[vsnet-grb-info 8160] GRB 090717: Fermi GBM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9692
SUBJECT: GRB 090717: Fermi GBM detection
DATE:    09/07/20 14:54:27 GMT
FROM:    Sylvain Guiriec at UAH  <sylvain.guiriec at lpta.in2p3.fr>

E. Kara (NASA MSFC/Barnard College), S. Guiriec (UAH) and V. Chaplin (UAH)
report on behalf of the Fermi GBM Team:

"At 00:49:32.11 UT on 17 July 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090717 (trigger 269484574 / 090717034).

The on-ground calculated location, using the GBM trigger
data, is RA = 86.8, DEC = -64.2 (J2000 degrees,
equivalent to 05 h 47 m, -64 d 12 '), with an uncertainty
of 1.0 degree (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 70 degrees.

This burst was also independently detected by INTEGRAL SPI-ACS.


The GBM light curve shows two peaks
with a duration (T90) of about 70 s (8-1000 keV).
The time-averaged spectrum of the two peaks fit
together from T0+2.8 s to T0+12.0 s and T0+44.8 to T0+52.0 is
adequately fit by a Band function with Epeak = 120 +/- 5 keV,
alpha = -0.88 +/- 0.04, and beta = -2.33 +/- 0.06

(chi squared 967 for 845 d.o.f.).

The event fluence (8-1000 keV) in this time interval is
(4.5 +/- 0.2)E-07 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+2.8 s in the 8-1000 keV band
is 7.8 +/- 0.7 ph/s/cm^2.

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