[vsnet-grb-info 16964] GRB 150906A: Fermi GBM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  18245
SUBJECT: GRB 150906A: Fermi GBM detection
DATE:    15/09/07 16:30:19 GMT
FROM:    Oliver Roberts at UCD/Fermi  <oliver.roberts at ucd.ie>

O.J. Roberts (UCD), G. Younes (GWU), and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 22:38:47.31 UT on the 6th of September 2015, the Fermi
Gamma-Ray Burst Monitor triggered and located GRB 150906A
(trigger 463271931 / 150906944).

The on-ground calculated location, using the GBM trigger
data, is RA = 212.04, DEC = 1.09 (J2000 degrees,
equivalent to 14h 08m 9.6s, +01d 5' 24" ), with an uncertainty of
5.19 degrees (radius, 1-sigma containment, statistical
only; there is additionally a systematic error which we
have characterized as a core-plus-tail model, with 90%
of GRBs having a 3.7 deg error and a small tail suffering
a larger than 10 deg systematic error.
[Connaughton et al. 2015, ApJS, 216, 32]).

The angle from the Fermi LAT boresight at the GBM trigger
time is 29 degrees.

The trigger resulted in an Autonomous Repoint Request
(ARR) by the GBM Flight Software owing to the high peak
flux and hardness of the GRB. This ARR was accepted and
the spacecraft slewed to the GBM in-flight location.

The GBM light curve consists of a single short pulse, with
a duration (T90) of about 1 s (50-300 keV). The
time-averaged spectrum from T0-0.064 s to T0+0.064 s is
adequately fit by a power law function with an exponential
high-energy cutoff. The power law index is -0.60 +/- 0.16
and the cutoff energy, parameterized as Epeak,
is 597 +/- 130 keV

The event fluence (10-1000 keV) in this time interval is
4.944 +/- 0.384)E-07 erg/cm^2. The 64 ms peak photon flux
measured starting from T0-0.064 s in the 8-1000 keV band
is 13.6 +/- 1.4 ph/s/cm^2.

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