{
  "bibcode": "2021GCN.29539....1K",
  "body": "Amit Kumar (ARIES), Rahul Gupta (ARIES), Ankur Ghosh (ARIES), Dimple\n(ARIES), Tushar Tripathi (ARIES), Shubham Kishore (ARIES), Amar Aryan\n(ARIES), Shashi B. Pandey (ARIES), Brajesh Kumar (ARIES), and Kuntal Misra\n(ARIES) report:\n\nWe observed the optical afterglow of the Swift detected GRB 210217A\n(Simpson et al. GCN 29521; Evans et al., GCN 29525) with the 1.3m Devsthal\nFast Optical Telescope (DFOT) at Aryabhatta Research Institute of\nObservational Sciences (ARIES), Nainital (India), on 2021-02-18 from UT\n17:31:22 to 19:09:31 (corresponding to 18.094 to 19.730 hours from the GRB\ntrigger time). We observed a series of 30x120s exposures in the Bessel R\nfilter and a series of 20x120s exposures in the Bessel I filter. We clearly\ndetected the optical afterglow of GRB 210217A in the stacked frames within\nthe Swift XRT error circle (Simpson et al. GCN 29521) as also reported by\nZhu et al., GCN 29523; Zheng & Filippenko GCN 29533; Shrestha et al. GCN\n29535.\n\nThe estimated preliminary magnitudes are as follows:\n\nT_start-T0 (hours) Start Date (UTC) Filter Magnitude (mag)\n-----------------------------------------------------------\n-----------------------------------------------------------\n18.09 2021-02-18T17:31:22 R 21.80 +- 0.08\n19.73 2021-02-18T19:09:31 I 21.56 +- 0.12\n\nThe magnitudes are not corrected for the Galactic extinction in the\ndirection of the burst. Photometric calibration is performed using the\nstandard stars from the USNO-B1.0 catalog.\n\nThis circular may be cited.",
  "circularId": 29539,
  "createdOn": 1613763142000,
  "email": "amitkundu515@gmail.com",
  "subject": "GRB 210217A: 1.3m DFOT optical detection",
  "submitter": "Amit Kumar at ARIES, India  <amitkundu515@gmail.com>",
  "eventId": "GRB 210217A"
}