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  • 1.
    Barklem, Paul
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics, Observational Astronomy.
    Kochukhov, Oleg
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics, Observational Astronomy.
    Piskunov, Nikolai
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics, Observational Astronomy.
    O'Mara, B. J.
    Stempels, H. C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics, Observational Astronomy.
    Hydrogen Line Formation in Cool Stars2001In: 11th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun / [ed] Garcia Lopez, Ramon J.; Rebolo, Rafael; Zapaterio Osorio, Mario Rosa, San Francisco: Astronomical Society of the Pacific , 2001, p. 766-Conference paper (Other academic)
  • 2.
    Barklem, Paul
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics, Observational Astronomy.
    Stempels, H.C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics, Observational Astronomy.
    Allende Prieto, C.
    Kochukhov, Oleg
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics, Observational Astronomy.
    Piskunov, Nikolai
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics, Observational Astronomy.
    O'Mara, B.J.
    Detailed analysis of Balmer lines in cool dwarf stars2002In: Astronomy & Astrophysics, ISSN 0004-6361, Vol. 385, p. 951-Article in journal (Refereed)
  • 3.
    Barklem, Paul
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics, Observational Astronomy.
    Stempels, H.C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics, Observational Astronomy.
    Kochukhov, Oleg
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics, Observational Astronomy.
    Piskunov, Nikolai
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics, Observational Astronomy.
    O'Mara, J.B.
    Balmer lines and effective temperatures in cool stars2003In: 12th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, 2003, p. 1103-Conference paper (Other academic)
  • 4. Bedding, Timothy R.
    et al.
    Kjeldsen, Hans
    Campante, Tiago L.
    Appourchaux, Thierry
    Bonanno, Alfio
    Chaplin, William J.
    Garcia, Rafael A.
    Martic, Milena
    Mosser, Benoit
    Butler, R. Paul
    Bruntt, Hans
    Kiss, Laszlo L.
    O'Toole, Simon J.
    Kambe, Eiji
    Ando, Hiroyasu
    Izumiura, Hideyuki
    Sato, Bun'ei
    Hartmann, Michael
    Hatzes, Artie
    Barban, Caroline
    Berthomieu, Gabrielle
    Michel, Eric
    Provost, Janine
    Turck-Chieze, Sylvaine
    Lebrun, Jean-Claude
    Schmitt, Jerome
    Bertaux, Jean-Loup
    Benatti, Serena
    Claudi, Riccardo U.
    Cosentino, Rosario
    Leccia, Silvio
    Frandsen, Soren
    Brogaard, Karsten
    Glowienka, Lars
    Grundahl, Frank
    Stempels, Eric
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Arentoft, Torben
    Bazot, Michael
    Christensen-Dalsgaard, Jorgen
    Dall, Thomas H.
    Karoff, Christoffer
    Lundgreen-Nielsen, Jens
    Carrier, Fabien
    Eggenberger, Patrick
    Sosnowska, Danuta
    Wittenmyer, Robert A.
    Endl, Michael
    Metcalfe, Travis S.
    Hekker, Saskia
    Reffert, Sabine
    A multi-site campaign to measure solar-like oscillations in Procyon. II. mode frequencies2010In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 713, no 2, p. 935-949Article in journal (Refereed)
    Abstract [en]

    We have analyzed data from a multi-site campaign to observe oscillations in the F5 star Procyon. The data consist of high-precision velocities that we obtained over more than three weeks with 11 telescopes. A new method for adjusting the data weights allows us to suppress the sidelobes in the power spectrum. Stacking the power spectrum in a so-called echelle diagram reveals two clear ridges, which we identify with even and odd values of the angular degree (l = 0 and 2, and l = 1 and 3, respectively). We interpret a strong, narrow peak at 446 mu Hz that lies close to the l = 1 ridge as a mode with mixed character. We show that the frequencies of the ridge centroids and their separations are useful diagnostics for asteroseismology. In particular, variations in the large separation appear to indicate a glitch in the sound-speed profile at an acoustic depth of similar to 1000 s. We list frequencies for 55 modes extracted from the data spanning 20 radial orders, a range comparable to the best solar data, which will provide valuable constraints for theoretical models. A preliminary comparison with published models shows that the offset between observed and calculated frequencies for the radial modes is very different for Procyon than for the Sun and other cool stars. We find the mean lifetime of the modes in Procyon to be 1.29(-0.49)(+0.55) days, which is significantly shorter than the 2-4 days seen in the Sun.

  • 5. Bouchy, F.
    et al.
    Hebb, L.
    Skillen, I.
    Cameron, A. Collier
    Smalley, B.
    Udry, S.
    Anderson, D. R.
    Boisse, I.
    Enoch, B.
    Haswell, C. A.
    Hebrard, G.
    Hellier, C.
    Joshi, Y.
    Kane, S. R.
    Maxted, P. F. L.
    Mayor, M.
    Moutou, C.
    Pepe, F.
    Pollacco, D.
    Queloz, D.
    Segransan, D.
    Simpson, E. K.
    Smith, A. M. S.
    Stempels, H. C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Street, R.
    Triaud, A. H. M. J.
    West, R. G.
    Wheatley, P. J.
    WASP-21b: a hot-Saturn exoplanet transiting a thick disc star2010In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 519, p. A98-Article in journal (Refereed)
    Abstract [en]

    We report the discovery of WASP-21b, a new transiting exoplanet discovered by the Wide Angle Search for Planets ( WASP) Consortium and established and characterized with the FIES, SOPHIE, CORALIE and HARPS fiber-fed echelle spectrographs. A 4.3-d period, 1.1% transit depth and 3.4-h duration are derived for WASP-21b using SuperWASP-North and high precision photometric observations at the Liverpool Telescope. Simultaneous fitting to the photometric and radial velocity data with a Markov Chain Monte Carlo procedure leads to a planet in the mass regime of Saturn. With a radius of 1.07 R-Jup and mass of 0.30 M-Jup, WASP-21b has a density close to 0.24 rho(Jup) corresponding to the distribution peak at low density of transiting gaseous giant planets. With a host star metallicity [Fe/H] of -0.46, WASP-21b strengthens the correlation between planetary density and host star metallicity for the five known Saturn-like transiting planets. Furthermore there are clear indications that WASP-21b is the first transiting planet belonging to the thick disc.

  • 6. Chew, Yilen Gomez Maqueo
    et al.
    Stassun, Keivan G.
    Prsa, Andrej
    Stempels, Eric
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Hebb, Leslie
    Barnes, Rory
    Heller, Rene
    Mathieu, Robert D.
    Luminosity Discrepancy in the Equal-Mass, Pre-Main-Sequence Eclipsing Binary Par 1802: Non-Coevality or Tidal Heating?2012In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 745, no 1, p. 58-Article in journal (Refereed)
    Abstract [en]

    Parenago 1802, a member of the similar to 1 Myr Orion Nebula Cluster, is a double-lined, detached eclipsing binary in a 4.674 day orbit, with equal-mass components (M-2/M-1 = 0.985 +/- 0.029). Here we present extensive VI(C)JHK(S) light curves (LCs) spanning similar to 15 yr, as well as a Keck/High Resolution Echelle Spectrometer (HIRES) optical spectrum. The LCs evince a third light source that is variable with a period of 0.73 days, and is also manifested in the high-resolution spectrum, strongly indicating the presence of a third star in the system, probably a rapidly rotating Classical T Tauri star. We incorporate this third light into our radial velocity and LC modeling of the eclipsing pair, measuring accurate masses (M-1 = 0.391 +/- 0.032 and M-2 = 0.385 +/- 0.032 M-circle dot), radii (R-1 = 1.73 +/- 0.02 and R-2 = 1.62 +/- 0.02 R-circle dot), and temperature ratio (T-eff,T-1/T-eff,T-2 = 1.0924 +/- 0.0017). Thus, the radii of the eclipsing stars differ by 6.9% +/- 0.8%, the temperatures differ by 9.2% +/- 0.2%, and consequently the luminosities differ by 62% +/- 3%, despite having masses equal to within 3%. This could be indicative of an age difference of similar to 3 x 10(5) yr between the two eclipsing stars, perhaps a vestige of the binary formation history. We find that the eclipsing pair is in an orbit that has not yet fully circularized, e = 0.0166 +/- 0.003. In addition, we measure the rotation rate of the eclipsing stars to be 4.629 +/- 0.006 days; they rotate slightly faster than their 4.674 day orbit. The non-zero eccentricity and super-synchronous rotation suggest that the eclipsing pair should be tidally interacting, so we calculate the tidal history of the system according to different tidal evolution theories. We find that tidal heating effects can explain the observed luminosity difference of the eclipsing pair, providing an alternative to the previously suggested age difference.

  • 7. 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.

  • 8.
    Dorn, Reinhold J.
    et al.
    European Org Astron Res Southern Hemisphere, Karl Schwarzschild Str 2, D-85748 Garching, Germany..
    Follert, Roman
    Thuringer Landessternwarte Tautenburg, Sternwarte 5, D-07778 Tautenburg, Germany..
    Bristow, Paul
    European Org Astron Res Southern Hemisphere, Karl Schwarzschild Str 2, D-85748 Garching, Germany..
    Cumani, Claudio
    European Org Astron Res Southern Hemisphere, Karl Schwarzschild Str 2, D-85748 Garching, Germany..
    Eschbaumer, Siegfried
    European Org Astron Res Southern Hemisphere, Karl Schwarzschild Str 2, D-85748 Garching, Germany..
    Grunhut, Jason
    European Org Astron Res Southern Hemisphere, Karl Schwarzschild Str 2, D-85748 Garching, Germany..
    Haimerl, Andreas
    European Org Astron Res Southern Hemisphere, Karl Schwarzschild Str 2, D-85748 Garching, Germany..
    Hatzes, Artie
    Thuringer Landessternwarte Tautenburg, Sternwarte 5, D-07778 Tautenburg, Germany..
    Heiter, Ulrike
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Hinterschuster, Renate
    European Org Astron Res Southern Hemisphere, Karl Schwarzschild Str 2, D-85748 Garching, Germany..
    Ives, Derek J.
    European Org Astron Res Southern Hemisphere, Karl Schwarzschild Str 2, D-85748 Garching, Germany..
    Jung, Yves
    European Org Astron Res Southern Hemisphere, Karl Schwarzschild Str 2, D-85748 Garching, Germany..
    Kerber, Florian
    European Org Astron Res Southern Hemisphere, Karl Schwarzschild Str 2, D-85748 Garching, Germany..
    Klein, Barbara
    European Org Astron Res Southern Hemisphere, Karl Schwarzschild Str 2, D-85748 Garching, Germany..
    Lavail, Alexis
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy. European Org Astron Res Southern Hemisphere, Karl Schwarzschild Str 2, D-85748 Garching, Germany..
    Lizon, Jean Louis
    European Org Astron Res Southern Hemisphere, Karl Schwarzschild Str 2, D-85748 Garching, Germany..
    Loewinger, Tom
    Thuringer Landessternwarte Tautenburg, Sternwarte 5, D-07778 Tautenburg, Germany..
    Molina-Conde, Ignacio
    European Org Astron Res Southern Hemisphere, Karl Schwarzschild Str 2, D-85748 Garching, Germany..
    Nicholson, Belinda
    European Org Astron Res Southern Hemisphere, Karl Schwarzschild Str 2, D-85748 Garching, Germany..
    Marquart, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Oliva, Ernesto
    INAF Arcetri Osservatorio, Largo E Fermi 5, I-50125 Florence, Italy..
    Origlia, Livia
    INAF Bologna Observ, Via Ranzani 1, I-40127 Bologna, Italy..
    Pasquini, Luca
    European Org Astron Res Southern Hemisphere, Karl Schwarzschild Str 2, D-85748 Garching, Germany..
    Paufique, Jerome
    European Org Astron Res Southern Hemisphere, Karl Schwarzschild Str 2, D-85748 Garching, Germany..
    Piskunov, Nikolai
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Reiners, Ansgar
    Univ Gottingen, Inst Astrophys, Friedrich Hund Pl 1, D-37077 Gottingen, Germany..
    Seemann, Ulf
    Univ Gottingen, Inst Astrophys, Friedrich Hund Pl 1, D-37077 Gottingen, Germany..
    Stegmeier, Jorg
    European Org Astron Res Southern Hemisphere, Karl Schwarzschild Str 2, D-85748 Garching, Germany..
    Stempels, Eric
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Tordo, Sebastien
    European Org Astron Res Southern Hemisphere, Karl Schwarzschild Str 2, D-85748 Garching, Germany..
    The " plus " for CRIRES: enabling better science at infrared wavelength and high spectral resolution at the ESO VLT2016In: GROUND-BASED AND AIRBORNE INSTRUMENTATION FOR ASTRONOMY VI / [ed] Christopher J Evans, 2016, Vol. 9908, article id 99080IConference paper (Refereed)
    Abstract [en]

    The adaptive optics (AO) assisted CRIRES instrument was a IR (0.92 - 5.2 mu m) high-resolution spectrograph in operation from 2006 to 2014 at the Very Large Telescope (VLT) observatory. CRIRES was a unique instrument, accessing a parameter space (wavelength range and spectral resolution) up to now largely uncharted. It consisted of a single-order spectrograph providing long-slit (40 arcsecond) spectroscopy with a resolving power up to R=100 000. However the setup was limited to a narrow, single-shot, spectral range of about 1/70 of the central wavelength, resulting in low observing efficiency for many scientific programmes requiring a broad spectral coverage. The CRIRES upgrade project, CRIRES, transfouns this VLT instrument into a cross-dispersed spectrograph to increase the simultaneously covered wavelength range by a factor of ten. A new and larger detector focal plane array of three Hawaii 2RG detectors with 5.3 mu m cut-off wavelength will replace the existing detectors. For advanced wavelength calibration, custom-made absorption gas cells and an etalon system will be added. A spectro-polarimetric unit will allow the recording of circular and linear polarized spectra. This upgrade will be supported by dedicated data reduction software allowing the community to take full advantage of the new capabilities. CRIRES has now entered its assembly and integration phase and will return with all new capabilities by the beginning of 2018 to the Very Large Telescope in Chile. This article will provide the reader with an update of the current status of the instrument as well as the remaining steps until final installation at the Paranal Observatory.

