{
  "bibcode": "2023GCN.33576....1O",
  "body": "S. R. Oates (U. Birmingham) and K. L. Page (U. Leicester)\nreport on behalf of the Swift/UVOT team:\n\nThe Swift/UVOT began settled observations of the field of GRB 230405B\n75 s after the BAT trigger (Page et al., GCN Circ. 33571).\nNo optical afterglow consistent with the XRT position\n(Beardmore et al. GCN Circ. 33574)\nis detected in the initial UVOT exposures.\nPreliminary 3-sigma upper limits using the UVOT photometric system\n(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first\nfinding chart (FC) exposure and subsequent exposures are:\n\nFilter         T_start(s)   T_stop(s)      Exp(s)         Mag\n\nwhite_FC            75          224          147         >20.5\nu_FC               287          537          246         >19.7\nwhite               75         1363          373         >20.7\nv                  618         4860          274         >19.1\nb                  542         1339           78         >19.0\nu                  287         1313          304         >19.7\nw1                 668         1289           78         >18.5\nm2                 642         5065          274         >19.4\nw2                 593         1389           97         >18.8\n\nThe magnitudes in the table are not corrected for the Galactic extinction\ndue to the reddening of E(B-V) = 0.166 in the direction of the burst\n(Schlegel et al. 1998).",
  "circularId": 33576,
  "createdOn": 1680768413000,
  "email": "samantha.oates@alumni.ucl.ac.uk",
  "subject": "GRB 230405B: Swift/UVOT Upper Limits",
  "submitter": "Samantha Oates at MSSL  <samantha.oates@alumni.ucl.ac.uk>",
  "eventId": "GRB 230405B"
}