GCN Circular 3304
Subject
GRB 050421: ROTSE-III Optical Limits
Date
2005-04-21T15:24:42Z (19 years ago)
From
Eli Rykoff at U of Michigan/ROTSE <erykoff@umich.edu>
E.S. Rykoff (U Mich), S.A. Yost (U Mich), H. Swan (U Mich) report on
behalf of the ROTSE collaboration:
ROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB
050421 (Swift trigger 115135), producing images beginning 9.7 s after
the GCN notice time. An automated response took the first image at
04:12:58.8 UT, 67.2 s after the burst, under good conditions. These
observations were affected by the bright moon. We took 10 5-sec, and 350
20-sec eposures. These unfiltered images are calibrated relative to USNO
A2.0 (R).
Comparison to the DSS (second epoch) reveals no new sources within the
3-sigma BAT error circle including the 3-sigma XRT error circle (GCN
3301). Individual images have limiting magnitudes ranging from
16.49-17.34. In particular, we set a limit of magnitude 16.49 in a
single 5 s exposure, starting 67.1 s after the burst. Coadding images
into sets of 10 reveals no new sources down to limits of 17.8 (t0+61.7s
- t0+130.7s) and 18.4 (t0+144s - t0+431s)