  • 9.
    Dubernet, M. L.
    et al.
    Univ Paris 06, Univ Sorbonne, CNRS, LERMA,Observ Paris,PSL Res Univ, 5 Pl Janssen, F-92190 Meudon, France..
    Antony, B. K.
    Indian Sch Mines, Dept Appl Phys, Dhanbad 826004, Bihar, India..
    Ba, Y. A.
    Univ Paris 06, Univ Sorbonne, CNRS, LERMA,Observ Paris,PSL Res Univ, 5 Pl Janssen, F-92190 Meudon, France..
    Babikov, Yu L.
    Russian Acad Sci, Inst Atmospher Opt, Zuev Sq 1, Tomsk 634021, Russia.;Tomsk State Univ, Tomsk 634050, Russia..
    Bartschat, K.
    Drake Univ, Dept Phys & Astron, Des Moines, IA 50311 USA..
    Boudon, V.
    Univ Bourgogne Franche Comte, CNRS, UMR 6303, Lab Interdisciplinaire Carnot Bourgogne, 9 Ave Alain Savary,BP 47 870, F-21078 Dijon, France..
    Braams, B. J.
    IAEA, Vienna Int Ctr, Div Phys & Chem Sci, Nucl Data Sect, A-1400 Vienna, Austria..
    Chung, H-K
    IAEA, Vienna Int Ctr, Div Phys & Chem Sci, Nucl Data Sect, A-1400 Vienna, Austria..
    Daniel, F.
    Univ Grenoble Alpes, CNRS, IPAG, F-38000 Grenoble, France..
    Delahaye, F.
    Univ Paris 06, Univ Sorbonne, CNRS, LERMA,Observ Paris,PSL Res Univ, 5 Pl Janssen, F-92190 Meudon, France..
    Del Zanna, G.
    Ctr Math Sci, DAMTP, Wilberforce Rd, Cambridge CB3 0WA, England..
    de Urquijo, J.
    Univ Nacl Autonoma Mexico, Inst Ciencias Fis, POB 48-3, Cuernavaca 62251, Morelos, Mexico..
    Dimitrijevic, M. S.
    Univ Paris 06, Univ Sorbonne, CNRS, LERMA,Observ Paris,PSL Res Univ, 5 Pl Janssen, F-92190 Meudon, France.;Astron Observ, Volgina 7, Belgrade 11060, Serbia..
    Domaracka, A.
    UCN, ENSICAEN, CNRS, CIMAP,UMR 6252,CEA, Bd Henri Becquerel,BP 5133, F-14070 Caen 5, France..
    Doronin, M.
    Univ Paris 06, Univ Sorbonne, CNRS, LERMA,Observ Paris,PSL Res Univ, 5 Pl Janssen, F-92190 Meudon, France..
    Drouin, B. J.
    CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA..
    Endres, C. P.
    Max Planck Inst Extraterr Phys, Giessenbachstr, D-85748 Garching, Germany..
    Fazliev, A. Z.
    Russian Acad Sci, Inst Atmospher Opt, Zuev Sq 1, Tomsk 634021, Russia..
    Gagarin, S. V.
    Russian Fed Nucl Ctr All Russian Inst Tech Phys R, Snezhinsk, Russia..
    Gordon, I. E.
    Harvard Smithsonian Ctr Astrophys, Atom & Mol Phys Div, MS50,60 Garden St, Cambridge, MA 02138 USA..
    Gratier, P.
    Univ Bordeaux, LAB, UMR 5804, F-33270 Florac, France.;CNRS, LAB, UMR 5804, F-33270 Florac, France..
    Heiter, Ulrike
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Hill, C.
    UCL, Dept Phys & Astron, Mortimer St, London WC1E 6BT, England..
    Jevremovic, D.
    Astron Observ, Volgina 7, Belgrade 11060, Serbia..
    Joblin, C.
    Univ Toulouse, UPS OMP, CNRS, Inst Rech Astrophys & Planetol, 9 Av Colonel Roche, F-31028 Toulouse 4, France..
    Kasprzak, A.
    Observ Paris, SRCV, 61 Av Denfert Rochereau, F-75014 Paris, France..
    Krishnakumar, E.
    Tata Inst Fundamental Res, Dept Nucl & Atom Phys, Homi Bhabha Rd, Bombay 400005, Maharashtra, India..
    Leto, G.
    INAF Osservatorio Astrofis Catania, Via S Sofia 78, I-95123 Catania, Italy..
    Loboda, P. A.
    Russian Fed Nucl Ctr All Russian Inst Tech Phys R, Snezhinsk, Russia.;Natl Res Nucl Univ, Moscow Engn Phys Inst MEPhI, Moscow, Russia..
    Louge, T.
    Univ Toulouse, UPS OMP, CNRS, Inst Rech Astrophys & Planetol, 9 Av Colonel Roche, F-31028 Toulouse 4, France..
    Maclot, S.
    UCN, ENSICAEN, CNRS, CIMAP,UMR 6252,CEA, Bd Henri Becquerel,BP 5133, F-14070 Caen 5, France.;Univ Caen Normandie, Esplanade Paix, CS 14032, F-14032 Caen 5, France..
    Marinkovic, B. P.
    Univ Belgrade, Inst Phys Belgrade, POB 57, Belgrade 11001, Serbia..
    Markwick, A.
    Univ Manchester, Sch Phys & Astron, Jodrell Bank Ctr Astrophys, Oxford Rd, Manchester M13 9PL, Lancs, England..
    Marquart, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Mason, H. E.
    Ctr Math Sci, DAMTP, Wilberforce Rd, Cambridge CB3 0WA, England..
    Mason, N. J.
    Open Univ, Dept Phys Sci, Walton Hall, Milton Keynes MK7 6AA, Bucks, England..
    Mendoza, C.
    IVIC, Ctr Fis, POB 20632, Caracas 1020A, Venezuela..
    Mihajlov, A. A.
    Univ Belgrade, Inst Phys Belgrade, POB 57, Belgrade 11001, Serbia..
    Millar, T. J.
    Queens Univ Belfast, Sch Math & Phys, Univ Rd, Belfast BT7 1NN, Antrim, North Ireland..
    Moreau, N.
    Univ Paris 06, Univ Sorbonne, CNRS, LERMA,Observ Paris,PSL Res Univ, 5 Pl Janssen, F-92190 Meudon, France..
    Mulas, G.
    Univ Toulouse, UPS OMP, CNRS, Inst Rech Astrophys & Planetol, 9 Av Colonel Roche, F-31028 Toulouse 4, France.;Osservatorio Astron Cagliari, Ist Nazl AstroFis, Via Sci 5, I-09047 Selargius, CA, Italy..
    Pakhomov, Yu
    RAS, Inst Astron, Pyatnitskaya 48, Moscow 119017, Russia..
    Palmeri, P.
    Univ Mons, Phys Atom & Astrophys, B-7000 Mons, Belgium..
    Pancheshnyi, S.
    ABB Corp Res, Segelhofstr 1K, CH-5405 Baden, Switzerland..
    Perevalov, V. I.
    Russian Acad Sci, Inst Atmospher Opt, Zuev Sq 1, Tomsk 634021, Russia..
    Piskunov, Nikolai
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Postler, J.
    Univ Innsbruck, Inst Ion Phys & Appl Phys, Technikerstr 25-3, A-6020 Innsbruck, Austria..
    Quinet, P.
    Univ Mons, Phys Atom & Astrophys, B-7000 Mons, Belgium.;Univ Liege, IPNAS, B-4000 Liege, Belgium..
    Quintas-Sanchez, E.
    Univ Paris 06, Univ Sorbonne, CNRS, LERMA,Observ Paris,PSL Res Univ, 5 Pl Janssen, F-92190 Meudon, France..
    Ralchenko, Yu
    NIST, Atom Spect Grp, Gaithersburg, MD 20899 USA..
    Rhee, Y-J
    Korea Atom Energy Res Inst, Nucl Data Ctr, Taejon 305353, South Korea..
    Rixon, G.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England..
    Rothman, L. S.
    Harvard Smithsonian Ctr Astrophys, Atom & Mol Phys Div, MS50,60 Garden St, Cambridge, MA 02138 USA..
    Roueff, E.
    Univ Paris 06, Univ Sorbonne, CNRS, LERMA,Observ Paris,PSL Res Univ, 5 Pl Janssen, F-92190 Meudon, France..
    Ryabchikova, T.
    RAS, Inst Astron, Pyatnitskaya 48, Moscow 119017, Russia..
    Sahal-Brechot, S.
    Univ Paris 06, Univ Sorbonne, CNRS, LERMA,Observ Paris,PSL Res Univ, 5 Pl Janssen, F-92190 Meudon, France..
    Scheier, P.
    Univ Innsbruck, Inst Ion Phys & Appl Phys, Technikerstr 25-3, A-6020 Innsbruck, Austria..
    Schlemmer, S.
    Univ Cologne, Inst Phys 1, zulpicher Str 77, D-50937 Kln, Germany..
    Schmitt, B.
    Univ Grenoble Alpes, CNRS, IPAG, F-38000 Grenoble, France..
    Stempels, Eric H. C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Tashkun, S.
    Russian Acad Sci, Inst Atmospher Opt, Zuev Sq 1, Tomsk 634021, Russia..
    Tennyson, J.
    UCL, Dept Phys & Astron, Mortimer St, London WC1E 6BT, England..
    Tyuterev, Vl G.
    Univ Reims, GSMA, UMR CNRS 7331, Reims, France..
    Vujcic, V.
    Astron Observ, Volgina 7, Belgrade 11060, Serbia.;Univ Belgrade, Fac Org Sci, Jove Ilica 33, Belgrade 11000, Serbia..
    Wakelam, V.
    Univ Bordeaux, LAB, UMR 5804, F-33270 Florac, France.;CNRS, LAB, UMR 5804, F-33270 Florac, France..
    Walton, N. A.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England..
    Zatsarinny, O.
    Drake Univ, Dept Phys & Astron, Des Moines, IA 50311 USA..
    Zeippen, C. J.
    Univ Paris 06, Univ Sorbonne, CNRS, LERMA,Observ Paris,PSL Res Univ, 5 Pl Janssen, F-92190 Meudon, France..
    Zwoelf, C. M.
    Univ Paris 06, Univ Sorbonne, CNRS, LERMA,Observ Paris,PSL Res Univ, 5 Pl Janssen, F-92190 Meudon, France..
    The virtual atomic and molecular data centre (VAMDC) consortium2016In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 49, no 7, article id 074003Article in journal (Refereed)
    Abstract [en]

    The Virtual Atomic and Molecular Data Centre (VAMDC) Consortium is a worldwide consortium which federates atomic and molecular databases through an e-science infrastructure and an organisation to support this activity. About 90% of the inter-connected databases handle data that are used for the interpretation of astronomical spectra and for modelling in many fields of astrophysics. Recently the VAMDC Consortium has connected databases from the radiation damage and the plasma communities, as well as promoting the publication of data from Indian institutes. This paper describes how the VAMDC Consortium is organised for the optimal distribution of atomic and molecular data for scientific research. It is noted that the VAMDC Consortium strongly advocates that authors of research papers using data cite the original experimental and theoretical papers as well as the relevant databases.

