sommarive 9, I-38123 Trento, Italy..
    Deller, J.
    Max Planck Inst Sonnensyst Forsch, Justus Von Liebig Weg 3, D-37077 Gottingen, Germany..
    Fornasier, S.
    Univ Paris Diderot, UPMC Univ Paris 06, CNRS, LESIA,Observ Paris, 5 Pl J Janssen, F-92195 Meudon, France..
    Fulle, M.
    INAF Osservat Astron Trieste, Via Tiepolo 11, I-34143 Trieste, Italy..
    Gicquel, A.
    Max Planck Inst Sonnensyst Forsch, Justus Von Liebig Weg 3, D-37077 Gottingen, Germany..
    Groussin, O.
    Aix Marseille Univ, LAM, CNRS, UMR 7326, F-13388 Marseille, France..
    Gutierrez, P. J.
    CSIC, Inst Astrofis Andalucia, E-18008 Granada, Spain..
    Hofmann, M.
    Max Planck Inst Sonnensyst Forsch, Justus Von Liebig Weg 3, D-37077 Gottingen, Germany..
    Hviid, S. F.
    DLR, Inst Planetary Res, Rutherfordstr 2, D-12489 Berlin, Germany..
    Ip, W. -H
    Jorda, L.
    Aix Marseille Univ, LAM, CNRS, UMR 7326, F-13388 Marseille, France..
    Keller, H. U.
    TU Braunschweig, Inst Geophys & Extraterr Phys, D-38106 Braunschweig, Germany..
    Knollenberg, J.
    DLR, Inst Planetary Res, Rutherfordstr 2, D-12489 Berlin, Germany..
    Kramm, J. -R
    Kuehrt, E.
    DLR, Inst Planetary Res, Rutherfordstr 2, D-12489 Berlin, Germany..
    Kueppers, M.
    ESA ESAC, POB 78, E-28691 Villanueva De La Cananda, Spain..
    Lara, L. M.
    CSIC, Inst Astrofis Andalucia, E-18008 Granada, Spain..
    Lazzarin, M.
    Univ Padua, Dept Phys & Astron G Galilei, Vic Osservat 3, I-35122 Padua, Italy..
    Lopez Moreno, J. J.
    CSIC, Inst Astrofis Andalucia, E-18008 Granada, Spain..
    Marzari, F.
    Univ Padua, Dept Phys & Astron G Galilei, Vic Osservat 3, I-35122 Padua, Italy..
    Naletto, G.
    Univ Padua, Ctr Ateneo Studi Attivita Spaziali Giuseppe Colom, Via Venezia 15, I-35131 Padua, Italy.;CNR IFN UOS Padova LUXOR, Via Trasea 7, I-35131 Padua, Italy.;Univ Padua, Dept Informat Engn, Via Gradenigo 6-B, I-35131 Padua, Italy..
    Oklay, N.
    Max Planck Inst Sonnensyst Forsch, Justus Von Liebig Weg 3, D-37077 Gottingen, Germany..
    Shi, X.
    Max Planck Inst Sonnensyst Forsch, Justus Von Liebig Weg 3, D-37077 Gottingen, Germany..
    Thomas, N.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland..
    Acceleration of individual, decimetre-sized aggregates in the lower coma of comet 67P/Churyumov-Gerasimenko2016In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 462, p. S78-S88Article in journal (Refereed)
    Abstract [en]

    We present observations of decimetre-sized, likely ice-containing aggregates ejected from a confined region on the surface of comet 67P/Churyumov-Gerasimenko. The images were obtained with the narrow angle camera of the Optical, Spectroscopic, and Infrared Remote Imaging System on board the Rosetta spacecraft in 2016 January when the comet was at 2 au from the Sun outbound from perihelion. We measure the acceleration of individual aggregates through a 2 h image series. Approximately 50 per cent of the aggregates are accelerated away from the nucleus, and 50 per cent towards it, and likewise towards either horizontal direction. The accelerations are up to one order of magnitude stronger than local gravity, and are most simply explained by the combined effect of gas drag accelerating all aggregates upwards, and the recoil force from asymmetric outgassing, either from rotating aggregates with randomly oriented spin axes and sufficient thermal inertia to shift the temperature maximum away from an aggregate's subsolar region, or from aggregates with variable ice content. At least 10 per cent of the aggregates will escape the gravity field of the nucleus and feed the comet's debris trail, while others may fall back to the surface and contribute to the deposits covering parts of the Northern hemisphere. The rocket force plays a crucial role in pushing these aggregates back towards the surface. Our observations show the future back fall material in the process of ejection, and provide the first direct measurement of the acceleration of aggregates in the innermost coma (<2 km) of a comet, where gas drag is still significant.

  • 5. Alentiev, D.
    et al.
    Kochukhov, Oleg
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Ryabchikova, T.
    Cunha, M.
    Tsymbal, V.
    Weiss, W.
    Discovery of the longest period rapidly oscillating Ap star HD1777652012In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 421, no 1, p. L82-L86Article in journal (Refereed)
    Abstract [en]

    We present the discovery of a long-period, rapidly oscillating Ap (roAp) star, HD177765. Using high-resolution time-series observations obtained with the Ultraviolet and Visual Echelle Spectrograph at the European Southern Observatory Very Large Telescope, we found radial velocity variations with amplitudes 7-150 ms(-1) and a period of 23.6 min, exceeding that of any previously known roAp star. The largest pulsation amplitudes are observed for Eu III, Ce III and for the narrow core of H alpha. We derived the atmospheric parameters and chemical composition of HD177765, showing this star to be similar to other long-period roAp stars. Comparison with theoretical pulsational models indicates an advanced evolutionary state for HD177765. Abundance analyses of this and other roAp stars suggest a systematic variation with age of the rare-earth line anomalies seen in cool Ap stars.

  • 6.
    Alvarado-Gomez, Julian D.
    et al.
    Harvard Smithsonian Ctr Astrophys, 60 Garden St, Cambridge, MA 02138 USA..
    Hussain, Gaitee A. J.
    European Southern Observ, Karl Schwarzschild Str 1, D-85748 Garching, Germany.;Univ Toulouse, Inst Rech Astrophys & Planetol, UPS OMP, F-31400 Toulouse, France..
    Drake, Jeremy J.
    Harvard Smithsonian Ctr Astrophys, 60 Garden St, Cambridge, MA 02138 USA..
    Donati, Jean-Francois
    CNRS, IRAP, 14 Ave Edouard Belin, F-31400 Toulouse, France..
    Sanz-Forcada, Jorge
    CSIC, INTA, Ctr Astrobiol, ESAC Campus, E-28692 Madrid, Spain..
    Stelzer, Beate
    Eberhard Karls Univ Tubingen, Inst Astron & Astrophys, Sand 1, D-72076 Tubingen, Germany..
    Cohen, Ofer
    Univ Massachusetts, Dept Phys & Appl Phys, 600 Suffolk St, Lowell, MA 01854 USA..
    Amazo-Gomez, Eliana M.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany.;Georg August Univ Gottingen, Inst Astrophys, Friedrich Hund Pl 1, D-37077 Gottingen, Germany..
    Grunhut, Jason H.
    Univ Toronto, Dunlap Inst Astron & Astrophys, 50 St George St, Toronto, ON M5S 3H4, Canada..
    Garraffo, Cecilia
    Harvard Smithsonian Ctr Astrophys, 60 Garden St, Cambridge, MA 02138 USA..
    Moschou, Sofia P.
    Harvard Smithsonian Ctr Astrophys, 60 Garden St, Cambridge, MA 02138 USA..
    Silvester, James
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Oksala, Mary E.
    Univ Paris Diderot, Sorbonne Paris Cite, Univ Paris 06,LESIA, UPMC,Sorbonne Univ,CNRS,PSL Res Univ,Observ Paris, 5 Pl Jules Janssen, F-92195 Meudon, France.;Calif Lutheran Univ, Dept Phys, 60 West Olsen Rd 3700, Thousand Oaks, CA 91360 USA..
    Far beyond the Sun - I. The beating magnetic heart in Horologium2018In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 473, no 4, p. 4326-4338Article in journal (Refereed)
    Abstract [en]

    A former member of the Hyades cluster, iota Horologii (iota Hor) is a planet-hosting Sun-like star which displays the shortest coronal activity cycle known to date (P-cyc similar to 1.6 yr). With an age of similar to 625 Myr, iota Hor is also the youngest star with a detected activity cycle. The study of its magnetic properties holds the potential to provide fundamental information to understand the origin of cyclic activity and stellar magnetism in late-type stars. In this series of papers, we present the results of a comprehensive project aimed at studying the evolving magnetic field in this star and how this evolution influences its circumstellar environment. This paper summarizes the first stage of this investigation, with results from a long-term observing campaign of iota Hor using ground-based high-resolution spectropolarimetry. The analysis includes precise measurements of the magnetic activity and radial velocity of the star, and their multiple time-scales of variability. In combination with values reported in the literature, we show that the long-term chromospheric activity evolution of iota Hor follows a beating pattern, caused by the superposition of two periodic signals of similar amplitude at P-1 similar or equal to 1.97 +/- 0.02 yr and P-2 similar or equal to 1.41 +/- 0.01 yr. Additionally, using the most recent parameters for iota Hor b in combination with our activity and radial velocity measurements, we find that stellar activity dominates the radial velocity residuals, making the detection of additional planets in this system challenging. Finally, we report here the first measurements of the surface longitudinal magnetic field strength of iota Hor, which displays varying amplitudes within +/- 4G and served to estimate the rotation period of the star (P-rot = 7.70(-0.67)(+0.18) d).

  • 7.
    Amarsi, A. M.
    et al.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia..
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy. Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany..
    Asplund, M.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia..
    Barklem, Paul S.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
    Collet, R.
    Aarhus Univ, Dept Phys & Astron, Stellar Astrophys Ctr, Ny Munkegade 120, DK-8000 Aarhus C, Denmark..
    Non-LTE line formation of Fe in late-type stars - III. 3D non-LTE analysis of metal-poor stars2016In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 463, no 2, p. 1518-1533Article in journal (Refereed)
    Abstract [en]

    As one of the most important elements in astronomy, iron abundance determinations need to be as accurate as possible. We investigate the accuracy of spectroscopic iron abundance analyses using archetypal metal-poor stars. We perform detailed 3D non-LTE radiative transfer calculations based on 3D hydrodynamic STAGGER model atmospheres, and employ a new model atom that includes new quantum-mechanical neutral hydrogen collisional rate coefficients. With the exception of the red giant HD122563, we find that the 3D non-LTE models achieve Fe I/Fe II excitation and ionization balance as well as not having any trends with equivalent width to within modelling uncertainties of 0.05 dex, all without having to invoke any microturbulent broadening; for HD122563 we predict that the current best parallax-based surface gravity is overestimated by 0.5 dex. Using a 3D non-LTE analysis, we infer iron abundances from the 3D model atmospheres that are roughly 0.1 dex higher than corresponding abundances from 1D MARCS model atmospheres; these differences go in the same direction as the non-LTE effects themselves. We make available grids of departure coefficients, equivalent widths and abundance corrections, calculated on 1D MARCS model atmospheres and horizontally and temporally averaged 3D STAGGER model atmospheres.

  • 8.
    André, Mats
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Odelstad, Elias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Space Plasma Physics.
    Graham, Daniel B.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Eriksson, Anders I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Karlsson, T.
    KTH Royal Inst Technol, Sch Elect Engn, Dept Space & Plasma Phys, Stockholm, Sweden.
    Wieser, G. Stenberg
    Swedish Inst Space Phys, Kiruna, Sweden.
    Vigren, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Norgren, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Space Plasma Physics.
    Johansson, Fredrik L.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Henri, P.
    Lab Phys & Chim Environm & Espace, Orleans, France.
    Rubin, M.
    Univ Bern, Phys Inst, Bern, Switzerland.
    Richter, I.
    TU Braunschweig, Inst Geophys & Extraterr Phys, Braunschweig, Germany.
    Lower hybrid waves at comet 67P/Churyumov-Gerasimenko2017In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 469, p. S29-S38Article in journal (Refereed)
    Abstract [en]

    We investigate the generation of waves in the lower hybrid frequency range by density gradients in the near plasma environment of comet 67P/Churyumov-Gerasimenko. When the plasma is dominated by water ions from the comet, a situation with magnetized electrons and unmagnetized ions is favourable for the generation of lower hybrid waves. These waves can transfer energy between ions and electrons and reshape the plasma environment of the comet. We consider cometocentric distances out to a few hundred km. We find that when the electron motion is not significantly interrupted by collisions with neutrals, large average gradients within tens of km of the comet, as well as often observed local large density gradients at larger distances, are often likely to be favourable for the generation of lower hybrid waves. Overall, we find that waves in the lower hybrid frequency range are likely to be common in the near plasma environment.

  • 9.
    Asadi, Saghar
    et al.
    Stockholm Univ, Oscar Klein Ctr, Dept Astron, AlbaNova, SE-10691 Stockholm, Sweden..
    Zackrisson, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Freeland, Emily
    Stockholm Univ, Oscar Klein Ctr, Dept Astron, AlbaNova, SE-10691 Stockholm, Sweden..
    Probing cold dark matter subhaloes with simulated ALMA observations of macrolensed sub-mm galaxies2017In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 472, no 1, p. 129-140Article in journal (Refereed)
    Abstract [en]

    If the dark matter haloes of galaxies contain large numbers of subhaloes as predicted by the Lambda cold dark matter model, these subhaloes are expected to appear in strong galaxy-galaxy lens systems as small-scale perturbations in individual images. We simulate observations of multiply lensed sub-mm galaxies at z similar to 2 as a probe of the dark matter halo of a lens galaxy at z similar to 0.5. We present detection limits for dark substructures based on a visibility plane analysis of simulated Atacama Large Millimeter/submillimeter Array (ALMA) data in bands 7, 8 and 9. We explore two effects: local surface brightness anomalies on angular scales similar to the Einstein radius and the astrometric shift of macroimages. This improves the sensitivity of our lens modelling to the mass of the lens perturber. We investigate the sensitivity of the detection of low-mass subhaloes to the projected position of the subhalo on the image plane as well as the source structure and inner density profile of the lens. We demonstrate that, using the most extended ALMA configuration, pseudo-Jaffe subhaloes can be detected with 99 per cent confidence down to M = 10(7)M(circle dot) . We show how the detection threshold for the three ALMA bands depends on the projected position of the subhalo with respect to the lensed images and conclude that, despite the highest nominal angular resolution, band 9 provides the poorest sensitivity due to observational noise. All simulations use the ALMA Full ops most extended ALMA configuration setup in CASA.

  • 10.
    Bancelin, D.
    et al.
    Univ Vienna, Inst Astrophys, Turkenschanzstr 17, A-1180 Vienna, Austria.
    Nordlander, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics. Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2511, Australia.
    Pilat-Lohinger, E.
    Univ Vienna, Inst Astrophys, Turkenschanzstr 17, A-1180 Vienna, Austria.
    Loibnegger, B.
    Univ Vienna, Inst Astrophys, Turkenschanzstr 17, A-1180 Vienna, Austria.
    Dynamics of passing-stars-perturbed binary star systems2019In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 486, no 4, p. 4773-4780Article in journal (Refereed)
    Abstract [en]

    In this work, we investigate the dynamical effects of a sequence of close encounters over 200 Myr varying in the interval of 10 000-100 000 au between a binary star system and passing stars with masses ranging from 0.1 to 10 M-circle dot. We focus on binaries consisting of two Sun-like stars with various orbital separations a(0) from 50 to 200 au initially on circular planar orbits. We treat the probletn statistically since each sequence is clotted 1000 dines. Our study shows that orbits of binaries initially at a(0) = 50 au will slightly be perturbed by each close encounter and exhibit a small deviation in eccentricity (+0.03) and in periapsis distance (+1 and -2 au) around the mean value, However increasing a(0) will drastically increase these variances: up to +0.45 in eccentricity and between +63 and -106 au in periapsis, leading to a higher rate of disrupted binaries up to 50 per cent after the sequence of close encounters. Even though the secondary star can remain bound to the primary, similar to 20 per cent of the final orbits will have inclinations greater than 10 degrees. As planetary formation already takes place when stars are still members of their birth cluster, we show that the variances in eccentricity and periapsis distance of Jupiter- and Saturn-like planets will inversely decrease with a(0) after successive fly-bys. This leads to higher ejection rate at a(0) = 50 au but to a higher extent for Saturn-likes (60 percent) as those planets' apoapsis distances cross the critical stability distance for such binary separation.

  • 11.
    Bergvall, Nils
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Zackrisson, Erik
    Caldwell, Brady
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    The red haloes of SDSS low surface brightness disc galaxies2010In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 405, no 4, p. 2697-2716Article in journal (Refereed)
    Abstract [en]

    The faint stellar haloes of galaxies contain key information about the oldest stars and the process of galaxy formation. A previous study of stacked SDSS images of disc galaxies has revealed a halo with an abnormally red r - i colour, seemingly inconsistent with our current understanding of the stellar populations inhabiting stellar haloes. Measurements of this type are, however, plagued by large uncertainties which calls for follow-up studies. Here, we investigate the statistical properties of the faint envelopes of low surface brightness disc galaxies to look for further support for a red excess. A total of 1510 nearly edge-on, bulgeless low surface brightness galaxies were selected from the SDSS Data Release 5, rescaled to the same apparent size, aligned and stacked. This procedure allows us to reach a surface brightness of mu(r) similar to 31 mag arcsec-2. After a careful assessment of instrumental light scattering effects in the stacked images, we derive median and average radial surface brightness and colour profiles in g, r and i. The sample is then divided into three subsamples according to g - r colour. All three samples exhibit a red colour excess in r - i in the thick disc/halo region. The halo colours of the full sample, g - r = 0.60 +/- 0.15 and r - i = 0.80 +/- 0.15, are found to be incompatible with the colours of any normal type of stellar population. The fact that no similar colour anomaly is seen at comparable surface brightness levels along the disc rules out a sky subtraction residual as the source of the extreme colours. A number of possible explanations for these abnormally red haloes are discussed. We find that two different scenarios - dust extinction of extragalactic background light and a stellar population with a very bottom-heavy initial mass function - appear to be broadly consistent with our observations and with similar red excesses reported in the haloes of other types of galaxies.

