GCN Circular 17863

H.-F. Yu (MPE) reports on behalf of the Fermi GBM Team:

"At 09:29:48.08 UT on 23 May 2015, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 150523A (trigger 454066191 / 150523396).

The on-ground calculated location, using the GBM trigger
data, is RA = 121.2, Dec = -37.3 (J2000 degrees, equivalent 
to 08h 05m, -37d 20'), with an uncertainty of 1.7 degrees 
(radius, 1-sigma containment, statistical only; there is 
additionally a systematic error which is currently estimated 
to be 2 to 3 degrees).

The trigger resulted in an Autonomous Repoint Request (ARR) 
that was accepted and the spacecraft slewed to the GBM in-flight 
location. The initial angle from the Fermi LAT boresight
is 22 degrees.

The GBM light curve consists of two pulses with a duration (T90) 
of about 74.2 s (50-300 keV). The time-averaged spectrum 
from T0-4.352 s to T0+40.705 s is best fit by a power law function 
with an exponential high-energy cutoff. The power law index 
is -0.64 +/- 0.03 and the cutoff energy, parameterized as Epeak, 
is 574 +/- 24 keV.

The event fluence (10-1000 keV) in this time interval is
(3.57 +/- 0.05)E-05 erg/cm^2. The 1.024-sec peak photon flux 
measured starting from T0+32.769 s in the 10-1000 keV band
is 8.34 +/- 0.25 ph/s/cm^2.

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