{
  "bibcode": "2021GCN.29414....1T",
  "body": "Teja, R.S.; Dutta, Anirban (IIA, Bengaluru); Kumar, Harsh (IIT, Bombay);\nSujith, D.S.; Sahu, D.K.; Anupama, G.C.; Barway, Sudhansu (IIA,\nBengaluru); Bhalerao, Varun (IIT, Bombay) \n\nWe observed the field of GRB 210204A / ZTF21aagwbjr (Fermi-GBM, GCN\n#29390; Li et al., GCN #29392; Izzo et al., GCN #29411) with the\nHimalayan Faint Object Spectrograph and Camera (HFOSC) mounted on the\n2-m Himalayan Chandra Telescope (IAO, Hanle, India). Multiple frames\n(each 300 sec) of the GRB field in Bessell R and I bands were obtained\nwith an average airmass of 1.21 under good seeing conditions.\nPreliminary PSF photometry on the stacked images was performed and\ncalibrated against USNO-B1 catalogue. We clearly detected an OT in the\nstacked images in both the bands. The estimated magnitudes of the OT\n(not corrected for the Galactic extinction) are as under - \n\n-------------------------------------------------------------------------------------\nDate | UT (mean) | Filter | Exp. time x No. of frames | Magnitude (err)\n-------------------------------------------------------------------------------------\n2021-02-06 15:11:11    R             300 sec x 4                   20.07\n(0.13)\n2021-02-06 15:40:29    I              300 sec X 4                  19.79\n(0.15)\n-------------------------------------------------------------------------------------\nThe observations were carried out under the ToO program HCT-2021-C1-P2.\nWe thank the staff at IAO and CREST for helping us with the\nobservations.",
  "circularId": 29414,
  "createdOn": 1612673184000,
  "email": "anirban.dutta@iiap.res.in",
  "subject": "GRB 210204A: Optical Observations from HCT",
  "submitter": "Anirban Dutta at Indian Inst. of Astrophysics  <anirban.dutta@iiap.res.in>",
  "eventId": "GRB 210204A"
}