  • 12.
    Bertelli Motta, C.
    et al.
    Heidelberg Univ, Zentrum Astron, Astron Rechen Inst, Monchhofstr 12-14, D-69120 Heidelberg, Germany.
    Pasquali, A.
    Heidelberg Univ, Zentrum Astron, Astron Rechen Inst, Monchhofstr 12-14, D-69120 Heidelberg, Germany.
    Richer, J.
    Univ Montreal, Dept Phys, Montreal, PQ H3C 3J7, Canada.
    Michaud, G.
    Univ Montreal, Dept Phys, Montreal, PQ H3C 3J7, Canada.
    Salaris, M.
    Liverpool John Moores Univ, Astrophys Res Inst, 146 Brownlow Hill, Liverpool L3 5RF, Merseyside, England.
    Bragaglia, A.
    INAF Osservatorio Astrofis Sci Spazio, Via Gobetti 93-3, I-40129 Bologna, Italy.
    Magrini, L.
    INAF Osservatorio Astrofis Arcetri, Largo E Fermi 5, I-50125 Florence, Italy.
    Randich, S.
    INAF Osservatorio Astrofis Arcetri, Largo E Fermi 5, I-50125 Florence, Italy.
    Grebel, E. K.
    Heidelberg Univ, Zentrum Astron, Astron Rechen Inst, Monchhofstr 12-14, D-69120 Heidelberg, Germany.
    Adibekyan, V.
    Univ Porto, CAUP, Inst Astrofis Ciencias Espaco, Rua Estrelas, P-4150762 Porto, Portugal.
    Blanco-Cuaresma, S.
    Harvard Smithsonian Ctr Astrophys, 60 Garden St, Cambridge, MA 02138 USA.
    Drazdauskas, A.
    Vilnius Univ, Inst Theoret Phys & Astron, Sauletekio Av 3, LT-10257 Vilnius, Lithuania.
    Fu, X.
    Univ Bologna, Dipartimento Fis & Astron, Via Gobetti 93-2, I-40129 Bologna, Italy.
    Martell, S.
    Univ New South Wales, Sch Phys, Sydney, NSW 2052, Australia.
    Tautvaisiene, G.
    Vilnius Univ, Inst Theoret Phys & Astron, Sauletekio Av 3, LT-10257 Vilnius, Lithuania.
    Gilmore, G.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England.
    Alfaro, E. J.
    CSIC, Inst Astrofis Andalucia, Glorieta Astron S-N, E-18008 Granada, Spain.
    Bensby, T.
    Lund Observ, Dept Astron & Theoret Phys, Box 43, SE-22100 Lund, Sweden.
    Flaccomio, E.
    INAF Osservatorio Astron Palermo, Piazza Parlamento 1, I-90134 Palermo, Italy.
    Koposov, S. E.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England;Carnegie Mellon Univ, McWilliams Ctr Cosmol, Dept Phys, 5000 Forbes Ave, Pittsburgh, PA 15213 USA.
    Korn, Andreas J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Lanzafame, A. C.
    Univ Catania, Sez Astrofis, Dipartimento Fis & Astron, Via S Sofia 78, I-95123 Catania, Italy.
    Smiljanic, R.
    Polish Acad Sci, Nicolaus Copernicus Astron Ctr, Ul Bartycka 18, PL-00716 Warsaw, Poland.
    Bayo, A.
    Univ Valparaiso, Fac Ciencias, Inst Fis & Astron, Av Gran Bretana 1111, Valparaiso, Chile;Univ Valparaiso, Nucl Milenio Formac Planetaria NPF, Av Gran Bretana 1111, Valparaiso, Chile.
    Carraro, G.
    Univ Padua, Dipartimento Fis & Astron, Vicolo Osservatorio 3, I-35122 Padua, Italy.
    Casey, A. R.
    Monash Univ, Sch Phys & Astron, Clayton, Vic 3800, Australia;Monash Univ, Fac Informat Technol, Clayton, Vic 3800, Australia.
    Costado, M. T.
    Univ Cadiz, Dept Didact, E-11519 Puerto Real, Cadiz, Spain.
    Damiani, F.
    INAF Osservatorio Astron Palermo, Piazza Parlamento 1, I-90134 Palermo, Italy.
    Franciosini, E.
    INAF Osservatorio Astrofis Arcetri, Largo E Fermi 5, I-50125 Florence, Italy.
    Heiter, Ulrike
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Hourihane, A.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England.
    Jofre, P.
    Univ Diego Port, Nucl Astron, Av Ejercito 441, Santiago, Chile.
    Lardo, C.
    EPFL, Lab Astrophys, Observ Sauverny, CH-1290 Versoix, Switzerland.
    Lewis, J.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England.
    Monaco, L.
    Univ Andres Bello, Dept Ciencias Fis, Fernandez Concha 700, Santiago, Chile.
    Morbidelli, L.
    INAF Osservatorio Astrofis Arcetri, Largo E Fermi 5, I-50125 Florence, Italy.
    Sacco, G. G.
    INAF Osservatorio Astrofis Arcetri, Largo E Fermi 5, I-50125 Florence, Italy.
    Sousa, S. G.
    Univ Porto, CAUP, Inst Astrofis Ciencias Espaco, Rua Estrelas, P-4150762 Porto, Portugal.
    Worley, C. C.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England.
    Zaggia, S.
    Univ Padua, Dipartimento Fis & Astron, Vicolo Osservatorio 3, I-35122 Padua, Italy.
    The Gaia-ESO Survey: evidence of atomic diffusion in M67?2018In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 478, no 1, p. 425-438Article in journal (Refereed)
    Abstract [en]

    Investigating the chemical homogeneity of stars born from the same molecular cloud at virtually the same time is very important for our understanding of the chemical enrichment of the interstellar medium and with it the chemical evolution of the Galaxy. One major cause of inhomogeneities in the abundances of open clusters is stellar evolution of the cluster members. In this work, we investigate variations in the surface chemical composition of member stars of the old open cluster M67 as a possible consequence of atomic diffusion effects taking place during the main-sequence phase. The abundances used are obtained from high-resolution UVES/FLAMES spectra within the framework of the Gaia-ESO Survey. We find that the surface abundances of stars on the main sequence decrease with increasing mass reaching a minimum at the turn-off. After deepening of the convective envelope in subgiant branch stars, the initial surface abundances are restored. We found the measured abundances to be consistent with the predictions of stellar evolutionary models for a cluster with the age and metallicity of M67. Our findings indicate that atomic diffusion poses a non-negligible constraint on the achievable precision of chemical tagging methods.

  • 13.
    Bertini, I.
    et al.
    Univ Padua, Dept Phys & Astron G Galilei, Vicolo Osservatorio 3, I-35122 Padua, Italy.
    La Forgia, F.
    Univ Padua, Dept Phys & Astron G Galilei, Vicolo Osservatorio 3, I-35122 Padua, Italy.
    Tubiana, C.
    Max Planck Inst Solar Syst Res, Justus von Liebig Weg 3, D-37077 Gottingen, Germany.
    Guettler, C.
    Max Planck Inst Solar Syst Res, Justus von Liebig Weg 3, D-37077 Gottingen, Germany.
    Fulle, M.
    INAF, Astron Observ Trieste, Via Tiepolo 11, I-34143 Trieste, Italy.
    Moreno, F.
    CSIC, Inst Astrophys Andalusia, Glorieta Astronomia S-N, E-18008 Granada, Spain.
    Frattin, E.
    Univ Padua, Dept Phys & Astron G Galilei, Vicolo Osservatorio 3, I-35122 Padua, Italy;INAF, Astron Observ Padova, Vicolo Osservatorio 5, I-35122 Padua, Italy.
    Kovacs, G.
    Max Planck Inst Solar Syst Res, Justus von Liebig Weg 3, D-37077 Gottingen, Germany.
    Pajola, M.
    NASA, Ames Res Ctr, Moffett Field, CA 94035 USA;Univ Padua, Ctr Studies & Activ Space CISAS G Colombo, Via Venezia 15, I-35131 Padua, Italy.
    Sierks, H.
    Max Planck Inst Solar Syst Res, Justus von Liebig Weg 3, D-37077 Gottingen, Germany.
    Barbieri, C.
    Univ Padua, Dept Phys & Astron G Galilei, Vicolo Osservatorio 3, I-35122 Padua, Italy;Univ Padua, Ctr Studies & Activ Space CISAS G Colombo, Via Venezia 15, I-35131 Padua, Italy.
    Lamy, P.
    Aix Marseille Univ, CNRS, LAM, UMR 7326, F-13388 Marseille, France.
    Rodrigo, R.
    CSIC, INTA, Ctr Astrobiol, Madrid 28850, Spain;Int Space Sci Inst, Hallerstr 6, CH-3012 Bern, Switzerland.
    Koschny, D.
    ESA, European Space Res & Technol Ctr, Sci Support Off, Keplerlaan 1,Postbus 299, NL-2201 AZ Noordwijk, Netherlands.
    Rickman, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics. PAS Space Res Ctr, Bartycka 18A, PL-00716 Warsaw, Poland.
    Keller, H. U.
    Tech Univ Carolo Wilhelmina Braunschweig, IGEP, Mendelssohnstr 3, D-38106 Braunschweig, Germany;Deutsches Zentrum Luft & Raumfahrt DLR, Inst Planeten Forsch, Rutherfordstr 2, D-12489 Berlin, Germany.
    Agarwal, J.
    Max Planck Inst Solar Syst Res, Justus von Liebig Weg 3, D-37077 Gottingen, Germany.
    A'Hearn, M. F.
    Max Planck Inst Solar Syst Res, Justus von Liebig Weg 3, D-37077 Gottingen, Germany;Univ Maryland, Dept Astron, College Pk, MD 20742 USA.
    Barucci, M. A.
    Univ Paris Diderot 5, Univ Pierre & Marie Curie, CNRS, LESIA,Observ Paris, Pl J Janssen, F-92195 Meudon, France.
    Bertaux, J-L
    Bodewits, D.
    Univ Maryland, Dept Astron, College Pk, MD 20742 USA.
    Cremonese, G.
    INAF, Astron Observ Padova, Vicolo Osservatorio 5, I-35122 Padua, Italy.
    Da Deppo, V.
    CNR, IFN UOS Padova LUXOR, Via Trasea 7, I-35131 Padua, Italy.
    Davidsson, B.
    Jet Prop Lab, M-S 183-301,4800 Oak Grove Dr, Pasadena, CA 91109 USA.
    Debei, S.
    Univ Padua, Dept Ind Engn, Via Venezia 1, I-35131 Padua, Italy.
    De Cecco, M.
    Univ Trento, Via Sommarive 9, I-38123 Trento, Italy.
    Drolshagen, E.
    Carl von Ossietzky Univ Oldenburg, Ammerlander Heerstr 114, D-26111 Oldenburg, Germany.
    Ferrari, S.
    Univ Padua, Ctr Studies & Activ Space CISAS G Colombo, Via Venezia 15, I-35131 Padua, Italy.
    Ferri, F.
    Univ Padua, Ctr Studies & Activ Space CISAS G Colombo, Via Venezia 15, I-35131 Padua, Italy.
    Fornasier, S.
    Univ Paris Diderot 5, Univ Pierre & Marie Curie, CNRS, LESIA,Observ Paris, Pl J Janssen, F-92195 Meudon, France.
    Gicquel, A.
    Max Planck Inst Solar Syst Res, Justus von Liebig Weg 3, D-37077 Gottingen, Germany;Jet Prop Lab, M-S 183-301,4800 Oak Grove Dr, Pasadena, CA 91109 USA.
    Groussin, O.
    Aix Marseille Univ, CNRS, LAM, UMR 7326, F-13388 Marseille, France.
    Gutierrez, P. J.
    CSIC, Inst Astrophys Andalusia, Glorieta Astronomia S-N, E-18008 Granada, Spain.
    Hasselmann, P. H.
    Univ Paris Diderot 5, Univ Pierre & Marie Curie, CNRS, LESIA,Observ Paris, Pl J Janssen, F-92195 Meudon, France.
    Hviid, S. F.
    Deutsches Zentrum Luft & Raumfahrt DLR, Inst Planeten Forsch, Rutherfordstr 2, D-12489 Berlin, Germany.
    Ip, W. -H
    Jorda, L.
    Aix Marseille Univ, CNRS, LAM, UMR 7326, F-13388 Marseille, France.
    Knollenberg, J.
    Deutsches Zentrum Luft & Raumfahrt DLR, Inst Planeten Forsch, Rutherfordstr 2, D-12489 Berlin, Germany.
    Kramm, J. R.
    Max Planck Inst Solar Syst Res, Justus von Liebig Weg 3, D-37077 Gottingen, Germany.
    Kuehrt, E.
    Deutsches Zentrum Luft & Raumfahrt DLR, Inst Planeten Forsch, Rutherfordstr 2, D-12489 Berlin, Germany.
    Kuppers, M.
    ESA, European Space Astron Ctr, Operat Dept, POB 78, E-28691 Villanueva De LaCanada, Madrid, Spain.
    Lara, L. M.
    CSIC, Inst Astrophys Andalusia, Glorieta Astronomia S-N, E-18008 Granada, Spain.
    Lazzarin, M.
    Univ Padua, Dept Phys & Astron G Galilei, Vicolo Osservatorio 3, I-35122 Padua, Italy.
    Lin, Z. -Y
    Lopez Moreno, J. J.
    CSIC, Inst Astrophys Andalusia, Glorieta Astronomia S-N, E-18008 Granada, Spain.
    Lucchetti, A.
    INAF, Astron Observ Padova, Vicolo Osservatorio 5, I-35122 Padua, Italy.
    Marzari, F.
    Univ Padua, Dept Phys & Astron G Galilei, Vicolo Osservatorio 3, I-35122 Padua, Italy.
    Massironi, M.
    Univ Padua, Ctr Studies & Activ Space CISAS G Colombo, Via Venezia 15, I-35131 Padua, Italy;Univ Padua, Dept Geosci, Via G Gradenigo 6, I-35131 Padua, Italy.
    Mottola, S.
    Deutsches Zentrum Luft & Raumfahrt DLR, Inst Planeten Forsch, Rutherfordstr 2, D-12489 Berlin, Germany.
    Naletto, G.
    Univ Padua, Ctr Studies & Activ Space CISAS G Colombo, Via Venezia 15, I-35131 Padua, Italy;CNR, IFN UOS Padova LUXOR, Via Trasea 7, I-35131 Padua, Italy;Univ Padua, Dept Informat Engn, Via Gradenigo 6-B, I-35131 Padua, Italy.
    Oklay, N.
    Deutsches Zentrum Luft & Raumfahrt DLR, Inst Planeten Forsch, Rutherfordstr 2, D-12489 Berlin, Germany.
    Ott, T.
    Carl von Ossietzky Univ Oldenburg, Ammerlander Heerstr 114, D-26111 Oldenburg, Germany.
    Penasa, L.
    Univ Padua, Ctr Studies & Activ Space CISAS G Colombo, Via Venezia 15, I-35131 Padua, Italy.
    Thomas, N.
    Univ Bern, Phys Inst, CH-3012 Bern, Switzerland.
    Vincent, J. -B
    The scattering phase function of comet 67P/Churyumov-Gerasimenko coma as seen from the Rosetta/OSIRIS instrument2017In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 469, p. S404-S415Article in journal (Refereed)
    Abstract [en]

    The study of dust, the most abundant material in cometary nuclei, is pivotal in understanding the original materials forming the Solar system. Measuring the coma phase function provides a tool to investigate the nature of cometary dust. Rosetta/OSIRIS sampled the coma phase function of comet 67P/Churyumov-Gerasimenko, covering a large phase angle range in a small amount of time. Twelve series were acquired in the period from 2015 March to 2016 February for this scientific purpose. These data allowed, after stray light removal, measuring the phase function shape, its reddening, and phase reddening while varying heliocentric and nucleocentric distances. Despite small dissimilarities within different series, we found a constant overall shape. The reflectance has a u-shape with minimum at intermediate phase angles, reaching similar values at the smallest and largest phase angle sampled. The comparison with cometary phase functions in literature indicates OSIRIS curves being consistent with the ones found in many other single comets. The dust has a negligible phase reddening at alpha < 90 degrees, indicating a coma dominated by single scattering. We measured a reddening of [11-14] %/100 nm between 376 and 744 nm. No trend with heliocentric or nucleocentric distance was found, indicating the coma doesn't change its spectrum with time. These results are consistent with single coma grains and close-nucleus coma photometric results. Comparison with nucleus photometry indicates a different backscattering phase function shape and similar reddening values only at alpha < 30 degrees. At larger phase angles, the nucleus becomes significantly redder than the coma.

  • 14.
    Beth, A.
    et al.
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England..
    Altwegg, K.
    Univ Bern, Phys Inst, CH-3012 Bern, Switzerland..
    Balsiger, H.
    Univ Bern, Phys Inst, CH-3012 Bern, Switzerland..
    Berthelier, J. -J
    Calmonte, U.
    Univ Bern, Phys Inst, CH-3012 Bern, Switzerland..
    Combi, M. R.
    Univ Michigan, Dept Atmospher Ocean & Space Sci, 2455 Hayward, Ann Arbor, MI 48109 USA..
    De Keyser, J.
    Royal Belgian Inst Space Aeron, BIRA, IASB, Ringlaan 3, B-1180 Brussels, Belgium..
    Dhooghe, F.
    Royal Belgian Inst Space Aeron, BIRA, IASB, Ringlaan 3, B-1180 Brussels, Belgium..
    Fiethe, B.
    TU Braunschweig, Inst Comp & Network Engn IDA, Hans Sommer Str 66, D-38106 Braunschweig, Germany..
    Fuselier, S. A.
    Univ Texas San Antonio, Dept Phys & Astron, San Antonio, TX 78228 USA.;Southwest Res Inst San Antonio, San Antonio, TX 78228 USA..
    Galand, M.
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England..
    Gasc, S.
    Univ Bern, Phys Inst, CH-3012 Bern, Switzerland..
    Gombosi, T. I.
    Univ Michigan, Dept Atmospher Ocean & Space Sci, 2455 Hayward, Ann Arbor, MI 48109 USA..
    Hansen, K. C.
    Univ Michigan, Dept Atmospher Ocean & Space Sci, 2455 Hayward, Ann Arbor, MI 48109 USA..
    Hassig, M.
    Univ Bern, Phys Inst, CH-3012 Bern, Switzerland.;Univ Texas San Antonio, Dept Phys & Astron, San Antonio, TX 78228 USA..
    Heritier, K. L.
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England..
    Kopp, E.
    Univ Bern, Phys Inst, CH-3012 Bern, Switzerland..
    Le Roy, L.
    Univ Bern, Phys Inst, CH-3012 Bern, Switzerland..
    Mandt, K. E.
    Univ Texas San Antonio, Dept Phys & Astron, San Antonio, TX 78228 USA.;Southwest Res Inst San Antonio, San Antonio, TX 78228 USA..
    Peroy, S.
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England..
    Rubin, M.
    Univ Bern, Phys Inst, CH-3012 Bern, Switzerland..
    Semon, T.
    Univ Bern, Phys Inst, CH-3012 Bern, Switzerland..
    Tzou, C. -Y
    Vigren, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    First in situ detection of the cometary ammonium ion NH4+ (protonated ammonia NH3) in the coma of 67P/C-G near perihelion2016In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 462, p. S562-S572Article in journal (Refereed)
    Abstract [en]

    In this paper, we report the first in situ detection of the ammonium ion NH4+ at 67P/Churyumov-Gerasimenko (67P/C-G) in a cometary coma, using the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA)/Double Focusing Mass Spectrometer (DFMS). Unlike neutral and ion spectrometers onboard previous cometary missions, the ROSINA/DFMS spectrometer, when operated in ion mode, offers the capability to distinguish NH4+ from H2O+ in a cometary coma. We present here the ion data analysis of mass-to-charge ratios 18 and 19 at high spectral resolution and compare the results with an ionospheric model to put these results into context. The model confirms that the ammonium ion NH4+ is one of the most abundant ion species, as predicted, in the coma near perihelion.

  • 15.
    Binggeli, Christian
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Zackrisson, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Pelckmans, Kristiaan
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Cubo, Rubén
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Jensen, Hannes
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Shimizu, Ikko
    Osaka Univ, Dept Earth & Space Sci, Theoret Astrophys, 1-1 Machikaneyama, Toyonaka, Osaka 5600043, Japan.
    Lyman continuum leakage versus quenching with the James Webb Space Telescope: the spectral signatures of quenched star formation activity in reionization-epoch galaxies2018In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 479, no 1, p. 368-376Article in journal (Refereed)
    Abstract [en]

    In this paper, we study the effects of a recent drop in star formation rate (SFR) on the spectra of epoch of reionization (EoR) galaxies, and the resulting degeneracy with the spectral features produced by extreme Lyman continuum leakage. In order to study these effects in the wavelength range relevant for the upcoming James Webb Space Telescope (JWST), we utilize synthetic spectra of simulated EoR galaxies from cosmological simulations together with synthetic spectra of partially quenched mock galaxies. We find that rapid declines in the SFR of EoR galaxies could seriously affect the applicability of methods that utilize the equivalent width of Balmer lines and the ultraviolet spectral slope to assess the escape fraction of EoR galaxies. In order to determine if the aforementioned degeneracy can be avoided by using the overall shape of the spectrum, we generate mock NIRCam observations and utilize a classification algorithm to identify galaxies that have undergone quenching. We find that while there are problematic cases, JWST/NIRCam or NIRSpec should be able to reliably identify galaxies with redshifts z similar to 7 that have experienced a significant decrease in the SFR (by a factor of 10-100) in the past 50-100 Myr with a success rate greater than or similar to 85 per cent. We also find that uncertainties in the dust-reddening effects on EoR galaxies significantly affect the performance of the results of the classification algorithm. We argue that studies that aim to characterize the dust extinction law most representative in the EoR would be extremely useful.

