[vsnet-grb-info 28482] GRB 210801A: Fermi GBM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  30585
SUBJECT: GRB 210801A: Fermi GBM detection
DATE:    21/08/02 15:53:21 GMT
FROM:    Oliver J Roberts at USRA/NASA  <oliver.roberts at nasa.gov>

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

"At 13:57:18.60 UT on 01 August 2021, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 210801A (trigger 649519043 / 210801581).

The on-ground calculated location, using the GBM trigger data, is 
RA = 252.77, DEC = -45.82 (J2000 degrees, 
equivalent to 16 h 51 m, -45 d 49 '), with a statistical uncertainty
of 1.6 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 120 degrees.

The GBM light curve shows two pulses (the second is much brighter than the 
first), with a duration (T90) of about 14 s (50-300 keV). The time-averaged 
spectrum from T0-0.2 s to T0+13.4 s is best fit by a Band function with 
Epeak = 41.8 +/- 1.5 keV, alpha = -1.51 +/- 0.05, and beta = -2.98 +/- 0.3.

A power law function with an exponential high-energy cutoff fits the spectrum 
equally well with a power law index of -1.56 +/- 0.04 and a cutoff energy, 
parameterized as Epeak, of 43.0 +/- 1.5 keV

The event fluence (10-1000 keV) in this time interval is
(1.44 +/- 0.04)E-05  erg/cm^2. The 1-sec peak photon flux measured
starting from T0+10.3 s in the 10-1000 keV band is 70 +/- 1 ph/s/cm^2.

We note that the position of this burst lies along the galactic plane.

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/"