GCN Circular 4380
Subject
GRB 051221A: RAPTOR Fading Counterpart Constraint
Date
2005-12-22T02:54:22Z (19 years ago)
From
James Wren at LANL <jwren@nis.lanl.gov>
J. Wren, W.T. Vestrand, R. White, P. Wozniak, and S. Evans report
on behalf of the RAPTOR team at Los Alamos National Laboratory:
Starting at 02:57:05 UT (1.1 hours after the burst), the RAPTOR-S
telescope began a manually initiated response to the short burst
identified by Swift (Parsons et al. 4363). Within the XRT error circle
(Burrows et al. 4366) at a position consistent with the location of the
candidate J-band infrared (Bloom, GCN 4368) and R-band optical (Berger,
GCN 4369) counterparts, a stack of 20 30-second unfiltered RAPTOR images
yields a marginal detection of a source. Using the USNO-B1 catalog for
calibration and ignoring any extinction along the line of sight, our
derived 5-sigma upper limit on the brightness of an optical counterpart
at that epoch (1.3 hours after the trigger) is R=20.2+/-0.2 magnitude.