  • 16.
    Bland-Hawthorn, Joss
    et al.
    Univ Sydney, Sch Phys, Sydney Inst Astron, A28, Sydney, NSW 2006, Australia;Ctr Excellence Astrophys Three Dimens ASTRO 3D, Hawthorn, Vic, Australia;Univ Calif Berkeley, Miller Inst, Berkeley, CA 94720 USA.
    Sharma, Sanjib
    Univ Sydney, Sch Phys, Sydney Inst Astron, A28, Sydney, NSW 2006, Australia;Ctr Excellence Astrophys Three Dimens ASTRO 3D, Hawthorn, Vic, Australia.
    Tepper-Garcia, Thor
    Univ Sydney, Sch Phys, Sydney Inst Astron, A28, Sydney, NSW 2006, Australia;Ctr Excellence Astrophys Three Dimens ASTRO 3D, Hawthorn, Vic, Australia.
    Binney, James
    Clarendon Lab, Rudolf Peierls Ctr Theoret Phys, Oxford OX1 3PU, England.
    Freeman, Ken C.
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia.
    Hayden, Michael R.
    Univ Sydney, Sch Phys, Sydney Inst Astron, A28, Sydney, NSW 2006, Australia;Ctr Excellence Astrophys Three Dimens ASTRO 3D, Hawthorn, Vic, Australia.
    Kos, Janez
    Univ Sydney, Sch Phys, Sydney Inst Astron, A28, Sydney, NSW 2006, Australia.
    De Silva, Gayandhi M.
    Univ Sydney, Sch Phys, Sydney Inst Astron, A28, Sydney, NSW 2006, Australia;Macquarie Univ, Dept Phys & Astron, N Ryde, NSW 2109, Australia.
    Ellis, Simon
    Macquarie Univ, Dept Phys & Astron, N Ryde, NSW 2109, Australia.
    Lewis, Geraint F.
    Univ Sydney, Sch Phys, Sydney Inst Astron, A28, Sydney, NSW 2006, Australia.
    Asplund, Martin
    Ctr Excellence Astrophys Three Dimens ASTRO 3D, Hawthorn, Vic, Australia;Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia.
    Buder, Sven
    MPIA, Koenigstuhl 17, D-69117 Heidelberg, Germany;Heidelberg Univ, Int Max Planck Res Sch Astron & Cosm Phys, Heidelberg, Germany.
    Casey, Andrew R.
    Monash Univ, Monash Ctr Astrophys, Clayton, Vic 3800, Australia;Monash Univ, Sch Phys & Astron, Clayton, Vic 3800, Australia.
    D'Orazi, Valentina
    INAF Astron Observ Padova, I-36012 Asiago, Italy.
    Duong, Ly
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia.
    Khanna, Shourya
    Univ Sydney, Sch Phys, Sydney Inst Astron, A28, Sydney, NSW 2006, Australia;Ctr Excellence Astrophys Three Dimens ASTRO 3D, Hawthorn, Vic, Australia.
    Lin, Jane
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia.
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy. MPIA, Koenigstuhl 17, D-69117 Heidelberg, Germany.
    Martell, Sarah L.
    Ctr Excellence Astrophys Three Dimens ASTRO 3D, Hawthorn, Vic, Australia;UNSW, Sch Phys, Sydney, NSW 2052, Australia.
    Ness, Melissa K.
    Columbia Univ, Dept Astron, Pupin Phys Labs, New York, NY 10027 USA;Flatiron Inst, Ctr Computat Astrophys, 162 Fifth Ave, New York, NY 10010 USA.
    Simpson, Jeffrey D.
    UNSW, Sch Phys, Sydney, NSW 2052, Australia.
    Zucker, Daniel B.
    Macquarie Univ, Dept Phys & Astron, N Ryde, NSW 2109, Australia.
    Zwitter, Tomaz
    Univ Ljubljana, Fac Math & Phys, Jadranska 19, Ljubljana 1000, Slovenia.
    Kafle, Prajwal R.
    Univ Western Australia, ICRAR, 35 Stirling Highway, Crawley, WA 6009, Australia.
    Quillen, Alice C.
    Univ Rochester, Dept Phys & Astron, Rochester, NY 14627 USA.
    Ting, Yuan-Sen
    Inst Adv Study, Olden Lane, Princeton, NJ 08540 USA;Princeton Univ, Dept Astrophys Sci, Princeton, NJ 08544 USA;Observ Carnegie Inst Washington, 813 Santa Barbara St, Pasadena, CA 91101 USA.
    Wyse, Rosemary F. G.
    Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA.
    The GALAH survey and Gaia DR2: dissecting the stellar disc's phase space by age, action, chemistry, and location2019In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 486, no 1, p. 1167-1191Article in journal (Refereed)
    Abstract [en]

    We use the second data releases of the European Space Agency Gaia astrometric survey and the high-resolution Galactic Archaeology with HERMES (GALAH) spectroscopic survey to analyse the structure of our Galaxy's disc components. With GALAH, we separate the alpha-rich and alpha-poor discs (with respect to Fe), which are superposed in both position and velocity space, and examine their distributions in action space. We study the distribution of stars in the zV(z) phase plane, for both V-phi and V-R, and recover the remarkable 'phase spiral' discovered by Gaia. We identify the anticipated quadrupole signature in zV(z) of a tilted velocity ellipsoid for stars above and belowtheGalactic plane. By connecting ourwork with earlier studies, we show that the phase spiral is likely to extend well beyond the narrow solar neighbourhood cylinder in which it was found. The phase spiral is a signature of corrugated waves that propagate through the disc, and the associated non-equilibrium phase mixing. The radially asymmetric distribution of stars involved in the phase spiral reveals that the corrugation, which is mostly confined to the alpha-poor disc, grows in z-amplitude with increasing radius. We present new simulations of tidal disturbance of the Galactic disc by the Sagittarius (Sgr) dwarf. The effect on the zV(z) phase plane lasts greater than or similar to 2 Gyr, but a subsequent disc crossing wipes out the coherent structure. We find that the phase spiral was excited less than or similar to 0.5 Gyr ago by an object like Sgr with total mass similar to 3 x 10(10) M-circle dot (stripped down from similar to 5 x 10(10) M-circle dot when it first entered the halo) passing through the plane.

  • 17. Boyajian, T.
    et al.
    von Braun, K.
    Feiden, Gregory
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
    Huber, D.
    Basu, S.
    Demarque, P.
    Fischer, D. A.
    Schaefer, G.
    Mann, A. W.
    White, T. R.
    Maestro, V.
    Brewer, J.
    Lamell, C. B.
    Spada, F.
    López-Morales, M.
    Ireland, M.
    Farrington, C.
    van Belle, G. T.
    Kane, S. R.
    Jones, J.
    ten Brummelaar, T. A.
    Ciardi, D. R.
    McAlister, H. A.
    Ridgway, S.
    Goldfinger, P. J.
    Turner, N. H.
    Sturmann, L.
    Stellar diameters and temperatures - VI. High angular resolution measurements of the transiting exoplanet host stars HD 189733 and HD 209458 and implications for models of cool dwarfs2015In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 447, no 1, p. 846-857Article in journal (Refereed)
    Abstract [en]

    We present direct radii measurements of the well-known transiting exoplanet host stars HD 189733 and HD 209458 using the CHARA Array interferometer. We find the limb-darkened angular diameters to be thetaLD = 0.3848 +/- 0.0055 and 0.2254 +/- 0.0072 milliarcsec for HD 189733 and HD 209458, respectively. HD 189733 and HD 209458 are currently the only two transiting exoplanet systems where detection of the respective planetary companion's orbital motion from high resolution spectroscopy has revealed absolute masses for both star and planet. We use our new measurements together with the orbital information from radial velocity and photometric time series data, Hipparcos distances, and newly measured bolometric fluxes to determine the stellar effective temperatures (Teff = 4875 +/- 43, 6093 +/- 103 K), stellar linear radii (R* = 0.805 +/- 0.016, 1.203 +/- 0.061 Rsun), mean stellar densities (rho* = 1.62 +/- 0.11, 0.58 +/- 0.14 rhosun), planetary radii (Rp = 1.216 +/- 0.024, 1.451 +/- 0.074 RJup), and mean planetary densities (rhop = 0.605 +/- 0.029, 0.196 +/- 0.033 rhoJup) for HD 189733 b and HD 209458 b, respectively. The stellar parameters for HD 209458, a F9 dwarf, are consistent with indirect estimates derived from spectroscopic and evolutionary modeling. However, we find that models are unable to reproduce the observational results for the K2 dwarf, HD 189733. We show that, for stellar evolutionary models to match the observed stellar properties of HD 189733, adjustments lowering the solar-calibrated mixing length parameter from 1.83 to 1.34 need to be employed.

  • 18.
    Brogaard, K.
    et al.
    Aarhus Univ, Stellar Astrophys Ctr, Dept Phys & Astron, Ny Munkegade 120, DK-8000 Aarhus C, Denmark;Univ Birmingham, Sch Phys & Astron, Birmingham B15 2TT, W Midlands, England.
    Christiansen, S. M.
    Aarhus Univ, Stellar Astrophys Ctr, Dept Phys & Astron, Ny Munkegade 120, DK-8000 Aarhus C, Denmark.
    Grundahl, F.
    Aarhus Univ, Stellar Astrophys Ctr, Dept Phys & Astron, Ny Munkegade 120, DK-8000 Aarhus C, Denmark.
    Miglio, A.
    Aarhus Univ, Stellar Astrophys Ctr, Dept Phys & Astron, Ny Munkegade 120, DK-8000 Aarhus C, Denmark;Univ Birmingham, Sch Phys & Astron, Birmingham B15 2TT, W Midlands, England.
    Izzard, R. G.
    Univ Surrey, Fac Engn & Phys Sci, Astrophys Res Grp, Guildford GU2 7XH, Surrey, England.
    Tauris, T. M.
    Univ Bonn, Argelander Inst Astron, Hugel 71, D-53121 Bonn, Germany;Max Planck Inst Radioastron, D-53121 Bonn, Germany;Aarhus Univ, Dept Phys & Astron, Ny Munkegade 120, DK-8000 Aarhus C, Denmark.
    Sandquist, E. L.
    San Diego State Univ, Dept Astron, San Diego, CA 92182 USA.
    VandenBerg, D. A.
    Univ Victoria, Dept Phys & Astron, POB 1700 STN CSC, Victoria, BC V8W 2Y2, Canada.
    Jessen-Hansen, J.
    Aarhus Univ, Stellar Astrophys Ctr, Dept Phys & Astron, Ny Munkegade 120, DK-8000 Aarhus C, Denmark.
    Arentoft, T.
    Aarhus Univ, Stellar Astrophys Ctr, Dept Phys & Astron, Ny Munkegade 120, DK-8000 Aarhus C, Denmark.
    Bruntt, H.
    Aarhus Univ, Stellar Astrophys Ctr, Dept Phys & Astron, Ny Munkegade 120, DK-8000 Aarhus C, Denmark.
    Frandsen, S.
    Aarhus Univ, Stellar Astrophys Ctr, Dept Phys & Astron, Ny Munkegade 120, DK-8000 Aarhus C, Denmark.
    Orosz, J. A.
    San Diego State Univ, Dept Astron, San Diego, CA 92182 USA.
    Feiden, Gregory A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
    Mathieu, R.
    Univ Wisconsin, Dept Astron, Madison, WI 53706 USA.
    Geller, A.
    Univ Wisconsin, Dept Astron, Madison, WI 53706 USA.
    Shetrone, M.
    Univ Texas, McDonald Observ, HC75 Box 1337-L, Ft Davis, TX 79734 USA.
    Ryde, N.
    Lund Univ, Lund Observ, Dept Astron & Theoret Phys, Box 43, SE-22100 Lund, Sweden.
    Stello, D.
    Aarhus Univ, Stellar Astrophys Ctr, Dept Phys & Astron, Ny Munkegade 120, DK-8000 Aarhus C, Denmark;Univ Sydney, Sch Phys, Sydney Inst Astron SIfA, Sydney, NSW 2006, Australia;Univ New South Wales, Sch Phys, Sydney, NSW 2052, Australia.
    Platais, I.
    Johns Hopkins Univ, Dept Phys & Astron, 3400 North Charles St, Baltimore, MD 21218 USA.
    Meibom, S.
    Harvard Smithsonian Ctr Astrophys, 60 Garden St, Cambridge, MA 02138 USA.
    The blue straggler V106 in NGC 6791: a prototype progenitor of old single giants masquerading as young2018In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 481, no 4, p. 5062-5072Article in journal (Refereed)
    Abstract [en]

    We determine the properties of the binary star V106 in the old open cluster NGC 6791. We identify the system to be a blue straggler cluster member by using a combination of ground-based and Kepler photometry and multi-epoch spectroscopy. The properties of the primary component are found to be M-p similar to 1.67 M-circle dot, more massive than the cluster turn-off, with R-p similar to 1.91 R-circle dot and T-eff = 7110 +/- 100 K. The secondary component is highly oversized and overluminous for its low mass with M-s similar to 0.182 M-circle dot, R-s similar to 0.864 R-circle dot, and T-eff = 6875 +/- 200 K. We identify this secondary star as a bloated (proto) extremely low-mass helium white dwarf. These properties of V106 suggest that it represents a typical Algol-paradox system and that it evolved through a mass-transfer phase, which provides insight into its past evolution. We present a detailed binary stellar evolution model for the formation of V106 using the MESA code and find that the mass-transfer phase only ceased about 40 Myr ago. Due to the short orbital period (P = 1.4463 d), another mass-transfer phase is unavoidable once the current primary star evolves towards the red giant phase. We argue that V106 will evolve through a common-envelope phase within the next 100 Myr and merge to become a single overmassive giant. The high mass will make it appear young for its true age, which is revealed by the cluster properties. Therefore, V106 is potentially a prototype progenitor of old field giants masquerading as young.

  • 19.
    Broiles, Thomas W.
    et al.
    Southwest Res Inst, Div Space Sci & Engn, 6220 Culebra Rd, San Antonio, TX 78238 USA..
    Burch, J. L.
    Southwest Res Inst, Div Space Sci & Engn, 6220 Culebra Rd, San Antonio, TX 78238 USA..
    Chae, K.
    Southwest Res Inst, Div Space Sci & Engn, 6220 Culebra Rd, San Antonio, TX 78238 USA..
    Clark, G.
    Johns Hopkins Univ, Appl Phys Lab, 11100 Johns Hopkins Rd, Laurel, MD 20723 USA..
    Cravens, T. E.
    Univ Kansas, Dept Phys & Astron, 1450 Jayhawk Blvd, Lawrence, KS 66045 USA..
    Eriksson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Fuselier, S. A.
    Southwest Res Inst, Div Space Sci & Engn, 6220 Culebra Rd, San Antonio, TX 78238 USA.;Univ Texas San Antonio, Dept Phys & Astron, San Antonio, TX 78249 USA..
    Frahm, R. A.
    Southwest Res Inst, Div Space Sci & Engn, 6220 Culebra Rd, San Antonio, TX 78238 USA..
    Gasc, S.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland..
    Goldstein, R.
    Southwest Res Inst, Div Space Sci & Engn, 6220 Culebra Rd, San Antonio, TX 78238 USA..
    Henri, P.
    CNRS, LPC2E, F-45071 Orleans, France..
    Koenders, C.
    Tech Univ Carolo Wilhelmina Braunschweig, Inst Geophys & Extraterr Phys, Mendelssohnstr 3, D-38106 Braunschweig, Germany..
    Livadiotis, G.
    Southwest Res Inst, Div Space Sci & Engn, 6220 Culebra Rd, San Antonio, TX 78238 USA..
    Mandt, K. E.
    Southwest Res Inst, Div Space Sci & Engn, 6220 Culebra Rd, San Antonio, TX 78238 USA.;Univ Texas San Antonio, Dept Phys & Astron, San Antonio, TX 78249 USA..
    Mokashi, P.
    Southwest Res Inst, Div Space Sci & Engn, 6220 Culebra Rd, San Antonio, TX 78238 USA..
    Nemeth, Z.
    Wigner Res Ctr Phys, H-1121 Budapest, Hungary..
    Odelstad, Elias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Space Plasma Physics. Univ Kansas, Dept Phys & Astron, 1450 Jayhawk Blvd, Lawrence, KS 66045 USA..
    Rubin, M.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland..
    Samara, M.
    Goddard Space Flight Ctr, Heliophys Div, 8800 Greenbelt Rd, Greenbelt, MD 20771 USA..
    Statistical analysis of suprathermal electron drivers at 67P/Churyumov-Gerasimenko2016In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 462, p. S312-S322Article in journal (Refereed)
    Abstract [en]

    We use observations from the Ion and Electron Sensor (IES) on board the Rosetta spacecraft to study the relationship between the cometary suprathermal electrons and the drivers that affect their density and temperature. We fit the IES electron observations with the summation of two kappa distributions, which we characterize as a dense and warm population (similar to 10 cm(-3) and similar to 16 eV) and a rarefied and hot population (similar to 0.01 cm(-3) and similar to 43 eV). The parameters of our fitting technique determine the populations' density, temperature, and invariant kappa index. We focus our analysis on the warm population to determine its origin by comparing the density and temperature with the neutral density and magnetic field strength. We find that the warm electron population is actually two separate sub-populations: electron distributions with temperatures above 8.6 eV and electron distributions with temperatures below 8.6 eV. The two sub-populations have different relationships between their density and temperature. Moreover, the two sub-populations are affected by different drivers. The hotter sub-population temperature is strongly correlated with neutral density, while the cooler sub-population is unaffected by neutral density and is only weakly correlated with magnetic field strength. We suggest that the population with temperatures above 8.6 eV is being heated by lower hybrid waves driven by counterstreaming solar wind protons and newly formed, cometary ions created in localized, dense neutral streams. To the best of our knowledge, this represents the first observations of cometary electrons heated through wave-particle interactions.

  • 20.
    Buder, Sven
    et al.
    MPIA, Koenigstuhl 17, D-69117 Heidelberg, Germany;Heidelberg Univ, Int Max Planck Res Sch Astron & Cosm Phys, Heidelberg, Germany.
    Asplund, Martin
    Ctr Excellence Astrophys Three Dimens ASTRO 3D, Sydney, NSW, Australia;Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia.
    Duong, Ly
    Kos, Janez
    Univ Sydney, Sydney Inst Astron, Sch Phys, A28, Sydney, NSW 2006, Australia.
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy. MPIA, Koenigstuhl 17, D-69117 Heidelberg, Germany.
    Ness, Melissa K.
    Columbia Univ, Dept Astron, Pupin Phys Labs, New York, NY 10027 USA;Flatiron Inst, Ctr Computat Astrophys, 162 Fifth Ave, New York, NY 10010 USA.
    Sharma, Sanjib
    Univ Sydney, Sydney Inst Astron, Sch Phys, A28, Sydney, NSW 2006, Australia;Ctr Excellence Astrophys Three Dimens ASTRO 3D, Sydney, NSW, Australia.
    Bland-Hawthorn, Joss
    Univ Sydney, Sydney Inst Astron, Sch Phys, A28, Sydney, NSW 2006, Australia;Ctr Excellence Astrophys Three Dimens ASTRO 3D, Sydney, NSW, Australia;Univ Calif Berkeley, Miller Inst, Berkeley, CA 94720 USA.
    Casey, Andrew R.
    Monash Univ, Monash Ctr Astrophys, Clayton, Vic 3800, Australia;Monash Univ, Sch Phys & Astron, Clayton, Vic 3800, Australia.
    De Silva, Gayandhi M.
    Univ Sydney, Sydney Inst Astron, Sch Phys, A28, Sydney, NSW 2006, Australia;Australian Astron Observ, 105 Delhi Rd, N Ryde, NSW 2113, Australia.
    D'Orazi, Valentina
    Ist Nazl Astrofis, Osservatorio Astron Padova, Vicolo Osservatorio 5, I-35122 Padua, Italy.
    Freeman, Ken C.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia.
    Lewis, Geraint F.
    Univ Sydney, Sydney Inst Astron, Sch Phys, A28, Sydney, NSW 2006, Australia.
    Lin, Jane
    Ctr Excellence Astrophys Three Dimens ASTRO 3D, Sydney, NSW, Australia;Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia.
    Martell, Sarah L.
    UNSW, Sch Phys, Sydney, NSW 2052, Australia.
    Schlesinger, Katharine J.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia.
    Simpson, Jeffrey D.
    Australian Astron Observ, 105 Delhi Rd, N Ryde, NSW 2113, Australia.
    Zucker, Daniel B.
    Australian Astron Observ, 105 Delhi Rd, N Ryde, NSW 2113, Australia;Macquarie Univ, Dept Phys & Astron, Sydney, NSW 2109, Australia.
    Zwitter, Tomaz
    Univ Ljubljana, Fac Math & Phys, Jadranska 19, Ljubljana 1000, Slovenia.
    Amarsi, Anish M.
    MPIA, Koenigstuhl 17, D-69117 Heidelberg, Germany.
    Anguiano, Borja
    Univ Virginia, Dept Astron, Charlottesville, VA 22904 USA.
    Carollo, Daniela
    INAF, Astrophys Observ Turin, Turin, Italy.
    Casagrande, Luca
    Ctr Excellence Astrophys Three Dimens ASTRO 3D, Sydney, NSW, Australia;Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia.
    Cotar, Klemen
    Univ Ljubljana, Fac Math & Phys, Jadranska 19, Ljubljana 1000, Slovenia.
    Cottrell, Peter L.
    Univ Canterbury, Sch Phys & Chem Sci, Christchurch, New Zealand;Monash Univ, Sch Phys & Astron, Clayton, Vic 3800, Australia.
    Da Costa, Gary
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia.
    Gao, Xudong D.
    MPIA, Koenigstuhl 17, D-69117 Heidelberg, Germany.
    Hayden, Michael R.
    Univ Sydney, Sydney Inst Astron, Sch Phys, A28, Sydney, NSW 2006, Australia;Ctr Excellence Astrophys Three Dimens ASTRO 3D, Sydney, NSW, Australia.
    Horner, Jonathan
    Univ Southern Queensland, Toowoomba, Qld 4350, Australia.
    Ireland, Michael J.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia.
    Kafle, Prajwal R.
    Univ Western Australia, ICRAR, 35 Stirling Highway, Crawley, WA 6009, Australia.
    Munari, Ulisse
    INAF Astron Observ Padova, I-36012 Asiago, Italy.
    Nataf, David M.
    Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA.
    Nordlander, Thomas
    Ctr Excellence Astrophys Three Dimens ASTRO 3D, Sydney, NSW, Australia;Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia.
    Stello, Dennis
    Ctr Excellence Astrophys Three Dimens ASTRO 3D, Sydney, NSW, Australia;Aarhus Univ, Dept Phys & Astron, Stellar Astrophys Ctr, DK-8000 Aarhus C, Denmark;UNSW, Sch Phys, Sydney, NSW 2052, Australia.
    Ting, Yuan-Sen
    Observ Carnegie Inst Washington, 813 Santa Barbara St, Pasadena, CA 91101 USA;Inst Adv Study, Olden Lane, Princeton, NJ 08540 USA;Princeton Univ, Dept Astrophys Sci, Princeton, NJ 08544 USA.
    Traven, Gregor
    Univ Ljubljana, Fac Math & Phys, Jadranska 19, Ljubljana 1000, Slovenia.
    Watson, Fred
    Western Sydney Univ, Locked Bag 1797, Penrith, NSW 2751, Australia;Australian Astron Observ, 105 Delhi Rd, N Ryde, NSW 2113, Australia.
    Wittenmyer, Robert A.
    Univ Southern Queensland, Computat Engn & Sci Res Ctr, Toowoomba, Qld 4350, Australia.
    Wyse, Rosemary F. G.
    Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA.
    Yong, David
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia.
    Zinn, Joel C.
    Ohio State Univ, Dept Astron, 140 West 18th Ave, Columbus, OH 43210 USA.
    Zerjal, Marusa
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia.
    The GALAH Survey: second data release2018In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 478, no 4, p. 4513-4552Article in journal (Refereed)
    Abstract [en]

    The Galactic Archaeology with HERMES (GALAH) survey is a large-scale stellar spectroscopic survey of the Milky Way, designed to deliver complementary chemical information to a large number of stars covered by the Gaia mission. We present the GALAH second public data release (GALAH DR2) containing 342 682 stars. For these stars, the GALAH collaboration provides stellar parameters and abundances for up to 23 elements to the community. Here we present the target selection, observation, data reduction, and detailed explanation of how the spectra were analysed to estimate stellar parameters and element abundances. For the stellar analysis, we have used a multistep approach. We use the physics-driven spectrum synthesis of Spectroscopy Made Easy (SME) to derive stellar labels (T-eff, log g, [Fe/H], [X/Fe], v(mic), vsin i, AKS) for a representative training set of stars. This information is then propagated to the whole sample with the data-driven method of The Cannon. Special care has been exercised in the spectral synthesis to only consider spectral lines that have reliable atomic input data and are little affected by blending lines. Departures from local thermodynamic equilibrium (LTE) are considered for several key elements, including Li, O, Na, Mg, Al, Si, and Fe, using 1D MARCS stellar atmosphere models. Validation tests including repeat observations, Gaia benchmark stars, open and globular clusters, and K2 asteroseismic targets lend confidence to our methods and results. Combining the GALAH DR2 catalogue with the kinematic information from Gaia will enable a wide range of Galactic Archaeology studies, with unprecedented detail, dimensionality, and scope.

