TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  3813
SUBJECT: GRB 050815: ROTSE-III Optical Limits 
DATE:    05/08/15 21:58:18 GMT
FROM:    Eli Rykoff at U of Michigan/ROTSE  <erykoff@umich.edu>

Fang Yuan, E.S. Rykoff (U Mich) report on behalf of the ROTSE collaboration:

ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia, 
responded to GRB 050815 (Swift trigger 150532), producing images 
beginning 7.2 s after the GCN notice time. An automated response took 
the first image at 17:25:54.2 UT, 35.5 s after the burst, under fair 
conditions. We took 10 5-sec, 10 20-sec and 130 60-sec eposures. 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; however, we are limited as the field is severely crowded. 
Furthermore, we do not detect any new objects in the XRT error circle 
(Morris et al, GCN 3812). Individual images have limiting magnitudes 
ranging from 14.9-15.8; we set the following specific limits.

start UT       end UT      t_exp(s)   mlim   t_start-tGRB(s)  Coadd?
--------------------------------------------------------------------
17:25:54.2   17:25:59.2         5     14.9           35.5       N
17:25:54.2   17:27:25.2        91     15.8           35.5       Y
17:27:25.9   17:32:20.9       295     16.1          127.2       Y