TITLE:   GCN CIRCULAR
NUMBER:  32811
SUBJECT: GRB 221009A: 1.3m DFOT Optical Observations
DATE:    22/10/21 07:11:24 GMT
FROM:    Rahul Gupta at ARIES, India  <rahulbhu.c157@gmail.com>

Rahul Gupta, Amit Kumar Ror, S. B. Pandey, A. Aryan, A. Ghosh, Dimple, and
K. Misra (ARIES) report as a part of a larger international collaboration:


We performed target of opportunity observations of the extremely bright GRB
221009A (Dichiara et al., GCN 32632; Kennea and Williams, GCN 32635; Veres
et al., GCN 32636; Bissaldi et al., GCN 32637; Svinkin et al., GCN 32641; Ursi
et al., GCN 32650; Piano et al., GCN 32657; Pillera et al., GCN 32658; Gotz
et al., GCN 32660; Xiao et al., GCN 32661; Frederiks et al., GCN 32668; Ripa
et al., GCN 32685) using the 2Kx2K CCD Imager mounted at the 1.3m Devasthal
Fast Optical Telescope (DFOT) located at the Devasthal observatory of
Aryabhatta Research Institute of Observational Sciences (ARIES), India. The
observations were started on 2022-10-16 at 14:41:41 UT, i.e., ~ 7.06 days
after the detection. We have taken multiple frames in the R filter at
different epochs. We clearly detected the optical afterglow of GRB
221009A (GCNs
32632, 32635, 32636, 32641, 32657, 32658, 32660, 32666, 32668, 32670,
32671, 32676, 32677, 32678, 32679, 32680, 32683, 32684, 32685, 32686,
32691, 32692, 32693, 32694, 32695, 32700, 32705, 32707, 32709, 32727,
32729, 32730, 32736, 32738, 32739, 32740, 32743, 32746, 32749, 32750;
32752; 32753; 32755; 32758; 32765; 32769; 32771; 32795; 32799; 32800;
32803; 32804; 32809) in our stacked image. The preliminary photometric
estimate of the afterglow is the following :

Date Start UT   T-T0 (mid, days) Filter  Exp time (sec)   Magnitude

=========================================================
2022-10-16 14:41:41   ~7.09       R           200*25          21.30 +/- 0.04


Further follow-up observations are planned. The magnitude is not corrected
for the Galactic extinction in the direction of the burst. Photometric
calibration is performed using the standard stars from the USNO-B1.0
catalog.

This circular may be cited.