TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4010
SUBJECT: GRB 050922B: ROTSE-III Optical Limits
DATE:    05/09/22 17:20:37 GMT
FROM:    Brad Schaefer at LSU  <schaefer@grb.phys.lsu.edu>

B. E. Schaefer (Louisiana State), R. Quimby (U Texas), S.A. Yost (U Mich), 
W. Rujopakarn (U Mich) report on behalf of the ROTSE collaboration:

ROTSE-IIIa, located at Siding Spring Observatory, Australia, responded to 
GRB 050922B (Swift trigger 156434), producing images beginning 5.6 s after 
the GCN notice time. An automated response took the first image at 
15:05:06.6 UT, 186.3 s after the burst, under excellent conditions. 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 circles for both the BAT and the XRT, for both single images 
and coadding into sets of 10. The field is not crowded but the gibbous 
moon was 57 degree away. Individual images have limiting magnitudes 
ranging from 15.4-16.5; we set the following specific limits.

start UT end UT t_exp(s) mlim t_start-tGRB(s) Coadd?
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15:05:06.6 15:07:30.6 144 17.3 186.3 Y