TITLE:   GCN CIRCULAR
NUMBER:  29421
SUBJECT: GRB 210207B: optical detection with 3.6m Devasthal Optical Telescope
DATE:    21/02/07 23:39:21 GMT
FROM:    Amit Kumar at ARIES, India  <amitkundu515@gmail.com>

 Amit Kumar (ARIES), Shashi B. Pandey (ARIES), Rahul Gupta (ARIES), Ankur
Ghosh (ARIES), Dimple  (ARIES), Amar Aryan (ARIES), Brajesh Kumar (ARIES),
and Kuntal Misra (ARIES) report:

We observed the Swift detected GRB 210207B (Lien et al., GCN 29420) using
the 4Kx4K CCD Imager (Pandey et al. 2018, 2018BSRSL..87...42P) mounted at
the axial port of the 3.6m Devasthal Optical Telescope (DOT) of ARIES
Nainital. The observations were carried out on 2021-02-07 in Bessel
UBVRI-bands starting from UT 22:32:31.875 (corresponding to 40.38 minutes
after the burst). We clearly detect the optical transient reported by Lien
et al., GCN 29420. In the first I band image the afterglow has a I band
magnitude of 15.61+/-0.01 mag. Further processing of the data is in
progress.

The quoted magnitude is calibrated with the nearby USNO-B1 stars and not
corrected for Galactic extinction in the direction of the GRB.
3.6m Devasthal Optical Telescope (DOT) is a recently commissioned facility
in the Northern Himalayan region of India (long:79 41 04E, lat:29 21 40N,
alt:2540m) owned and operated by the Aryabhatta Research Institute of
Observational Sciences (ARIES), Nainital (https://www.aries.res.in).
Authors of this GCN circular thankfully acknowledge consistent support from
the staff members to run and maintain the 3.6m DOT. This circular may be
cited.