  • 10.
    Feiden, Gregory A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
    Stempels, Eric
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Hebb, L.
    Hobart & William Smith Coll, Dept Phys, Geneva, NY 14456 USA..
    Mack, C. E. , I I I
    Chaboyer, B.
    Dartmouth Coll, Dept Phys & Astron, Hanover, NH 03755 USA..
    Spectroscopic Study of the Low Mass Benchmark Eclipsing Binary UV Piscium2015In: Living Together: Planets, Host Stars, and Binaries, 2015, Vol. 496, p. 174-174Conference paper (Refereed)
  • 11. Follert, R.
    et al.
    Dorn, R. J.
    Oliva, E.
    Lizon, J. L.
    Hatzes, A.
    Piskunov, Nikolai
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Reiners, A.
    Seemann, U.
    Stempels, Eric
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Heiter, Ulrike
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Marquart, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Lockhart, Matthew
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Anglada-Escude, G.
    Loewinger, T.
    Baade, D.
    Grunhut, J.
    Bristow, P.
    Klein, B.
    Jung, Y.
    Ives, D. J.
    Kerber, F.
    Pozna, E.
    Paufique, J.
    Kaeufl, H. U.
    Origlia, L.
    Valenti, E.
    Gojak, D.
    Hilker, M.
    Pasquini, L.
    Smette, A.
    Smoker, J.
    CRIRES plus: a cross-dispersed high-resolution infrared spectrograph for the ESO VLT2014In: GROUND-BASED AND AIRBORNE INSTRUMENTATION FOR ASTRONOMY V, 2014, Vol. 9147, article id 914719Conference paper (Refereed)
    Abstract [en]

    High-resolution infrared spectroscopy plays an important role in astrophysics from the search for exoplanets to cosmology. Yet, many existing infrared spectrographs are limited by a rather small simultaneous wavelength coverage. The AO assisted CRIRES instrument, installed at the ESO VLT on Paranal, is one of the few IR (0.92-5.2 mu m) high-resolution spectrographs in operation since 2006. However it has a limitation that hampers its efficient use: the wavelength range covered in a single exposure is limited to similar to 15 nanometers. The CRIRES Upgrade project (CRIRES+) will transform CRIRES into a cross-dispersed spectrograph and will also add new capabilities. By introducing cross-dispersion elements the simultaneously covered wavelength range will be increased by at least a factor of 10 with respect to the present configuration, while the operational wavelength range will be preserved. For advanced wavelength calibration, new custom made absorption gas cells and etalons will be added. A spectro-polarimetric unit will allow one for the first time to record circularly polarized spectra at the highest spectral resolution. This will be all supported by a new data reduction software which will allow the community to take full advantage of the new capabilities of CRIRES+.

  • 12.
    Follert, Roman
    et al.
    Thuringer Landessternwarte Tautenburg, Sternwarte 5, D-07778 Tautenburg, Germany..
    Taubert, Dieter
    Phys Tech Bundesanstalt, Fachbereich Detektorradiometrie & Strahlungstherm, Abbestr 2-12, D-10587 Berlin, Germany..
    Hollandt, Joerg
    Phys Tech Bundesanstalt, Fachbereich Detektorradiometrie & Strahlungstherm, Abbestr 2-12, D-10587 Berlin, Germany..
    Monte, Christian
    Phys Tech Bundesanstalt, Fachbereich Detektorradiometrie & Strahlungstherm, Abbestr 2-12, D-10587 Berlin, Germany..
    Oliva, Ernesto
    INAF Osservatori Arcetri, Largo E Fermi 5, I-50125 Florence, Italy..
    Seemann, Ulf
    Georg August Univ Gottingen, Inst Astrophys, Friedrich Hund Pl 1, D-37077 Gottingen, Germany..
    Loewinger, Tom
    Thuringer Landessternwarte Tautenburg, Sternwarte 5, D-07778 Tautenburg, Germany..
    Anwand-Heerwart, Heiko
    Georg August Univ Gottingen, Inst Astrophys, Friedrich Hund Pl 1, D-37077 Gottingen, Germany..
    Schmidt, Christof
    Georg August Univ Gottingen, Zent Werkstatt Fak Phys, Friedrich Hund Pl 1, D-37077 Gottingen, Germany..
    Dorn, Reinhold J.
    European Org Astron Res Southern Hemisphere, Karl Schwarzschild Str 2, D-85748 Garching, Germany..
    Bristow, Paul
    European Org Astron Res Southern Hemisphere, Karl Schwarzschild Str 2, D-85748 Garching, Germany..
    Hatzes, Artie
    Thuringer Landessternwarte Tautenburg, Sternwarte 5, D-07778 Tautenburg, Germany..
    Reiners, Ansgar
    Georg August Univ Gottingen, Inst Astrophys, Friedrich Hund Pl 1, D-37077 Gottingen, Germany..
    Piskunov, Nikolai
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Heiter, Ulrike
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Stempels, Eric
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Marquart, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Lavail, Alexis
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Cumani, Claudio
    European Org Astron Res Southern Hemisphere, Karl Schwarzschild Str 2, D-85748 Garching, Germany..
    Grunhut, Jason
    European Org Astron Res Southern Hemisphere, Karl Schwarzschild Str 2, D-85748 Garching, Germany..
    Haimerl, Andreas
    European Org Astron Res Southern Hemisphere, Karl Schwarzschild Str 2, D-85748 Garching, Germany..
    Hinterschuster, Renate
    European Org Astron Res Southern Hemisphere, Karl Schwarzschild Str 2, D-85748 Garching, Germany..
    Ives, Derek J.
    European Org Astron Res Southern Hemisphere, Karl Schwarzschild Str 2, D-85748 Garching, Germany..
    Jung, Yves
    European Org Astron Res Southern Hemisphere, Karl Schwarzschild Str 2, D-85748 Garching, Germany..
    Kerber, Florian
    European Org Astron Res Southern Hemisphere, Karl Schwarzschild Str 2, D-85748 Garching, Germany..
    Klein, Barbara
    European Org Astron Res Southern Hemisphere, Karl Schwarzschild Str 2, D-85748 Garching, Germany..
    Lizon, Jean Louis
    European Org Astron Res Southern Hemisphere, Karl Schwarzschild Str 2, D-85748 Garching, Germany..
    Molina-Conde, Ignacio
    European Org Astron Res Southern Hemisphere, Karl Schwarzschild Str 2, D-85748 Garching, Germany..
    Nicholson, Belinda
    European Org Astron Res Southern Hemisphere, Karl Schwarzschild Str 2, D-85748 Garching, Germany..
    Origlia, Livia
    INAF Osservatorio Bologna, Via Ranzani 1, I-40127 Bologna, Italy..
    Pasquini, Luca
    European Org Astron Res Southern Hemisphere, Karl Schwarzschild Str 2, D-85748 Garching, Germany..
    Paufique, Jerome
    European Org Astron Res Southern Hemisphere, Karl Schwarzschild Str 2, D-85748 Garching, Germany..
    Stegmeier, Joerg
    European Org Astron Res Southern Hemisphere, Karl Schwarzschild Str 2, D-85748 Garching, Germany..
    Tordo, Sebastien
    European Org Astron Res Southern Hemisphere, Karl Schwarzschild Str 2, D-85748 Garching, Germany..
    Characterizing the cross dispersion reflection gratings of CRIRES2016In: Advances In Optical And Mechanical Technologies For Telescopes And Instrumentation Ii, 2016, article id UNSP 99122BConference paper (Refereed)
    Abstract [en]

    The CRIRES+ project attempts to upgrade the CRIRES instrument into a cross dispersed echelle spectrograph with a simultaneous recording of 8-10 diffraction orders. In order to transform the CRIRES spectrograph into a cross-dispersing instrument, a set of six reflection gratings, each one optimized for one of the wavelength bands CRIRES+ will operate in (YJHKLM), will be used as cross dispersion elements in CRIRES+. Due to the upgrade nature of the project, the choice of gratings depends on the fixed geometry of the instrument. Thus, custom made gratings would be required to achieve the ambitious design goals. Custom made gratings have the disadvantage, though, that they come at an extraordinary price and with lead times of more than 12 months. To mitigate this, a set of off-the-shelf gratings was obtained which had grating parameters very close to the ones being identified as optimal. To ensure that the rigorous specifications for CRIRES+ will be fulfilled, the CRIRES+ team started a collaboration with the Physikalisch-Technische Bundesanstalt Berlin (PTB) to characterize gratings under conditions similar to the operating conditions in CRIRES+ (angle of incidence, wavelength range). The respective test setup was designed in collaboration between PTB and the CRIRES+ consortium. The PTB provided optical radiation sources and calibrated detectors for each wavelength range. With this setup, it is possible to measure the absolute efficiency of the gratings both wavelength dependent and polarization state dependent in a wavelength range from 0.9 mu m to 6 mu m.

  • 13. Fossati, L.
    et al.
    Haswell, C. A.
    Froning, C. S.
    Hebb, L.
    Holmes, S.
    Kolb, U.
    Helling, Ch.
    Carter, A.
    Wheatley, P.
    Cameron, A. C.
    Loeillet, B.
    Pollacco, D.
    Street, R.
    Stempels, Henricus
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Simpson, E.
    Udry, S.
    Joshi, Y. C.
    West, R. G.
    Skillen, I.
    Wilson, D.
    Metals in the exosphere of the highly irradiated planet WASP-12b2010In: Astrophysical Journal Letters, ISSN 2041-8205, Vol. 714, no 2, p. L222-L227Article in journal (Refereed)
    Abstract [en]

    We present near-UV transmission spectroscopy of the highly irradiated transiting exoplanet WASP-12b, obtained with the Cosmic Origins Spectrograph on the Hubble Space Telescope. The spectra cover three distinct wavelength ranges: NUVA (2539-2580 angstrom), NUVB (2655-2696 angstrom), and NUVC (2770-2811 angstrom). Three independent methods all reveal enhanced transit depths attributable to absorption by resonance lines of metals in the exosphere of WASP-12b. Light curves of total counts in the NUVA and NUVC wavelength ranges show a detection at a 2.5 sigma level. We detect extra absorption in the Mg II lambda lambda 2800 resonance line cores at the 2.8 sigma level. The NUVA, NUVB, and NUVC light curves imply effective radii of 2.69 +/- 0.24 R-J, 2.18 +/- 0.18 R-J, and 2.66 +/- 0.22 R-J respectively, suggesting the planet is surrounded by an absorbing cloud which overfills the Roche lobe. We detect enhanced transit depths at the wavelengths of resonance lines of neutral sodium, tin, and manganese, and at singly ionized ytterbium, scandium, manganese, aluminum, vanadium, and magnesium. We also find the statistically expected number of anomalous transit depths at wavelengths not associated with any known resonance line. Our data are limited by photon noise, but taken as a whole the results are strong evidence for an extended absorbing exosphere surrounding the planet. The NUVA data exhibit an early ingress, contrary to model expectations; we speculate this could be due to the presence of a disk of previously stripped material.

  • 14. Gahm, G. F.
    et al.
    Stempels, H. C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Walter, F. M.
    Petrov, P. P.
    Herczeg, G. J.
    Face to phase with RU Lupi2013In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 560, p. A57-Article in journal (Refereed)
    Abstract [en]

    Context. Some classical T Tauri stars, with intense line and continuous excess emission, show extremely complex spectral variations. Aims. We aim to map and interpret the spectral variations in one such extreme T Tauri star, namely RU Lupi, and to explore how the changes are related to stellar brightness and rotational phase.

    Methods. We followed the star over three observing runs, each covering a few days, collecting high-resolution optical spectra. In connection to the third run, complementary NIR spectra, multicolour photometric data, and X-ray observations were obtained.

