{
  "bibcode": "2020GCN.28781....1K",
  "body": "Amit Kumar (ARIES), Rahul Gupta (ARIES), Dimple (ARIES), Ankur Ghosh\n(ARIES), Kaushal Sharma (ARIES), Amar Aryan (ARIES), Brajesh Kumar\n(ARIES), Kuntal Misra (ARIES), and Shashi B. Pandey (ARIES) report:\n\nWe followed-up Fermi GBM triggered GRB 201020B (Fermi team, GCN 28702;\nLipunov et al. GCN 28704; Malacaria and Meegan, GCN 28710; Ursi et al.\nGCN 28714; Arimoto et al., GCN 28716; Lipunov et al., GCN 28718; Xu et\nal., GCN 28719; Kann et al. GCN 28765) using the 1.3m Devasthal Fast\nOptical Telescope (DFOT) at Devasthal observatory of Aryabhatta\nResearch Institute of observational sciencES (ARIES), India.\nThe observations were carried out on 2020-10-23 (from 19:14:51 to\n19:26:16 UT) and 2020-10-24 (from 18:18:43 to 19:24:14 UT) in multiple\nbands. We took a series of images with the exposure time of 120\nseconds in multiple Bessel filters, covering Swift UVOT position\n(Sbarufatti et al. GCN 28740).\nThe optical transient reported by V. Lipunov et. al. GCN 28718; D. Xu\net. al. GCN 28719 is clearly visible in the stacked images.\n\nThe R-band magnitudes of the GRB afterglow estimated from the\nphotometry of stacked images are as follows:\n\nDate       Start_UT   T_start-T0 (hrs)  Filter  Exp time (s)\nMagnitude   Mag_error\n----------------------------------------------------------------------------------------------------------------------------\n\n2020-10-23   19:14:51   73.683            R      15*120         21.34       0.05\n2020-10-24   19:24:14   97.839            R      30*120         21.83\n     0.05\n----------------------------------------------------------------------------------------------------------------------------\n\nThe estimated magnitudes have not been corrected for the Galactic\nextinction in the direction of the GRB. Photometric calibration is\nperformed using the following standard stars from the USNO-B1.0\ncatalog:\n\n1670-0037558\n1670-0037526\n1670-0037460\n1670-0037451\n1670-0037450\n1670-0037447\nOur estimated magnitudes in the R-band, along with the measurements\nreported by Belkin et al., GCN 28725; Vinko et al. GCN 28750; Belkin\net al. GCN 28768; Vinko et al. GCN 28769; Dimple et al. GCN 28772;\nNicastro et al. GCN 28773, and Kumar et al. GCN 28776, suggest that\nthe afterglow of GRB 201020B is fading with a power-law index of 1.66\n+/- 0.12.\nThe magnitudes reported by Vinko et al. GCN 28750, Vinko et al. GCN\n28769, and Nicastro et al. GCN 28773 are convetred to R-band\nmagnitudes using the tranformation equations provided by Lupton et al.\n(2005).\nThis power-law index is well consistent with those reported by Kumar\net al. GCN 28753 and Belkin et al. GCN 28768.\n\nThis circular may be cited.",
  "circularId": 28781,
  "createdOn": 1603715006000,
  "email": "amitkundu515@gmail.com",
  "subject": "GRB 201020B: 1.3m DFOT continued optical follow-up observations",
  "submitter": "Amit Kumar at ARIES, India  <amitkundu515@gmail.com>",
  "eventId": "GRB 201020B"
}