[vsnet-grb-info 6813] GRB 081024B: Fermi Gamma-ray Burst Monitor detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8408
SUBJECT: GRB 081024B:  Fermi Gamma-ray Burst Monitor detection
DATE:    08/10/25 19:00:20 GMT
FROM:    Valerie Connaughton at MSFC  <valerie at nasa.gov>

Valerie Connaughton and Michael Briggs (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:

"At 21:22:40.86 UT on 24 October 2008, the Fermi Gammay-Ray Burst
Monitor (GBM) triggered on GRB 081024B (trigger 246576161 /
081024.891). The calculated location is consistent with the
Fermi LAT-detected GRB reported by N. Omodei in GCN Circular 8407.

This GRB was about 800 ms long with 2 main peaks.  The first peak
lasted 200 ms and its spectrum is best fit using a power-law index
with an exponential cutoff.  The power-law index is -0.70 ± 0.13, and
the cutoff energy, parameterized as EPeak, is 1583 ± 520 keV. The
seond peak lasted 600 ms and is best fit by a power-law spectrum
with an index of -1.28 ± 0.04.

The fluence between 50 and 300 keV of this short burst is
3.4 ± 0.1 x 10-7 erg/cm2, with a peak flux measured over
a 64 ms timescale of of 4.2 ± 0.2 photons/cm2/sec.  Between
15 and 150 keV the 64 ms peak flux is 7.4 ± 0.4 photons/cm2/sec.

The analysis results presented above are preliminary and further
analysis is being performed; the final results will be published
in the GBM GRB Catalog."