    Results. The stellar photospheric absorption line spectrum is weakened by superimposed emission, and this veiling becomes extremely high on occasion. Interpreted as a variable continuous excess emission, its contribution would amount to several times the stellar continuum brightness. However, the stellar brightness does not change much when the veiling changes, and we conclude that the veiling is dominated by narrow line emission that fills in the photospheric lines. Continuous emission, originating at the hot spot on the stellar surface, plays a dominant role only at lower degrees of veiling. The radial velocity of narrow emission components in lines of He I vary periodically in anti-phase with the stellar velocity, reflecting the location and motion of the accretion footprint. The blue-shifted wings in He I, related to a stellar wind, are remarkably stable in equivalent width. This implies that the line flux responds directly to changes in the veiling, which in turn is related to the accretion rate close to the star. In contrast, the equivalent widths of the red-shifted wings change with rotational phase. From the pattern of variability we infer that these wings originate in accreting gas close to the star, and that the accretion funnels are bent and trail the hot spot. The profiles of the forbidden lines of [O I] and [S II] are very stable in strength and shape over the entire observing period, and like a system of narrow, blue-shifted absorption features seen in lines of Ca II and Na I, they originate at larger distances from the star in the disk wind. Slightly blue-shifted emission components are present in the forbidden lines and might be related to a wide angle molecular disk wind proposed by others.

  • 15. Galan, C.
    et al.
    Mikolajewski, M.
    Tomov, T.
    Graczyk, D.
    Apostolovska, G.
    Barzova, I.
    Bellas-Velidis, I.
    Bilkina, B.
    Blake, R. M.
    Bolton, C. T.
    Bondar, A.
    Brat, L.
    Brozek, T.
    Budzisz, B.
    Cikala, M.
    Csak, B.
    Dapergolas, A.
    Dimitrov, D.
    Dobierski, P.
    Drahus, M.
    Drozdz, M.
    Dvorak, S.
    Elder, L.
    Frackowiak, S.
    Galazutdinov, G.
    Gazeas, K.
    Georgiev, L.
    Gere, B.
    Gozdziewski, K.
    Grinin, V. P.
    Gromadzki, M.
    Hajduk, M.
    Heras, T. A.
    Hopkins, J.
    Iliev, I.
    Janowski, J.
    Kocian, R.
    Kolaczkowski, Z.
    Kolev, D.
    Kopacki, G.
    Krzesinski, J.
    Kucakova, H.
    Kuligowska, E.
    Kundera, T.
    Kurpinska-Winiarska, M.
    Kuzmicz, A.
    Liakos, A.
    Lister, T. A.
    Maciejewski, G.
    Majcher, A.
    Majewska, A.
    Marrese, P. M.
    Michalska, G.
    Migaszewski, C.
    Miller, I.
    Munari, U.
    Musaev, F.
    Myers, G.
    Narwid, A.
    Nemeth, P.
    Niarchos, P.
    Niemczura, E.
    Ogloza, W.
    Oegmen, Y.
    Oksanen, A.
    Osiwala, J.
    Peneva, S.
    Pigulski, A.
    Popov, V.
    Pych, W.
    Pye, J.
    Ragan, E.
    Roukema, B. F.
    Rozanski, P. T.
    Semkov, E.
    Siwak, M.
    Staels, B.
    Stateva, I.
    Stempels, Henricus C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Steslicki, M.
    Swierczynski, E.
    Szymanski, T.
    Tomov, N.
    Waniak, W.
    Wiecek, M.
    Winiarski, M.
    Wychudzki, P.
    Zajczyk, A.
    Zola, S.
    Zwitter, T.
    International observational campaigns of the last two eclipses in EE Cephei: 2003 and 2008/92012In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 544, p. A53-Article in journal (Refereed)
    Abstract [en]

    Context. EECep is an unusual long-period (5.6 yr) eclipsing binary discovered during the mid-twentieth century. It undergoes almost-grey eclipses that vary in terms of both depth and duration at different epochs. The system consists of a Be type star and a dark dusty disk around an invisible companion. EECep together with the widely studied epsilon Aur are the only two known cases of long-period eclipsing binaries with a dark, dusty disk component responsible for periodic obscurations.

    Aims. Two observational campaigns were carried out during the eclipses of EECep in 2003 and 2008/9 to verify whether the eclipsing body in the system is indeed a dark disk and to understand the observed changes in the depths and durations of the eclipses.

    Methods. Multicolour photometric data and spectroscopic observations performed at both low and high resolutions were collected with several dozen instruments located in Europe and North America. We numerically modelled the variations in brightness and colour during the eclipses. We tested models with different disk structure, taking into consideration the inhomogeneous surface brightness of the Be star. We considered the possibility of disk precession.

    Results. The complete set of observational data collected during the last three eclipses are made available to the astronomical community. The 2003 and 2008/9 eclipses of EECep were very shallow. The latter is the shallowest among all observed. The very high quality photometric data illustrate in detail the colour evolution during the eclipses for the first time. Two blue maxima in the colour indices were detected during these two eclipses, one before and one after the photometric minimum. The first (stronger) blue maximum is simultaneous with a "bump" that is very clear in all the UBV(RI)(C) light curves. A temporary increase in the I-band brightness at the orbital phase similar to 0.2 was observed after each of the last three eclipses. Variations in the spectral line profiles seem to be recurrent during each cycle. The Na I lines always show at least three absorption components during the eclipse minimum and strong absorption is superimposed on the H alpha emission.

    Conclusions. These observations confirm that the eclipsing object in EECep system is indeed a dark, dusty disk around a low luminosity object. The primary appears to be a rapidly rotating Be star that is strongly darkened at the equator and brightened at the poles. Some of the conclusions of this work require verification in future studies: (i) a complex, possibly multi-ring structure of the disk in EECep; (ii) our explanation of the "bump" observed during the last two eclipses in terms of the different times of obscuration of the hot polar regions of the Be star by the disk; and (iii) our suggested period of the disk precession (similar to 11-12 P-orb) and predicted depth of about 2(m) for the forthcoming eclipse in 2014.

  • 16. Hebb, L.
    et al.
    Cegla, H. M.
    Stassun, K. G.
    Stempels, Henricus Cornelis
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Cargile, P. A.
    Palladino, L. E.
    Precise orbit solution of MML 53, a low-mass, pre-main sequence eclipsing binary in Upper Centaurus Lupus2011In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 531, p. A61-Article in journal (Refereed)
    Abstract [en]

    Aims. We present a double-lined orbit solution for MML 53, the recently discovered low-mass pre-main sequence eclipsing binary. Methods. Using high-resolution spectra from the SMARTS 1.5 m echelle spectrograph, we measure precise radial velocities and derive the orbital parameters of the system. Results. The 2.1 d orbit of the eclipsing pair is circular, and we find the minimum masses of the eclipsing components to be M(1) sin(3) i = 0.97 M(circle dot) and M(2) sin(3) i = 0.84 M(circle dot), with formal uncertainties of 2.0% and an additional systematic uncertainty of approximate to 2.5% most likely caused by large star spots on the primary star. MML 53 has been previously identified as a member of the Upper Centaurus Lupus (UCL) star forming region (age similar to 15 Myr). The systemic radial velocity from our orbit solution, v(gamma) = + 1.4 +/- 0.3 +/- 0.8 km s(-1) (statistical and systematic), is also consistent with kinematic membership in this association. In addition, we detect a change in v(gamma) between 2006 and 2009 providing further evidence for the presence of a the third body in a wide (several year) orbit.

  • 17. Hebb, L.
    et al.
    Stempels, Henricus
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Aigrain, S.
    Collier-Cameron, A.
    Hodgkin, S. T.
    Irwin, J. M.
    Maxted, P. F. L.
    Pollacco, D.
    Street, R. A.
    Wilson, D. M.
    Stassun, K. G.
    MML 53: a new low-mass, pre-main sequence eclipsing binary in the Upper Centaurus-Lupus region discovered by SuperWASP2010In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 522, no 2, p. A37-Article in journal (Refereed)
    Abstract [en]

    We announce the discovery of a new low-mass, pre-main sequence eclipsing binary, MML 53. Previous observations of MML 53 found it to be a pre-main sequence spectroscopic multiple associated with the 15-22 Myr Upper Centaurus-Lupus cluster. We identify the object as an eclipsing binary for the first time through the analysis of multiple seasons of time series photometry from the SuperWASP transiting planet survey. Re-analysis of a single archive spectrum shows MML 53 to be a spatially unresolved triple system of young stars which all exhibit significant lithium absorption. Two of the components comprise an eclipsing binary with period, P = 2.097891(6) +/- 0.000005 and mass ratio, q similar to 0.8. Here, we present the analysis of the discovery data.

  • 18. Houdebine, E. R.
    et al.
    Stempels, Henricus C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Oliveira, J. H.
    Observation and modelling of main sequence star chromospheres - XIII. The Na i D1 and D2, and He i D3 lines in dM1 stars2009In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 400, no 1, p. 238-247Article in journal (Refereed)
    Abstract [en]

    We investigate spectral lines of interest in dM1 stars, namely the Na i D1 and D2 and He i 5876 lines. We study in detail the line shapes of the Na i D1 and D2 lines. We find that these lines are strong and broad in normal dM1 stars and become weaker and narrower when metallicity is low, although our sample is insufficient in order to find out an empirical correlation between these parameters. We find correlations between the Ca ii resonance line-mean equivalent width (EW) and v sin i as well as between the Na i mean line core relative flux and v sin i. These correlations include low activity dM1 stars and show that the Na i mean line core flux is a good chromospheric diagnostic. We find a good correlation between the Na i D1 line core flux and the Na i D2 line core flux. This correlation shows that the line core optical depths decrease with an increasing activity level, that is the opposite of what was found for the Ca ii lines. The Na i D1 and D2 mean line core flux also correlates well with the Ca ii mean EW and with the H alpha EW. We also compare these correlations to the available model computations. We investigate in detail the shapes of the Na i D1 and D2 lines through the full line widths at 85 per cent, 62 per cent and 35 per cent of the continuum. The significant differences from one star to another cannot be explained at this stage. Detailed modelling of the stellar photospheres will be necessary to interpret the observed differences. The He i 5876 line is detected in only one dM1 star in our sample. We obtain activity correlations between the He i 5876 line EW and the Ca ii mean EW, and the H alpha EW.

  • 19. Johns-Krull, Christopher M.
    et al.
    Chen, Wei
    Valenti, Jeff A.
    Jeffers, Sandra V.
    Piskunov, Nikolai E.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Kochukhov, Oleg
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Makaganiuk, Vitalii
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Stempels, Eric
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Snik, Frans
    Keller, Christoph
    Rodenhuis, M.
    Magnetically Controlled Accretion on the Classical T Tauri Stars GQ Lupi and TW Hydrae2013In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 765, no 1, p. 11-Article in journal (Refereed)
    Abstract [en]

    We present high spectral resolution (R approximate to 108,000) Stokes V polarimetry of the classical T Tauri stars (CTTSs) GQ Lup and TW Hya obtained with the polarimetric upgrade to the HARPS spectrometer on the ESO 3.6 m telescope. We present data on both photospheric lines and emission lines, concentrating our discussion on the polarization properties of the He I emission lines at 5876 angstrom and 6678 angstrom. The He I lines in these CTTSs contain both narrow emission cores, believed to come from near the accretion shock region on these stars, and broad emission components which may come from either a wind or the large-scale magnetospheric accretion flow. We detect strong polarization in the narrow component of the two He I emission lines in both stars. We observe a maximum implied field strength of 6.05 +/- 0.24 kG in the 5876 angstrom line of GQ Lup, making it the star with the highest field strength measured in this line for a CTTS. We find field strengths in the two He I lines that are consistent with each other, in contrast to what has been reported in the literature on at least one star. We do not detect any polarization in the broad component of the He I lines on these stars, strengthening the conclusion that they form over a substantially different volume relative to the formation region of the narrow component of the He I lines.

