{
  "submitter": "Brendan O'Connor at UMD  <oconnorb@umd.edu>",
  "editedBy": "Vidushi Sharma at NASA GSFC/UMBC <vidushi.sharma@nasa.gov> on behalf of Leo P. Singer at NASA/GSFC <leo.p.singer@nasa.gov>",
  "createdOn": 1662843380000,
  "circularId": 32542,
  "bibcode": "2022GCN.32542....1O",
  "eventId": "GRB 220831A",
  "body": "B. O'Connor (UMD/GWU), E. Troja (UTV/ASU), S. Dichiara (PSU),\non behalf of a larger collaboration:\n\nWe performed target of opportunity observations of GRB 220831A\n(Tohuvavohu et al. GCN 32506) with the FLAMINGOS-2 spectrograph\nmounted on the Gemini-South telescope. Observations were taken\nin the J and Ks filters with total exposure of 1785 and 1635 s,\nrespectively. The observations began at 2022-09-09 03:27:01 UT,\ncorresponding to ~8.6 d after the burst. Further observations\nwere obtained the following night (~9.6 d) in J-band for\n2000 s exposure.\n\nAt the location of the optical, infrared, and X-ray counterpart\n(Dichiara et al. GCN 32510, D'Avanzo et al. GCN 32513, Freeburn\net al. GCN 32516, Gordon et al. GCN 32535), we detect a faint\nsource with brightness J ~ 24.5 AB mag. This result confirms the\nfading of the infrared source reported by D'Avanzo et al.\nGCN 32513.\n\nOur measurement implies a very red color, r-J >2, of the late\ntime emission. At present it is not clear whether this is due\nto the onset of a kilonova or to the contribution of an underlying\nhost galaxy. Assuming a behavior similar to AT2017gfo, the\napparent J-band magnitude implies a distance of ~200 Mpc. However,\nthe nearby galaxy noted by D'Avanzo et al. GCN 32513 is significantly\ncloser at only 4 Mpc.\n\nIf instead the source is dominated by the host galaxy contribution,\nthe red color suggests that GRB 220831A was a distant event\n(see, e.g., O'Connor et al. 2022, MNRAS, 515, 4890).\n\nFurther observations are planned.\n\nMagnitudes are calibrated against stars in the 2MASS catalog\nand are not corrected for Galactic extinction.\n\nWe thank the staff of the Gemini Observatory, in particular\nJoan Font-Serra and Yijung Kang, for rapid scheduling of\nthese observations.",
  "editedOn": 1713971091541,
  "email": "oconnorb@umd.edu",
  "subject": "GRB 220831A: Gemini-South Infrared Observations",
  "version": 2
}