[vsnet-grb-info 16280] GRB 150309A: Fermi GBM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  17561
SUBJECT: GRB 150309A: Fermi GBM detection
DATE:    15/03/10 15:13:46 GMT
FROM:    Oliver Roberts at UCD/Fermi  <oliver.roberts at ucd.ie>

O.J Roberts (UCD) and M. Stanbro (UAH) report on behalf
of the Fermi GBM Team:

"At 22:59:50.66 UT on the 9th of March 2015, the Fermi
Gamma-Ray Burst Monitor triggered and located
GRB 150309A (trigger 447634793/150309958), the second
episode of which was also detected by Swift
(Cummings et al. 2015, GCN 17553). The GBM on-ground
location is consistent with the Swift position.

The angle from the Fermi LAT boresight is 60 degrees.

The Swift trigger is observed in the GBM light curve at
T0+200 s as a very soft, weak event with a duration of
about 60 s. The immediate light curve at the GBM trigger
time consists of a bright, main peak of unresolved emission
episodes, with a duration (T90) of about 52 s (50-300 keV).
The time-averaged spectrum from T0+0.0 s to T0+52.6 s is
best fit by a Band function with Epeak= 165 +/- 4 keV,
alpha = -0.59 +/- 0.02 and beta = -2.59 +/- 0.10.

The event fluence (10-1000 keV) in this time interval is
(3.9 +/- 0.1)E-05 erg/cm^2. The 1-sec peak photon flux
measured starting from T0+17.5 s in the 10-1000 keV band
is 15.2 +/- 0.3 ph/s/cm^2.

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