GRB 210801A

F. Kunzweiler, B. Biltzinger, F. Berlato, J. Burgess & J. Greiner (all MPE Garching) report:

The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger
649519043 at 13:57:18 on 01 Aug. 2021 were automatically fitted for spectrum
and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427;
Berlato et al. 2019, ApJ 873, 60).

The best-fit position (1 sigma statistical errors) is:
RA(2000.0) = 238.2+/-1.5 deg
Decl.(2000.0) = -40.8+/-0.9 deg
We estimate an additional systematic error of 2 deg.

Further details are available at:
https://grb.mpe.mpg.de/grb/GRB210801581/

The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB210801581/healpix

The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB210801581/json

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/"