[vsnet-grb-info 4283] GRB 070208: ROTSE-III Optical Limits

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6076
SUBJECT: GRB 070208: ROTSE-III Optical Limits
DATE:    07/02/08 10:13:07 GMT
FROM:    Fang Yuan at ROTSE  <yuanfang at umich.edu>

F. Yuan (U Mich), W. Rujopakarn (U Arizona), H. Swan (U Mich), E. S. 
Rykoff (U Mich) report on behalf of the ROTSE collaboration:

ROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB 
070208 (Swift trigger 259714, GCN 6074, Sato, et al), producing images 
beginning 5.8 s after the GCN notice time. An automated response took 
the first image at 09:11:14.8 UT, 40.5 s after the burst, under fair 
conditions. We took 10 5-sec, 10 20-sec and 20 60-sec exposures. These 
unfiltered images are calibrated relative to USNO A2.0 (R).

Comparison to the DSS (second epoch) reveals no new sources within both 
the BAT and the XRT error circles, for both single images and coadding 
into sets of 10. We marginally detect one of the DSS objects detected by 
Mirabal & Halpern (GCN 6075) in our deepest images. Individual images 
have limiting magnitudes ranging from 15.9-17.0; we set the following 
specific limits.

start UT       end UT      t_exp(s)   mlim   t_start-tGRB(s)  Coadd?
--------------------------------------------------------------------
09:11:14.8   09:11:19.8         5     16.0           40.5       N
09:11:14.8   09:12:21.9        67     17.5           40.5       Y
09:12:29.9   09:17:25.5       295     18.2          115.6       Y