[vsnet-grb-info 28279] GRB 210704B: Fermi GBM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  30382
SUBJECT: GRB 210704B: Fermi GBM detection
DATE:    21/07/05 18:33:57 GMT
FROM:    Christian Malacaria at NASA-MSFC/USRA  <cmalacaria at usra.edu>

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

At 16:25:18.89  UT on 04 July 2021, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 210704B (trigger 647108723 / 210704684).

The on-ground calculated location, using the GBM trigger
data, is RA = 203.44, DEC = -41.87 (J2000 degrees,
equivalent to 13 h 33 m, -41 d 52 '), with a statistical uncertainty
of 1.00 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 87 degrees.

The GBM light curve shows multiple peaks
with a duration (T90) of about 43.5 s (50-300 keV).
The time-averaged spectrum from T0-0.5 s to T0+8.7 s is
best fit by a power law function with an exponential
high-energy cutoff.  The power law index is -0.64 +/- 0.06 and
the cutoff energy, parameterized as Epeak, is 350.8 +/- 26.3 keV.

The event fluence (10-1000 keV) in this time interval is
(8.1 +/- 0.4)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+28.6 s in the 10-1000 keV band
is 16.1 +/- 0.4 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/"