  • 21.
    Casamiquela, L.
    et al.
    Univ Barcelona, Dept Fis Quant & Astrofis, ICC IEEC, E-08007 Barcelona, Spain..
    Carrera, R.
    Inst Astrofis Canarias, E-38205 Tenerife, Spain.;Univ La Laguna, Dept Astrofis, E-38207 San Cristobal la Laguna, Spain..
    Blanco-Cuaresma, S.
    Univ Geneva, Observ Geneve, CH-1290 Versoix, Switzerland..
    Jordi, C.
    Univ Barcelona, Dept Fis Quant & Astrofis, ICC IEEC, E-08007 Barcelona, Spain..
    Balaguer-Nunez, L.
    Univ Barcelona, Dept Fis Quant & Astrofis, ICC IEEC, E-08007 Barcelona, Spain..
    Pancino, E.
    INAF Osservatorio Astrofis Arcetri, Largo Enrico Fermi 5, I-50125 Florence, Italy.;ASI Sci Data Ctr, Via Politecn SNC, I-00133 Rome, Italy..
    Anders, F.
    Leibniz Inst Astrophys Potsdam AIP, Sternwarte 16, D-14482 Potsdam, Germany..
    Chiappini, C.
    Leibniz Inst Astrophys Potsdam AIP, Sternwarte 16, D-14482 Potsdam, Germany..
    Diaz-Perez, L.
    Inst Astrofis Canarias, E-38205 Tenerife, Spain.;Univ La Laguna, Dept Astrofis, E-38207 San Cristobal la Laguna, Spain..
    Aguado, D. S.
    Inst Astrofis Canarias, E-38205 Tenerife, Spain.;Univ La Laguna, Dept Astrofis, E-38207 San Cristobal la Laguna, Spain..
    Aparicio, A.
    Inst Astrofis Canarias, E-38205 Tenerife, Spain.;Univ La Laguna, Dept Astrofis, E-38207 San Cristobal la Laguna, Spain..
    Garcia-Dias, R.
    Inst Astrofis Canarias, E-38205 Tenerife, Spain.;Univ La Laguna, Dept Astrofis, E-38207 San Cristobal la Laguna, Spain..
    Heiter, Ulrike
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Martinez-Vazquez, C. E.
    Inst Astrofis Canarias, E-38205 Tenerife, Spain.;Univ La Laguna, Dept Astrofis, E-38207 San Cristobal la Laguna, Spain..
    Murabito, S.
    Inst Astrofis Canarias, E-38205 Tenerife, Spain.;Univ La Laguna, Dept Astrofis, E-38207 San Cristobal la Laguna, Spain..
    del Pino, A.
    Polish Acad Sci, Nicolaus Copernicus Astron Ctr, Ul Bartycka 18, PL-00716 Warsaw, Poland..
    OCCASO - II. Physical parameters and Fe abundances of red clump stars in 18 open clusters2017In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 470, no 4, p. 4363-4381Article in journal (Refereed)
    Abstract [en]

    Open clusters have long been used to study the chemodynamical evolution of the Galactic disc. This requires a homogeneously analysed sample covering a wide range of ages and distances. In this paper, we present the Open Clusters Chemical Abundances from Spanish Observatories (OCCASO) second data release. This comprises a sample of high-resolution (R > 65 000) and high signal-to-noise spectra of 115 red clump stars in 18 open clusters. We derive atmospheric parameters (T-eff, log g, xi), and [Fe/H] abundances using two analysis techniques: equivalent widths and spectral synthesis. A detailed comparison and a critical review of the results of the two methods are made. Both methods are carefully tested between them, with the Gaia FGK benchmark stars, and with an extensive sample of literature values. We perform a membership study using radial velocities and the resulting abundances. Finally, we compare our results with a chemodynamical model of the Milky Way thin disc concluding that the oldest open clusters are consistent with the models only when dynamical effects are taken into account.

  • 22.
    Casey, A. R.
    et al.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England..
    Ruchti, G.
    Lund Observ, Dept Astron & Theoret Phys, Box 43, SE-22100 Lund, Sweden..
    Masseron, T.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England..
    Randich, S.
    Osserv Astrofis Arcetri, INAF, Largo E Fermi 5, I-50125 Florence, Italy..
    Gilmore, G.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England..
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy. Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany..
    Kennedy, G. M.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England..
    Koposov, S. E.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England..
    Hourihane, A.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England..
    Franciosini, E.
    Osserv Astrofis Arcetri, INAF, Largo E Fermi 5, I-50125 Florence, Italy..
    Lewis, J. R.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England..
    Magrini, L.
    Osserv Astrofis Arcetri, INAF, Largo E Fermi 5, I-50125 Florence, Italy..
    Morbidelli, L.
    Osserv Astrofis Arcetri, INAF, Largo E Fermi 5, I-50125 Florence, Italy..
    Sacco, G. G.
    Osserv Astrofis Arcetri, INAF, Largo E Fermi 5, I-50125 Florence, Italy..
    Worley, C. C.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England..
    Feltzing, S.
    Lund Observ, Dept Astron & Theoret Phys, Box 43, SE-22100 Lund, Sweden..
    Jeffries, R. D.
    Keele Univ, Astrophys Grp, Keele ST5 5BG, Staffs, England..
    Vallenari, A.
    Padova Observ, INAF, Vicolo Osservatorio 5, I-35122 Padua, Italy..
    Bensby, T.
    Lund Observ, Dept Astron & Theoret Phys, Box 43, SE-22100 Lund, Sweden..
    Bragaglia, A.
    Osservatorio Astron Bologna, INAF, Via Ranzani 1, I-40127 Bologna, Italy..
    Flaccomio, E.
    Osserv Astron Palermo, INAF, Piazza Parlamento 1, I-90134 Palermo, Italy..
    Francois, P.
    Univ Paris Diderot, CNRS, Observ Paris, GEPI, 5 Pl Jules Janssen, F-92190 Meudon, France..
    Korn, Andreas J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
    Lanzafame, A.
    Univ Catania, Sez Astrofis, Dipartimento Fis & Astron, Via S Sofia 78, I-95123 Catania, Italy..
    Pancino, E.
    Osserv Astrofis Arcetri, INAF, Largo E Fermi 5, I-50125 Florence, Italy.;ASI Sci Data Ctr, Via Politecn SNC, I-00133 Rome, Italy..
    Recio-Blanco, A.
    Univ Nice Sophia Antipolis, CNRS, Observ Cote Azur, Lab Lagrange,UMR7293, CS 34229, F-06304 Nice 4, France..
    Smiljanic, R.
    Nicolaus Copernicus Astron Ctr, Dept Astrophys, Ul Rabianska 8, PL-87100 Torun, Poland..
    Carraro, G.
    European Southern Observ, Alonso Cordova 3107 Vitacura, Santiago, Chile..
    Costado, M. T.
    CSIC, Inst Astrofis Andalucia, Apdo 3004, E-18080 Granada, Spain..
    Damiani, F.
    Osserv Astron Palermo, INAF, Piazza Parlamento 1, I-90134 Palermo, Italy..
    Donati, P.
    Univ Bologna, Dipartimento Fis & Astron, Viale Berti Pichat 6-2, I-40127 Bologna, Italy..
    Frasca, A.
    Osserv Astrofis Catania, INAF, Via S Sofia 78, I-95123 Catania, Italy..
    Jofre, P.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England..
    Lardo, C.
    Liverpool John Moores Univ, Astrophys Res Inst, 146 Brownlow Hill, Liverpool L3 5RF, Merseyside, England..
    de Laverny, P.
    Univ Nice Sophia Antipolis, CNRS, Observ Cote Azur, Lab Lagrange,UMR7293, CS 34229, F-06304 Nice 4, France..
    Monaco, L.
    Univ Andres Bello, Dept Ciencias Fis, Republ 220, Santiago, Chile..
    Prisinzano, L.
    Osserv Astron Palermo, INAF, Piazza Parlamento 1, I-90134 Palermo, Italy..
    Sbordone, L.
    Millennium Inst Astrophys, Av Vicuna Mackenna 4860, Santiago 7820436, Chile.;Pontificia Univ Catolica Chile, Av Vicuna Mackenna 4860, Santiago 7820436, Chile..
    Sousa, S. G.
    Univ Porto, CAUP, Inst Astrofis & Ciencias Espaco, Rua Estrelas, P-4150762 Oporto, Portugal..
    Tautvaisiene, G.
    Vilnius Univ, Inst Theoret Phys & Astron, A Gostauto 12, LT-01108 Vilnius, Lithuania..
    Zaggia, S.
    Padova Observ, INAF, Vicolo Osservatorio 5, I-35122 Padua, Italy..
    Zwitter, T.
    Univ Ljubljana, Fac Math & Phys, Jadranska 19, Ljubljana 1000, Slovenia..
    Delgado Mena, E.
    Univ Porto, CAUP, Inst Astrofis & Ciencias Espaco, Rua Estrelas, P-4150762 Oporto, Portugal..
    Chorniy, Y.
    Vilnius Univ, Inst Theoret Phys & Astron, A Gostauto 12, LT-01108 Vilnius, Lithuania..
    Martell, S. L.
    Univ New South Wales, Sch Phys, Sydney, NSW 2052, Australia..
    Aguirre, V. Silva
    Aarhus Univ, Dept Phys & Astron, Stellar Astrophys Ctr, Ny Munkegade 120, DK-8000 Aarhus C, Denmark..
    Miglio, A.
    Univ Birmingham, Sch Phys & Astron, Birmingham B15 2TT, W Midlands, England..
    Chiappini, C.
    Leibniz Inst Astrophys Potsdam AIP, Sternwarte 16, D-14482 Potsdam, Germany..
    Montalban, J.
    Univ Padua, Dept Phys & Astron G Galilei, Vicolo Osservatorio 3, I-35122 Padua, Italy..
    Morel, T.
    Univ Liege, Inst Astrophys & Geophys, Quartier Agora, Bat B5c,Allee 6 Aout 19c, B-4000 Liege, Belgium..
    Valentini, M.
    Leibniz Inst Astrophys Potsdam AIP, Sternwarte 16, D-14482 Potsdam, Germany..
    The Gaia-ESO Survey: revisiting the Li-rich giant problem2016In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 461, no 3, p. 3336-3352Article in journal (Refereed)
    Abstract [en]

    The discovery of lithium-rich giants contradicts expectations from canonical stellar evolution. Here we report on the serendipitous discovery of 20 Li-rich giants observed during the Gaia-ESO Survey, which includes the first nine Li-rich giant stars known towards the CoRoT fields. Most of our Li-rich giants have near-solar metallicities and stellar parameters consistent with being before the luminosity bump. This is difficult to reconcile with deep mixing models proposed to explain lithium enrichment, because these models can only operate at later evolutionary stages: at or past the luminosity bump. In an effort to shed light on the Li-rich phenomenon, we highlight recent evidence of the tidal destruction of close-in hot Jupiters at the sub-giant phase. We note that when coupled with models of planet accretion, the observed destruction of hot Jupiters actually predicts the existence of Li-rich giant stars, and suggests that Li-rich stars should be found early on the giant branch and occur more frequently with increasing metallicity. A comprehensive review of all known Li-rich giant stars reveals that this scenario is consistent with the data. However, more evolved or metal-poor stars are less likely to host close-in giant planets, implying that their Li-rich origin requires an alternative explanation, likely related to mixing scenarios rather than external phenomena.

  • 23. Cruzalebes, P.
    et al.
    Jorissen, A.
    Rabbia, Y.
    Chiavassa, A.
    Paladini, C.
    Sacuto, Stéphane
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Siopis, C.
    Sadowski, G.
    Spang, A.
    Chesneau, O.
    Measuring deviation from centrosymmetry for a source brightness distribution observed by spectro-interferometry2014In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 443, no 4, p. 3550-3563Article in journal (Refereed)
    Abstract [en]

    We report on the testing of the centrosymmetry parameter (CSP), an indicator of deviation from centrosymmetry of a source brightness distribution. This indicator is derived from the spectral distribution of the triple product measured over three baselines of an optical interferometer. Numerical simulations using parametric toy-models (separated or transiting binary, one-spot model), generated with the SPIDAST software, are applied to the VLTI/AMBER facility in the K band (2.2 mu m). The simulations show that, in case of centrosymmetry, the CSP parameter is in agreement with the usual phase of the spectral mean of the triple product (called GCP, global closure phase). To justify the preferential use of CSP rather than GCP, we show situations with asymmetric geometries for which GCP diagnoses centrosymmetry, while CSP does not. Using realistic Roche lobe-filling binary and hydrodynamic convective models, we show that CSP can also be used as an indicator for geometric similarity between physical and toy-models. Thus, dealing with real data, the toy-model parameters can be fitted on the measured CSP values, in order to assess the input-parameter values of the most suitable complex physical model that will be used to interpret the data.

  • 24. Cruzalebes, P.
    et al.
    Jorissen, A.
    Rabbia, Y.
    Sacuto, S.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Chiavassa, A.
    Pasquato, E.
    Plez, B.
    Eriksson, Kjell
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
    Spang, A.
    Chesneau, O.
    Fundamental parameters of 16 late-type stars derived from their angular diameter measured with VLTI/AMBER(star)2013In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 434, no 1, p. 437-450Article in journal (Refereed)
    Abstract [en]

    Thanks to their large angular dimension and brightness, red giants and supergiants are privileged targets for optical long-baseline interferometers. 16 red giants and supergiants have been observed with the VLTI/AMBER facility over a 2-year period, at medium spectral resolution (R = 1500) in the K band. The limb-darkened angular diameters are derived from fits of stellar atmospheric models on the visibility and the triple product data. The angular diameters do not show any significant temporal variation, except for one target: TX Psc, which shows a variation of 4 per cent using visibility data. For the eight targets previously measured by long-baseline interferometry (LBI) in the same spectral range, the difference between our diameters and the literature values is less than 5 per cent, except for TX Psc, which shows a difference of 11 per cent. For the eight other targets, the present angular diameters are the first measured from LBI. Angular diameters are then used to determine several fundamental stellar parameters, and to locate these targets in the Hertzsprung-Russell diagram (HRD). Except for the enigmatic Tc-poor low-mass carbon star W Ori, the location of Tc-rich stars in the HRD matches remarkably well the thermally-pulsating asymptotic giant branch, as it is predicted by the stellar evolution models. For pulsating stars with periods available, we compute the pulsation constant and locate the stars along the various sequences in the period-luminosity diagram. We confirm the increase in mass along the pulsation sequences, as predicted by theory, except for W Ori which, despite being less massive, appears to have a longer period than T Cet along the first-overtone sequence.

  • 25. Cruzalebes, P.
    et al.
    Rabbia, Y.
    Jorissen, A.
    Spang, A.
    Sacuto, S.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics, The Uppsala Astronomical Observatory.
    Pasquato, E.
    Chiavassa, A.
    Chesneau, O.
    Freville, P.
    SPIDAST: a new modular software to process spectrointerferometric measurements2013In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 432, no 2, p. 1658-1671Article in journal (Refereed)
    Abstract [en]

    Extracting stellar fundamental parameters from Spectrointerferometric (SPI) data requires reliable estimates of observables and with robust uncertainties (visibility, triple product, phase closure). A number of fine calibration procedures are necessary throughout the reduction process. Testing departures from centrosymmetry of brightness distributions is a useful complement. Developing a set of automatic routines called spidast (made available to the community) to reduce, calibrate and interpret raw data sets of instantaneous spectrointerferograms at the spectral channel level, we complement (and in some respects improve) the ones contained in the amdlib Data Reduction Software. Our new software spidast is designed to work in an automatic mode, free from subjective choices, while being versatile enough to suit various processing strategies. spidast performs the following automated operations: weighting of non-aberrant SPI data (visibility, triple product), fine spectral calibration (subpixel level), accurate and robust determinations of stellar diameters for calibrator sources (and their uncertainties as well), correction for the degradations of the interferometer response in visibility and triple product, calculation of the centrosymmetry parameter from the calibrated triple product, fit of parametric chromatic models on SPI observables, to extract model parameters. spidast is currently applied to the scientific study of 18 cool giant and supergiant stars, observed with the VLTI/AMBER facility at medium resolution in the K band. Because part of their calibrators have no diameter in the current catalogues, spidast provides new determinations of the angular diameters of all calibrators. Comparison of spidast final calibrated observables with amdlib determinations shows good agreement, under good and poor seeing conditions.

  • 26. Cukanovaite, E.
    et al.
    Tremblay, P. -E
    Freytag, Bernd
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
    Ludwig, H. -G
    Bergeron, P.
    Pure-helium 3D model atmospheres of white dwarfs2018In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 481, no 2, p. 1522-1537Article in journal (Refereed)
    Abstract [en]

    We present the first grid of 3D simulations for the pure-helium atmospheres of DB white dwarfs. The simulations were computed with the co(5) BOLD radiation-hydrodynamics code and cover effective temperatures and surface gravities between 12 000 K less than or similar to T-eff less than or similar to 34 000 K and 7.5 <= log g (cgs units) <= 9.0, respectively. In this introductory work, synthetic spectra calculated from the 3D simulations are compared to appropriate 1 D model spectra under a differential approach. This results in the derivation of 3D corrections for the spectroscopically derived atmospheric parameters of DB stars with respect to the 1D ML2/alpha = 1.25 mixing-length parametrization. No significant T-eff corrections are found for the V777 Her instability strip region, and therefore no 3D revision is expected for the empirical blue and red edges of the strip. However, large log g corrections are found in the range 12 000 K < T-eff < 23 000 K for all log g values covered by the 3D grid. These corrections indicate that 1D model atmospheres overpredict log g, reminiscent of the results found from 3D simulations of pure-hydrogen white dwarfs. The next step will be to compute 3D simulations with mixed helium and hydrogen atmospheres to comprehend the full implications for the stellar parameters of DB and DBA white dwarfs.

