TITLE:   GCN CIRCULAR
NUMBER:  9880
SUBJECT: GRB 090904A: ROTSE-III Optical Limits
DATE:    09/09/04 01:25:32 GMT
FROM:    Shashi Bhushan Pandey at ROTSE  <shaship@umich.edu>

S. B. Pandey (U Mich), W. Rujopakarn (Steward), W. Zheng (U Mich) report on
behalf of the ROTSE collaboration:

ROTSE-IIId, located at the Turkish National Observatory at Bakirlitepe,
Turkey, responded to GRB 090904A (Swift trigger 361830; Perri M., GCN
9879), producing images beginning 9.5 s after the GCN notice time. An
automated response took the first image at 01:02:31.6 UT, 84.7 s after the
burst, and during the gamma-ray emission, 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 or the XRT error circle, for both single
images and coadding into sets of 10. Individual images have limiting
magnitudes ranging from 15.8-16.6; we set the following specific limits.

start UT       end UT      t_exp(s)   mlim   t_start-tGRB(s)  Coadd?
--------------------------------------------------------------------
01:02:31.5   01:02:36.5         5     15.8           84.6       N
01:04:48.1   01:09:27.0       278     17.8          221.2       Y