TITLE:   GCN CIRCULAR
NUMBER:  8787
SUBJECT: GRB 090107B: ROTSE-III Optical Limits  
DATE:    09/01/07 17:48:17 GMT
FROM:    Tolga Guver at UA  <tolga@physics.arizona.edu>

GRB 090107B: ROTSE-III Optical Limits

T. Guver (U Arizona), H. Swan (U Mich), report on behalf of the ROTSE  
collaboration:
ROTSE-IIId, located at the TUBITAK National Observatory at  
Bakirlitepe, Turkey, responded to GRB 090107B (INTEGRAL trigger 5398;  
D. Gotz, GCN 8786), producing images beginning 0.0 s after the GCN  
notice time. An automated response took the first image at 16:20:40.7  
UT, 4.7 s after the burst, and during the gamma-ray emission, under  
fair conditions. We took 10 5-sec, 10 20-sec and 63 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 INTEGRAL/IBIS error circle, for both single images and  
coadding into sets of 10. Individual images have limiting magnitudes  
ranging from 16.2-16.6; we set the following specific limits.

start UT	end UT 	t_exp(s) mlim t_start-tGRB(s) Coadd?
--------------------------------------------------------------------
16:26:35.8	16:26:55.8	20	16.6	359.8	N
16:28:03.0	16:32:41.6	278	17.7	447.0	Y