  • 27.
    Cunha, M. S.
    et al.
    Univ Porto, Inst Astrofis & Ciencias Espaco, CAUP, Rua Estrelas, PT-4150762 Porto, Portugal.
    Antoci, V.
    Aarhus Univ, Stellar Astrophys Ctr, Ny Munkegade 120, DK-8000 Aarhus, Denmark.
    Holdsworth, D. L.
    Univ Cent Lancashire, Jeremiah Horrocks Inst, Preston PR1 2HE, Lancs, England.
    Kurtz, D. W.
    Univ Cent Lancashire, Jeremiah Horrocks Inst, Preston PR1 2HE, Lancs, England.
    Balona, L. A.
    South African Astron Observ, POB 9, Cape Town, South Africa.
    Bognar, Zs.
    MTA CSFK, Konkoly Observ, Konkoly Thege Miklos Ut 15-17, H-1121 Budapest, Hungary;MTA CSFK Lendulet Near Field Cosmol Res Grp, Budapest, Hungary.
    Bowman, D. M.
    Katholieke Univ Leuven, Inst Astron, Celestijnenlaan 200D, B-3001 Leuven, Belgium.
    Guo, Z.
    Penn State Univ, Ctr Exoplanets & Habitable Worlds, 525 Davey Lab, University Pk, PA 16802 USA;Polish Acad Sci, Copernicus Astron Ctr, Bartycka 18, PL-00716 Warsaw, Poland.
    Kolaczek-Szymanski, P. A.
    Univ Wroclaw, Astron Inst, Ul Kopernika 11, PL-51622 Wroclaw, Poland.
    Lares-Martiz, M.
    CSIC, Inst Astrofis Andalucia, Glorieta Astron S-N, E-18008 Granada, Spain.
    Paunzen, E.
    Masaryk Univ, Dept Theoret Phys & Astrophys, Kotlarska 2, CS-61137 Brno, Czech Republic.
    Skarka, M.
    Masaryk Univ, Dept Theoret Phys & Astrophys, Kotlarska 2, CS-61137 Brno, Czech Republic;Czech Acad Sci, Astron Inst, Fricova 298, Ondrejov 25165, Czech Republic.
    Smalley, B.
    Keele Univ, Astrophys Grp, Keele ST5 5BG, Staffs, England.
    Sodor, A.
    MTA CSFK, Konkoly Observ, Konkoly Thege Miklos Ut 15-17, H-1121 Budapest, Hungary;MTA CSFK Lendulet Near Field Cosmol Res Grp, Budapest, Hungary.
    Kochukhov, Oleg
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Pepper, J.
    Lehigh Univ, Dept Phys, 16 Mem Dr East, Bethlehem, PA 18015 USA.
    Richey-Yowell, T.
    Arizona State Univ, Sch Earth & Space Explorat, Tempe, AZ 85281 USA.
    Ricker, G. R.
    MIT, Dept Phys, Cambridge, MA 02139 USA;MIT, Kavli Inst Astrophys & Space Res, 77 Massachusetts Ave, Cambridge, MA 02139 USA.
    Seager, S.
    MIT, Dept Phys, Cambridge, MA 02139 USA;MIT, Kavli Inst Astrophys & Space Res, 77 Massachusetts Ave, Cambridge, MA 02139 USA;MIT, Earth & Planetary Sci, 77 Massachusetts Ave, Cambridge, MA 02139 USA.
    Buzasi, D. L.
    Florida Gulf Coast Univ, Dept Chem & Phys, 10501 FGCU Blvd S, Ft Myers, FL 33965 USA.
    Fox-Machado, L.
    Univ Nacl Autonoma Mexico, Inst Astron, Ap P 877, Ensenada 22860, BC, Mexico.
    Hasanzadeh, A.
    Univ Zanjan, Dept Phys, Zanjan, Iran.
    Niemczura, E.
    Univ Wroclaw, Astron Inst, Ul Kopernika 11, PL-51622 Wroclaw, Poland.
    Quitral-Manosalva, P.
    Univ Porto, Inst Astrofis & Ciencias Espaco, CAUP, Rua Estrelas, PT-4150762 Porto, Portugal;Univ Porto, Dept Fis & Astron, Fac Ciencias, Porto, Portugal.
    Monteiro, M. J. P. F. G.
    Univ Porto, Inst Astrofis & Ciencias Espaco, CAUP, Rua Estrelas, PT-4150762 Porto, Portugal;Univ Porto, Dept Fis & Astron, Fac Ciencias, Porto, Portugal.
    Stateva, I.
    Bulgarian Acad Sci, Inst Astron, Blvd Tsarigradsko Chaussee 72, BU-1784 Sofia, Bulgaria;Bulgarian Acad Sci, NAO, Blvd Tsarigradsko Chaussee 72, BU-1784 Sofia, Bulgaria.
    De Cat, P.
    Royal Observ Belgium, Ringlaan 3, B-1180 Brussels, Belgium.
    Garcia Hernandez, A.
    Univ Granada, Dept Fis Teor & Cosmos, Campus Fuentenueva S-N, E-18071 Granada, Spain.
    Ghasemi, H.
    IASBS, Dept Phys, Zanjan 4513766731, Iran.
    Handler, G.
    Polish Acad Sci, Copernicus Astron Ctr, Bartycka 18, PL-00716 Warsaw, Poland.
    Hey, D.
    Aarhus Univ, Stellar Astrophys Ctr, Ny Munkegade 120, DK-8000 Aarhus, Denmark;Univ Sydney, Sydney Inst Astron, Sch Phys, Sydney, NSW 2006, Australia.
    Matthews, J. M.
    Univ British Columbia, Dept Phys & Astron, Vancouver, BC, Canada.
    Nemec, J. M.
    Camosun Coll, Dept Phys & Astron, Victoria, BC, Canada.
    Pascual-Granado, J.
    CSIC, Inst Astrofis Andalucia, Glorieta Astron S-N, E-18008 Granada, Spain.
    Safari, H.
    Univ Zanjan, Dept Phys, Zanjan, Iran.
    Suarez, J. C.
    CSIC, Inst Astrofis Andalucia, Glorieta Astron S-N, E-18008 Granada, Spain;Univ Granada, Dept Fis Teor & Cosmos, Campus Fuentenueva S-N, E-18071 Granada, Spain.
    Szabo, R.
    MTA CSFK, Konkoly Observ, Konkoly Thege Miklos Ut 15-17, H-1121 Budapest, Hungary;MTA CSFK Lendulet Near Field Cosmol Res Grp, Budapest, Hungary.
    Tkachenko, A.
    Katholieke Univ Leuven, Inst Astron, Celestijnenlaan 200D, B-3001 Leuven, Belgium.
    Weiss, W. W.
    Univ Vienna, Dept Astrophys, Tuerkenschanzstr 17, A-1180 Vienna, Austria.
    Rotation and pulsation in Ap stars: first light results from TESS sectors 1 and 22019In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 487, no 3, p. 3523-3549Article in journal (Refereed)
    Abstract [en]

    We present the first results from the Transiting Exoplanet Survey Satellite (TESS) on the rotational and pulsational variability of magnetic chemically peculiar A-type stars. We analyse TESS 2-min cadence data from sectors 1 and 2 on a sample of 83 stars. Five new rapidly oscillating Ap (roAp) stars are announced. One of these pulsates with periods around 4.7 min, making it the shortest period roAp star known to date. Four out of the five new roAp stars are multiperiodic. Three of these and the singly periodic one show the presence of rotational mode splitting. Individual frequencies are provided in all cases. In addition, seven previously known roAp stars are analysed. Additional modes of oscillation are found in some stars, while in others we are able to distinguish the true pulsations from possible aliases present in the ground-based data. We find that the pulsation amplitude in the TESS filter is typically a factor of 6 smaller than that in the B filter, which is usually used for ground-based observations. For four roAp stars we set constraints on the inclination angle and magnetic obliquity, through the application of the oblique pulsator model. We also confirm the absence of roAp-type pulsations down to amplitude limits of 6 and 13 mu mag, respectively, in two of the best characterized non-oscillating Ap (noAp) stars. We announce 27 new rotational variables along with their rotation periods, and provide different rotation periods for seven other stars. Finally, we discuss how these results challenge state-of-the-art pulsation models for roAp stars.

  • 28.
    David-Uraz, A.
    et al.
    Univ Delaware, Dept Phys & Astron, Newark, DE 19716 USA.
    Neiner, C.
    Univ Paris Diderot, Sorbonne Univ, PSL Univ, LESIA,Observ Paris,CNRS,Sorbonne Paris Cite, 5 Pl Jules Janssen, F-92195 Meudon, France.
    Sikora, J.
    Queens Univ, Dept Phys Engn Phys & Astron, Kingston, ON K7L 3N6, Canada;Royal Mil Coll Canada, Dept Phys & Space Phys, POB 17000, Kingston, ON K7K 7B4, Canada.
    Bowman, D. M.
    Katholieke Univ Leuven, Inst Sterrenkunde, Celestijnenlaan 200D, B-3001 Leuven, Belgium.
    Petit, V.
    Univ Delaware, Dept Phys & Astron, Newark, DE 19716 USA.
    Chowdhury, S.
    Nicolaus Copernicus Astron Ctr, Bartycka 18, PL-00716 Warsaw, Poland.
    Handler, G.
    Nicolaus Copernicus Astron Ctr, Bartycka 18, PL-00716 Warsaw, Poland.
    Pergeorelis, M.
    Univ Delaware, Dept Phys & Astron, Newark, DE 19716 USA.
    Cantiello, M.
    Flatiron Inst, Ctr Computat Astrophys, 162 5th Ave, New York, NY 10010 USA;Princeton Univ, Dept Astrophys Sci, Princeton, NJ 08544 USA.
    Cohen, D. H.
    Swarthmore Coll, Dept Phys & Astron, Swarthmore, PA 19081 USA.
    Erba, C.
    Univ Delaware, Dept Phys & Astron, Newark, DE 19716 USA.
    Keszthelyi, Z.
    Queens Univ, Dept Phys Engn Phys & Astron, Kingston, ON K7L 3N6, Canada;Royal Mil Coll Canada, Dept Phys & Space Phys, POB 17000, Kingston, ON K7K 7B4, Canada.
    Khalack, V.
    Univ Moncton, Dept Phys & Astron, Moncton, NB E1A 3E9, Canada.
    Kobzar, O.
    Univ Moncton, Dept Phys & Astron, Moncton, NB E1A 3E9, Canada.
    Kochukhov, Oleg
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Labadie-Bartz, J.
    Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, Rua Matao 1226,Cidade Univ, BR-05508900 Sao Paulo, SP, Brazil.
    Lovekin, C. C.
    Mt Allison Univ, Dept Phys, Sackville, NB E4L 1E6, Canada.
    MacInnis, R.
    Univ Delaware, Dept Phys & Astron, Newark, DE 19716 USA.
    Owocki, S. P.
    Univ Delaware, Dept Phys & Astron, Newark, DE 19716 USA.
    Pablo, H.
    AAVSO Headquarters, 49 Bay State Rd, Cambridge, MA 02138 USA.
    Shultz, M. E.
    Univ Delaware, Dept Phys & Astron, Newark, DE 19716 USA.
    Ud-Doula, A.
    Penn State Scranton, 120 Ridge View Dr, Dunmore, PA 18512 USA.
    Wade, G. A.
    Royal Mil Coll Canada, Dept Phys & Space Phys, POB 17000, Kingston, ON K7K 7B4, Canada.
    Magnetic OB[A] Stars with TESS: probing their Evolutionary and Rotational properties (MOBSTER) - I. First-light observations of known magnetic B and A stars2019In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 487, no 1, p. 304-317Article in journal (Refereed)
    Abstract [en]

    In this paper we introduce the MOBSTER collaboration and lay out its scientific goals. We present first results based on the analysis of 19 previously known magnetic O, B, and A stars observed in 2-min cadence in sectors 1 and 2 of the Transiting Exoplanet Survey Satellite (TESS) mission. We derive precise rotational periods from the newly obtained light curves and compare them to previously published values. We also discuss the overall photometric phenomenology of the known magnetic massive and intermediate-mass stars and propose an observational strategy to augment this population by taking advantage of the high-quality observations produced by TESS.

  • 29. De Silva, G. M.
    et al.
    Freeman, K. C.
    Bland-Hawthorn, J.
    Martell, S.
    de Boer, E. Wylie
    Asplund, M.
    Keller, S.
    Sharma, S.
    Zucker, D. B.
    Zwitter, T.
    Anguiano, B.
    Bacigalupo, C.
    Bayliss, D.
    Beavis, M. A.
    Bergemann, M.
    Campbell, S.
    Cannon, R.
    Carollo, D.
    Casagrande, L.
    Casey, A. R.
    Da Costa, G.
    D'Orazi, V.
    Dotter, A.
    Duong, L.
    Heger, A.
    Ireland, M. J.
    Kafle, P. R.
    Kos, J.
    Lattanzio, J.
    Lewis, G. F.
    Lin, J.
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Munari, U.
    Nataf, D. M.
    O'Toole, S.
    Parker, Q.
    Reid, W.
    Schlesinger, K. J.
    Sheinis, A.
    Simpson, J. D.
    Stello, D.
    Ting, Y. -S
    Traven, G.
    Watson, F.
    Wittenmyer, R.
    Yong, D.
    Zerjal, M.
    The GALAH survey: scientific motivation2015In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 449, no 3, p. 2604-2617Article in journal (Refereed)
    Abstract [en]

    The Galactic Archaeology with HERMES (GALAH) survey is a large high-resolution spectroscopic survey using the newly commissioned High Efficiency and Resolution Multi-Element Spectrograph (HERMES) on the Anglo-Australian Telescope. The HERMES spectrograph provides high-resolution (R similar to 28 000) spectra in four passbands for 392 stars simultaneously over a 2 deg field of view. The goal of the survey is to unravel the formation and evolutionary history of the Milky Way, using fossil remnants of ancient star formation events which have been disrupted and are now dispersed throughout the Galaxy. Chemical tagging seeks to identify such dispersed remnants solely from their common and unique chemical signatures; these groups are unidentifiable from their spatial, photometric or kinematic properties. To carry out chemical tagging, the GALAH survey will acquire spectra for a million stars down to V similar to 14. The HERMES spectra of FGK stars contain absorption lines from 29 elements including light proton-capture elements, alpha-elements, odd-Z elements, iron-peak elements and n-capture elements from the light and heavy s-process and the r-process. This paper describes the motivation and planned execution of the GALAH survey, and presents some results on the first-light performance of HERMES.

  • 30. de Val-Borro, M.
    et al.
    Edgar, R. G.
    Artymowicz, P.
    Ciecielag, P.
    Cresswell, P.
    D'Angelo, G.
    Delgado-Donate, E. J.
    Dirksen, G.
    Fromang, S.
    Gawryszczak, A.
    Klahr, H.
    Kley, W.
    Lyra, Wladimir
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics, The Uppsala Astronomical Observatory.
    Masset, F.
    Mellema, G.
    Nelson, R. P.
    Paardekooper, S. -J
    Peplinski, A.
    Pierens, A.
    Plewa, T.
    Rice, K.
    Schaefer, C.
    Speith, R.
    A comparative study of disc-planet interaction2006In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 370, no 2, p. 529-558Article in journal (Refereed)
    Abstract [en]

    We perform numerical simulations of a disc-planet system using various grid-based and smoothed particle hydrodynamics (SPH) codes. The tests are run for a simple setup where Jupiter and Neptune mass planets on a circular orbit open a gap in a protoplanetary disc during a few hundred orbital periods. We compare the surface density contours, potential vorticity and smoothed radial profiles at several times. The disc mass and gravitational torque time evolution are analysed with high temporal resolution. There is overall consistency between the codes. The density profiles agree within about 5 per cent for the Eulerian simulations. The SPH results predict the correct shape of the gap although have less resolution in the low-density regions and weaker planetary wakes. The disc masses after 200 orbital periods agree within 10 per cent. The spread is larger in the tidal torques acting on the planet which agree within a factor of 2 at the end of the simulation. In the Neptune case, the dispersion in the torques is greater than for Jupiter, possibly owing to the contribution from the not completely cleared region close to the planet.

  • 31. de Val-Borro, M.
    et al.
    Gahm, G. F.
    Stempels, Henricus C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Peplinski, A.
    Modelling circumbinary gas flows in close T Tauri binaries star2011In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 413, no 4, p. 2679-2688Article in journal (Refereed)
    Abstract [en]

    Young close binaries open central gaps in the surrounding circumbinary accretion disc, but the stellar components may still gain mass from gas crossing through the gap. It is not well understood how this process operates and how the stellar components are affected by such inflows. Our main goal is to investigate how gas accretion takes place and evolves in close T Tauri binary systems. In particular, we model the accretion flows around two close T Tauri binaries, V4046 Sgr and DQ Tau, both showing periodic changes in emission lines, although their orbital characteristics are very different. In order to derive the density and velocity maps of the circumbinary material, we employ two-dimensional hydrodynamic simulations with a locally isothermal equation of state. The flow patterns become quasi-stable after a few orbits in the frame corotating with the system. Gas flows across the circumbinary gap through the corotating Lagrangian points, and local circumstellar discs develop around both components. Spiral density patterns develop in the circumbinary disc that transport angular momentum efficiently. Mass is preferentially channelled towards the primary and its circumstellar disc is more massive than the disc around the secondary. We also compare the derived density distribution to observed line profile variability. The line profile variability tracing the gas flows in the central cavity shows clear similarities with the corresponding observed line profile variability in V4046 Sgr, but only when the local circumstellar disc emission was excluded. Closer to the stars normal magnetospheric accretion may dominate, while further out the dynamic accretion process outlined here dominates. Periodic changes in the accretion rates on to the stars can explain the outbursts of line emission observed in eccentric systems such as DQ Tau.

  • 32.
    Deshapriya, J. D. P.
    et al.
    Univ Paris Diderot, UPMC Univ Paris 06, CNRS, Observ Paris,LESIA, 5 Pl J Janssen, F-92195 Meudon, France..
    Barucci, M. A.
    Univ Paris Diderot, UPMC Univ Paris 06, CNRS, Observ Paris,LESIA, 5 Pl J Janssen, F-92195 Meudon, France..
    Fornasier, S.
    Univ Paris Diderot, UPMC Univ Paris 06, CNRS, Observ Paris,LESIA, 5 Pl J Janssen, F-92195 Meudon, France..
    Feller, C.
    Univ Paris Diderot, UPMC Univ Paris 06, CNRS, Observ Paris,LESIA, 5 Pl J Janssen, F-92195 Meudon, France..
    Hasselmann, P. H.
    Univ Paris Diderot, UPMC Univ Paris 06, CNRS, Observ Paris,LESIA, 5 Pl J Janssen, F-92195 Meudon, France..
    Sierks, H.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    El-Maarry, M. R.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland..
    Pajola, M.
    NASA, Ames Res Ctr, Moffett Field, CA 94035 USA..
    Barbieri, C.
    Univ Padua, Dept Phys & Astron G Galilei, Vic Osservatorio 3, I-35122 Padua, Italy..
    Lamy, P. L.
    CNRS, UMR 7326, Lab Astrophys Marseille, F-13388 Marseille 13, France.;Aix Marseille Univ, F-13388 Marseille 13, France..
    Rodrigo, R.
    CSIC, INTA, Ctr Astrobiol, E-28850 Madrid, Spain.;Int Space Sci Inst, Hallerstr 6, CH-3012 Bern, Switzerland..
    Koschny, D.
    European Space Agcy, Res & Sci Support Dept, NL-2201 Noordwijk, Netherlands..
    Rickman, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics. PAS Space Reserch Ctr, Poland.
    Agarwal, J.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    A'Hearn, M. F.
    Univ Maryland, Dept Astron, College Pk, MD 20742 USA..
    Bertaux, J. -L
    Bertini, I.
    Univ Padua, Dept Phys & Astron G Galilei, Vic Osservatorio 3, I-35122 Padua, Italy..
    Boudreault, S.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Cremonese, G.
    INAF, Osservatorio Astron Padova, Vicolo Osservatorio 5, I-35122 Padua, Italy..
    Da Deppo, V.
    CNR, IFN UOS Padova LUXOR, Via Trasea 7, I-35131 Padua, Italy..
    Davidsson, B. J. R.
    JPL, 4800 Oak Grove Dr, Pasadena, CA 91109 USA..
    Debei, S.
    Univ Padua, Dept Mech Engn, Via Venezia 1, I-35131 Padua, Italy..
    Deller, J.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    De Cecco, M.
    Univ Trento, UNITN, Via Mesiano 77, I-38100 Trento, Italy..
    Fulle, M.
    INAF, Osservatorio Astron Trieste, Via Tiepolo 11, I-34143 Trieste, Italy..
    Gicquel, A.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Groussin, O.
    CNRS, UMR 7326, Lab Astrophys Marseille, F-13388 Marseille 13, France.;Aix Marseille Univ, F-13388 Marseille 13, France..
    Gutierrez, P. J.
    CSIC, Inst Astrofis Andalucia, E-18080 Granada, Spain..
    Guettler, C.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Hofmann, M.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Hviid, S. F.
    DLR, Inst Planetary Res, Rutherfordstr 2, D-12489 Berlin, Germany..
    Ip, W.
    Natl Cent Univ, Inst Space Sci, Chungli 32054, Taiwan..
    Jorda, L.
    CNRS, UMR 7326, Lab Astrophys Marseille, F-13388 Marseille 13, France.;Aix Marseille Univ, F-13388 Marseille 13, France..
    Keller, H. U.
    TU Braunschweig, Inst Geophys & Extraterr Phys, D-38106 Braunschweig, Germany..
    Knollenberg, J.
    DLR, Inst Planetary Res, Rutherfordstr 2, D-12489 Berlin, Germany..
    Kramm, R.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Kuehrt, E.
    DLR, Inst Planetary Res, Rutherfordstr 2, D-12489 Berlin, Germany..
    Kueppers, M.
    ESA, ESAC, POB 78, E-28691 Villanueva De La Canada, Spain..
    Lara, L.
    CSIC, Inst Astrofis Andalucia, E-18080 Granada, Spain..
    Lazzarin, M.
    Univ Padua, Dept Phys & Astron G Galilei, Vic Osservatorio 3, I-35122 Padua, Italy..
    Lopez Moreno, J. J.
    CSIC, Inst Astrofis Andalucia, E-18080 Granada, Spain..
    Marzari, F.
    Univ Padua, Dept Phys & Astron G Galilei, Vic Osservatorio 3, I-35122 Padua, Italy..
    Mottola, S.
    DLR, Inst Planetary Res, Rutherfordstr 2, D-12489 Berlin, Germany..
    Naletto, G.
    CNR, IFN UOS Padova LUXOR, Via Trasea 7, I-35131 Padua, Italy.;Univ Padua, Dept Informat Engn, Via Gradenigo 6, I-35131 Padua, Italy.;Univ Padua, Ctr Studies & Act Space CISAS G Colombo, Via Venezia 15, I-35131 Padua, Italy..
    Oklay, N.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Perna, D.
    Univ Paris Diderot, UPMC Univ Paris 06, CNRS, Observ Paris,LESIA, 5 Pl J Janssen, F-92195 Meudon, France..
    Pommerol, A.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland..
    Thomas, N.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland..
    Tubiana, C.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Vincent, J. -B
    Spectrophotometry of the Khonsu region on the comet 67P/Churyumov-Gerasimenko using OSIRIS instrument images2016In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 462, p. S274-S286Article in journal (Refereed)
    Abstract [en]

    Our work focuses on the spectrophotometric analysis of selected terrain and bright patches in the Khonsu region on the comet 67P/Churyumov-Gerasimenko. Despite the variety of geological features, their spectrophotometric properties appear to indicate a similar composition. It is noticeable that the smooth areas in Khonsu possess similar spectrophotometric behaviour to some other regions of the comet. We observed bright patches on Khonsu with an estimation of >40 per cent of normal albedo and suggest that they are associated with H2O ice. One of the studied bright patches has been observed to exist on the surface for more than 5 months without a major decay of its size, implying the existence of potential sub-surface icy layers. Its location may be correlated with a cometary outburst during the perihelion passage of the comet in 2015 August, and we interpret it to have triggered the surface modifications necessary to unearth the stratified icy layers beneath the surface. A boulder analysis on Khonsu leads to a power-law index of -3.1 + 0.2/-0.3 suggesting a boulder formation, shaped by varying geological processes for different morphological units.