  • 20.
    Kochukhov, Oleg
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Makaganiuk, Vitalii
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Piskunov, Nikolai
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Jeffers, S. V.
    Johns-Krull, C. M.
    Keller, C. U.
    Rodenhuis, M.
    Snik, F.
    Stempels, H. C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Valenti, J. A.
    Are there tangled magnetic fields on HgMn stars?2013In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 554, p. A61-Article in journal (Refereed)
    Abstract [en]

    Context. Several recent spectrophotometric studies failed to detect significant global magnetic fields in late-B HgMn chemically peculiar stars, but some investigations have suggested the presence of strong unstructured or tangled fields in these objects. Aims. We used detailed spectrum synthesis analysis to search for evidence of tangled magnetic fields in high-quality observed spectra of eight slowly rotating HgMn stars and one normal late-B star. We also evaluated recent sporadic detections of weak longitudinal magnetic fields in HgMn stars based on the moment technique. Methods. Our spectrum synthesis code calculated the Zeeman broadening of metal lines in HARPS spectra, assuming an unstructured, turbulent magnetic field. A simple line formation model with a homogeneous radial field distribution was applied to assess compatibility between previous longitudinal field measurements and the observed mean circular polarization signatures. Results. Our analysis of the Zeeman broadening of magnetically sensitive spectral lines reveals no evidence of tangled magnetic fields in any of the studied HgMn or normal stars. We infer upper limits of 200-700 G for the mean magnetic field modulus - much smaller than the field strengths implied by studies based on differential magnetic line intensification and quadratic field diagnostics. The new HARPSpol longitudinal field measurements for the extreme HgMn star HD65949 and the normal late-B star 21 Peg are consistent with zero at a precision of 3-6 G. Re-analysis of our Stokes V spectra of the spotted HgMn star HD11753 shows that the recent moment technique measurements retrieved from the same data are incompatible with the lack of circular polarization signatures in the spectrum of this star. Conclusions. We conclude that there is no evidence for substantial tangled magnetic fields on the surfaces of studied HgMn stars. We cannot independently confirm the presence of very strong quadratic or marginal longitudinal fields for these stars, so results from the moment technique are likely to be spurious.

  • 21.
    Kochukhov, Oleg
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Makaganiuk, Vitalii
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Piskunov, Nikolai
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Jeffers, S. V.
    Johns-Krull, C. M.
    Keller, C. U.
    Rodenhuis, M.
    Snik, F.
    Stempels, Henricus C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Valenti, J. A.
    No magnetic field in the spotted HgMn star mu Leporis2011In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 534, p. L13-Article in journal (Refereed)
    Abstract [en]

    Context. Chemically peculiar stars of the mercury-manganese (HgMn) type represent a new class of spotted late-B stars, in which evolving surface chemical inhomogeneities are apparently unrelated to the presence of strong magnetic fields but are produced by some hitherto unknown astrophysical mechanism.

    Aims. The goal of this study is to perform a detailed line profile variability analysis and carry out a sensitive magnetic field search for one of the brightest HgMn stars -mu Lep.

    Methods. We acquired a set of very high-quality intensity and polarization spectra of mu Lep with the HARPSpol polarimeter. These data were analyzed with the multiline technique of least-squares deconvolution in order to extract information on the magnetic field and line profile variability.

    Results. Our spectra show very weak but definite variability in the lines of Sc, all Fe-peak elements represented in the spectrum of mu Lep, as well as Y, Sr, and Hg. Variability might also be present in the lines of Si and Mg. Anomalous profile shapes of Ti II and YII lines suggest a dominant axisymmetric distribution of these elements. At the same time, we found no evidence of the magnetic field in mu Lep, with the 3 sigma upper limit of only 3 G for the mean longitudinal magnetic field. This is the most stringent upper limit on the possible magnetic field derived for a spotted HgMn star.

    Conclusions. The very weak variability detected for many elements in the spectrum mu Lep suggests that low-contrast chemical inhomogeneities may be common in HgMn stars and that they have not been recognized until now due to the limited precision of previous spectroscopic observations and a lack of time-series data. The null result of the magnetic field search reinforces the conclusion that formation of chemical spots in HgMn stars is not magnetically driven.

  • 22. Kupka, F.
    et al.
    Piskunov, Nikolai
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics, Observational Astronomy.
    Ryabchikova, T. A.
    Stempels, H. C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics, The Uppsala Astronomical Observatory.
    Weiss, W. W.
    VALD-2: Progress of the Vienna Atomic Line Data Base1999In: Astronomy and Astrophysics Supplement Series, ISSN 0365-0138, E-ISSN 1286-4846, Vol. 138, no 1, p. 119-133Article in journal (Refereed)
  • 23. Lamzin, S.A.
    et al.
    Stempels, H.C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics.
    Piskunov, N.E.
    Formation of Fe X-Fe XIV coronal lines in the accretion shock of T Tauri stars2001In: Astronomy & Astrophysics, ISSN 0004-6361, Vol. 369, no -, p. 965-970Article in journal (Refereed)
  • 24. Lamzin, SA
    et al.
    Stempels, HC
    Piskunov, Nikolai
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics, Observational Astronomy.
    Formation of Fe x-Fe XIV coronal lines in the accretion shock of T Tauri stars2001In: Astronomy & Astrophysics, ISSN 0004-6361, Vol. 369, no 3, p. 965-970Article in journal (Refereed)
  • 25.
    Lockhart, Matthew
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Piskunov, Nikolai
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Stempels, Eric
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Escuti, Michael
    Oliva, Ernesto
    Kaeufl, Hans-Ulrich
    Heiter, Ulrike
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Marquart, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Anglada-Escude, Guillem
    Baade, Dietrich
    Bristow, Paul
    Dorn, Reinhold J.
    Follert, Roman
    Gojak, Domingo
    Grunhut, Jason H.
    Hatzes, Artie
    Hilker, Michael
    Ives, Derek
    Jung, Yves
    Kerber, Florian
    Klein, Barbara
    Lizon, Jean-Louis
    Loewinger, Tom
    Origlia, Livia
    Pasquini, Luca
    Paufique, Jerome
    Pozna, Eszter
    Reiners, Ansgar
    Seemann, Ulf
    Smette, Alain
    Smoker, Jonathan
    Valenti, Elena
    Novel infrared polarimeter for the ESO CRIRES plus instrument2014In: GROUND-BASED AND AIRBORNE INSTRUMENTATION FOR ASTRONOMY V, 2014, Vol. 9147, article id 91478PConference paper (Refereed)
    Abstract [en]

    The CRIRES infrared spectrograph at the European Southern Observatory (ESO) Very Large Telescope (VLT) facility will soon receive an upgrade. This upgrade will include the addition of a module for performing high-resolution spectropolarimetry. The polarimetry module will incorporate a novel infrared beamsplitter based on polarization gratings (PGs). The beamsplitter produces a pair of infrared output beams, with opposite circular polarizations, which are then fed into the spectrograph. Visible light passes through the module virtually unaltered and is then available for use by the CRIRES adaptive optics system. We present the design of the polarimetry module and measurements of PG behavior in the 1 to 2.7 mu m wavelength range.

  • 26.
    Makaganiuk, Vitalii
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Kochukhov, Oleg
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Piskunov, Nikolai
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Jeffers, S. V.
    Johns-Krull, C. M.
    Keller, C. U.
    Rodenhuis, M.
    Snik, F.
    Stempels, H. C.
    Valenti, J. A.
    Chemical spots in the absence of magnetic field in the binary HgMn star 66 Eridani2011In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 529, p. A160-Article in journal (Refereed)
    Abstract [en]

    Context. According to our current understanding, a subclass of the upper main-sequence chemically peculiar stars, called mercury-manganese (HgMn), is non-magnetic. Nevertheless, chemical inhomogeneities were recently discovered on their surfaces. At the same time, no global magnetic fields stronger than 1-100 G are detected by systematic studies. Aims. The goals of our study are to search for a magnetic field in the HgMn binary system 66 Eri and to investigate chemical spots on the stellar surfaces of both components.

    Methods. Our analysis is based on high-quality spectropolarimetric time-series observations obtained during 10 consecutive nights with the HARPSpol instrument at the ESO 3.6-m telescope. To increase the sensitivity of the magnetic field search we employed a least-squares deconvolution (LSD). We used spectral disentangling to measure radial velocities and study the line profile variability. Chemical spot geometry was reconstructed using multi-line Doppler imaging.

    Results. We report a non-detection of magnetic field in 66 Eri, with error bars 10-24 G for the longitudinal field. Circular polarization profiles also do not indicate any signatures of complex surface magnetic fields. For a simple dipolar field configuration we estimated an upper limit of the polar field strength to be 60-70 G. For the HgMn component we found variability in spectral lines of Ti, Ba, Y, and Sr with the rotational period equal to the orbital one. The surface maps of these elements reconstructed with the Doppler imaging technique show a relative underabundance on the hemisphere facing the secondary component. The contrast of chemical inhomogeneities ranges from 0.4 for Ti to 0.8 for Ba.

  • 27.
    Makaganiuk, Vitalii
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Kochukhov, Oleg
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Piskunov, Nikolai
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Jeffers, S. V.
    Johns-Krull, C. M.
    Keller, C. U.
    Rodenhuis, M.
    Snik, F.
    Stempels, H. C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Valenti, Jeff A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    The search for magnetic fields in mercury-manganese stars2011In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 525, p. A97-Article in journal (Refereed)
    Abstract [en]

    Context. A subclass of the upper main-sequence chemically peculiar stars, mercury-manganese (HgMn) stars were traditionally considered to be non-magnetic, showing no evidence of variability in their spectral line profiles. However, discoveries of chemical inhomogeneities on their surfaces imply that this assumption should be investigated. In particular, spectroscopic time-series of AR Aur, a And, and five other HgMn stars indicate the presence of chemical spots. At the same time, no signatures of global magnetic fields have been detected. Aims. We attempt to understand the physical mechanism that causes the formation of chemical spots in HgMn stars and gain insight into the potential magnetic field properties at their surfaces; we performed a highly sensitive search for magnetic fields for a large set of HgMn stars. Methods. With the aid of a new polarimeter attached to the HARPS spectrometer at the ESO 3.6 m-telescope, we obtained high-quality circular polarization spectra of 41 single and double HgMn stars. Using a multi-line analysis technique on each star, we co-added information from hundreds of spectral lines to ensure significantly greater sensitivity to the presence of magnetic fields, including very weak fields. Results. For the 47 individual objects studied, including six components of SB2 systems, we do not detect any magnetic fields at greater than the 3 sigma level. The lack of detection in the circular polarization profiles indicates that if strong fields are present on these stars, they must have complex surface topologies. For simple global fields, our detection limits imply upper limits to the fields present of 2-10 Gauss in the best cases. Conclusions. We conclude that HgMn stars lack large-scale magnetic fields, which is typical of spotted magnetic Ap stars, of sufficient strength to form and sustain the chemical spots observed on HgMn stars. Our study confirms that in addition to magnetically altered atomic diffusion, there exists another differentiation mechanism operating in the atmospheres of late-B main sequence stars that can produce compositional inhomogeneities on their surfaces.

  • 28.
    Makaganiuk, Vitalii
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Kochukhov, Oleg
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Piskunov, Nikolai
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Jeffers, Sandra
    Sterrekundig Instituut, Universiteit Utrecht.
    Johns-Krull, Chris
    Department of Physics and Astronomy, Rice University.
    Keller, Christoph
    Sterrekundig Instituut, Universiteit Utrecht.
    Rodenhuis, Michael
    Sterrekundig Instituut, Universiteit Utrecht.
    Snik, Frans
    Sterrekundig Instituut, Universiteit Utrecht.
    Stempels, Henricus C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Valenti, Jeff
    Space Telescope Science Institute.
    Magnetism, chemical spots, and stratification in the HgMn star ϕ Phoenicis2012In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 539, p. A142-Article in journal (Refereed)
    Abstract [en]

    Context. Mercury-manganese (HgMn) stars have been considered as non-magnetic and non-variable chemically peculiar (CP) starsfor a long time. However, recent discoveries of the variability in spectral line profiles have suggested an inhomogeneous surfacedistribution of chemical elements in some HgMn stars. From the studies of other CP stars it is known that magnetic field plays a keyrole in the formation of surface spots. All attempts to find magnetic fields in HgMn stars have yielded negative results.Aims. In this study, we investigate the possible presence of a magnetic field in ϕ Phe (HD 11753) and reconstruct surface distributionof chemical elements that show variability in spectral lines.We also test a hypothesis that a magnetic field is concentrated in chemicalspots and look into the possibility that some chemical elements are stratified with depth in the stellar atmosphere.Methods. Our analysis is based on high-quality spectropolarimetric time-series observations, covering a full rotational period ofthe star. Spectra were obtained with the HARPSpol at the ESO 3.6-m telescope. To increase the sensitivity of the magnetic fieldsearch, we employed the least-squares deconvolution (LSD) technique. Using Doppler imaging code INVERS10, we reconstructedsurface chemical distributions by utilising information from multiple spectral lines. The vertical stratification of chemical elementswas calculated with the DDAFit program.Results. Combining information from all suitable spectral lines, we set an upper limit of 4 G on the mean longitudinal magnetic field.For chemical spots, an upper limit on the longitudinal field varies between 8 and 15 G. We confirmed the variability of Y, Sr, and Tiand detected variability in Cr lines. Stratification analysis showed that Y and Ti are not concentrated in the uppermost atmosphericlayers.Conclusions. Our spectropolarimetric observations rule out the presence of a strong, globally-organised magnetic field in ϕ Phe.This implies an alternative mechanism of spot formation, which could be related to a non-equilibrium atomic diffusion. However, thetypical time scales of the variation in stratification predicted by the recent time-dependent diffusion models exceed significantly thespot evolution time-scale reported for ϕ Phe.

