{
  "bibcode": "2021GCN.30481....1K",
  "body": "H. Kumar(IITB), S. Joharle (Fergusson College), J. Stanzin (IAO), V.\nBhalerao(IITB), G. C. Anupama(IIA), S. Barway(IIA) report on behalf of the GIT\nteam:\n\nWe observed GRB 210722A detected by Swift Burst Alert Telescope (P.\nD'Avanzo et al., GCN #30475) and optical afterglow detected by P. D'Avanzo\net al., GCN #30475; Z.P. Zhu et al., GCN #30476; N. Pankov et al., GCN\n#30477; with 0.7m GROWTH-India Telescope (GIT). We obtained multiple\nexposures in the g', r' filters. The image depth was shallower than usual\ndue to weather conditions. We clearly detected the afterglow in our images\nat R.A.= 1:48:07.29, DEC.= -6:20:49.85, which agrees with the swift UVOT\nposition (GCN #30475). The photometric results follow as:\n\n------------------------------------------------------------------------\n\nT_start - T0 (days) | Exposure (sec) | Filter | Magnitude (AB)| Notes |\n\n------------------------------------------------------------------------\n\n 0.014938 | 100  | g' | 15.95 +/- 0.23 | Low significance detection\n\n 0.012057 | 100  | r' | 15.11 +/- 0.08 |\n\n 0.032546 | 4x100 | r' | 16.34 +/- 0.08 | Stacked image\n\n 0.050742 | 100  | r' | 16.81 +/- 0.19 |\n\n 0.053035 | 100  | r' | 16.88 +/- 0.07 |\n\n ------------------------------------------------------------------------\n\nBased on our observations, we found that the GRB is decaying with a\npower-law index of 1.14 +/- 0.03 in r' band. Our observations are in\nagreement with magnitudes reported by Z.P. Zhu et al., GCN #30476, and N.\nPankov et al., GCN #30477. The magnitudes are calibrated against PanSTARRS\n(Flewelling et al., 2018) and not corrected for Galactic extinction.\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": 30481,
  "createdOn": 1627047845000,
  "email": "harshkosli13@gmail.com",
  "subject": "GRB 210722A: GIT optical detection and preliminary analysis",
  "submitter": "Harsh Kumar at Indian Inst of Tech,Bombay  <harshkosli13@gmail.com>",
  "eventId": "GRB 210722A"
}