CONSTRAINING THE HIGH-ENERGY EMISSION FROM GAMMA-RAY BURSTS WITH FERMI

Simple item page
dc.citation.firstpage121en_US
dc.citation.journalTitleThe Astrophysical Journalen_US
dc.citation.lastpage141en_US
dc.citation.volumeNumber754en_US
dc.contributor.authorBaring, M.G.en_US
dc.contributor.authorThe Fermi Large Area Telescope Teamen_US
dc.date.accessioned2013-03-13T18:53:15Zen_US
dc.date.available2014-03-19T05:10:03Zen_US
dc.date.issued2012en_US
dc.description.abstractWe examine 288 gamma-ray bursts (GRBs) detected by the Fermi Gamma-ray Space Telescope’s Gamma-ray Burst Monitor (GBM) that fell within the field of view of Fermi’s Large Area Telescope (LAT) during the first 2.5 years of observations, which showed no evidence for emission above 100 MeV.We report the photon flux upper limits in the 0.1–10 GeV range during the prompt emission phase as well as for fixed 30 s and 100 s integrations starting from the trigger time for each burst.We compare these limits with the fluxes that would be expected from extrapolations of spectral fits presented in the first GBM spectral catalog and infer that roughly half of the GBM-detected bursts either require spectral breaks between the GBM and LAT energy bands or have intrinsically steeper spectra above the peak of the νFν spectra (Epk). In order to distinguish between these two scenarios, we perform joint GBM and LAT spectral fits to the 30 brightest GBM-detected bursts and find that a majority of these bursts are indeed softer above Epk than would be inferred from fitting the GBM data alone. Approximately 20% of this spectroscopic subsample show statistically significant evidence for a cutoff in their high-energy spectra, which if assumed to be due to γγ attenuation, places limits on the maximum Lorentz factor associated with the relativistic outflow producing this emission. All of these latter bursts have maximum Lorentz factor estimates that are well below the minimum Lorentz factors calculated for LAT-detected GRBs, revealing a wide distribution in the bulk Lorentz factor of GRB outflows and indicating that LAT-detected bursts may represent the high end of this distribution.en_US
dc.embargo.terms1 yearen_US
dc.identifier.citationBaring, M.G. and The Fermi Large Area Telescope Team. "CONSTRAINING THE HIGH-ENERGY EMISSION FROM GAMMA-RAY BURSTS WITH FERMI." <i>The Astrophysical Journal,</i> 754, (2012) The American Astronomical Society: 121-141. http://dx.doi.org/10.1088/0004-637X/754/2/121.en_US
dc.identifier.doihttp://dx.doi.org/10.1088/0004-637X/754/2/121en_US
dc.identifier.urihttps://hdl.handle.net/1911/70565en_US
dc.language.isoengen_US
dc.publisherThe American Astronomical Societyen_US
dc.rightsArticle is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.en_US
dc.subject.keywordgamma-ray bursten_US
dc.subject.keywordgeneral – gamma raysen_US
dc.subject.keywordgeneralen_US
dc.titleCONSTRAINING THE HIGH-ENERGY EMISSION FROM GAMMA-RAY BURSTS WITH FERMIen_US
dc.typeJournal articleen_US
dc.type.dcmiTexten_US
dc.type.publicationpublisher versionen_US
Files
Original bundle
Now showing 1 - 1 of 1
Thumbnail Image
Name:
CONSTRAINING-HIGH-ENERGY.pdf
Size:
1.91 MB
Format:
Adobe Portable Document Format
Download
License bundle
Now showing 1 - 1 of 1
No Thumbnail Available
Name:
license.txt
Size:
1.61 KB
Format:
Item-specific license agreed upon to submission
Description:
Download
Collections
Physics and Astronomy Publications
Faculty Publications