[vsnet-grb-info 7883] GRB 090520B: Fermi GBM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9427
SUBJECT: GRB 090520B: Fermi GBM detection
DATE:    09/05/28 13:19:11 GMT
FROM:    Narayana Bhat at U Alabama/Huntsville/GBM  <Narayana.Bhat at nasa.gov>

P. N. Bhat (UAH) 
report on behalf of the Fermi GBM Team:

"At 19:57:53.98 UT on 20 May 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090520B (trigger 264542275 / 090520832).

[which was the second GRB trigger of the day while the first was
 detected by the Swift-BAT (Cummings et al. 2008, GCN 9417)]

The on-ground calculated location, using the GBM trigger
data, is RA = 332.0, DEC = 43.2 (J2000 degrees,
equivalent to 22 h 08 m, 43 d 12'), with an uncertainty
of 12 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 10 degrees.

The GBM light curve consists of a single pulse
with a duration (T90) of about 1.5 s (8-1000 keV).
The time-averaged spectrum from T0-0.384 s to T0+0.256 s is
adequately fit by a simple power law function with index -1.4 +/- 0.1

(chi squared 98 for 122 d.o.f.).

The event fluence (8-1000 keV) in this time interval is
(4.5 +/- 0.2)E-7 erg/cm^2. The 1-sec peak photon flux measured
starting from T0 s in the 8-1000 keV band
is 4.1 +/- 0.2 ph/s/cm^2.

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