{
  "subject": "Liverpool Telecope observations of AT 2025dws / GRB 250309B",
  "eventId": "GRB 250309B",
  "submittedHow": "web",
  "bibcode": "2025GCN.39646....1P",
  "createdOn": 1741578726045,
  "submitter": "Daniel Perley at Liverpool JMU <d.a.perley@ljmu.ac.uk>",
  "circularId": 39646,
  "format": "text/plain",
  "body": "D. A. Perley (LJMU), A. Bochenek (LJMU), and A. Y. Q. Ho (Cornell) report:\n \nWe obtained imaging observations of AT2025dws (Stein et al., GCN 39639), a possible optical counterpart of GRB 250309B (Preis & Greiner, GCN 39629; McDermott et al., GCN 39635) with IO:O on the Liverpool Telescope on UT 2025 March 10 between 01:46:53 and 02:01:08 UT.  Two 100s exposures were acquired in each of the g, r, i, and z bands.  The source was weakly detected in all four filters.  We report the following photometry, calibrated relative to SDSS standards (dt is reported relative to the GRB 250309B GBM trigger time; McDermott et al., GCN 39642):\n \nMJD         dt     filter mag    err\n60744.07423 0.7558    g   20.47  0.19\n60744.07708 0.7587    r   20.30  0.14\n60744.07991 0.7615    i   20.07  0.19\n60744.08274 0.7643    z   19.44  0.17\n \nThe red colours and significant fading are consistent with the interpretation of this source as the afterglow (see also Pérez-Fournon et al., GCN 39643; Stein et al., GCN 39644; Alexander et al., 39645).\n \nNo host galaxy subtraction or extinction correction has been performed.\n"
}