主要内容:
由于更新了光子重建的程序,导致伽马暴的LAT光子也要重新分析。
看来最可靠的LAT的结果得等他们的最终catalog了,鬼知道什么时候他们又重新reconstruction一把。
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文章信息:
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Title: |
| New Fermi-LAT Event Reconstruction Reveals More High-energy Gamma Rays from Gamma-Ray Bursts |
Authors: |
| Atwood, W. B.; Baldini, L.; Bregeon, J.; Bruel, P.; Chekhtman, A.; Cohen-Tanugi, J.; Drlica-Wagner, A.; Granot, J.; Longo, F.; Omodei, N.; Pesce-Rollins, M.; Razzaque, S.; Rochester, L. S.; Sgrò, C.; Tinivella, M.; Usher, T. L.; Zimmer, S. |
Affiliation: |
| AA(Santa
Cruz Institute for Particle Physics, Department of Physics and
Department of Astronomy and Astrophysics, University of California at
Santa Cruz, Santa Cruz, CA 95064, USA melissa.pesce.rollins@pi.infn.it), ... |
Publication: |
| The Astrophysical Journal, Volume 774, Issue 1, article id. 76, 6 pp. (2013). (ApJ Homepage) |
Publication Date: |
| 09/2013 |
Origin: |
| IOP |
Astronomy Keywords: |
| astroparticle physics, cosmology: observations, gamma rays: general, methods: data analysis |
DOI: |
| 10.1088/0004-637X/774/1/76 |
Bibliographic Code: |
| 2013ApJ...774...76A |
Abstract
Based on the experience gained during the four and a half years of the
mission, the Fermi-LAT Collaboration has undertaken a comprehensive
revision of the event-level analysis going under the name of Pass 8.
Although it is not yet finalized, we can test the improvements in the
new event reconstruction with the special case of the prompt phase of
bright gamma-ray bursts (GRBs), where the signal-to-noise ratio is large
enough that loose selection cuts are sufficient to identify gamma rays
associated with the source. Using the new event reconstruction, we have
re-analyzed 10 GRBs previously detected by the Large Area Telescope
(LAT) for which an X-ray/optical follow-up was possible and found four
new gamma rays with energies greater than 10 GeV in addition to the
seven previously known. Among these four is a 27.4 GeV gamma ray from
GRB 080916C, which has a redshift of 4.35, thus making it the gamma ray
with the highest intrinsic energy (~147 GeV) detected from a GRB. We
present here the salient aspects of the new event reconstruction and
discuss the scientific implications of these new high-energy gamma rays,
such as constraining extragalactic background light models, Lorentz
invariance violation tests, the prompt emission mechanism, and the bulk
Lorentz factor of the emitting region.
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