[vsnet-grb-info 27258] GRB 210120A: Fermi GBM detection
GCN Circulars
gcncirc at capella2.gsfc.nasa.gov
Wed Jan 27 10:40:51 JST 2021
TITLE: GCN CIRCULAR
NUMBER: 29361
SUBJECT: GRB 210120A: Fermi GBM detection
DATE: 21/01/27 01:39:51 GMT
FROM: Stephen Lesage at Fermi-GBM Team <sjl0014 at uah.edu>
S. Lesage (UAH), R. Dunwoody (UCD), J. Mangan (UCD), C. Meegan (UAH)
report on behalf of the Fermi GBM Team:
"At 07:10:44.70 UT on 20 January 2021, the Fermi Gamma-Ray Burst Monitor
(GBM)
triggered and located GRB 210120A (trigger 632819449 / 210120.299),
the optical counterpart for which was detected by MASTER (Lipunov et al.
2021,
GCN 29339) and confirmed (Pozanenko et al. 2021, GCN 29341; Dimple et al.
2021,
GCN 29345). The GBM Fermi GBM Final Real-time Localization (GCN 29334) is
consistent
with the MASTER OT follow-up observations.
The angle from the Fermi LAT boresight at the GBM trigger time is 82
degrees.
The GBM light curve consists of a single peak
with a duration (T90) of about 22.2 s (50-300 keV).
The time-averaged spectrum from T0-0.32 s to T0+22.21 s is
best fit by a power law function with an exponential
high-energy cutoff. The power law index is -0.62 +/- 0.12 and
the cutoff energy, parameterized as Epeak, is 94 +/- 6 keV
The event fluence (10-1000 keV) in this time interval is
(2.9 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+ 2.6 s in the 10-1000 keV band
is 3.6 +/- 0.2 ph/s/cm^2.
A Band function fits the spectrum equally well
with Epeak= 95 +/- 6 keV, alpha = -0.63 +/- 0.12 and beta = -29 +/- 6E12.
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/"
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