{
  "bibcode": "2023GCN.33447....1O",
  "body": "B. O'Connor (UMD, GWU), S. Dichiara (PSU), E. Troja (UTV, ASU),\nJ. Gillanders (UTV), S. B. Cenko (NASA, UMD), C. Kouveliotou (GWU):\n\nWe observed GRB 230307A (GBM team GCN 33405, Xiong et al. GCN 33406,\nKozyrev et al. GCN 33425) with the GMOS-S instrument mounted on\nGemini-South in Cerro Pachon, Chile through Director's Time.\nObservations began at  00:06:47 UT on 2023-03-10, corresponding to\n2.35 d after the GRB trigger.\n\nIn a 30 s acquisition image, we detect the optical afterglow reported\nby Levan et al. (GCN 33439) and Lipunov et al. (GCN 33441). With\npreliminary photometry calibrated to the SkyMapper catalog we derive\na magnitude of r~22.0+/-0.3 mag. This confirms fading of the reported\ncounterpart and solidifies the connection to the GRB.\n\nAnalysis of the spectroscopic observations is underway.\n\nWe thank the staff of the Gemini Observatory for rapidly approving and\nexecuting these observations.",
  "circularId": 33447,
  "createdOn": 1678419456000,
  "email": "oconnorb@umd.edu",
  "subject": "GRB 230307A: Gemini-South Confirmation of the Optical Afterglow",
  "submitter": "Brendan O'Connor at UMD  <oconnorb@umd.edu>",
  "eventId": "GRB 230307A"
}