371 research outputs found
The origin of the optical flashes: The case study of GRB 080319B and GRB 130427A
Correlations between optical flashes and gamma-ray emissions in gamma-ray
bursts have been searched in order to clarify the question whether these
emissions occur at internal and/or external shocks. Among the most powerful
gamma-ray bursts ever recorded are GRB 080319B and GRB 130427A which at early
phase presented bright optical flashes possible correlated with -ray
components. Additionally, both bursts were fortuitously located within the
field of view of the TeV -ray Milagro and HAWC observatories, and
although no statistically significant excess of counts were collected, upper
limits were placed on the GeV - TeV emission. Considering the synchrotron
self-Compton emission from internal shocks and requiring the GeV-TeV upper
limits we found that the optical flashes and the -ray components are
produced by different electron populations. Analyzing the optical flashes
together the multiwavelength afterglow observation, we found that these flashes
can be interpreted in the framework of the synchrotron reverse-shock model when
outflows have arbitrary magnetizations.Comment: 9 pages, 5 figures and 4 tables. Accepted for publication in Ap
Study of TeV variability of Mrk 421 from 3 years of monitoring with the Milagro Observatory
The Milagro experiment was a TeV gamma-ray observatory designed to
continuously monitor the overhead sky in the 0.1-100 TeV energy range. It
operated from 2000 and 2008 and was characterized by a large field of view
( 2 sr) and a high duty cycle ( 90). Here we report on the
long-term monitoring of the blazar Mrk 421 with Milagro over the period from
September 21, 2005 to March 15, 2008. We present a study of the TeV variability
of the source and provide upper limits for the measured flux for different time
scales, ranging from one week up to one year.Comment: 3 pages, 2 figures. Paper to appear in the Proceedings of the
Thirteen Marcel Grossmann Meeting, held in Stockholm, Sweden, on July 2012,
World Scientific, Singapore, in pres
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