  • 29.
    Makaganiuk, Vitalii
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Kochukhov, Oleg
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Piskunov, Nikolai
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Jeffers, Sandra V.
    Johns-Krull, Christopher M.
    Keller, Christoph U.
    Rodenhuis, Michiel
    Snik, Frans
    Stempels, Henricus C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Valenti, Jeff A.
    The search for magnetic fields in mercury-manganese stars2011In: Active OB stars: Structure, evolution, mass-loss, and critical limits / [ed] Neiner, C. et al., 2011, Vol. 272, p. 202-203Conference paper (Refereed)
    Abstract [en]

    Mercury-manganese (HgMn) stars were considered to be non-magnetic, showing no evidence of surface spots. However, recent investigations revealed that some stars in this class possess an inhomogeneous distribution of chemical elements on their surfaces. According to our current understanding, the most probable mechanism of spot formation involves magnetic fields. Taking the advantage of a newly-built polarimeter attached to the HARPS spectrometer at the ESO 3.6m-telescope, we performed a high-precision spectropolarimetric survey of a large group of HgMn stars. The main purpose of this study was to find out how typical it is for HgMn stars to have weak magnetic fields. We report no magnetic field detection for any of the studied objects, with a typical precision of the longitudinal field measurements of 10 G and down to 1 Gauss for some of the stars. We conclude that HgMn stars lack large-scale magnetic fields typical of spotted magnetic Ap stars and probably lack any fields capable of creating and sustaining chemical spots. Our study confirms that alongside the magnetically altered atomic diffusion, there must be other structure formation mechanism operating in the atmospheres of late-B main sequence stars.

  • 30.
    Marconi, A.
    et al.
    Univ Florence, Dipartimento Fis & Astron, Via G Sansone 1, I-50019 Florence, Italy.;INAF Osservatorio Astrofis Arcetri, Largo E Fermi 2, I-50125 Florence, Italy..
    Di Marcantonio, P.
    INAF Osservatorio Astron Trieste, Via Giambattista Tiepolo 11, I-34131 Trieste, Italy..
    D'Odorico, V.
    INAF Osservatorio Astron Trieste, Via Giambattista Tiepolo 11, I-34131 Trieste, Italy..
    Cristiani, S.
    INAF Osservatorio Astron Trieste, Via Giambattista Tiepolo 11, I-34131 Trieste, Italy.;Natl Inst Nucl Phys, INFN, Via Valerio 2, I-34127 Trieste, Italy..
    Maiolino, R.
    Univ Cambridge, Cavendish Lab, JJ Thomson Ave, Cambridge CB3 0HE, England..
    Oliva, E.
    INAF Osservatorio Astrofis Arcetri, Largo E Fermi 2, I-50125 Florence, Italy..
    Origlia, L.
    INAF Osservatorio Astron Bologna, Via Ranzani,1, I-40127 Bologna, Italy..
    Riva, M.
    INAF Osservatorio Astron Brera, Via Bianchi 46, I-23807 Merate, Italy..
    Valenziano, L.
    INAF IASF Bologna, V Piero Gobetti,101, I-40129 Bologna, Italy..
    Zerbi, F. M.
    INAF, Sci Directorate, Viale Parco Mellini 84, I-00036 Rome, Italy..
    Abreu, M.
    Univ Lisbon, Inst Astrofis & Ciencias Espaco, Campus Lumiar Estrada Paco Lumiar 22,Edif D, P-1649038 Lisbon, Portugal.;Univ Porto, Inst Astrofis & Ciencias Espaco, Fac Ciencias, Campo Grande, P-1749016 Oporto, Portugal..
    Adibekyan, V.
    Univ Porto, Inst Astrofis & Ciencias Espaco, CAUP, Rua Estrelas, P-4150762 Oporto, Portugal..
    Allende Prieto, C.
    IAC, C Via Lactea,S-N, E-38205 San Cristobal la Laguna, Tenerife, Spain..
    Amado, P. J.
    CSIC, Inst Astrofis Andalucia, Glorieta Astron S-N, Granada 18008, Spain..
    Benz, W.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland..
    Boisse, I.
    CNRS, Lab Astrophys Marseille, Rue Frederic Joliot Curie, F-13013 Marseille, France..
    Bonfils, X.
    Univ Grenoble, Observ Sci, Grenoble, France..
    Bouchy, F.
    CNRS, Lab Astrophys Marseille, Rue Frederic Joliot Curie, F-13013 Marseille, France.;Univ Geneva, Dept Astron, Chem Maillettes 51, CH-1290 Sauverny, Versoix, Switzerland..
    Buchhave, L.
    Univ Copenhagen, Ctr Star & Planet Format, Oster Voldgade 5-7, DK-1350 Copenhagen, Denmark..
    Buscher, D.
    Univ Cambridge, Cavendish Lab, JJ Thomson Ave, Cambridge CB3 0HE, England..
    Cabral, A.
    Univ Lisbon, Inst Astrofis & Ciencias Espaco, Campus Lumiar Estrada Paco Lumiar 22,Edif D, P-1649038 Lisbon, Portugal.;Univ Porto, Inst Astrofis & Ciencias Espaco, Fac Ciencias, Campo Grande, P-1749016 Oporto, Portugal..
    Canto Martins, B. L.
    Univ Fed Rio Grande do Norte, Board Observat Astron, Campus Univ, BR-59078970 Natal, RN, Brazil..
    Chiavassa, A.
    Univ Cote Azur, Lab Lagrange, Observ Cote Azur, CNRS, Blvd Observ CS34229, F-06004 Nice 4, France..
    Coelho, J.
    Univ Lisbon, Inst Astrofis & Ciencias Espaco, Campus Lumiar Estrada Paco Lumiar 22,Edif D, P-1649038 Lisbon, Portugal.;Univ Porto, Inst Astrofis & Ciencias Espaco, Fac Ciencias, Campo Grande, P-1749016 Oporto, Portugal..
    Christensen, L. B.
    Dark Cosmol Ctr, Juliane Manes Vej 30, DK-2100 Copenhagen, Denmark..
    Delgado-Mena, E.
    Univ Porto, Inst Astrofis & Ciencias Espaco, CAUP, Rua Estrelas, P-4150762 Oporto, Portugal..
    De Medeiros, J. R.
    Univ Fed Rio Grande do Norte, Board Observat Astron, Campus Univ, BR-59078970 Natal, RN, Brazil..
    Di Varano, I.
    Leibniz Inst Astrophys Potsdam AIP, An Sternwarte 16, D-14482 Potsdam, Germany..
    Figueirall, P.
    Univ Porto, Inst Astrofis & Ciencias Espaco, CAUP, Rua Estrelas, P-4150762 Oporto, Portugal..
    Fisher, M.
    Univ Cambridge, Cavendish Lab, JJ Thomson Ave, Cambridge CB3 0HE, England..
    Fynbo, J. P. U.
    Dark Cosmol Ctr, Juliane Manes Vej 30, DK-2100 Copenhagen, Denmark..
    Glasse, A. C. H.
    UK Astron Technol Ctr, Sci & Technol Facil Council, Blackford Hill, Edinburgh EH9 3HJ, Midlothian, Scotland..
    Haehnelt, M.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0JA, England..
    Haniff, C.
    Univ Cambridge, Cavendish Lab, JJ Thomson Ave, Cambridge CB3 0HE, England..
    Hansen, C. J.
    Dark Cosmol Ctr, Juliane Manes Vej 30, DK-2100 Copenhagen, Denmark..
    Hatzes, A.
    Thuringer Landessternwarte, Sternwarte 5, D-07778 Tautenburg, Germany..
    Huke, P.
    Univ Gottingen, Inst Astrophys, Friedrich Hund Pl 1, D-37077 Gottingen, Germany..
    Korn, Andreas J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
    Leao, I. C.
    Univ Fed Rio Grande do Norte, Board Observat Astron, Campus Univ, BR-59078970 Natal, RN, Brazil..
    Liske, J.
    Univ Hamburg, Hamburger Sternwarte, Gojenbergsweg 112, D-21029 Hamburg, Germany..
    Lovis, C.
    Univ Geneva, Dept Astron, Chem Maillettes 51, CH-1290 Sauverny, Versoix, Switzerland..
    Maslowski, P.
    Nicolaus Copernicus Univ Torun, Fac Phys Astron & Appl Informat, Gagarina 11, PL-87100 Torun, Poland..
    Matute, I.
    Univ Lisbon, OAL, Inst Astrofis & Ciencias Espaco, P-1349018 Lisbon, Portugal..
    McCracken, R. A.
    Heriot Watt Univ, Sch Engn & Phys Sci, Inst Photon & Quantum Sci, SUPA, Edinburgh EH14 4AS, Midlothian, Scotland..
    Martins, C. J. A. P.
    Univ Porto, Inst Astrofis & Ciencias Espaco, CAUP, Rua Estrelas, P-4150762 Oporto, Portugal..
    Monteiro, M. J. P. F. G.
    Univ Porto, Inst Astrofis & Ciencias Espaco, CAUP, Rua Estrelas, P-4150762 Oporto, Portugal.;Univ Porto, Fac Ciencias, Dept Fis & Astron, Rua Campo Alegre, P-4169007 Oporto, Portugal..
    Morris, S.
    Univ Durham, Dept Phys, Ctr Adv Instrumentat, South Rd, Durham DH1 3LE, England..
    Morris, T.
    Univ Durham, Dept Phys, Ctr Adv Instrumentat, South Rd, Durham DH1 3LE, England..
    Nicklas, H.
    Univ Gottingen, Inst Astrophys, Friedrich Hund Pl 1, D-37077 Gottingen, Germany..
    Niedzielski, A.
    Nicolaus Copernicus Univ Torun, Fac Phys Astron & Appl Informat, Gagarina 11, PL-87100 Torun, Poland..
    Nunes, N. J.
    Univ Porto, Inst Astrofis & Ciencias Espaco, Fac Ciencias, Campo Grande, P-1749016 Oporto, Portugal..
    Palle, E.
    IAC, C Via Lactea,S-N, E-38205 San Cristobal la Laguna, Tenerife, Spain..
    Parr-Burman, P.
    UK Astron Technol Ctr, Sci & Technol Facil Council, Blackford Hill, Edinburgh EH9 3HJ, Midlothian, Scotland..
    Parro, V.
    Inst Maud Tecnol, 1 Maud, BR-09580900 Sao Caetano do Sul, SP, Brazil..
    Parry, I.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0JA, England..
    Pepe, F.
    Univ Geneva, Dept Astron, Chem Maillettes 51, CH-1290 Sauverny, Versoix, Switzerland..
    Piskunov, Nikolai
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Queloz, D.
    Univ Cambridge, Cavendish Lab, JJ Thomson Ave, Cambridge CB3 0HE, England..
    Quirrenbach, A.
    Heidelberg Univ, Zentrum Astron, Landessternwarte, Konigstuhl 12, D-69117 Heidelberg, Germany..
    Rebolo Lopez, R.
    IAC, C Via Lactea,S-N, E-38205 San Cristobal la Laguna, Tenerife, Spain..
    Reiners, A.
    Univ Gottingen, Inst Astrophys, Friedrich Hund Pl 1, D-37077 Gottingen, Germany..
    Reid, D. T.
    Heriot Watt Univ, Sch Engn & Phys Sci, Inst Photon & Quantum Sci, SUPA, Edinburgh EH14 4AS, Midlothian, Scotland..
    Santos, N.
    Univ Porto, Inst Astrofis & Ciencias Espaco, CAUP, Rua Estrelas, P-4150762 Oporto, Portugal.;Univ Porto, Fac Ciencias, Dept Fis & Astron, Rua Campo Alegre, P-4169007 Oporto, Portugal..
    Seifert, W.
    Heidelberg Univ, Zentrum Astron, Landessternwarte, Konigstuhl 12, D-69117 Heidelberg, Germany..
    Sousa, S.
    Univ Porto, Inst Astrofis & Ciencias Espaco, CAUP, Rua Estrelas, P-4150762 Oporto, Portugal..
    Stempels, Eric H.C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Strassmeier, K.
    Leibniz Inst Astrophys Potsdam AIP, An Sternwarte 16, D-14482 Potsdam, Germany..
    Sun, X.
    Univ Cambridge, Cavendish Lab, JJ Thomson Ave, Cambridge CB3 0HE, England..
    Udry, S.
    Univ Geneva, Dept Astron, Chem Maillettes 51, CH-1290 Sauverny, Versoix, Switzerland..
    Vanzi, L.
    Pontificia Univ Catolica Chile, Ctr Astro Ingn, Avda Libertador Bernardo OHiggins 340, Santiago, Chile..
    Vestergaard, M.
    Dark Cosmol Ctr, Juliane Manes Vej 30, DK-2100 Copenhagen, Denmark..
    Weber, M.
    Leibniz Inst Astrophys Potsdam AIP, An Sternwarte 16, D-14482 Potsdam, Germany..
    Zackrisson, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    EELT-HIRES the high-resolution spectrograph for the E-ELT2016In: GROUND-BASED AND AIRBORNE INSTRUMENTATION FOR ASTRONOMY VI / [ed] Christopher J Evans, 2016, Vol. 9908, article id UNSP 990823Conference paper (Refereed)
    Abstract [en]

