[vsnet-grb-info 2550] GRB 051221B: ROTSE-III Optical Limits

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4387
SUBJECT: GRB 051221B: ROTSE-III Optical Limits
DATE:    05/12/22 14:52:55 GMT
FROM:    Brad Schaefer at LSU  <schaefer at grb.phys.lsu.edu>

B. E. Schaefer (Louisiana State Univ.) report on behalf of the ROTSE 
collaboration:

ROTSE-IIId, located at the Turkish National Observatory at Bakirlitepe,
Turkey, responded to GRB 051221B (Swift trigger 173904), producing images
beginning 10 s after the GCN notice time. An automated response took the
first image at 20:06:57.2 UT, 217.1 s after the burst, under excellent
conditions. We took 10 5-sec, 138 20-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.  
In particular, we find nothing unusual inside the Swift XRT positional
circle (Fenimore et al. GCN4382).  Individual images have limiting
magnitudes ranging from 15.1-17.1; we set the following specific limits.

start UT       end UT      t_exp(s)   mlim   t_start-tGRB(s)  Coadd?
--------------------------------------------------------------------
20:06:57.2   20:07:02.2         5     16.6          217.1       N
20:06:57.2   20:09:02.9       125     17.4          217.1       Y