TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4283
SUBJECT: GRB 051117B: ROTSE-III Optical Limits
DATE:    05/11/17 16:55:47 GMT
FROM:    Wiphu Rujopakarn at U Michigan/ROTSE  <wiphu@umich.edu>

W. Rujopakarn (U Mich), H. Swan (U Mich), B. Schaefer (Louisiana State), F. Yuan
(U Mich), T. Guver (U Istanbul), report on behalf of the ROTSE collaboration:

ROTSE-IIIa, located at Siding Spring Observatory, Australia, responded to GRB
051117B (Swift trigger 164279), producing images beginning 18 s after the GCN
notice time. An automated response took the first image at 13:24:11.0 UT, 75.6
s after the burst, under windy conditions. These observations were affected by
proximity to the full moon yielding shallow limiting magnitudes. We took 10
5-sec, and 140 20-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. Individual
images have limiting magnitudes ranging from 13.9-16.3; we set the following
specific limits.

start UT       end UT      t_exp(s)   mlim   t_start-tGRB(s)  Coadd?
--------------------------------------------------------------------
13:24:12.0   13:24:17.0         5     14.2           76.6       N
13:24:12.0   13:27:07.8       175     15.8           76.6       Y