GCN Circular 3580

S.A. Yost, E.S. Rykoff, W. Rujopakarn (U Mich), K. Alatalo (Berkeley), B. 
Schaefer (Louisiana State) report on behalf of the ROTSE collaboration:

ROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB
050713A (Swift trigger 145675), producing images beginning 10.7 s
after the GCN notice time. An automated response took the first image
at 04:29:24.8 UT, 22.4 s after the burst, under fair conditions. We
took 10 5-sec, 10 20-sec and 10 60-sec eposures. These unfiltered
images are calibrated relative to USNO A2.0 (R).

Comparison to the DSS (second epoch) reveals no new sources within the
3-sigma error circle or at the XRT position, for both single images
and coadding into sets of 10. Individual images have limiting
magnitudes ranging from 16.2-17.7; we set the following limit, noting
it is adversely affected by the glare from the nearby bright star SAO
10034 (V=6.6), 67" from the XRT position.

start UT       end UT      t_exp(s)   mlim   t_start-tGRB(s)  Coadd?
--------------------------------------------------------------------
04:29:24.8    4:30:46.8        82     17.7           22.4       Y