TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4236
SUBJECT: GRB 051109B: ROTSE-III Optical Limits
DATE:    05/11/09 20:35:40 GMT
FROM:    Wiphu Rujopakarn at U Michigan/ROTSE  <wiphu@umich.edu>

W. Rujopakarn (U Mich), E.S. Rykoff (U Mich), F. Yuan (U Mich) report on
behalf of the ROTSE collaboration:

ROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB
051109B (Swift trigger 163170), producing images beginning 9.1 s after
the GCN notice time. An automated response took the first image at
08:40:29.1 UT, 50.7 s after the burst, under fair conditions. We took 10
5-sec, 10 20-sec and 50 60-sec exposures. 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 error circle, for both single images and coadding into sets of
10. We also note that we found no new object within the error circle of
XRT position given by Campana et al. (GCN 4226). Individual images have
limiting magnitudes ranging from 15.8-17.8; we set the following
specific limits.

start UT       end UT      t_exp(s)   mlim   t_start-tGRB(s)  Coadd?
--------------------------------------------------------------------
08:40:29.1   08:40:34.1      5        16.8        49.8          N
08:40:29.1   08:41:51.1     82        18.0        49.8          Y
08:41:51.4   08:44:50.4    299        17.4       132.1          Y

[GCN_OPS_NOTE(10nov05): Per author's request, the 'mlim' for the last
entry in the table was changed from 17.4 to 18.5.]