  • 33. Dhawan, S.
    et al.
    Bulla, M.
    Goobar, A.
    Lunnan, R.
    Johansson, Joel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Fransson, C.
    Kulkarni, S. R.
    Papadogiannakis, S.
    Miller, A. A.
    iPTF16abc and the population of Type Ia supernovae: comparing the photospheric, transitional, and nebular phases2018In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 480, no 2, p. 1445-1456Article in journal (Refereed)
    Abstract [en]

    Key information about the progenitor system and the explosion mechanism of Type Ia supernovae (SNe Ia) can be obtained from early observations, within a few days from explosion. iPTF16abc was discovered as a young SN Ia with excellent early time data. Here, we present photometry and spectroscopy of the SN in the nebular phase. A comparison of the early time data with a sample of SNe Ia shows distinct features, differing from normal SNe Ia at early phases but similar to normal SNe Ia at a few weeks after maximum light (i.e. the transitional phase) and well into the nebular phase. The transparency time-scales (t0) for this sample of SNe Ia range between ∼25 and 41 d indicating a diversity in the ejecta masses. t0 also weakly correlates with the peak bolometric luminosity, consistent with the interpretation that SNe with higher ejecta masses would produce more 56Ni" role="presentation">56Ni . Comparing the t0 and the maximum luminosity, Lmax distribution of a sample of SNe Ia to predictions from a wide range of explosion models we find an indication that the sub-Chandrasekhar mass models span the range of observed values. However, the bright end of the distribution can be better explained by Chandrasekhar mass delayed detonation models, hinting at multiple progenitor channels to explain the observed bolometric properties of SNe Ia. iPTF16abc appears to be consistent with the predictions from the Mch models.

  • 34. Distefano, E.
    et al.
    Lanzafame, A. C.
    Lanza, A. F.
    Messina, S.
    Korn, Andreas J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Eriksson, Kjell
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
    Cuypers, J.
    Determination of rotation periods in solar-like stars with irregular sampling: the Gaia case2012In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 421, no 4, p. 2774-2785Article in journal (Refereed)
    Abstract [en]

    We present a study on the determination of rotation periods (P) of solar-like stars from the photometric irregular time sampling of the European Space Agency Gaia mission, currently scheduled for launch in 2013, taking into account its dependence on ecliptic coordinates. We examine the case of solar twins as well as thousands of synthetic time series of solar-like stars rotating faster than the Sun. In the case of solar twins, we assume that the Gaia unfiltered photometric passband G will mimic the variability of the total solar irradiance as measured by the Variability of solar IRradiance and Gravity Oscillations (VIRGO) experiment. For stars rotating faster than the Sun, light curves are simulated using synthetic spectra for the quiet atmosphere, the spots and the faculae combined by applying semi-empirical relationships relating the level of photospheric magnetic activity to the stellar rotation and the Gaia instrumental response. The capabilities of the Deeming, LombScargle and phase dispersion minimization methods in recovering the correct rotation periods are tested and compared. The false alarm probability is computed using Monte Carlo simulations and compared with analytical formulae. The Gaia scanning law makes the rate of correct detection of rotation periods strongly dependent on the ecliptic latitude (beta). We find that for P? 1 d, the rate of correct detection increases with beta from 2030 per cent at beta? 0 to a peak of 70 per cent at beta= 45 degrees; then it abruptly falls below 10 per cent at beta > 45 degrees. For P > 5 d, the rate of correct detection is quite low and for solar twins is only 5 per cent on average.

  • 35.
    Doughty, Caitlin
    et al.
    New Mexico State Univ, Dept Astron, Las Cruces, NM 88001 USA..
    Finlator, Kristian
    New Mexico State Univ, Dept Astron, Las Cruces, NM 88001 USA..
    Oppenheimer, Benjamin D.
    Univ Colorado, Dept Astrophys & Planetary Sci, CASA, 389-UCB, Boulder, CO 80309 USA..
    Dave, Romeel
    Royal Observ, Inst Astron, Edinburgh EH9 3HJ, Midlothian, Scotland.;Univ Western Cape, Dept Phys & Astron, ZA-7535 Cape Town, South Africa..
    Zackrisson, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Aligned metal absorbers and the ultraviolet background at the end of reionization2018In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 475, no 4, p. 4717-4727Article in journal (Refereed)
    Abstract [en]

    We use observations of spatially aligned C II, C IV, Si II, Si IV, and O I absorbers to probe the slope and intensity of the ultraviolet background (UVB) at z similar to 6. We accomplish this by comparing observations with predictions from a cosmological hydrodynamic simulation using three trial UVBs applied in post-processing: a spectrally soft, fluctuating UVB calculated using multifrequency radiative transfer; a soft, spatially uniform UVB; and a hard, spatially uniform 'quasars-only' model. When considering our paired high-ionization absorbers (C IV/Si IV), the observed statistics strongly prefer the hard, spatially uniform UVB. This echoes recent findings that cosmological simulations generically underproduce strong C IV absorbers at z > 5. A single low/high ionization pair (Si II/Si IV), by contrast, shows a preference for the HM12 UVB, whereas two more (C II/C IV and O I/C IV) show no preference for any of the three UVBs. Despite this, future observations of specific absorbers, particularly Si IV/C IV, with next-generation telescopes probing to lower column densities should yield tighter constraints on the UVB.

  • 36.
    Duong, L.
    et al.
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia.
    Freeman, K. C.
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia.
    Asplund, M.
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia.
    Casagrande, L.
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia.
    Buder, S.
    Max Planck Inst Astron, Koenigstuhl 17, D-69117 Heidelberg, Germany.
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy. Max Planck Inst Astron, Heidelberg, Germany.
    Ness, M.
    Max Planck Inst Astron, Koenigstuhl 17, D-69117 Heidelberg, Germany.
    Bland-Hawthorn, J.
    Univ Sydney, Sch Phys A28, Sydney Inst Astron, Sydney, NSW 2006, Australia.
    De Silva, G. M.
    Univ Sydney, Sch Phys A28, Sydney Inst Astron, Sydney, NSW 2006, Australia;Australian Astron Observ, N Ryde, NSW 1670, Australia.
    D'Orazi, V.
    INAF, Osservatorio Astron Padova, Vicolo Osservatorio 5, I-35122 Padua, Italy.
    Kos, J.
    Univ Sydney, Sch Phys A28, Sydney Inst Astron, Sydney, NSW 2006, Australia.
    Lewis, G. F.
    Univ Sydney, Sch Phys A28, Sydney Inst Astron, Sydney, NSW 2006, Australia.
    Lin, J.
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia.
    Martell, S. L.
    Univ New South Wales, Sch Phys, Sydney, NSW 2052, Australia.
    Schlesinger, K.
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia.
    Sharma, S.
    Univ Sydney, Sch Phys A28, Sydney Inst Astron, Sydney, NSW 2006, Australia.
    Simpson, J. D.
    Australian Astron Observ, N Ryde, NSW 1670, Australia.
    Zucker, D. B.
    Macquarie Univ, Dept Phys & Astron, Sydney, NSW 2109, Australia.
    Zwitter, T.
    Univ Ljubljana, Fac Math & Phys, Jadranska 19, Ljubljana 1000, Slovenia.
    Anguiano, B.
    Macquarie Univ, Dept Phys & Astron, Sydney, NSW 2109, Australia;Univ Virginia, Dept Astron, POB 400325, Charlottesville, VA 22904 USA.
    Da Costa, G. S.
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia.
    Hyde, E.
    Western Sydney Univ, Locked Bag 1797, Penrith, NSW 1797, Australia.
    Horner, J.
    Univ Southern Queensland, Toowoomba, Qld 4350, Australia.
    Kafle, P. R.
    Univ Western Australia, ICRAR, 35 Stirling Highway, Crawley, WA 6009, Australia.
    Nataf, D. M.
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia;Johns Hopkins Univ, Ctr Astrophys Sci, Baltimore, MD 21218 USA;Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA.
    Reid, W.
    Macquarie Univ, Dept Phys & Astron, Sydney, NSW 2109, Australia;Western Sydney Univ, Locked Bag 1797, Penrith, NSW 2751, Australia;Aarhus Univ, Stellar Astrophys Ctr, Dept Phys & Astron, DK-8000 Aarhus C, Denmark.
    Stello, D.
    Univ Sydney, Sch Phys A28, Sydney Inst Astron, Sydney, NSW 2006, Australia;Macquarie Univ, Dept Phys & Astron, Sydney, NSW 2109, Australia;Inst Adv Study, Olden Lane, Princeton, NJ 08540 USA.
    Ting, Y. -S
    Wyse, R. F. G.
    Johns Hopkins Univ, Ctr Astrophys Sci, Baltimore, MD 21218 USA;Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA.
    The GALAH survey: properties of the Galactic disc(s) in the solar neighbourhood2018In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 476, no 4, p. 5216-5232Article in journal (Refereed)
    Abstract [en]

    Using data from the GALAH pilot survey, we determine properties of the Galactic thin and thick discs near the solar neighbourhood. The data cover a small range of Galactocentric radius (7.9 less than or similar to R-GC less than or similar to 9.5 kpc), but extend up to 4 kpc in height from the Galactic plane, and several kpc in the direction of Galactic anti-rotation (at longitude 260 degrees <= l <= 280 degrees). This allows us to reliably measure the vertical density and abundance profiles of the chemically and kinematically defined 'thick' and 'thin' discs of the Galaxy. The thin disc (low-alpha population) exhibits a steep negative vertical metallicity gradient, at d[M/H]/dz = -0.18 +/- 0.01 dex kpc(-1), which is broadly consistent with previous studies. In contrast, its vertical alpha-abundance profile is almost flat, with a gradient of d[alpha/M]/dz = 0.008 +/- 0.002 dex kpc(-1). The steep vertical metallicity gradient of the low-a population is in agreement with models where radial migration has a major role in the evolution of the thin disc. The thick disc (high-alpha population) has a weaker vertical metallicity gradient d[M/H]/dz = -0.058 +/- 0.003 dex kpc(-1). The aabundance of the thick disc is nearly constant with height, d[alpha/M]/dz = 0.007 +/- 0.002 dex kpc(-1). The negative gradient in metallicity and the small gradient in [alpha/M] indicate that the high-alpha population experienced a settling phase, but also formed prior to the onset of major Type I alpha supernova enrichment. We explore the implications of the distinct alpha-enrichments and narrow [alpha/M] range of the sub-populations in the context of thick disc formation.

  • 37.
    Edberg, Niklas J. T.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Alho, M.
    Aalto Univ, Sch Elect Engn, Dept Radio Sci & Engn, POB 13000, FI-00076 Aalto, Finland..
    André, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Andrews, David J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Behar, E.
    Swedish Inst Space Phys, Box 812, SE-98128 Kiruna, Sweden..
    Burch, J. L.
    Southwest Res Inst, 6220 Culebra Rd, San Antonio, TX 78238 USA..
    Carr, C. M.
    Imperial Coll London, Exhibit Rd, London SW7 2AZ, England..
    Cupido, E.
    Imperial Coll London, Exhibit Rd, London SW7 2AZ, England..
    Engelhardt, Ilka. A. D.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Eriksson, Anders I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Glassmeier, K. -H
    Goetz, C.
    TU Braunschweig, Inst Geophys & Extraterr Phys, Mendelssohnstr 3, D-38106 Braunschweig, Germany..
    Goldstein, R.
    Southwest Res Inst, 6220 Culebra Rd, San Antonio, TX 78238 USA..
    Henri, P.
    Lab Phys & Chim Environm & Espace, F-45071 Orleans 2, France..
    Johansson, Fredrik L.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Koenders, C.
    TU Braunschweig, Inst Geophys & Extraterr Phys, Mendelssohnstr 3, D-38106 Braunschweig, Germany..
    Mandt, K.
    Southwest Res Inst, 6220 Culebra Rd, San Antonio, TX 78238 USA.;Univ Texas San Antonio, Dept Phys & Astron, San Antonio, TX 78249 USA..
    Moestl, C.
    Austrian Acad Sci, Space Res Inst, Schmiedlstr 6, A-8042 Graz, Austria..
    Nilsson, H.
    Swedish Inst Space Phys, Box 812, SE-98128 Kiruna, Sweden..
    Odelstad, Elias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Richter, I.
    TU Braunschweig, Inst Geophys & Extraterr Phys, Mendelssohnstr 3, D-38106 Braunschweig, Germany..
    Wedlund, C. Simon
    Univ Oslo, Dept Phys, Box 1048 Blindern, N-0316 Oslo, Norway..
    Wieser, G. Stenberg
    Swedish Inst Space Phys, Box 812, SE-98128 Kiruna, Sweden..
    Szego, K.
    Wigner Res Ctr Phys, Konkoly Thege Miklos Ut 29-33, H-1121 Budapest, Hungary..
    Vigren, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Volwerk, M.
    Austrian Acad Sci, Space Res Inst, Schmiedlstr 6, A-8042 Graz, Austria..
    CME impact on comet 67P/Churyumov-Gerasimenko2016In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 462, p. S45-S56Article in journal (Refereed)
    Abstract [en]

    We present Rosetta observations from comet 67P/Churyumov-Gerasimenko during the impact of a coronal mass ejection (CME). The CME impacted on 2015 Oct 5-6, when Rosetta was about 800 km from the comet nucleus, and 1.4 au from the Sun. Upon impact, the plasma environment is compressed to the level that solar wind ions, not seen a few days earlier when at 1500 km, now reach Rosetta. In response to the compression, the flux of suprathermal electrons increases by a factor of 5-10 and the background magnetic field strength increases by a factor of similar to 2.5. The plasma density increases by a factor of 10 and reaches 600 cm(-3), due to increased particle impact ionization, charge exchange and the adiabatic compression of the plasma environment. We also observe unprecedentedly large magnetic field spikes at 800 km, reaching above 200 nT, which are interpreted as magnetic flux ropes. We suggest that these could possibly be formed by magnetic reconnection processes in the coma as the magnetic field across the CME changes polarity, or as a consequence of strong shears causing Kelvin-Helmholtz instabilities in the plasma flow. Due to the limited orbit of Rosetta, we are not able to observe if a tail disconnection occurs during the CME impact, which could be expected based on previous remote observations of other CME-comet interactions.

  • 38.
    Engelhardt, Ilka. A. D.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Space Plasma Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Eriksson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Stenberg Wieser, G.
    Goetz, C.
    Rubin, M.
    Henri, P.
    Nilsson, H.
    Odelstad, Elias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Space Plasma Physics.
    Hajra, R.
    Valliéres, X.
    Plasma Density Structures at Comet 67P/Churyumov-Gerasimenko2018In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 477, no 1, p. 1296-1307Article in journal (Refereed)
    Abstract [en]

    We present Rosetta RPC case study from four events at various radial distance, phase angle and local time from autumn 2015, just after perihelion of comet 67P/Churyumov-Gerasimenko. Pulse like (high amplitude, up to minutes in time) signatures are seen with several RPC instruments in the plasma density (LAP, MIP), ion energy and flux (ICA) as well as magnetic field intensity (MAG). Furthermore the cometocentric distance relative to the electron exobase is seen to be a good organizing parameter for the measured plasma variations. The closer Rosetta is to this boundary, the more pulses are measured. This is consistent with the pulses being filaments of plasma originating from the diamagnetic cavity boundary as predicted by simulations. 

  • 39.
    Farihi, J.
    et al.
    UCL, Dept Phys & Astron, London WC1E 6BT, England..
    Fossati, L.
    Austrian Acad Sci, Space Res Inst, A-8042 Graz, Austria..
    Wheatley, P. J.
    Univ Warwick, Dept Phys, Coventry CV4 7AL, W Midlands, England..
    Metzger, B. D.
    Columbia Univ, Dept Phys, 538 W 120th St, New York, NY 10027 USA..
    Mauerhan, J.
    Univ Calif Berkeley, Dept Astron, 601 Campbell Hall, Berkeley, CA 94720 USA..
    Bachman, S.
    Indiana Univ Penn, Dept Phys, Indiana, PA 15705 USA.;Wesleyan Univ, Astron Dept, Middletown, CT 06459 USA.;Wesleyan Univ, Van Vleck Observ, Middletown, CT 06459 USA..
    Gänsicke, B. T.
    Univ Warwick, Dept Phys, Coventry CV4 7AL, W Midlands, England..
    Redfield, S.
    Wesleyan Univ, Astron Dept, Middletown, CT 06459 USA.;Wesleyan Univ, Van Vleck Observ, Middletown, CT 06459 USA..
    Cauley, P. W.
    Wesleyan Univ, Astron Dept, Middletown, CT 06459 USA.;Wesleyan Univ, Van Vleck Observ, Middletown, CT 06459 USA..
    Kochukhov, Oleg
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Achilleos, N.
    UCL, Dept Phys & Astron, London WC1E 6BT, England..
    Stone, N.
    Columbia Univ, Dept Astron, New York, NY 10027 USA..
    Magnetism, X-rays and accretion rates in WD 1145+017 and other polluted white dwarf systems2018In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 474, no 1, p. 947-960Article in journal (Refereed)
    Abstract [en]

    This paper reports circular spectropolarimetry and X-ray observations of several polluted white dwarfs including WD 1145+017, with the aim to constrain the behaviour of disc material and instantaneous accretion rates in these evolved planetary systems. Two stars with previously observed Zeeman splitting, WD 0322-019 and WD 2105-820, are detected above 5 sigma and < B-z > > 1 kG, while WD 1145+017, WD 1929+011, and WD 2326+049 yield (null) detections below this minimum level of confidence. For these latter three stars, high-resolution spectra and atmospheric modelling are used to obtain limits on magnetic field strengths via the absence of Zeeman splitting, finding B-* < 20 kG based on data with resolving power R approximate to 40 000. An analytical framework is presented for bulk Earth composition material falling on to the magnetic polar regions of white dwarfs, where X-rays and cyclotron radiation may contribute to accretion luminosity. This analysis is applied to X-ray data for WD 1145+017, WD 1729+371, and WD 2326+049, and the upper bound count rates are modelled with spectra for a range of plasma kT = 1-10 keV in both the magnetic and non-magnetic accretion regimes. The results for all three stars are consistent with a typical dusty white dwarf in a steady state at 108-109 g s(-1). In particular, the non-magnetic limits for WD 1145+017 are found to be well below previous estimates of up to 10(12) g s(-1), and likely below 1010 g s(-1), thus suggesting the star-disc system may be average in its evolutionary state, and only special in viewing geometry.

