[vsnet-grb-info 7965] GRB 090610B: Fermi GBM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9508
SUBJECT: GRB 090610B: Fermi GBM detection
DATE:    09/06/12 16:28:34 GMT
FROM:    Adam Goldstein at Fermi-GBM/UAH  <adam.m.goldstein at msfc.nasa.gov>

A. Goldstein (UAH) reports on behalf of the Fermi GBM Team: 

"At 17:21:31.90 UT on 10 June 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090610B (trigger 266347293 / 090610723).

The on-ground calculated location, using the GBM trigger 
data, is RA = 276.0, DEC = -42.1 (J2000 degrees, 
equivalent to 18h 24m, -42d 06'), with an uncertainty 
of 9.5 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 91 degrees.

The GBM light curve consists of a single short pulse at trigger time
followed by a broad pulse starting at T0+80 s with a total duration 
(T90) of about 202.5 s (8-1000 keV). 

The time-averaged spectrum for the first pulse from T0-6.2 s to 
T0+4.1 s is best fit by a power law function with an exponential
high energy cutoff.  The power law index is -0.46 +/- 0.36 and
the cutoff energy, parameterized as Epeak, is 104.90 +/- 16.70 keV
(chi squared 338.8 for 359 d.o.f.).

The time-averaged spectrum for the second pulse from T0+79.9 s to
T0+161.8 s is best fit by a simple power law function with index
-1.66 +/- 0.07 (chi squared 454.9 for 360 d.o.f.).

The event fluence (8-1000 keV) in the total time interval is 
(4.13 +/- 0.24)E-06 erg/cm^2. The 1-sec peak photon flux measured 
starting from T0+2.0 s in the 8-1000 keV band 
is 1.54 +/- 0.43 ph/s/cm^2.

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