TITLE:   GCN CIRCULAR
NUMBER:  13969
SUBJECT: GRB 121117A: ROTSE-III Optical Limits
DATE:    12/11/17 13:05:41 GMT
FROM:    Weikang Zheng at U.of Michigan  <zwk@umich.edu>

W. Zheng (U Mich), report on behalf of the ROTSE collaboration: 

 

ROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB 121117A
(Swift trigger 538696; Cummings et al., GCN 13967), producing images
beginning 9.1 s after the GCN notice time. An automated response took the
first image at 08:51:21.1 UT, 24.1 s after the burst, under fair conditions.
We took 10 5-sec, 10 20-sec and 20 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 Swift/BAT error circle. Individual images have limiting magnitudes
ranging from 14.9-16.4; we set the following specific limits. 

 

start UT       end UT      t_exp(s)   mlim   Coadd?

---------------------------------------------------

08:50:57.0   08:55:57.0         5     15.0     N 

08:51:32.0   08:51:37.0         5     15.0     N 

08:51:43.0   08:51:48.0         5     15.4     N 

08:51:55.0   08:52:00.0         5     15.2     N 

08:52:07.0   08:52:12.0         5     15.2     N 

08:50:57.0   08:53:04.0        50     16.8     Y 

08:53:18.0   08:57:59.0       200     17.2     Y