    The first generation of E-ELT instruments will include an optical infrared High Resolution Spectrograph, conventionally indicated as EELT-HIRES, which will be capable of providing unique breakthroughs in the fields of exoplanets, star and planet formation, physics and evolution of stars and galaxies, cosmology and fundamental physics. A 2-year long phase A study for EELT-HIRES has just started and will be performed by a consortium composed of institutes and organisations from Brazil, Chile, Denmark, France, Germany, Italy, Poland, Portugal, Spain, Sweden, Switzerland and United Kingdom. In this paper we describe the science goals and the preliminary technical concept for EELT-HIRES which will be developed during the phase A, as well as its planned development and consortium organisation during the study.

  • 31. Oliva, E.
    et al.
    Tozzi, A.
    Ferruzzi, D.
    Origlia, L.
    Hatzes, A.
    Follert, R.
    Loewinger, T.
    Piskunov, Nikolai
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Heiter, Ulrike
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Lockhart, Matthew
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Marquart, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Stempels, Eric
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Reiners, A.
    Anglada-Escude, G.
    Seemann, U.
    Dorn, R. J.
    Bristow, P.
    Baade, D.
    Delabre, B.
    Gojak, D.
    Grunhut, J.
    Klein, B.
    Hilker, M.
    Ives, D. J.
    Jung, Y.
    Kaeufl, H. U.
    Kerber, F.
    Lizon, J. L.
    Pasquini, L.
    Paufique, J.
    Pozna, E.
    Smette, A.
    Smoker, J.
    Valenti, E.
    Concept and optical design of the cross-disperser module for CRIRES+2014In: GROUND-BASED AND AIRBORNE INSTRUMENTATION FOR ASTRONOMY V, 2014, Vol. 9147, article id 91477RConference paper (Refereed)
    Abstract [en]

    CRIRES, the ESO high resolution infrared spectrometer, is a unique instrument which allows astronomers to access a parameter space which up to now was largely uncharted. In its current setup, it consists of a single-order spectrograph providing long-slit, single-order spectroscopy with resolving power up to R=100,000 over a quite narrow spectral range. This has resulted in sub-optimal efficiency and use of telescope time for all the scientific programs requiring broad spectral coverage of compact objects (e.g. chemical abundances of stars and intergalactic medium, search and characterization of extra-solar planets). To overcome these limitations, a consortium was set-up for upgrading CRIRES to a cross-dispersed spectrometer, called CRIRES+. This paper presents the updated optical design of the cross-dispersion module for CRIRES+. This new module can be mounted in place of the current pre-disperser unit. The new system yields a factor of >10 increase in simultaneous spectral coverage and maintains a quite long slit (10"), ideal for observations of extended sources and for precise sky-background subtraction.

  • 32. Petrov, P. P.
    et al.
    Gahm, G. F.
    Stempels, Henricus C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Walter, F. M.
    Artemenko, S. A.
    Accretion-powered chromospheres in classical T Tauri stars2011In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 535, p. A6-Article in journal (Refereed)
    Abstract [en]

    Context. Optical spectra of classical T Tauri stars (cTTS) are rich in emission lines of low-excitation species that are composed of narrow and broad components, which indicates the existence of two emitting regions with different kinematics, densities, and temperatures. The photospheric spectrum is often veiled by an excess continuous emission. This veiling is usually attributed to radiation from a heated region beneath the accretion shock. The broad emission lines of H I, He II, Ca II, Fe II, and other species are thought to form in a larger volume of gas.

    Aims. The aim of this research is to clarify the nature of the veiling, and whether the narrow chromospheric lines of Fe I and other metals represent a standard chromosphere of a late-type star, or are induced by mass accretion.

    Methods. We carried out high-resolution spectroscopy of selected cTTS with a special focus on DR Tauri and followed variations of chromospheric features, such as narrow Fe I emission lines, and accretion signatures such as the veiling continuum and the He II line emission.

    Results. We found that the amount of veiling in DR Tau varies from practically nothing to factors more than 10 times the stellar continuum intensity, and that the veiling is caused by both a non-photospheric continuum and chromospheric line emission filling in the photospheric absorption lines. The latter causes differential veiling because stronger lines are more veiled. We developed methods to separate the two sources of veiling. Several veiled T Tauri stars show a common effect: the radial velocities of photospheric and chromospheric lines vary in anti-phase. This is caused by an area with enhanced chromospheric emission, which is offset from the pole of rotation and is associated with the hot spot formed at the footprint of the magnetic funnel of mass accretion.

    Conclusions. The enhanced chromospheric emission in cTTS is linked not only to solar-like magnetic activity, but is powered to a greater extent by the accreting gas. We suggest that the area of enhanced chromospheric emission is induced by mass accretion, which modifies the local structure of stellar atmosphere in an area that is more extended than the hot accretion spot. The narrow emission lines from this extended area are responsible for the extra component in the veiling through line-filling of photospheric absorption lines.

  • 33.
    Pettersson, Bertil
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics, Observational Astronomy.
    Stempels, Eric
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics, Observational Astronomy.
    Piskunov, Nikolai
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics, Observational Astronomy.
    A Fiber-Linked Four Stokes-Parameter Polarimeter for the SOFIN Spectrometer on the Nordic Optical Telescope1998In: Fiber Optics in Astronomy III, 1998, p. 343-Conference paper (Refereed)
  • 34.
    Piskunov, Nikolai
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Snik, F.
    Dolgopolov, A.
    Kochukhov, Oleg
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Rodenhuis, M.
    Valenti, J.
    Jeffers, S.
    Makaganiuk, Vitalii
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Johns-Krull, C.
    Stempels, Eric
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Keller, C.
    HARPSpol - The New Polarimetric Mode for HARPS2011In: The Messenger, Vol. 143, p. 7-10Article in journal (Other academic)
    Abstract [en]

    The HARPS spectrograph can now perform a full polarisation analysis of spectra. It has been equipped with a polarimetric unit, HARPSpol, which was jointly designed and produced by Uppsala, Utrecht and Rice Universities and by the STScI. Here we present the new instrument, demonstrate its polarisation capabilities and show the first scientific results.

  • 35. Rosenfeld, K. A.
    et al.
    Andrews, S. M.
    Wilner, D. J.
    Stempels, H. C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    A disk-based dynamical mass estimate for the young binary V4046 Sgr2012In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 759, no 2, p. 119-Article in journal (Refereed)
    Abstract [en]

    We present sensitive, arcsecond-resolution Submillimeter Array observations of the 12CO J = 2-1 line emission from the circumstellar disk orbiting the double-lined spectroscopic binary star V4046 Sgr. Based on a simple model of the disk structure, we use a novel Monte Carlo Markov Chain technique to extract the Keplerian velocity field of the disk from these data and estimate the total mass of the central binary. Assuming the distance inferred from kinematic parallax measurements in the literature (d 73pc), we determine a total stellar mass M * = 1.75 +0.09 0.06 M and a disk inclination i d = 335 +0.7 1.4 from face-on. These measurements are in excellent agreement with independent dynamical constraints made from multi-epoch monitoring of the stellar radial velocities, confirming the absolute accuracy of this precise (few percent uncertainties) disk-based method for estimating stellar masses and reaffirming previous assertions that the disk and binary orbital planes are well aligned (with |i d - i *| 01 ± 1°). Using these results as a reference, we demonstrate that various pre-main-sequence evolution models make consistent and accurate predictions for the masses of the individual components of the binary, and uniformly imply an advanced age of 5-30Myr. Taken together, these results verify that V4046 Sgr is one of the precious few nearby and relatively evolved pre-main-sequence systems that still hosts a gas-rich accretion disk.

  • 36.
    Rusomarov, Naum
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Kochukhov, Oleg
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Piskunov, Nikolai
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Jeffers, S. V.
    Johns-Krull, C. M.
    Keller, C. U.
    Makaganiuk, V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Rodenhuis, M.
    Snik, F.
    Stempels, Eric H. C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Valenti, J. A.
    Three-dimensional magnetic and abundance mapping of the cool Ap star HD 24712: I. Spectropolarimetric observations in all four Stokes parameters2013In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 558, p. A8-Article in journal (Refereed)
    Abstract [en]

    Context. High-resolution spectropolarimetric observations provide simultaneous information about stellar magnetic field topologies and three-dimensional distributions of chemical elements. High-quality spectra in the Stokes IQUV parameters are currently available for very few early-type magnetic chemically peculiar stars. Here we present analysis of a unique full Stokes vector spectropolarimetric data set, acquired for the cool magnetic Ap star HD 24712 with a recently commissioned spectropolarimeter. Aims. The goal of our work is to examine the circular and linear polarization signatures inside spectral lines and to study variation of the stellar spectrum and magnetic observables as a function of rotational phase. Methods. HD 24712 was observed with the HARPSpol instrument at the 3.6-m ESO telescope over a period of 2010-2011. We achieved full rotational phase coverage with 43 individual Stokes parameter observations. The resulting spectra have a signal-to-noise ratio of 300600 and resolving power exceeding 10(5). The multiline technique of least-squares deconvolution (LSD) was applied to combine information from the spectral lines of Fe-peak and rare earth elements. Results. We used the HARPSPol spectra of HD 24712 to study the morphology of the Stokes profile shapes in individual spectral lines and in LSD Stokes profiles corresponding to different line masks. From the LSD Stokes V profiles we measured the longitudinal component of the magnetic field, < Bz >, with an accuracy of 510 G. We also determined the net linear polarization from the LSD Stokes Q and U profiles. Combining previous < Bz > measurements with our data allowed us to determine an improved rotational period of the star, P-rot = 12.45812 +/- 0.00019 d. We also measured the longitudinal magnetic field from the cores of H alpha and H beta lines. The analysis of < Bz > measurements showed no evidence for a significant radial magnetic field gradient in the atmosphere of HD 24712. We used our < Bz > and net linear polarization measurements to determine parameters of the dipolar magnetic field topology. We found that magnetic observables can be reasonably well reproduced by the dipolar model, although significant discrepancies remain at certain rotational phases. We discovered rotational modulation of the H alpha core and related it to a non-uniform surface distribution of rare earth elements.

  • 37. Ryabchikova, T. A.
    et al.
    Piskunov, Nikolai
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics, Observational Astronomy.
    Stempels, H. C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics, The Uppsala Astronomical Observatory.
    Kupka, F.
    Weiss, W. W.
    The Vienna Atomic Line Data Base - a status report1999In: Physica scripta. T, ISSN 0281-1847, Vol. T83, p. 162-173Article in journal (Refereed)
  • 38. Ryabchikova, T.
    et al.
    Piskunov, Nikolai
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Kurucz, R. L.
    Stempels, Eric H. C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Heiter, Ulrike
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Pakhomov, Yu
    Barklem, Paul S.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    A major upgrade of the VALD database2015In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 90, no 5, article id 054005Article in journal (Refereed)
    Abstract [en]

    Vienna atomic line database (VALD) is a collection of critically evaluated laboratory parameters for individual atomic transitions, complemented by theoretical calculations. VALD is actively used by astronomers for stellar spectroscopic studies-model atmosphere calculations, atmospheric parameter determinations, abundance analysis etc. The two first VALD releases contained parameters for atomic transitions only. In a major upgrade of VALD-VALD3, publically available from spring 2014, atomic data was complemented with parameters of molecular lines. The diatomic molecules C-2, CH, CN, CO, OH, MgH, SiH, TiO are now included. For each transition VALD provides species name, wavelength, energy, quantum number J and Lande-factor of the lower and upper levels, radiative, Stark and van der Waals damping factors and a full description of electronic configurarion and term information of both levels. Compared to the previous versions we have revised and verify all of the existing data and added new measurements and calculations for transitions in the range between 20 angstrom and 200 microns. All transitions were complemented with term designations in a consistent way and electron configurations when available. All data were checked for consistency: listed wavelength versus Ritz, selection rules etc. A new bibliographic system keeps track of literature references for each parameter in a given transition throughout the merging process so that every selected data entry can be traced to the original source. The query language and the extraction tools can now handle various units, vacuum and air wavelengths. In the upgrade process we had an intensive interaction with data producers, which was very helpful for improving the quality of the VALD content.

