GRB 080825C
GCN Circular 8141
Subject
GRB080825C: GLAST Burst Monitor detection
Date
2008-08-27T03:38:23Z (17 years ago)
From
Alexander van der Horst at NASA/MSFC <avdhorst@science.uva.nl>
A.J. van der Horst (NASA/ORAU) and V. Connaughton (UAH) report on behalf
of the Fermi GBM Team:
"At 14:13:48 UT on 25 August 2008, the Fermi GBM triggered and located
GRB 080825C (trigger 241366429 / 080825.593).
The on-ground calculated location, using the GBM trigger data, is
RA = 232.2, Dec = -4.9 (J2000 degrees, equivalent to 15h 29m, -4d 54'),
with an uncertainty of 1.5 degrees (radius, 1-sigma containment,
statistical only; there is additionally a systematic error which is
currently estimated to be 2 to 3 degrees). The angle from the Fermi
LAT boresight is 60 degrees.
This GRB has several peaks, with T90 (50-300 keV) = 22 s and
T50 (50-300 keV) = 12 s. The time-averaged spectrum (8-910 keV)
from T0 to T0+22.1 s is best fit by a Band function with
Epeak = 155 +/- 5 keV, alpha = -0.39 +/- 0.04, and beta = -2.34 +/- 0.09.
The fluence (50-300 keV) is 2.4E-5 erg/cm^2.
The spectral analysis results presented above are preliminary; the final
results will be published in the GBM GRB Catalog."
GCN Circular 8183
Subject
GRB080825C: Fermi-LAT observations
Date
2008-09-05T17:45:46Z (17 years ago)
From
Aurelien Bouvier at Stanford <bouvier@stanford.edu>
A. Bouvier (SLAC), D. Band (GSFC), J. Bregeon (INFN Pisa), J. Chiang
(SLAC), S. Cutini (ASDC), B. Dingus (LANL), N. Gehrels (GSFC), Y.
Fukazawa (Hiroshima U), M. Hayashida (SLAC), F. Longo (INFN Trieste),
J. McEnery (GSFC), M. Ohno (JAXA), N. Omodei (INFN Pisa), V. Pelassa
(LPTA), F. Piron (LPTA), D. Sanchez (LLR), J. Scargle (NASA Ames), H.
Tajima (SLAC), T. Tanaka (SLAC), G. Thayer (SLAC) on behalf of the
Fermi LAT team:
We report a detection by the Fermi Large Area Telescope (LAT) of
emission from GRB080825C, which was triggered by the Fermi Gamma-ray
Burst Monitor (GBM) at 14:13:48 UT on August 25th 2008 (GCN 8141 by
Van der Horst et al.). The angle of the GBM best localization (ra,
dec=232.2,-4.6) with the LAT boresight was 60 deg at the time of the
trigger which is on the edge of our field of view.
The data from the Fermi LAT shows a significant increase in the event
rate within 10 degree of the GBM localization and up to 35 seconds
after the GBM trigger that is spatially and temporally correlated
with the GBM emission with a significance of more than 5 sigma. All
the LAT events detected during the GBM emission have energies below 1
GeV.
The best LAT on-ground localization is found to be
RA,DEC=233.96,-4.72 deg with a 90% containment radius of 1.5 deg
(statistical+systematics; 68% containment radius: 0.95 deg) which is
consistent with the GBM localization.
This circular is an official product of the Fermi LAT team.
GCN Circular 8184
Subject
GRB 080825C: Fermi GBM Spectral Analysis
Date
2008-09-05T18:01:27Z (17 years ago)
From
Alexander van der Horst at NASA/MSFC <avdhorst@science.uva.nl>
A.J. van der Horst (NASA/ORAU), V. Connaughton and M.S. Briggs (UAH)
report on behalf of the Fermi GBM Team:
"We have performed time-resolved spectroscopy of GRB 080825C (GCN 8141,
GCN 8183). The main emission up to 23 seconds is best fit by the Band
function. Time-resolved spectra of this emission period display the
commonly observed hard-to-soft spectral evolution, with Epeak decreasing
from 170 to 110 keV, while the spectral indices remain roughly constant
at alpha ~ -0.4 and beta ~ -2.4, consistent with the time-averaged
spectral result (GCN 8141).
Weaker emission following this period lasts a further 11 seconds and
deviates from this spectral behaviour. The spectrum of this tail over
the energy range 8-900 keV is best fit by a single power law with
index -1.41 +/- 0.09.
The spectral analysis results presented above are preliminary; the final
results will be published in the GBM GRB Catalog."