TITLE:   GCN CIRCULAR
NUMBER:  9357
SUBJECT: GRB 090515: ROTSE-III Optical Limits
DATE:    09/05/15 05:08:31 GMT
FROM:    Wiphu Rujopakarn at U AZ/Steward  <wiphu@as.arizona.edu>

W. Rujopakarn (Steward Observatory), B. E. Schaefer (Louisiana State), and
E.S. Rykoff (UCSB), report on behalf of the ROTSE collaboration:

ROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB
090515 (Swift trigger 352108; Beardmore et al., GCN 9356), producing
images beginning 6.5 s after the GCN notice time. An automated response
took the first image at 04:45:27.5 UT, 18.0 s after the burst, under fair
conditions. We took 10 5-sec and 10 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 16.4-17.8; we set the following specific limits.

start UT       end UT      t_exp(s)   mlim   t_start-tGRB(s)  Coadd?
--------------------------------------------------------------------
04:45:27.5   04:45:32.5         5     16.4           18.0       N
04:45:27.5   04:46:34.6        67     18.4           18.0       Y