[vsnet-grb-info 27565] GRB 210318B: Fermi GBM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  29668
SUBJECT: GRB 210318B: Fermi GBM detection
DATE:    21/03/18 21:59:41 GMT
FROM:    Christian Malacaria at NASA-MSFC/USRA  <cmalacaria at usra.edu>

C. Malacaria (NASA-MSFC/USRA) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:

At 03:08:46.50 UT on 18 March 2021, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 210318B (trigger 637729731 / 210318131),
which was also detected by the Swift/BAT (Troja et al. 2019, GCN 29663)
and by Konus-Wind (Svinkin et al. 2021, GCN 29664).
The GBM on-ground location is consistent with the Swift position.

The angle from the Fermi LAT boresight at the GBM trigger time is 91 degrees.

The GBM light curve shows a peak
with a duration (T90) of about 24.3 s (50-300 keV).
The time-averaged spectrum from T0-4.1 s to T0+0.0 s is
best fit by a power law function with an exponential
high-energy cutoff. The power law index is 2.72 +/- 1.53 and
the cutoff energy, parameterized as Epeak, is 84.5 +/- 8.7 keV.

The event fluence (10-1000 keV) in this time interval is
(2.537 +/- 0.393)E-07 erg/cm^2. The 1-sec peak photon flux measured
starting from T0-1.9 s in the 10-1000 keV band
is 1.4 +/- 0.2 ph/s/cm^2.


The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog:
https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html

For Fermi GBM data and info, please visit the official Fermi GBM Support Page:
https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/