{
  "bibcode": "2021GCN.29569....1G",
  "body": "Rahul Gupta, A. Kumar, Dimple, A. Ghosh, A. Aryan, V. Negi, B. Kumar,\nS. B. Pandey, and K. Misra (ARIES) report:\n\nWe observed the field of Swift detected GRB 210222B (Gropp et al., GCN\n29545) with 1.3m Devasthal Fast Optical Telescope (DFOT) located at\nDevasthal observatory of Aryabhatta Research Institute of\nObservational Sciences (ARIES), India. The observations were started\non 2021-02-23 at ~ 19:15 UT, i.e., ~ 20.6 hours after the BAT trigger.\nWe have taken multiple frames having an exposure time of 120 s in the\nR and I filters.  We stacked the images after the alignment. We did\nnot detect the optical afterglow reported previously (Gropp et al. GCN\n29545; Hu et al. GCN 29546; Strausbaugh et al. GCN 29547; Mong et al.\nGCN 29548, 29550; Perley et al. GCN 29549; Zhu et al. GCN 29551,\nFernandez et al. GCN 29552; Lipunov et al. GCN 29554; Jelinek et al.\nGCN 29557; Siegel et al. GCN 29559; Gokuldass et al. GCN 29562; Belkin\net al. GCN 29563; and D'Avanzo et al. GCN 29567) in our stacked image.\n\nWe obtain the following 3-sigma upper limit in the stacked image.\n\nDate Start_UT T_start-T0 (hour) Filter  Exp time (s)  Limiting magnitude\n====================================================\n2021-02-23 19:15   ~20.6          R   120*30      > 21.1\n\n\n\nThe magnitude is 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.\nThis circular may be cited.",
  "circularId": 29569,
  "createdOn": 1614320055000,
  "email": "rahulbhu.c157@gmail.com",
  "subject": "GRB 210222B: 1.3m DFOT Optical upper limit",
  "submitter": "Rahul Gupta at ARIES, India  <rahulbhu.c157@gmail.com>",
  "eventId": "GRB 210222B"
}