GRB 210116, GRB 210116A

D. Nadella (NITK), G. Waratkar (IITB), A. Vibhute (IUCAA), S. Gupta
(IUCAA), P. Sawant (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (IUCAA), A.
R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat
CZTI collaboration:

Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al, 2020,
arxiv:2011.07067) showed detection of a bright long GRB 210116A, which was
also detected by AstroSat LAXPC (GCN #29340
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 ).

The source was clearly detected in the 20-200 keV energy range. The light
curve showed a single strong peak at 2021-01-16 05:53:37.500 UT, in all
four quadrants of CZTI. Quadrant D was noisy, and we exclude it from
further analysis. The measured peak count rate associated with the burst is
781 (+54, -60) cts/s above the background in the combined data of three
quadrants (out of four), with a total of 3156 (+232, -222) cts. The local
mean background count rate was 395 (+3, -3) cts/s. Using cumulative rates,
we measure a T90 of 9.5 (+4.1, -1.8) s.

It was also clearly detected in the CsI anticoincidence (Veto) detector in
the 100-500 keV energy range. The light curve showed a single strong peak
of emission in all four quadrants, with the strongest peak consistent with
the above timing. The measured peak count rate is 3039 (+131, -62) cts/s
above the background in the combined Veto data of four quadrants, with a
total of 13614 (+475, -578) cts. The local mean background count rate was
1842 (+6, -6) cts/s. We measure a T90 of 8.8 (+1.7, -1.0) s from the
cumulative Veto light curve.

CZTI GRB detections are reported regularly on the payload site at
http://astrosat.iucaa.in/czti/?q=grb. CZTI is built by a TIFR-led
consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and
PRL. The Indian Space Research Organisation funded, managed and facilitated
the project.

H. M. Antia, Tilak Katoch, Parag Shah and Dhiraj Dedhia
TIFR, Mumbai, India.

Analysis of AstroSat LAXPC data showed the detection of a long
GRB 210116. The light curve showed a peak profile triggered at
T0 = 05h 53m 33s UT on 16 Jan 2021. The light curve showed a peak
profile with T90 = 9 sec. The measured peak count rate above the
background associated with the burst is 867 +/- 37 cts/s in
LAXPC10 and 773 +/- 31 cts/s in LAXPC20 at T0+4 sec. The total
counts in the peak are 3219 +/- 85 cts in LAXPC10 and 2683 +/- 68
in LAXPC 20.

Both LAXPC instruments (LAXPC10 and LAXPC20) have registered this
burst profile in the light curve. For LAXPC20 the nominal energy
range is 3-100 keV, but due to lower gain in LAXPC10 the energy
range is about 30-400 keV.

The background subtracted light curve with 1 sec time-bin is
available at the web-site:
https://www.tifr.res.in/~astrosat_laxpc/grb210116lc.jpg

LAXPC was built by TIFR in collaboration with the Indian Space
Research Organisation. The Indian Space Research Organisation
funded, managed and facilitated the project.