TITLE:   GCN CIRCULAR
NUMBER:  29996
SUBJECT: GRB 210511B: Fermi GBM observation
DATE:    21/05/11 21:37:39 GMT
FROM:    Elisabetta Bissaldi at INFN,Bari  <elisabetta.bissaldi@ba.infn.it>

E. Bissaldi (Politecnico and INFN Bari) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:


"At 11:26:39.26 UT on 11 May 2021, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 210511B (trigger 642425204 / 210511477),
which was also detected by GECAM (Cai et al., GCN 29990) and
by AGILE (Ursi et al., GCN 29991).
The Fermi GBM Final Real-time Localization was reported in GCN 29988.

The angle from the Fermi LAT boresight at the GBM trigger time is 49 degrees.

The GBM light curve consists of a bright emission episode
with a duration (T90) of about 6 s (50-300 keV).
The time-averaged spectrum from T0 to T0+8 s is
best fit by a Band function with Epeak = 128 +/- 5 keV,
alpha = -0.72 +/- 0.04, and beta = -2.47 +/- 0.10.

The event fluence (10-1000 keV) in this time interval is
(1.04 +/- 0.02)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+4.2 s in the 10-1000 keV band
is 23.3 +/- 0.3 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/"