TITLE:   GCN CIRCULAR
NUMBER:  9626
SUBJECT: GRB 090709: ROTSE-III Optical Limits
DATE:    09/07/09 08:32:56 GMT
FROM:    Fang Yuan at ROTSE  <yuanfang@umich.edu>

S. B. Pandey (U Mich), W. Rujopakarn (Steward), H. Flewelling (IfA/ 
Hawaii), F. Yuan (U Mich), B. E. Schaefer (Louisiana State), report on  
behalf of the ROTSE collaboration:

ROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB  
090709 (Swift trigger 356890; Morris D. C., GCN 9625), producing  
images beginning 5.6 s after the GCN notice time. An automated  
response took the first image at 07:39:00.6 UT, 26.0 s after the  
burst, and during the gamma-ray emission, under good conditions. We  
took 10 5-sec and 50 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 or the XRT error circle, for both  
single images and coadding into sets of 10. Individual images have  
limiting magnitudes ranging from 16.4-17.2; we set the following  
specific limits.

start UT       end UT      t_exp(s)   mlim   t_start-tGRB(s)  Coadd?
--------------------------------------------------------------------
07:39:00.6   07:39:05.6         5     16.5           26.0       N
07:39:00.6   07:40:07.7        67     17.8           26.0       Y
07:40:20.2   07:45:02.4       282     18.2          105.6       Y