TITLE:   GCN CIRCULAR
NUMBER:  7060
SUBJECT: GRB 071112B: ROTSE-III Rapid Optical Limits
DATE:    07/11/12 19:18:52 GMT
FROM:    Eli Rykoff at UCSB  <erykoff@physics.ucsb.edu>

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

ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia, 
responded to the short/hard GRB 071112B (Swift trigger 296503; Perri et 
al., GCN 7058), producing images beginning 6.8 s after the GCN notice 
time. An automated response took the first image at 18:23:55.8 UT, 24.3 
s after the burst, under fair conditions. We took 10 5-sec, and 10 
20-sec exposures before ROTSE-IIIc repointed at Swift trigger 296504 
(GRB071111C). 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 Swift/BAT error circle, for both single images and coadding into 
sets of 10. Individual images have limiting magnitudes ranging from 
15.3-16.3; we set the following specific limits.

start UT       end UT      t_exp(s)   mlim   t_start-tGRB(s)  Coadd?
--------------------------------------------------------------------
18:23:55.8   18:24:00.8         5     15.5           24.3       N
18:23:55.8   18:25:45.1       109     16.6           24.3       Y
18:25:53.0   18:31:02.2       309     17.3          141.5       Y