  • 39. Seemann, U.
    et al.
    Anglada-Escude, G.
    Baade, D.
    Bristow, P.
    Dorn, R. J.
    Follert, R.
    Gojak, D.
    Grunhut, J.
    Hatzes, A. P.
    Heiter, Ulrike
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Ives, D. J.
    Jeep, P.
    Jung, Y.
    Kaeufl, H. -U
    Kerber, F.
    Klein, B.
    Lizon, J. -L
    Lockhart, M.
    Loewinger, T.
    Marquart, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Oliva, E.
    Paufique, J.
    Piskunov, Nikolai
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Pozna, E.
    Reiners, A.
    Smette, A.
    Smoker, J.
    Stempels, Eric
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Valenti, E.
    Wavelength calibration from 1-5 mu m for the CRIRES plus high-resolution spectrograph at the VLT2014In: GROUND-BASED AND AIRBORNE INSTRUMENTATION FOR ASTRONOMY V, 2014, Vol. 9147, article id 91475GConference paper (Refereed)
    Abstract [en]

    CRIRES at the VLT is one of the few adaptive optics enabled instruments that offer a resolving power of 10 5 from 1 - 5 mu m. An instrument upgrade (CRIRES+) is proposed to implement cross-dispersion capabilities, spectro-polarimetry modes, a new detector mosaic, and a new gas absorption cell. CRIRES+ will boost the simultaneous wavelength coverage of the current instrument (similar to lambda/70 in a single-order) by a factor of greater than or similar to 10 in the cross-dispersed configuration, while still retaining a 10 arcsec slit suitable for long-slit spectroscopy. CRIRES+ dramatically enhances the instrument's observing efficiency, and opens new scientific opportunities. These include high-precision radial-velocity studies on the 3m/s level to characterize extra-solar planets and their athmospheres, which demand for specialized, highly accurate wavelength calibration techniques. In this paper, we present a newly developed absorption gas-cell to enable high-precision wavelength calibration for CRIRES+. We also discuss the strategies and developments to cover the full operational spectral range (1-5 mu m), employing hollow-cathode emission lamps, Fabry-Perot etalons, and absorption gas-cells.

  • 40. Simpson, E. K.
    et al.
    Barros, S. C. C.
    Brown, D. J. A.
    Cameron, A. Collier
    Pollacco, D.
    Skillen, I.
    Stempels, Henricus
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Boisse, I.
    Faedi, F.
    Hebrard, G.
    McCormac, J.
    Sorensen, P.
    Street, R. A.
    Anderson, D.
    Bento, J.
    Bouchy, F.
    Butters, O. W.
    Enoch, B.
    Haswell, C. A.
    Hebb, L.
    Hellier, C.
    Holmes, S.
    Horne, K.
    Keenan, F. P.
    Lister, T. A.
    Maxted, P. F. L.
    Miller, G. R. M.
    Moulds, V.
    Moutou, C.
    Norton, A. J.
    Parley, N.
    Santerne, A.
    Smalley, B.
    Smith, A. M. S.
    Todd, I.
    Watson, C. A.
    West, R. G.
    Wheatley, P. J.
    Independent Discovery of the Transiting Exoplanet HAT-P-14b2011In: Astronomical Journal, ISSN 0004-6256, E-ISSN 1538-3881, Vol. 141, no 5, p. 161-Article in journal (Refereed)
    Abstract [en]

    We present SuperWASP observations of HAT-P-14b, a hot Jupiter discovered by Torres et al. The planet was found independently by the SuperWASP team and named WASP-27b after follow-up observations had secured the discovery, but prior to the publication by Torres et al. Our analysis of HAT-P-14/WASP-27 is in good agreement with the values found by Torres et al. and we provide additional evidence against astronomical false positives. Due to the brightness of the host star, V-mag = 10, HAT-P-14b is an attractive candidate for further characterization observations. The planet has a high impact parameter and the primary transit is close to grazing. This could readily reveal small deviations in the orbital parameters indicating the presence of a third body in the system, which may be causing the small but significant orbital eccentricity. Our results suggest that the planet may undergo a grazing secondary eclipse. However, even a non-detection would tightly constrain the system parameters.

  • 41. Simpson, E. K.
    et al.
    Faedi, F.
    Barros, S. C. C.
    Brown, D. J. A.
    Cameron, A. Collier
    Hebb, L.
    Pollacco, D.
    Smalley, B.
    Todd, I.
    Butters, O. W.
    Hebrard, G.
    McCormac, J.
    Miller, G. R. M.
    Santerne, A.
    Street, R. A.
    Skillen, I.
    Triaud, A. H. M. J.
    Anderson, D. R.
    Bento, J.
    Boisse, I.
    Bouchy, F.
    Enoch, B.
    Haswell, C. A.
    Hellier, C.
    Holmes, S.
    Horne, K.
    Keenan, F. P.
    Lister, T. A.
    Maxted, P. F. L.
    Moulds, V.
    Moutou, C.
    Norton, A. J.
    Parley, N.
    Pepe, F.
    Queloz, D.
    Segransan, D.
    Smith, A. M. S.
    Stempels, H. C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Udry, S.
    Watson, C. A.
    West, R. G.
    Wheatley, P. J.
    WASP-37b: A 1.8 MJ exoplanet transiting a metal-poor star2011In: Astronomical Journal, ISSN 0004-6256, E-ISSN 1538-3881, Vol. 141, no 1, p. 8-Article in journal (Refereed)
    Abstract [en]

    We report on the discovery of WASP-37b, a transiting hot Jupiter orbiting an m(v) = 12.7 G2-type dwarf, with a period of 3.577469 +/- 0.000011 d, transit epoch T-0 = 2455338.6188 +/- 0.0006 (HJD; dates throughout the paper are given in Coordinated Universal Time (UTC)), and a transit duration 0.1304(-0.0017)(+0.0018) d. The planetary companion has a mass M-p = 1.80 +/- 0.17 M-J and radius R-p = 1.16(-0.06)(+0.07) R-J, yielding a mean density of 1.15(-0.15)(+0.12) rho(J). From a spectral analysis, we find that the host star has M-star = 0.925 +/- 0.120 M-circle dot, R-star = 1.003 +/- 0.053 R-circle dot, T-eff = 5800 +/- 150 K, and [Fe/H] = -0.40 +/- 0.12. WASP-37 is therefore one of the lowest metallicity stars to host a transiting planet.

  • 42. Simpson, E. K.
    et al.
    Pollacco, D.
    Cameron, A. Collier
    Hebrard, G.
    Anderson, D. R.
    Barros, S. C. C.
    Boisse, I.
    Bouchy, F.
    Faedi, F.
    Gillon, M.
    Hebb, L.
    Keenan, F. P.
    Miller, G. R. M.
    Moutou, C.
    Queloz, D.
    Skillen, I.
    Sorensen, P.
    Stempels, Henricus Cornelis
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Triaud, A.
    Watson, C. A.
    Wilson, P. A.
    The spin-orbit angles of the transiting exoplanets WASP-1b, WASP-24b, WASP-38b and HAT-P-8b from Rossiter-McLaughlin observations2011In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 414, no 4, p. 3023-3035Article in journal (Refereed)
    Abstract [en]

    We present observations of the Rossiter-McLaughlin effect for the transiting exoplanets WASP-1b, WASP-24b, WASP-38b and HAT-P-8b, and deduce the orientations of the planetary orbits with respect to the host stars' rotation axes. The planets WASP-24b, WASP-38b and HAT-P-8b appear to move in prograde orbits and be well aligned, having sky-projected spin-orbit angles consistent with zero: lambda = -4 degrees.7 +/- 4 degrees.0, 15 degrees(+43)(-33) and -9 degrees.7(-7.7)(+9.0), respectively. The host stars have T(eff) < 6250K and conform with the trend of cooler stars having low obliquities. WASP-38b is a massive planet on a moderately long period, eccentric orbit so may be expected to have a misaligned orbit given the high obliquities measured in similar systems. However, we find no evidence for a large spin-orbit angle. By contrast, WASP-1b joins the growing number of misaligned systems and has an almost polar orbit, lambda = -79 degrees.0(-4.3)(+4.5). It is neither very massive, eccentric nor orbiting a hot host star, and therefore does not share the properties of many other misaligned systems.

  • 43. Snik, F.
    et al.
    Kochukhov, Oleg
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Piskunov, Nikolai
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Rodenhuis, M.
    Jeffers, S.
    Keller, C.
    Dolgopolov, A.
    Stempels, Eric
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Makaganiuk, Vitalii
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Valenti, J.
    Johns-Krull, C.
    The HARPS Polarimeter2011In: Solar Polarization 6, 2011, Vol. 437Conference paper (Refereed)
    Abstract [en]

    We recently commissioned the polarimetric upgrade of the HARPS spectrograph at ESO’s 3.6-m telescope at La Silla, Chile. The HARPS polarimeter is capable of full Stokes spectropolarimetry with large sensitivity and accuracy, taking advantage of the large spectral resolution and stability of HARPS. In this paper we present the instrument design and its polarimetric performance. The first HARPSpol observations show that it can attain a polarimetric sensitivity of \tilde10$^-5$ (after addition of many lines) and that no significant instrumental polarization effects are present.

  • 44.
    Stempels, Eric H.C.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics.
    Piskunov, Nikolai
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics.
    The Photosphere and Veiling Spectrum of T Tauri Stars2003In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 408, no 2, p. 693-706Article in journal (Refereed)
    Abstract [en]

    Using recent high signal-to-noise and high spectral resolution ( ) observations with VLT/UVES, we have analysed the photosphere and veiling spectrum of five T Tauri stars. With a grid of 1-dimensional plane-parallel hydrostatic model atmospheres from the MARCS consortium we have determined their atmospheric properties, calculated synthetic spectra and determined the spectrum of the veiling continuum. Our analysis of the veiling spectrum supports the view that veiling can be represented by a combination of continuum sources. However, for the most strongly accreting stars we find a broad region around 5300 Å where the derived level of veiling is consistently higher than expected from continuum sources.

  • 45.
    Stempels, H.C.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics.
    Gahm, G.
    The close T Tauri binary V 4046 SagitariiManuscript (Other academic)
  • 46.
    Stempels, H.C.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics.
    Piskunov, N.
    Spectroscopy of T Tauri stars with UVES: Observations and analysis of RU Lup2002In: Astronomy & Astrophysics, ISSN 0004-6361, Vol. 391, no -, p. 595-608Article in journal (Refereed)
  • 47.
    Stempels, H.C.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics, Observational Astronomy.
    Piskunov, Nikolai
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics, Observational Astronomy.
    Probing Magnetospheric Infall onto CTTS with Time-resolved Veiling Measurements2003In: 12th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, 2003, p. 735-Conference paper (Other academic)
  • 48.
    Stempels, H.C.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics, Observational Astronomy.
    Piskunov, Nikolai
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics, Observational Astronomy.
    Spectroscopy of T Tauri stars with UVES. Observations and analysis of RU Lup2002In: Astronomy & Astrophysics, ISSN 0004-6361, Vol. 391, p. 595-Article in journal (Refereed)
  • 49.
    Stempels, H.C.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics, Observational Astronomy.
    Piskunov, Nikolai
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics, Observational Astronomy.
    Barklem, Paul
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics, Observational Astronomy.
    Recent Developments of the VALD Database2001In: 11th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun, 2001, p. 878-Conference paper (Other academic)
  • 50.
    Stempels, H.C.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics.
    von Rekowski, B.
    Piskunov, N.
    NLTE Calculations of Hydrogen Emission Lines in T Tauri StarsManuscript (Other academic)
12 1 - 50 of 57
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