[vsnet-grb-info 12370] GRB 120911A: ROTSE-III Optical Limits

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  13745
SUBJECT: GRB 120911A: ROTSE-III Optical Limits
DATE:    12/09/11 07:45:30 GMT
FROM:    Wiphu Rujopakarn at U AZ/Steward  <rujopakarn at gmail.com>

W. Rujopakarn (Steward), T. Guver (Sabanci U), report on behalf of the
ROTSE collaboration:

ROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB
120911A (Swift trigger 533268; Cannizzo et al., GCN 13744), producing
images beginning 9.2 s after the GCN notice time. An automated
response took the first image at 07:09:04.2 UT, 30.4 s after the
burst, under fair conditions. We took 10 5-sec, 10 20-sec and 40
60-sec exposures. These unfiltered images are calibrated relative to
USNO A2.0 (R). Imaging is on going.

Comparison to the DSS (second epoch) reveals no new sources within the
3-sigma Swift/BAT error circle; however, we are limited as the field
is somewhat crowded. Individual images have limiting magnitudes
ranging from 15.5-16.6; we set the following specific limits.

start UT       end UT      t_exp(s)   mlim   t_start-tGRB(s)  Coadd?
--------------------------------------------------------------------
07:09:04.2   07:09:09.2         5     15.5           30.4       N
07:09:04.2   07:10:46.4        50     16.9           30.4       Y