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NEW FERMI-LAT EVENT RECONSTRUCTION REVEALS MORE HIGH-ENERGY GAMMA RAYS FROM GAMMA-RAY BURSTS
- Publication Year :
- 2013
-
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 ten GRBs previously detected by the 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 (LIV) tests, the prompt emission mechanism and the bulk Lorentz factor of the emitting region.<br />Comment: 6 pages, 2 figures, accepted by ApJ
- Subjects :
- Astrophysics::High Energy Astrophysical Phenomena
FOS: Physical sciences
Astrophysics
astroparticle physics
cosmology: observations
gamma rays: general
methods: data analysis
symbols.namesake
data analysis [methods]
Event reconstruction
High Energy Astrophysical Phenomena (astro-ph.HE)
Physics
GRB 080916C
Gamma ray
astroparticle physic
Astronomy and Astrophysics
Redshift
Lorentz factor
Extragalactic background light
Space and Planetary Science
symbols
Astrophysics - High Energy Astrophysical Phenomena
Gamma-ray burst
general [gamma rays]
observation [cosmology]
Fermi Gamma-ray Space Telescope
Subjects
Details
- Language :
- English
- Database :
- OpenAIRE
- Accession number :
- edsair.doi.dedup.....027c6e8152524eda8ab02e19ac1bf3b1