TITLE: GCN CIRCULAR NUMBER: 29333 SUBJECT: GRB 210112A: 3.6m DOT optical detection DATE: 21/01/20 06:14:31 GMT FROM: Dimple Panchal at ARIES, India Dimple (ARIES), K. Misra (ARIES), A. Ghosh (ARIES), R. Gupta (ARIES), A. Kumar (ARIES), S.B. Pandey (ARIES) report: We carried out the follow-up observations of GRB 210112A (Ambrosi et al. GCN #29289) with Aries Devasthal Faint Object Spectrograph and Camera (ADFOSC) mounted on the 3.6m Devasthal Optical Telescope (DOT) at Devasthal observatory of Aryabhatta Research Institute of observational sciencES (ARIES), India. The observations started on 2021-01-13 at 23:59:18 UT in i-band (sdss). We observed a series of 6 images with an exposure time of 300 seconds each. We detect the afterglow at 1.933 days after the burst, reported by Ambrosi et al. GCN #29289; Ursi et al. GCN #29293; Kann et al. GCNs #29296,29300; Siegel et al. GCN #29303, in i-band with a magnitude of 23.19 +- 0.166 (AB mag), calibrated with the nearby PanSTARRS field. Our results are consistent with the power-law decay index of 0.8 reported by Kann et al. #29296. The magnitude is not corrected for Galactic extinction in the direction of the burst.