[vsnet-grb-info 13947] GRB 130925A: Fermi GBM Detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  15261
SUBJECT: GRB 130925A: Fermi GBM Detection
DATE:    13/09/26 15:42:20 GMT
FROM:    Peter Jenke at MSFC  <peter.a.jenke at nasa.gov>

P. Jenke (UAH) reports on behalf of the Fermi GBM Team:

"At 04:09:26.73 UT on September 25 2013, the Fermi Gamma-Ray
Burst Monitor triggered and located 
GRB 130925A (trigger 401774969/130925173), 
which was also detected by Swift (Lien et al. GCN 15246)
and MAXI (Suzuki et al., GCN 15248).

The trigger resulted in an Autonomous Repoint Request (ARR) 
that was accepted and the LAT slewed to the GBM in-flight 
location which was consistent with the Swift/XRT position 
(Evans et al. GCN 15251).  The angle from the Fermi LAT boresight
is 22 deg from Swift/XRT position.

The GBM light curve consists of multiple peaks with a 
duration (T90) of about 212 s (50-300 keV).
The time-averaged spectrum from T0-6 s to T0+288 s is 
best fit with a power law function with an exponential high-energy 
cutoff parameterized as Epeak = 107 +/- 3 keV and 
an Index = -1.50 +/- 0.05.

The event fluence (10-1000 keV) in this time interval is
(2.83 +/- 0.06)E-07 erg/cm^2. The 1.0-sec peak photon flux 
measured starting from T0+83 s in the 10-1000 keV band
is 11.5 +/- 0.3 ph/s/cm^2.

This event, although initially classified as a GRB, has been 
shown to exhibit behavior consistent with a Tidal Disruption 
Event (Burrows et al. GCN 15253). Its location suggests that 
it is the same source as 
GBM trigger 401774186/130925164 (G. Fitzpatrick GCN 15255). 

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