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Hallgren, Allan
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Publications (10 of 212) Show all publications
Aartsen, M. G., Ackermann, M., Adams, J., Aguilar, J. A., Ahlers, M., Ahrens, M., . . . Yuan, T. (2018). A Search for Neutrino Emission from Fast Radio Bursts with Six Years of IceCube Data. Astrophysical Journal, 857(2), Article ID 117.
Open this publication in new window or tab >>A Search for Neutrino Emission from Fast Radio Bursts with Six Years of IceCube Data
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2018 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 857, no 2, article id 117Article in journal (Refereed) Published
Abstract [en]

We present a search for coincidence between IceCube TeV neutrinos and fast radio bursts (FRBs). During the search period from 2010 May 31 to 2016 May 12, a total of 29 FRBs with 13 unique locations have been detected in the whole sky. An unbinned maximum likelihood method was used to search for spatial and temporal coincidence between neutrinos and FRBs in expanding time windows, in both the northern and southern hemispheres. No significant correlation was found in six years of IceCube data. Therefore, we set upper limits on neutrino fluence emitted by FRBs as a function of time window duration. We set the most stringent limit obtained to date on neutrino fluence from FRBs with an E-2 energy spectrum assumed, which is 0.0021 GeV cm(-2) per burst for emission timescales up to similar to 10(2) s from the northern hemisphere stacking search.

Keywords
astroparticle physics, cosmic rays, elementary particles, neutrinos, radiation mechanisms: non-thermal
National Category
Subatomic Physics Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:uu:diva-354962 (URN)10.3847/1538-4357/aab4f8 (DOI)000430745400007 ()
Funder
German Research Foundation (DFG)Swedish Research CouncilSwedish National Infrastructure for Computing (SNIC)Knut and Alice Wallenberg Foundation
Available from: 2018-06-25 Created: 2018-06-25 Last updated: 2018-06-25Bibliographically approved
Aartsen, M. G., Ackermann, M., Adams, J., Aguilar, J. A., Ahlers, M., Ahrens, M., . . . Zoll, M. (2018). Measurement of Atmospheric Neutrino Oscillations at 6-56 GeV with IceCube DeepCore. Physical Review Letters, 120(7), Article ID 071801.
Open this publication in new window or tab >>Measurement of Atmospheric Neutrino Oscillations at 6-56 GeV with IceCube DeepCore
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2018 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 120, no 7, article id 071801Article in journal (Refereed) Published
Abstract [en]

We present a measurement of the atmospheric neutrino oscillation parameters using three years of data from the IceCube Neutrino Observatory. The DeepCore infill array in the center of IceCube enables the detection and reconstruction of neutrinos produced by the interaction of cosmic rays in Earth's atmosphere at energies as low as similar to 5 GeV. That energy threshold permits measurements of muon neutrino disappearance, over a range of baselines up to the diameter of the Earth, probing the same range of L/E-v. as long-baseline experiments but with substantially higher- energy neutrinos. This analysis uses neutrinos from the full sky with reconstructed energies from 5.6 to 56 GeV. We measure Delta m(32)(2) = 2.31(-0.13)(+0.11) x 10(-3) eV(2) and sin(2) theta(23) = 0.51(- 0.09)(+0.07), assuming normal neutrino mass ordering. These results are consistent with, and of similar precision to, those from accelerator- and reactor-based experiments.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2018
National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-348112 (URN)10.1103/PhysRevLett.120.071801 (DOI)000424912000005 ()29542976 (PubMedID)
Funder
Swedish Research CouncilSwedish Polar Research SecretariatKnut and Alice Wallenberg FoundationSwedish National Infrastructure for Computing (SNIC)
Available from: 2018-04-12 Created: 2018-04-12 Last updated: 2018-04-12Bibliographically approved
Aartsen, M. G., Ackermann, M., Adams, J., Aguilar, J. A., Ahlers, M., Ahrens, M., . . . Sivakoff, G. R. (2018). Multimessenger observations of a flaring blazar coincident with high-energy neutrino IceCube-170922A. Science, 361(6398), Article ID eaat1378.
Open this publication in new window or tab >>Multimessenger observations of a flaring blazar coincident with high-energy neutrino IceCube-170922A
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2018 (English)In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 361, no 6398, article id eaat1378Article in journal (Refereed) Published
Abstract [en]

