[vsnet-grb-info 26672] GRB 201020B: 1.3m DFOT optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  28772
SUBJECT: GRB 201020B: 1.3m DFOT optical observations
DATE:    20/10/24 18:24:59 GMT
FROM:    Dimple Panchal at ARIES, India  <dimple at aries.res.in>

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

We carried out the follow-up observations of GRB 201020B ( Fermi team, GCN 28702; Lipunov et al. GCN 28704; Malacaria and Meegan, GCN 28710; Ursi et al. 28714; Arimoto et al., GCN 28716; Lipunov et al., GCN 28718; Xu et al., GCN 28719; Ridnaia et al., GCN 28723; Belkin et al., GCN 28725; Sbarufatti et al., GCN 28740; Breeveld et al., GCN 28743; Vinko et al. GCN 28750; Kumar et al. GCN 28753; Kann et al. GCN 28765; Belkin et al. GCN 28768; Vinko et al. GCN 28769 ) using 1.3m Devasthal Fast Optical Telescope (DFOT) at Devasthal observatory of Aryabhatta Research Institute of observational sciencES (ARIES), India. The observation was started on 2020-10-21 at 21:41:37 UT. We observed a series of images with the exposure time of 60 seconds in both R and I filters (Johnson-Cousins) covering Swift UVOT position RA, Dec = 05h 01m 52.03s, +77d 04' 05.9" ( Sbarufatti et al. GCN 28740). An uncataloged source is clearly visible in the stacked images in both the bands at the position consistent with V. Lipunov et. al. GCN 28718; D. Xu et. al. GCN 28719. 

Preliminary photometry of the optical transient in the combined images is following 
Date Start_UT T_start-T0 (hrs) Filter Exp time (s) Magnitude Mag_error 


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2020-10-21 21:41:37 28.280 R 15*60 19.741 0.0262 

2020-10-21 22:00:04 28.588 I 15*60 19.298 0.0468 

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Photometry is done based on the USNO-B1.0 catalog. This magnitude is not corrected for Galactic extinction in the direction of the GRB.