GCN Circular 3382

E.S. Rykoff (U Mich), H. Swan (U Mich), B. Schaefer (Louisiana State),
R. Quimby (U Texas), report on behalf of the ROTSE collaboration:

ROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB
050509B (Swift trigger 118749), producing images beginning 10.0 s after
the GCN notice time. An automated response took the first image at
04:00:43.0 UT, 23.7 s after the burst, under excellent conditions. We
took 10 5-sec, 10 20-sec and 60+ 60-sec eposures. These unfiltered
images are calibrated relative to USNO A2.0 (R).  Imaging is ongoing.

Comparison to the DSS (second epoch) reveals no new sources within the
3-sigma error circle, nor do we detect the tentative UVOT source
(Hurkett et al, GCN 3381
Not found
 
 
). Individual images have limiting magnitudes
ranging from 17.07-18.48. In particular, we set a limit of magnitude
17.25 in a single 5 s exposure, starting 23.7 s after the burst.
Coadding the images into sets of 10 reveals no new sources down to
limits of 18.63 (77 s effective length (t_end - t_start), beginning 
23.7s post-burst), 18.72 (298.5s effective length, beginning 100.6s 
post-burst), and 19.46 (695.6s effective length, beginning 399.1s 
post-burst).

[GCN OPS NOTE (09may05):  Per author's request, the two references to 050509A
were changed to the correct value of 050509B.]