[vsnet-grb-info 8086] GRB 090708: ROTSE-III Optical Limits

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9622
SUBJECT: GRB 090708: ROTSE-III Optical Limits
DATE:    09/07/08 03:58:49 GMT
FROM:    Fang Yuan at ROTSE  <yuanfang at umich.edu>

F. Yuan (U Mich), E.S. Rykoff (UCSB), H. Flewelling (IfA/Hawaii), T.  
Guver (U Arizona), S. B. Pandey (U Mich), W. Rujopakarn (Steward),  
report on behalf of the ROTSE collaboration:

ROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB  
090708 (Swift trigger 356776; Krimm et al., GCN 9621), producing  
images beginning 7.4 s after the GCN notice time. An automated  
response took the first image at 03:39:04.5 UT, 49.2 s after the  
burst, under fair conditions. We took 10 5-sec, 10 20-sec and 10 60- 
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 14.8-16.1; we set the following specific limits.

start UT       end UT      t_exp(s)   mlim   t_start-tGRB(s)  Coadd?
--------------------------------------------------------------------
03:39:04.5   03:39:09.5         5     15.0           49.2       N
03:39:04.5   03:40:11.6        67     16.6           49.2       Y
03:40:27.8   03:45:35.8       308     17.4          132.5       Y