{
  "bibcode": "2020GCN.28753....1K",
  "body": "H. Kumar(IITB), K. Sharma(IITB), J. Stanzin(IAO), V. Bhalerao(IITB), G. C.\nAnupama(IIA), S. Barway(IIA), report on behalf of the GROWTH-India\ncollaboration:\n\n\nWe followed-up GRB 201020B reported by Fermi GBM Team (GCN #28702, also\nsee: V. Lipunov et. al., GCN #28718; D. Xu et. al., GCN #28719) with 0.7m\nGROWTH-India telescope. We obtained 300-sec exposures in the SDSS r��� filter\nstarting at 2020-10-21T14:53:24.42 UT (~ 21.4 hrs after the burst detection\nby Fermi-GBM). We clearly detected uncataloged sources at a position\nconsistent with V. Lipunov et. al., GCN #28718; D. Xu et. al., GCN #28719.\n\nHere are the photometric results from GIT observations:-\n\n------------------------------------------------------------------\n\n JD (mid) | T_mid-T0(hrs) | Filter | Mag |\n\n------------------------------------------------------------------\n\n2459144.12392 | 21.45 | r | 19.36 +/- 0.07\n\n2459144.12752 | 21.53 | r | 19.49 +/- 0.08\n\n2459144.13110 | 21.62 | r | 19.37 +/- 0.07\n\n2459144.27999 | 25.15 | r | 19.64 +/- 0.02\n\n2459144.30582 | 25.77 | r | 19.79 +/- 0.02\n\n2459144.35140 | 26.86 | r | 19.83 +/- 0.03\n\n2459144.39582 | 27.91 | r | 19.83 +/- 0.03\n\n2459144.42656 | 28.67 | r | 19.89 +/- 0.02\n\n-----------------------------------------------------------------\n\nCombining our photometric results with r band measurements of D. Xu et.\nal., GCN #28719, we conclude that the source is fading with a power-law\nindex of 1.65 +/- 0.21. The magnitudes are calibrated against PanSTARRs PS1\ndata release, (Flewelling et al., 2018) and not corrected for galactic\nextinction. Extrapolating backwards to the epoch of MASTER observations (t0\n+ 3.2 min), the expected r magnitude is approximately 8.6, significantly\nhigher than the measured clear band magnitude of 13.7. This may be\nindicative of a break in the afterglow. Further observations are strongly\nencouraged.\n\nThe GROWTH India Telescope (GIT) is a 70-cm telescope with a 0.7 degree\nfield of view, set up by the Indian Institute of Astrophysics and the\nIndian Institute of Technology Bombay with support from the Indo-US Science\nand Technology Forum (IUSSTF) and the Science and Engineering Research\nBoard (SERB) of the Department of Science and Technology (DST), Government\nof India (https://sites.google.com/view/growthindia/). It is located at the\nIndian Astronomical Observatory (Hanle), operated by the Indian Institute\nof Astrophysics (IIA).",
  "circularId": 28753,
  "createdOn": 1603399036000,
  "email": "harshkosli13@gmail.com",
  "subject": "GRB 201020B: GROWTH-India Telescope optical observations",
  "submitter": "Harsh Kumar at Indian Inst of Tech,Bombay  <harshkosli13@gmail.com>",
  "eventId": "GRB 201020B"
}