  • 40.
    Feller, C.
    et al.
    Sorbonne Univ, UPMC Univ Paris 06, Univ Paris Diderot,CNRS, PSL Res Univ,LESIA,Observ Paris,Sorbanne Paris Ci, 5 Pl J Janssen, F-92195 Meudon, France..
    Fornasier, S.
    Sorbonne Univ, UPMC Univ Paris 06, Univ Paris Diderot,CNRS, PSL Res Univ,LESIA,Observ Paris,Sorbanne Paris Ci, 5 Pl J Janssen, F-92195 Meudon, France..
    Hasselmann, P. H.
    Sorbonne Univ, UPMC Univ Paris 06, Univ Paris Diderot,CNRS, PSL Res Univ,LESIA,Observ Paris,Sorbanne Paris Ci, 5 Pl J Janssen, F-92195 Meudon, France..
    Barucci, A.
    Sorbonne Univ, UPMC Univ Paris 06, Univ Paris Diderot,CNRS, PSL Res Univ,LESIA,Observ Paris,Sorbanne Paris Ci, 5 Pl J Janssen, F-92195 Meudon, France..
    Preusker, F.
    Deutsches Zentrum Luft & Raumfahrt DLR, Inst Planeten Forsch, Rutherfordstr 2, D-12489 Berlin, Germany..
    Scholten, F.
    Deutsches Zentrum Luft & Raumfahrt DLR, Inst Planeten Forsch, Rutherfordstr 2, D-12489 Berlin, Germany..
    Jorda, L.
    Aix Marseille Univ, CNRS, LAM, UMR 7326, 38 Rue Freder Joliot Curie, F-13388 Marseille, France..
    Pommerol, A.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland..
    Jost, B.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland..
    Poch, O.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland..
    ElMaary, M. R.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland..
    Thomas, N.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland..
    Belskaya, I.
    Kharkov Natl Univ, Inst Astron, Sumska Str 35, UA-61022 Kharkov, Ukraine..
    Pajola, M.
    NASA, Ames Res Ctr, Moett Field, CA 94035 USA.;Univ Padua, Ctr Studies & Activ Space CISAS G Colombo, Via Venezia 15, I-35131 Padua, Italy..
    Sierks, H.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Barbieri, C.
    Univ Padua, Dept Phys & Astron Galileo Galilei, Vicolo Osservatorio 3, I-35122 Padua, Italy..
    Lamy, P. L.
    Aix Marseille Univ, CNRS, LAM, UMR 7326, 38 Rue Freder Joliot Curie, F-13388 Marseille, France..
    Koschny, D.
    ESA, European Space Res & Technol Ctr, Res & Sci Support Off, Keplerlaan 1,Postbus 299, NL-2201 AZ Noordwijk, Netherlands..
    Rickman, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics. PAS Space Res Ctr, Poland..
    Rodrigo, R.
    CSIC, European Space Agcy, ESAC, Ctr Astrobiol,INTA, POB 78, Madrid, Spain.;Int Space Sci Inst, Hallerstr 6, CH-3012 Bern, Switzerland..
    Agarwal, J.
    A'Hearn, M.
    Univ Maryland, Dept Astron, College Pk, MD 20742 USA..
    Bertaux, J. -L
    Bertini, I.
    Univ Padua, Ctr Studies & Activ Space CISAS G Colombo, Via Venezia 15, I-35131 Padua, Italy..
    Boudreault, S.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Cremonese, G.
    INAF, Osservatorio Astron Padova, Vicolo Osservatorio 5, I-35122 Padua, Italy..
    Da Deppo, V.
    CNR, IFN, UOS Padova LUXOR, Via Trasea 7, I-35131 Padua, Italy..
    Davidsson, B. J. R.
    Jet Prop Lab, M-S 183-301,4800 Oak Grove Dr, Pasadena, CA 91109 USA..
    Debei, S.
    Univ Padua, Dept Ind Engn, Via Venezia 1, I-35131 Padua, Italy..
    De Cecco, M.
    Univ Trento, Via Mesiano 77, I-38100 Trento, Italy..
    Deller, J.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Fulle, M.
    INAF, Osservatorio Astron, Via Tiepolo 11, I-34014 Trieste, Italy..
    Giquel, A.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Groussin, O.
    Aix Marseille Univ, CNRS, LAM, UMR 7326, 38 Rue Freder Joliot Curie, F-13388 Marseille, France..
    Gutierrez, P. J.
    CSIC, Inst Astrofis Andalucia, C Glorieta Astron S-N, E-18008 Granada, Spain..
    Guettler, C.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Hofmann, M.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Hviid, S. F.
    Deutsches Zentrum Luft & Raumfahrt DLR, Inst Planeten Forsch, Rutherfordstr 2, D-12489 Berlin, Germany..
    Keller, H.
    Tech Univ Carolo Wilhelmina Braunschweig, IGEP, Mendelssohnstr 3, D-38106 Braunschweig, Germany..
    Ip, W. -H
    Knollenberg, J.
    Deutsches Zentrum Luft & Raumfahrt DLR, Inst Planeten Forsch, Rutherfordstr 2, D-12489 Berlin, Germany..
    Kovacs, G.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Kramm, J. -R
    Kuehrt, E.
    Deutsches Zentrum Luft & Raumfahrt DLR, Inst Planeten Forsch, Rutherfordstr 2, D-12489 Berlin, Germany..
    Kuppers, M.
    ESAC, ESA, POB 78, E-28691 Madrid, Spain..
    Lara, M. L.
    Lazzarin, M.
    Leyrat, C.
    Sorbonne Univ, UPMC Univ Paris 06, Univ Paris Diderot,CNRS, PSL Res Univ,LESIA,Observ Paris,Sorbanne Paris Ci, 5 Pl J Janssen, F-92195 Meudon, France..
    Moreno, J. J. Lopez
    Tech Univ Carolo Wilhelmina Braunschweig, IGEP, Mendelssohnstr 3, D-38106 Braunschweig, Germany..
    Marzari, F.
    Masoumzadeh, N.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Mottola, S.
    Deutsches Zentrum Luft & Raumfahrt DLR, Inst Planeten Forsch, Rutherfordstr 2, D-12489 Berlin, Germany..
    Naletto, G.
    Univ Padua, Ctr Studies & Activ Space CISAS G Colombo, Via Venezia 15, I-35131 Padua, Italy.;CNR, IFN, UOS Padova LUXOR, Via Trasea 7, I-35131 Padua, Italy.;Univ Padua, Dept Informat Engn, Via Gradenigo 6-B, I-35131 Padua, Italy..
    Perna, D.
    Sorbonne Univ, UPMC Univ Paris 06, Univ Paris Diderot,CNRS, PSL Res Univ,LESIA,Observ Paris,Sorbanne Paris Ci, 5 Pl J Janssen, F-92195 Meudon, France..
    Oklay, N.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Shi, X.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Tubiana, C.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Vincent, J. -B
    Decimetre-scaled spectrophotometric properties of the nucleus of comet 67P/Churyumov-Gerasimenko from OSIRIS observations2016In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 462, p. S287-S303Article in journal (Refereed)
    Abstract [en]

    We present the results of the photometric and spectrophotometric properties of the 67P/Churyumov-Gerasimenko nucleus derived with the Optical, Spectroscopic and Infrared Remote Imaging System instrument during the closest fly-by over the comet, which took place on 2015 February 14 at a distance of similar to 6 km from the surface. Several images covering the 0 degrees-33 degrees. phase angle range were acquired, and the spatial resolution achieved was 11 cm pixel(-1). The flown-by region is located on the big lobe of the comet, near the borders of the Ash, Apis and Imhotep regions. Our analysis shows that this region features local heterogeneities at the decimetre scale. We observed difference of reflectance up to 40 per cent between bright spots and sombre regions, and spectral slope variations up to 50 per cent. The spectral reddening effect observed globally on the comet surface by Fornasier et al. (2015) is also observed locally on this region, but with a less steep behaviour. We note that numerous metre-sized boulders, which exhibit a smaller opposition effect, also appear spectrally redder than their surroundings. In this region, we found no evidence linking observed bright spots to exposed water-ice-rich material. We fitted our data set using the Hapke 2008 photometric model. The region overflown is globally as dark as the whole nucleus (geometric albedo of 6.8 per cent) and it has a high porosity value in the uppermost layers (86 per cent). These results of the photometric analysis at a decimetre scale indicate that the photometric properties of the flown-by region are similar to those previously found for the whole nucleus.

  • 41.
    Finlator, Kristian
    et al.
    New Mexico State University, Las Cruces, NM 88003-8001, USACosmic Dawn Center (DAWN), Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen Ø; DTU-Space, Technical University of Denmark, DK-2800 Kgs. Lyngby .
    Keating, Laura
    Canadian Institute for Theoretical Astrophysics, 60 St. George Street, University of Toronto, ON M5S 3H8, Canada .
    Oppenheimer, Benjamin D.
    CASA, Department of Astrophysical and Planetary Sciences, University of Colorado, 389-UCB, Boulder, CO 80309, USA .
    Davé, Romeel
    University of the Western Cape, Bellville, Cape Town 7535, South AfricaSouth African Astronomical Observatory, Observatory, Cape Town 7925, South AfricaAfrican Institute for Mathematical Sciences, Muizenberg, Cape Town 7945, South AfricaCenter for Computational Astrophysics, Simons Foundation, New York, NY 10010, USAInstitute for Astronomy, Royal Observatory, Edinburgh EH9 3HJ, UK .
    Zackrisson, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Reionization in Technicolor2018In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 480, no 2, p. 2628-2649Article in journal (Refereed)
    Abstract [en]

    We present the Technicolor Dawn simulations, a suite of cosmological radiation hydrodynamic simulations of the first 1.2 billion yr. By modelling a spatially inhomogeneous ultraviolet background (UVB) on the fly with 24 frequencies and resolving dark matter haloes down to 10(8) M-circle dot within 12 h(-1) Mpc volumes, our simulations unify observations of the intergalactic and circumgalactic media, galaxies, and reionization into a common framework. The only empirically tuned parameter, the fraction f(esc,gal)(z) of ionizing photons that escape the interstellar medium, is adjusted to match observations of the Lyman-alpha forest and the cosmic microwave background. With this single calibration, our simulations reproduce the history of reionization; the stellar mass and star formation rate relation of galaxies; the number density and metallicity of damped Lyman-alpha absorbers (DLAs) at z similar to 5; the abundance of weak metal absorbers; the ultraviolet background amplitude; and the Lyman-a flux power spectrum at z = 5.4. The galaxy stellar mass and ultraviolet luminosity functions are underproduced by <= 2 x, suggesting an overly vigorous feedback model. The mean transmission in the Lyman-alpha forest is underproduced at z < 6, indicating tension between measurements of the UVB amplitude and Lyman-alpha transmission. The observed Si IV column density distribution is reasonably well reproduced (similar to 1 sigma low). By contrast, C IV remains significantly underproduced despite being boosted by an intense >4 Ryd UVB. Solving this problem by increasing metal yields would overproduce both weak absorbers and DLA metallicities. Instead, the observed strength of high-ionization emission from high-redshift galaxies and absorption from their environments suggest that the ionizing flux from conventional stellar population models is too soft.

  • 42.
    Finlator, Kristian
    et al.
    New Mexico State Univ, MSC 4500, Las Cruces, NM 88003 USA.;Univ Copenhagen, Niels Bohr Inst, Dark Cosmol Ctr, Juliane Maries Vej 30, DK-2100 Copenhagen O, Denmark..
    Oppenheimer, B. D.
    Univ Colorado, Dept Astrophys & Planetary Sci, CASA, 389 UCB, Boulder, CO 80309 USA..
    Dave, Romeel
    Univ Western Cape, ZA-7535 Cape Town, South Africa.;South African Astron Observ, ZA-7525 Cape Town, South Africa.;African Inst Math Sci, ZA-7545 Cape Town, South Africa..
    Zackrisson, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Thompson, Robert
    Univ Illinois, NCSA, Urbana, IL 61820 USA..
    Huang, Shuiyao
    Univ Massachussetts, Dept Astron, Amherst, MA 01003 USA..
    The soft, fluctuating UVB at z similar to 6 as traced by C IV, Si IV, and C II2016In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 459, no 3, p. 2299-2310Article in journal (Refereed)
    Abstract [en]

    The sources that drove cosmological reionization left clues regarding their identity in the slope and inhomogeneity of the ultraviolet ionizing background (UVB): bright quasars (QSOs) generate a hardUVBwith predominantly large-scale fluctuations while Population II stars generate a softer one with smaller scale fluctuations. Metal absorbers probe the UVB's slope because different ions are sensitive to different energies. Likewise, they probe spatial fluctuations because they originate in regions where a galaxy-driven UVB is harder and more intense. We take a first step towards studying the reionization-epoch UVB's slope and inhomogeneity by comparing observations of 12 metal absorbers at z similar to 6 versus predictions from a cosmological hydrodynamic simulation using three different UVBs: a soft, spatially inhomogeneous ' galaxies+QSOs' UVB; a homogeneous 'galaxies+QSOs' UVB, and a 'QSOs-only' model. All UVBs reproduce the observed column density distributions of CII, Si IV, and CIV reasonably well although high-column, high-ionization absorbers are underproduced, reflecting numerical limitations. With upper limits treated as detections, only a soft, fluctuating UVB reproduces both the observed Si IV/CIV and CII/CIV distributions. The QSOs-only UVB overpredicts both CIV/CII and CIV/Si IV, indicating that it is too hard. The Haardt & Madau (2012) UVB underpredicts CIV/Si IV, suggesting that it lacks amplifications near galaxies. Hence current observations prefer a soft, fluctuating UVB as expected from a predominantly Population II background although they cannot rule out a harder one. Future observations probing a factor of 2 deeper in metal column density will distinguish between the soft, fluctuating and QSOs-only UVBs.

  • 43.
    Finlator, Kristian
    et al.
    New Mexico State Univ, Dept Astron, Las Cruces, NM 88003 USA.;Univ Copenhagen, Niels Bohr Inst, Dark Cosmol Ctr, DK-2100 Copenhagen, Denmark..
    Prescott, Moire K. M.
    New Mexico State Univ, Dept Astron, Las Cruces, NM 88003 USA.;Univ Copenhagen, Niels Bohr Inst, Dark Cosmol Ctr, DK-2100 Copenhagen, Denmark..
    Oppenheimer, B. D.
    Univ Colorado, Dept Astrophys & Planetary Sci, CASA, 389 UCB, Boulder, CO 80309 USA..
    Dave, Romeel
    Univ Western Cape, Dept Phys, ZA-7535 Cape Town, South Africa.;South African Astron Observ, ZA-7525 Cape Town, South Africa.;African Inst Math Sci, ZA-7545 Cape Town, South Africa..
    Zackrisson, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Livermore, R. C.
    Univ Texas Austin, 2515 Speedway,Stop C1400, Austin, TX 78712 USA..
    Finkelstein, S. L.
    Univ Texas Austin, 2515 Speedway,Stop C1400, Austin, TX 78712 USA..
    Thompson, Robert
    Univ Illinois, NCSA, Urbana, IL 61820 USA..
    Huang, Shuiyao
    Univ Massachusetts, Dept Astron, Amherst, MA 01003 USA..
    The minimum halo mass for star formation at z=6-82017In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 464, no 2, p. 1633-1639Article in journal (Refereed)
    Abstract [en]

    Recent analysis of strongly lensed sources in the Hubble Frontier Fields indicates that the rest-frame UV luminosity function of galaxies at z=6-8 rises as a power law down to M-UV=-15, and possibly as faint as-12.5. We use predictions from a cosmological radiation hydrodynamic simulation to map these luminosities on to physical space, constraining the minimum dark matter halo mass and stellar mass that the Frontier Fields probe. While previously published theoretical studies have suggested or assumed that early star formation was suppressed in haloes less massive than 10(9)-10(11) M-circle dot, we find that recent observations demand vigorous star formation in haloes at least as massive as (3.1, 5.6, 10.5) x10(9) M-circle dot at z =(6, 7, 8). Likewise, we find that Frontier Fields observations probe down to stellar masses of (8.1, 18, 32) x10(6) M-circle dot: that is, they are observing the likely progenitors of analogues to Local Group dwarfs such as Pegasus and M32. Our simulations yield somewhat different constraints than two complementary models that have been invoked in similar analyses, emphasizing the need for further observational constraints on the galaxy-halo connection.

  • 44. Folsom, C. P.
    et al.
    Kochukhov, Oleg
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Wade, G. A.
    Silvester, J.
    Bagnulo, S.
    Magnetic field, chemical composition and line profile variability of the peculiar eclipsing binary star AR Aur2010In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 407, no 4, p. 2383-2392Article in journal (Refereed)
    Abstract [en]

    AR Aur is the only eclipsing binary known to contain a HgMn star, making it an ideal case for a detailed study of the HgMn phenomenon. HgMn stars are a poorly understood class of chemically peculiar stars, which have traditionally been thought not to possess significant magnetic fields. However, the recent discovery of line profile variability in some HgMn stars, apparently attributable to surface abundance patches, has brought this belief into question. In this paper we investigate the chemical abundances, line profile variability, and magnetic field of the primary and secondary of the AR Aur system, using a series of high-resolution spectropolarimetric observations. We find the primary is indeed a HgMn star, and present the most precise abundances yet determined for this star. We find the secondary is a weak Am star, and is possibly still on the pre-main sequence. Line profile variability was observed in a range of lines in the primary, and is attributed to inhomogeneous surface distributions of some elements. No magnetic field was detected in any observation of either stars, with an upper limit on the longitudinal magnetic field in both stars of 100 G. Modelling of the phase-resolve longitudinal field measurements leads to a 3 Sigma upper limit on any dipole surface magnetic field of about 400 G.

  • 45. Folsom, C. P.
    et al.
    Likuski, K.
    Wade, G. A.
    Kochukhov, Oleg
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Alecian, E.
    Shulyak, D.
    Orbital parameters, chemical composition and magnetic field of the Ap binary HD 980882013In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 431, no 2, p. 1513-1527Article in journal (Refereed)
    Abstract [en]

    HD 98088 is a synchronized, double-lined spectroscopic binary system with a magnetic Ap primary component and an Am secondary component. We study this rare system using high-resolution Multi-Site Continuous Spectroscopy spectropolarimetric data, to gain insight into the effect of binarity on the origin of stellar magnetism and the formation of chemical peculiarities in A-type stars. Using a new collection of 29 high-resolution Stokes VQU spectra we re-derive the orbital and stellar physical parameters and conduct the first disentangling of spectroscopic observations of the system to conduct spectral analysis of the individual stellar components. From this analysis we determine the projected rotational velocities of the stars and conduct a detailed chemical abundance analysis of each component using both the SYNTH3 and ZEEMAN spectrum synthesis codes. The surface abundances of the primary component are typical of a cool Ap star, while those of the secondary component are typical of an Am star. We present the first magnetic analysis of both components using modern data. Using least-squares deconvolution, we extract the longitudinal magnetic field strength of the primary component, which is observed to vary between +1170 and -920 G with a period consistent with the orbital period. There is no field detected in the secondary component. The magnetic field in the primary is predominantly dipolar, with the positive pole oriented approximately towards the secondary.

  • 46. Folsom, C. P.
    et al.
    Wade, G. A.
    Kochukhov, O.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics.
    Alecian, E.
    Catala, C.
    Bagnulo, S.
    Boehm, T.
    Bouret, J.-C.
    Donati, J.-F.
    Grunhut, J.
    Hanes, D. A.
    Landstreet, J. D.
    Magnetic fields and chemical peculiarities of the very young intermediate-mass binary system HD 721062008In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 391, no 2, p. 901-914Article in journal (Refereed)
    Abstract [en]

    The recently discovered magnetic Herbig Ae and Be stars may provide qualitatively new information about the formation and evolution of magnetic Ap and Bp stars. We have performed a detailed investigation of one particularly interesting binary system with a Herbig Ae secondary and a late B-type primary possessing a strong, globally ordered magnetic field. 20 high-resolution Stokes V spectra of the system were obtained with the ESPaDOnS instrument mounted on the Canada-France-Hawaii Telescope. In these observations we see clear evidence for a magnetic field in the primary, but no evidence for a magnetic field in the secondary. A detailed abundance analysis was performed for both stars, revealing strong chemical peculiarities in the primary and normal chemical abundances in the secondary. The primary is strongly overabundant in Si, Cr and other iron-peak elements, as well as Nd, and underabundant in He. The primary therefore appears to be a very young Bp star. In this context, line profile variations of the primary suggest non-uniform lateral distributions of surface abundances. Interpreting the 0.639 95 +/- 0.000 09 d variation period of the Stokes I and V profiles as the rotational period of the star, we have modelled the magnetic field geometry and the surface abundance distributions of Si, Ti, Cr and Fe using magnetic Doppler imaging. We derive a dipolar geometry of the surface magnetic field, with a polar strength B-d = 1230 G and an obliquity beta = 57 degrees. The distributions Ti, Cr and Fe are all qualitatively similar, with an elongated patch of enhanced abundance situated near the positive magnetic pole. The Si distribution is somewhat different, and its relationship to the magnetic field geometry less clear.