INTRODUCTION

Neutrinos are tracers of cosmic-ray acceleration: electrically neutral and traveling at nearly the speed of light, they can escape the densest environments and may be traced back to their source of origin. High-energy neutrinos are expected to be produced in blazars: intense extragalactic radio, optical, x-ray, and, in some cases, γ-ray sources characterized by relativistic jets of plasma pointing close to our line of sight. Blazars are among the most powerful objects in the Universe and are widely speculated to be sources of high-energy cosmic rays. These cosmic rays generate high-energy neutrinos and γ-rays, which are produced when the cosmic rays accelerated in the jet interact with nearby gas or photons. On 22 September 2017, the cubic-kilometer IceCube Neutrino Observatory detected a ~290-TeV neutrino from a direction consistent with the flaring γ-ray blazar TXS 0506+056. We report the details of this observation and the results of a multiwavelength follow-up campaign.

RATIONALE

Multimessenger astronomy aims for globally coordinated observations of cosmic rays, neutrinos, gravitational waves, and electromagnetic radiation across a broad range of wavelengths. The combination is expected to yield crucial information on the mechanisms energizing the most powerful astrophysical sources. That the production of neutrinos is accompanied by electromagnetic radiation from the source favors the chances of a multiwavelength identification. In particular, a measured association of high-energy neutrinos with a flaring source of γ-rays would elucidate the mechanisms and conditions for acceleration of the highest-energy cosmic rays. The discovery of an extraterrestrial diffuse flux of high-energy neutrinos, announced by IceCube in 2013, has characteristic properties that hint at contributions from extragalactic sources, although the individual sources remain as yet unidentified. Continuously monitoring the entire sky for astrophysical neutrinos, IceCube provides real-time triggers for observatories around the world measuring γ-rays, x-rays, optical, radio, and gravitational waves, allowing for the potential identification of even rapidly fading sources.

RESULTS

A high-energy neutrino-induced muon track was detected on 22 September 2017, automatically generating an alert that was distributed worldwide within 1 min of detection and prompted follow-up searches by telescopes over a broad range of wavelengths. On 28 September 2017, the Fermi Large Area Telescope Collaboration reported that the direction of the neutrino was coincident with a cataloged γ-ray source, 0.1° from the neutrino direction. The source, a blazar known as TXS 0506+056 at a measured redshift of 0.34, was in a flaring state at the time with enhanced γ-ray activity in the GeV range. Follow-up observations by imaging atmospheric Cherenkov telescopes, notably the Major Atmospheric Gamma Imaging Cherenkov (MAGIC) telescopes, revealed periods where the detected γ-ray flux from the blazar reached energies up to 400 GeV. Measurements of the source have also been completed at x-ray, optical, and radio wavelengths. We have investigated models associating neutrino and γ-ray production and find that correlation of the neutrino with the flare of TXS 0506+056 is statistically significant at the level of 3 standard deviations (sigma). On the basis of the redshift of TXS 0506+056, we derive constraints for the muon-neutrino luminosity for this source and find them to be similar to the luminosity observed in γ-rays.

CONCLUSION

The energies of the γ-rays and the neutrino indicate that blazar jets may accelerate cosmic rays to at least several PeV. The observed association of a high-energy neutrino with a blazar during a period of enhanced γ-ray emission suggests that blazars may indeed be one of the long-sought sources of very-high-energy cosmic rays, and hence responsible for a sizable fraction of the cosmic neutrino flux observed by IceCube.

National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:uu:diva-362010 (URN)10.1126/science.aat1378 (DOI)000438449200037 ()30002226 (PubMedID)
Funder
German Research Foundation (DFG)Swedish Research CouncilSwedish National Infrastructure for Computing (SNIC)Knut and Alice Wallenberg FoundationEU, Horizon 2020, 654215Swedish Polar Research Secretariat
Available from: 2018-10-04 Created: 2018-10-04 Last updated: 2018-10-04Bibliographically approved
Aartsen, M. G., Ackermann, M., Adams, J., Aguilar, J. A., Ahlers, M., Ahrens, M., . . . Yuan, T. (2018). Neutrino emission from the direction of the blazar TXS 0506+056 prior to the IceCube-170922A alert. Science, 361(6398), 147-151
Open this publication in new window or tab >>Neutrino emission from the direction of the blazar TXS 0506+056 prior to the IceCube-170922A alert