[vsnet-grb-info 12366] GRB 120908A: Fermi GBM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  13741
SUBJECT: GRB 120908A: Fermi GBM detection
DATE:    12/09/10 18:08:47 GMT
FROM:    Sinead McGlynn at Excellence Cluster/TUM  <smcglynn at tum.de>

Sinead McGlynn (MPE/TUM)
reports on behalf of the Fermi GBM Team:

"At 22:31:00.02  UT on 08 September 2012, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 120908A (trigger 368836263/120908938). GBM was triggered over 4 minutes earlier than the bright X-ray source reported as a MAXI/GSC detection by Morii et al. (GCN 13731). 

The on-ground GBM location is consistent with the MAXI/GSC reported location. As a result, and due to the presence of extended soft emission in the GBM data at the time of the MAXI/GSC detection, we associate the GBM trigger with GRB 120908A.

The angle from the Fermi LAT boresight is 87 degrees.

The GBM light curve consists of two spiky pulses with a duration (T90) of about 66  s (50-300 keV).
The time-averaged spectrum from T0-5.38 s to T0+15.1 s is best fit by a power law function with an exponential
high-energy cutoff.  The power law index is -1.21 +/- 0.11 and the cutoff energy, parameterized as Epeak, is 205.9 +/- 43.1 keV. In addition, weak longer-lived soft emission is observed close to the MAXI trigger time (200-300s post GBM trigger) up to approximately 50 keV.

The event fluence (10-1000 keV) in this time interval is (1.7 +/- 0.2)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+6 s in the 10-1000 keV band is 2.7 +/- 0.2 ph/s/cm^2.

The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."