  • 47.
    Fornasier, S.
    et al.
    Sorbonne Univ, UPMC Univ Paris 06, Univ Paris Diderot, PSL Res Univ,Sorbonne Paris Cite,Observ Paris,LES, 5 Pl J Janssen, F-92195 Meudon, France.
    Feller, C.
    Sorbonne Univ, UPMC Univ Paris 06, Univ Paris Diderot, PSL Res Univ,Sorbonne Paris Cite,Observ Paris,LES, 5 Pl J Janssen, F-92195 Meudon, France.
    Lee, J. -C
    Ferrari, S.
    Univ Padua, Dipartimento Geosci, Via G Gradenigo 6, I-35131 Padua, Italy.
    Massironi, M.
    Univ Padua, Dipartimento Geosci, Via G Gradenigo 6, I-35131 Padua, Italy;Univ Padua, Ctr Studies & Act Space CISAS G Colombo, Via Venezia 15, I-35131 Padua, Italy.
    Hasselmann, P. H.
    Sorbonne Univ, UPMC Univ Paris 06, Univ Paris Diderot, PSL Res Univ,Sorbonne Paris Cite,Observ Paris,LES, 5 Pl J Janssen, F-92195 Meudon, France.
    Deshapriya, J. D. P.
    Sorbonne Univ, UPMC Univ Paris 06, Univ Paris Diderot, PSL Res Univ,Sorbonne Paris Cite,Observ Paris,LES, 5 Pl J Janssen, F-92195 Meudon, France.
    Barucci, M. A.
    Sorbonne Univ, UPMC Univ Paris 06, Univ Paris Diderot, PSL Res Univ,Sorbonne Paris Cite,Observ Paris,LES, 5 Pl J Janssen, F-92195 Meudon, France.
    El-Maarry, M. R.
    Univ Colorado, Lab Atmospher & Space Phys, 3665 Discovery Dr, Boulder, CO 80301 USA.
    Giacomini, L.
    Univ Padua, Ctr Studies & Act Space CISAS G Colombo, Via Venezia 15, I-35131 Padua, Italy.
    Mottola, S.
    Deutsches Zentrum Luft & Raumfahrt DLR, Inst Planetenforsch Asteroiden & Kometen, Rutherfordstr 2, D-12489 Berlin, Germany.
    Keller, H. U.
    Deutsches Zentrum Luft & Raumfahrt DLR, Inst Planetenforsch Asteroiden & Kometen, Rutherfordstr 2, D-12489 Berlin, Germany;Tech Univ Carolo Wilhelmina Braunschweig, IGEP, Mendelssohnstr 3, D-38106 Braunschweig, Germany.
    Ip, W. -H
    Lin, Z. -Y
    Sierks, H.
    Max Planck Inst Sonnensyst Forschung, D-37077 Gottingen, Germany.
    Barbieri, C.
    Univ Padua, Dept Phys & Astron, Vicolo Osservatorio 3, I-35122 Padua, Italy.
    Lamy, P. L.
    Univ Aix Marseille, CNRS, Lab Astrophys Marseille, UMR 7326, 38 Rue Frederic Joliot Curie, F-13388 Marseille 13, France.
    Rodrigo, R.
    CSIC, INTA, Ctr Astrobiol, E-28850 Madrid, Spain;Int Space Sci Inst, Hallerstr 6, CH-3012 Bern, Switzerland.
    Koschny, D.
    ESA, European Space Res & Technol Ctr, Sci Support Off, Keplerlaan 1,Postbus 299, NL-2201 AZ Noordwijk, Netherlands.
    Rickman, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics. PAS Space Res Ctr, Bartycka 18A, PL-00716 Warsaw, Poland.
    Agarwal, J.
    Max Planck Inst Sonnensyst Forschung, D-37077 Gottingen, Germany.
    A'Hearn, M.
    Univ Maryland, Dept Astron, College Pk, MD 20742 USA.
    Bertaux, J. -L
    Bertini, I.
    Univ Padua, Dept Phys & Astron, Vicolo Osservatorio 3, I-35122 Padua, Italy.
    Cremonese, G.
    INAF, Osservatorio Astronom Padova, Padua, Italy.
    Da Deppo, V.
    IFN UOS Padova LUXOR, CNR, Via Trasea 7, I-35131 Padua, Italy.
    Davidsson, B.
    CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA.
    Debei, S.
    Univ Padua, Dept Mech Engn, Via Venezia 1, I-35131 Padua, Italy.
    De Cecco, M.
    Univ Trento, Via Mesiano 77, I-38100 Trento, Italy.
    Deller, J.
    Max Planck Inst Sonnensyst Forschung, D-37077 Gottingen, Germany.
    Fulle, M.
    INAF, Osservatorio Astronomico, Via Tiepolo 11, I-34014 Trieste, Italy.
    Groussin, O.
    Aix Marseille Univ, CNRS, LAM, UMR7326, 38 Rue Frederic Joliot Curie, F-13388 Marseille 13, France.
    Gutierrez, P. J.
    CSIC, Inst Astrofis Andalucia, C Glorieta Astron S-N, E-18008 Granada, Spain.
    Guettler, C.
    Max Planck Inst Sonnensyst Forschung, D-37077 Gottingen, Germany.
    Hofmann, M.
    Max Planck Inst Sonnensyst Forschung, D-37077 Gottingen, Germany.
    Hviid, S. F.
    Deutsches Zentrum Luft & Raumfahrt DLR, Inst Planetenforsch Asteroiden & Kometen, Rutherfordstr 2, D-12489 Berlin, Germany.
    Jorda, L.
    Aix Marseille Univ, CNRS, LAM, UMR7326, 38 Rue Frederic Joliot Curie, F-13388 Marseille 13, France.
    Knollenberg, J.
    Deutsches Zentrum Luft & Raumfahrt DLR, Inst Planetenforsch Asteroiden & Kometen, Rutherfordstr 2, D-12489 Berlin, Germany.
    Kovacs, G.
    Max Planck Inst Sonnensyst Forschung, D-37077 Gottingen, Germany.
    Kramm, R.
    Max Planck Inst Sonnensyst Forschung, D-37077 Gottingen, Germany.
    Kuehrt, E.
    Deutsches Zentrum Luft & Raumfahrt DLR, Inst Planetenforsch Asteroiden & Kometen, Rutherfordstr 2, D-12489 Berlin, Germany.
    Kuppers, M.
    ESA, European Space Astron Ctr, Operat Dept, POB 78, E-28691 Madrid, Spain.
    Lara, M. L.
    CSIC, Inst Astrofis Andalucia, C Glorieta Astron S-N, E-18008 Granada, Spain.
    Lazzarin, M.
    Univ Padua, Dept Phys & Astron, Vicolo Osservatorio 3, I-35122 Padua, Italy.
    Lopez Moreno, J. J.
    CSIC, Inst Astrofis Andalucia, C Glorieta Astron S-N, E-18008 Granada, Spain.
    Marzari, F.
    Univ Padua, Dept Phys & Astron, Vicolo Osservatorio 3, I-35122 Padua, Italy.
    Naletto, G.
    Univ Padua, Ctr Studies & Act Space CISAS G Colombo, Via Venezia 15, I-35131 Padua, Italy;IFN UOS Padova LUXOR, CNR, Via Trasea 7, I-35131 Padua, Italy;Univ Padua, Dept Informat Engn, Via Gradenigo 6-B, I-35131 Padua, Italy.
    Oklay, N.
    Deutsches Zentrum Luft & Raumfahrt DLR, Inst Planetenforsch Asteroiden & Kometen, Rutherfordstr 2, D-12489 Berlin, Germany.
    Pajola, M.
    NASA, Ames Res Ctr, Moffett Field, CA 94035 USA.
    Shi, X.
    Max Planck Inst Sonnensyst Forschung, D-37077 Gottingen, Germany.
    Thomas, N.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland.
    Toth, I.
    MTA CSFK Konkoly Observ, Budapest, Hungary.
    Tubiana, C.
    Max Planck Inst Sonnensyst Forschung, D-37077 Gottingen, Germany.
    Vincent, J. -B
    The highly active Anhur-Bes regions in the 67P/Churyumov-Gerasimenko comet: results from OSIRIS/ROSETTA observations2017In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 469, p. S93-S107Article in journal (Refereed)
    Abstract [en]

    The Southern hemisphere of the 67P/Churyumov-Gerasimenko comet has become visible from Rosetta only since 2015 March. It was illuminated during the perihelion passage and therefore it contains the regions that experienced the strongest heating and erosion rates, thus exposing the sub-surface most pristine material. In this work we investigate, thanks to the OSIRIS images, the geomorphology, the spectrophotometry and some transient events of two Southern hemisphere regions: Anhur and part of Bes. Bes is dominated by outcropping consolidated terrain covered with fine particle deposits, while Anhur appears strongly eroded with elongated canyon-like structures, scarp retreats, different kinds of deposits and degraded sequences of strata indicating a pervasive layering. We discovered a new 140 m long and 10 m high scarp formed in the Anhur-Bes boundary during/after the perihelion passage, close to the area where exposed CO2 and H2O ices were previously detected. Several jets have been observed originating from these regions, including the strong perihelion outburst, an active pit and a faint optically thick dust plume. We identify several areas with a relatively bluer slope (i.e. a lower spectral slope value) than their surroundings, indicating a surface composition enriched with some water ice. These spectrally bluer areas are observed especially in talus and gravitational accumulation deposits where freshly exposed material had fallen from nearby scarps and cliffs. The investigated regions become spectrally redder beyond 2 au outbound when the dust mantle became thicker, masking the underlying ice-rich layers.

  • 48. Fossati, L.
    et al.
    Folsom, C. P.
    Bagnulo, S.
    Grunhut, J. H.
    Kochukhov, Oleg
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Landstreet, J. D.
    Paladini, C.
    Wade, G. A.
    A detailed spectroscopic analysis of the open cluster NGC 54602011In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 413, no 2, p. 1132-1144Article in journal (Refereed)
    Abstract [en]

    Within the context of a large project aimed at studying early F-, A- and late B-type stars, we present the abundance analysis of the photospheres of 21 members of the open cluster NGC 5460, an intermediate-age cluster (log t similar to 8.2) previously not studied with spectroscopy. Our study is based on medium- and high-resolution spectra obtained with the Fibre Large Array Multi Element Spectrograph (FLAMES) instrument of the European Southern Observatory/Very Large Telescope. We show that cluster members have a nearly solar metallicity and that there is evidence that the abundances of magnesium and iron are correlated with the effective temperature, exhibiting a maximum around T-eff = 10 500 K. No correlations are found between abundances and projected equatorial velocity, except for marginal evidence of barium being more abundant in slower than in faster rotating stars. We discovered two He-weak stars and a binary system where the hotter component is an HgMn star. We provide new estimates for the cluster distance (720 +/- 50 pc), age (log t = 8.2 +/- 0.1) and mean radial velocity (-17.9 +/- 5.2 km s-1).

  • 49. Fossati, L.
    et al.
    Kolenberg, K.
    Shulyak, D. V.
    Elmasli, A.
    Tsymbal, V.
    Barnes, T. G.
    Guggenberger, E.
    Kochukhov, Oleg
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    An in-depth spectroscopic analysis of RR Lyr Variations over the pulsation cycle2014In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 445, no 4, p. 4094-4104Article in journal (Refereed)
    Abstract [en]

    The stellar parameters of RR Lyrae stars vary considerably over a pulsation cycle, and their determination is crucial for stellar modelling. We present a detailed spectroscopic analysis of the pulsating star RR Lyr, the prototype of its class, over a complete pulsation cycle, based on high-resolution spectra collected at the 2.7-m telescope of McDonald Observatory. We used simultaneous photometry to determine the accurate pulsation phase of each spectrum and determined the effective temperature, the shape of the depth-dependent microturbulent velocity, and the abundance of several elements, for each phase. The surface gravity was fixed to 2.4. Element abundances resulting from our analysis are stable over the pulsation cycle. However, a variation in ionization equilibrium is observed around minimum radius. We attribute this mostly to a dynamical acceleration contributing to the surface gravity. Variable turbulent convection on time-scales longer than the pulsation cycle has been proposed as a cause for the Blazhko effect. We test this hypothesis to some extent by using the derived variable depth-dependent microturbulent velocity profiles to estimate their effect on the stellar magnitude. These effects turn out to be wavelength dependent and much smaller than the observed light variations over the Blazhko cycle: if variations in the turbulent motions are entirely responsible for the Blazhko effect, they must surpass the scales covered by the microturbulent velocity. This work demonstrates the possibility of a self-consistent spectroscopic analysis over an entire pulsation cycle using static atmosphere models, provided one takes into account certain features of a rapidly pulsating atmosphere.

  • 50.
    Frattin, E.
    et al.
    Astron Observ Padova, INAF, Vicolo Osservatorio 5, I-35122 Padua, Italy;Univ Padua, Dipartimento Fis & Astron G Galilei, Vicolo Osservatorio 3, I-35122 Padua, Italy.
    Cremonese, G.
    Astron Observ Padova, INAF, Vicolo Osservatorio 5, I-35122 Padua, Italy.
    Simioni, E.
    Astron Observ Padova, INAF, Vicolo Osservatorio 5, I-35122 Padua, Italy;CNR, IFN, UOS Padova, LUXOR, Via Trasea 7, I-35131 Padua, Italy.
    Bertini, I.
    Univ Padua, Dipartimento Fis & Astron G Galilei, Vicolo Osservatorio 3, I-35122 Padua, Italy.
    Lazzarin, M.
    Univ Padua, Dipartimento Fis & Astron G Galilei, Vicolo Osservatorio 3, I-35122 Padua, Italy.
    Ott, T.
    Carl von Ossietzky Univ Oldenburg, Ammerlander Heerstr 11, D-26111 Oldenburg, Germany.
    Drolshagen, E.
    Carl von Ossietzky Univ Oldenburg, Ammerlander Heerstr 11, D-26111 Oldenburg, Germany.
    La Forgia, F.
    Univ Padua, Dipartimento Fis & Astron G Galilei, Vicolo Osservatorio 3, I-35122 Padua, Italy.
    Sierks, H.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany.
    Barbieri, C.
    Univ Padua, Dipartimento Fis & Astron G Galilei, Vicolo Osservatorio 3, I-35122 Padua, Italy.
    Lamy, P.
    CNRS, UMR 7326, Lab Astrophys Marseille, 38 Rue Frederic Joliot Curie, F-13388 Marseille 13, France.
    Rodrigo, R.
    INTA, CSIC, Ctr Astrobiol, E-28850 Madrid, Spain;Int Space Sci Inst, Hallerstr 6, CH-3012 Bern, Switzerland.
    Koschny, D.
    ESA, European Space Res & Technol Ctr, Sci Support Off, Keplerlaan 1,Postbus 299, NL-2201 AZ Noordwijk, Netherlands.
    Rickman, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics. PAS Space Res Ctr, Bartycka 18A, PL-00716 Warsaw, Poland.
    Keller, H. U.
    TU Braunschweig, Inst Geophys & Extraterr Phys, D-38106 Braunschweig, Germany.
    Agarwal, J.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany.
    A'Hearn, M. F.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany;Univ Maryland, Dept Astron, College Pk, MD 20742 USA.
    Barucci, M. A.
    UPMC Univ Paris 06, Univ Paris Diderot, Sorbonne Paris Cite, LESIA,Observ Paris,PSL Res Univ,Sorbonne Univ, 5 Pl J Janssen, F-92195 Meudon, France.
    Bertaux, J. -L
    Da Deppo, V.
    CNR, IFN, UOS Padova, LUXOR, Via Trasea 7, I-35131 Padua, Italy.
    Davidsson, Björn
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
    Debei, S.
    Univ Padua, Dept Ind Engn, Via Venezia 1, I-35131 Padua, Italy.
    De Cecco, M.
    Univ Trento, Via Sommar 9, I-38123 Trento, Italy.
    Deller, J.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany.
    Ferrari, S.
    Univ Padua, Ctr Studies & Act Space CISAS G Colombo, Via Venezia 15, I-35131 Padua, Italy.
    Ferri, F.
    Univ Padua, Ctr Studies & Act Space CISAS G Colombo, Via Venezia 15, I-35131 Padua, Italy.
    Fornasier, S.
    UPMC Univ Paris 06, Univ Paris Diderot, Sorbonne Paris Cite, LESIA,Observ Paris,PSL Res Univ,Sorbonne Univ, 5 Pl J Janssen, F-92195 Meudon, France.
    Fulle, M.
    Osserv Astron Trieste, INAF, Via Tiepolo 11, I-34014 Trieste, Italy.
    Gicquel, A.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany.
    Groussin, O.
    Aix Marseille Univ, CNRS, LAM, UMR 7326, F-13388 Marseille, France.
    Gutierrez, P. J.
    CSIC, Inst Astrofis Andalucia, E-18008 Granada, Spain.
    Guettler, C.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany.
    Hofmann, M.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany.
    Hviid, S. F.
    Deutsch Zentrum Luft & Raumfahrt DLR, Inst Planetenforsch, Rutherfordstr 2, D-12489 Berlin, Germany.
    Ip, W. -H
    Jorda, L.
    Aix Marseille Univ, CNRS, LAM, UMR 7326, F-13388 Marseille, France.
    Knollenberg, J.
    Deutsch Zentrum Luft & Raumfahrt DLR, Inst Planetenforsch, Rutherfordstr 2, D-12489 Berlin, Germany.
    Kramm, J. -R
    Kuehrt, E.
    Deutsch Zentrum Luft & Raumfahrt DLR, Inst Planetenforsch, Rutherfordstr 2, D-12489 Berlin, Germany.
    Kuppers, M.
    ESA, European Space Astron Ctr, Operat Dept, POB 78, E-28691 Madrid, Spain.
    Lara, L. M.
    CSIC, Inst Astrofis Andalucia, E-18008 Granada, Spain.
    Lopez Moreno, J. J.
    CSIC, Inst Astrofis Andalucia, E-18008 Granada, Spain.
    Lucchetti, A.
    Astron Observ Padova, INAF, Vicolo Osservatorio 5, I-35122 Padua, Italy;Univ Padua, Ctr Studies & Act Space CISAS G Colombo, Via Venezia 15, I-35131 Padua, Italy.
    Marzari, F.
    Univ Padua, Dipartimento Fis & Astron G Galilei, Vicolo Osservatorio 3, I-35122 Padua, Italy.
    Massironi, M.
    Univ Padua, Dept Geosci, Via G Gradenigo 6, I-35131 Padua, Italy.
    Mottola, S.
    Deutsch Zentrum Luft & Raumfahrt DLR, Inst Planetenforsch, Rutherfordstr 2, D-12489 Berlin, Germany.
    Naletto, G.
    CNR, IFN, UOS Padova, LUXOR, Via Trasea 7, I-35131 Padua, Italy;Univ Padua, Ctr Studies & Act Space CISAS G Colombo, Via Venezia 15, I-35131 Padua, Italy;Univ Padua, Dept Informat Engn, Via Gradenigo 6-B, I-35131 Padua, Italy.
    Oklay, N.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany.
    Pajola, M.
    Univ Padua, Ctr Studies & Act Space CISAS G Colombo, Via Venezia 15, I-35131 Padua, Italy;NASA, Ames Res Ctr, Moffett Field, CA 94035 USA.
    Penasa, L.
    Univ Padua, Ctr Studies & Act Space CISAS G Colombo, Via Venezia 15, I-35131 Padua, Italy.
    Shi, X.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany.
    Thomas, N.
    Univ Bern, Inst Phys, Sidlerstr 5, CH-3012 Bern, Switzerland.
    Tubiana, C.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany.
    Vincent, J. -B
    Post-perihelion photometry of dust grains in the coma of 67P Churyumov-Gerasimenko2017In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 469, p. S195-S203Article in journal (Refereed)
    Abstract [en]

    We present a photometric analysis of individual dust grains in the coma of comet 67P/Churyumov-Gerasimenko using OSIRIS images taken from 2015 July to 2016 January. We analysed a sample of 555 taken during 18 d at heliocentric distances ranging between 1.25 and 2.04 au and at nucleocentric distances between 80 and 437 km. An automated method to detect the tracks was specifically developed. The images were taken by OSIRIS NAC in four different filters: Near-IR (882 nm), Orange (649 nm), FarOrange (649 nm) and Blue (480 nm). It was not always possible to recognize all the grains in the four filters, hence we measured the spectral slope in two wavelengths ranges: in the interval [480-649] nm, for 1179 grains, and in the interval [649-882] nm, for 746 grains. We studied the evolution of the two populations' average spectral slopes. The data result scattered around the average value in the range [480-649] nm, while in the [649-882] nm we observe a slight decreasing moving away from the Sun as well as a slight increasing with the nucleocentric distance. A spectrophotometric analysis was performed on a subsample of 339 grains. Three major groups were defined, based on the spectral slope between [535-882] nm: (i) the steep spectra that may be related with organic material, (ii) the spectra with an intermediate slope, likely a mixture of silicates and organics and (iii) flat spectra that may be associated with a high abundance of water ice.

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