[AAVSO-HEN] GRB 091208: ROTSE-III Optical Limits

[grb at aavso.org]

The following is a GCN Circular circulated via the AAVSO network.
For an archive and more information on circulars visit:
http://lheawww.gsfc.nasa.gov/docs/gamcosray/legr/bacodine/gcn3_archive.html

TITLE:   GCN CIRCULAR
NUMBER:  10254
SUBJECT: GRB 091208: ROTSE-III Optical Limits
DATE:    09/12/08 09:16:45 GMT
FROM:    Fang Yuan at ROTSE  <yuanfang at umich.edu>

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

ROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB  
091208 (Swift trigger 378554; E. A. Hoversten et al, GCN 10253),  
producing images beginning 9.6 s after the GCN notice time. An  
automated response took the first image at 08:46:30.5 UT, 30.0 s after  
the burst. We took 10 5-sec and 42 20-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, for both single images and coadding  
into sets of 10. Individual images have limiting magnitudes ranging  
from 14.6-16.6; we set the following specific limits.

start UT       end UT      t_exp(s)   mlim   t_start-tGRB(s)  Coadd?
--------------------------------------------------------------------
08:52:40.1   08:57:21.5       281     17.3          399.6       Y
08:57:30.2   09:02:12.0       281     17.4          689.7       Y