{
  "bibcode": "2020GCN.28100....1O",
  "body": "B. O'Connor (GWU, UMD), S. Dichiara (UMD, NASA-GSFC),\nE. Troja (UMD, NASA-GSFC), S.B. Cenko (UMD, NASA-GSFC)\nreport on behalf of a larger collaboration:\n\nWe report on further observations of the short GRB 200522A (Evans et al.,\nGCN Circ. 27778) taken at 3.1 and 9.1 d post-burst in the r-band filter\nwith the Gemini Multi-Object Spectrograph (GMOS) mounted on the 8.1m Gemini\nNorth telescope. Image subtraction with HOTPANTS (Becker 2015) identifies\na low significance residual close to the candidate host galaxy's center\n(Fong et al., GCN Circ. 27779; Strausbaugh et al., GCN Circ. 27792),\nand at the edge of the XRT enhanced position (Beardmore et al., GCN Circ.\n27780). We independently reanalyzed the HST images (Fong et al., GCN Circ.\n27827; Kilpatrick et al., GCN Circ. 27904), and performed image subtraction\nbetween the two epochs at 3.5 and 16.3 d. Although the analysis is\ncomplicated by the presence of a bright galaxy's nucleus, a residual signal\nof brightness F125W ~ 25.6 AB mag is present at the location of the Gemini\noptical candidate. We suggest this to be the candidate optical/nIR\ncounterpart of GRB 200522A. The observed magnitude is much brighter than\nexpected for a kilonova like AT2017gfo, and suggests that the afterglow\nemission is the dominant component. The projected offset from the galaxy's\nnucleus is ~0.23 arcseconds, corresponding to 1.5 kpc at redshift z = 0.554\n(Dichiara et al., GCN Circ. 28038). This physical offset is low yet not\nunprecedented, falling in the bottom 15% of the short GRB offset\ndistribution\n(Fong & Berger, 2013).\n\nWe thank the Gemini North staff for efficiently executing\nthese observations.",
  "circularId": 28100,
  "createdOn": 1594754382000,
  "email": "oconnorb@umd.edu",
  "subject": "GRB 200522A: Candidate Optical/nIR Counterpart from Gemini and HST Imaging",
  "submitter": "Brendan O'Connor at UMD  <oconnorb@umd.edu>",
  "eventId": "GRB 200522A"
}