TITLE:   GCN CIRCULAR
NUMBER:  29345
SUBJECT: GRB 210120A : 1.3m DFOT optical observations
DATE:    21/01/22 20:35:52 GMT
FROM:    Dimple Panchal at ARIES, India  <dimplepanchal96@gmail.com>

Dimple (ARIES), A. Ghosh (ARIES), R. Gupta (ARIES), A. Kumar (ARIES), K.
Misra (ARIES), S.B. Pandey (ARIES) report:

We carried out the follow-up observations of  the MASTER OT
J105242.66+152355.0 / AT2021axc (Lipunov et al., GCN  #29339) in the field
of Fermi GRB 210120A  (Fermi GBM Team, GCN
29334; Biltzinger et al., GCN #29335) with 1.3m Devasthal Fast Optical
Telescope (DFOT) at Devasthal observatory of Aryabhatta Research Institute
of observational sciencES (ARIES), India. The observations started on
2021-01-21 at 20:51:55 in R-band. We observed a set of 18 images with an
exposure time of 300 seconds each, centered at 1.5937 days after the burst.
We clearly detect the optical afterglow candidate reported by  Lipunov
et al., GCN  #29339  in the stacked image with a magnitude of  22.60+-0.16. The
object is fading with time (S. Belkin et al. GCN #29341; Lipunov et al.,
GCN  #29339) which supports it as an afterglow candidate for GRB 210120A.

The magnitude is not corrected for the Galactic extinction in the direction
of the burst. The photometric calibration is performed using the standard
stars from the USNO-B1.0 catalog.