[vsnet-grb-info 20233] GRB 180113B: Fermi GBM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  22329
SUBJECT: GRB 180113B: Fermi GBM detection
DATE:    18/01/13 17:46:40 GMT
FROM:    Peter Veres at UAH  <veresp at gmail.com>

P. Veres and C. Meegan (both UAH)
report on behalf of the Fermi GBM Team:

"At 00:16:00.47 UT on 13 January 2018, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 180113B (trigger 537495365 / 180113011).

The on-ground calculated location, using the GBM trigger
data, is RA = 354.0, DEC = 13.5 (J2000 degrees,
equivalent to 23 h 36 m, 13 d 28 '), with an uncertainty
of 1.2 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 88 degrees.

The GBM light curve consists of multiple pulses
with a duration (T90) of about 15.9 s (50-300 keV).
The time-averaged spectrum from T0-5.6 s to T0+17.0 s is
best fit by a power law function with an exponential
high-energy cutoff.  The power law index is -0.95 +/- 0.02 and
the cutoff energy, parameterized as Epeak, is 670 +/- 41 keV.

A Band function fits the spectrum equally well with Epeak = 647 +/- 46 keV,
alpha = -0.95 +/- 0.02, and beta = -2.70 +/- 0.37.

The event fluence (10-1000 keV) in this time interval is
(1.539 +/- 0.017)E-5 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+3.2 s in the 10-1000 keV band
is 36.9 +/- 0.5 ph/s/cm^2.

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