TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4050
SUBJECT: GRB 051001: ROTSE-III Optical Limits
DATE:    05/10/01 11:50:50 GMT
FROM:    Eli Rykoff at U of Michigan/ROTSE  <erykoff@umich.edu>

E.S. Rykoff (U Mich), H. Swan (U Mich), B. Schaefer (Louisiana State), 
S.A. Yost (U Mich), F. Yuan (U Mich) report on behalf of the ROTSE 
collaboration:

ROTSE-IIIa, located at Siding Spring Observatory, Australia, responded 
to GRB 051001 (Swift trigger 157870), producing images beginning 7.9 s 
after the GCN notice time. An automated response took the first image at 
11:13:01.9 UT, 85.6 s after the burst, under fair conditions. We took 10 
5-sec, 10 20-sec and 20+ 60-sec eposures. Observations are ongoing. 
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 BAT error circle (or the possible X-ray position from the GCN 
notice), for both single images and coadding into sets of 10. Individual 
images have limiting magnitudes ranging from 16.1-17.4; we set the 
following specific limits.

start UT       end UT      t_exp(s)   mlim   t_start-tGRB(s)  Coadd?
--------------------------------------------------------------------
11:13:01.9   11:13:06.9         5     16.2           85.6       N
11:13:01.9   11:15:25.9       144     17.7           85.6       Y
11:15:26.6   11:20:19.6       293     18.1          230.3       Y