TITLE:   GCN CIRCULAR
NUMBER:  9515
SUBJECT: GRB 090618: ROTSE-III Detection of Optical Counterpart
DATE:    09/06/18 08:57:11 GMT
FROM:    Wiphu Rujopakarn at U AZ/Steward  <wiphu@as.arizona.edu>

W. Rujopakarn (Steward), T. Guver (U Arizona), S. B. Pandey (Michigan),
and F. Yuan (Michigan) report on behalf of the ROTSE collaboration:

ROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB
090618 (Swift trigger 355083, Schady et al., GCN 9512). The first image
was at 08:28:53.7 UT, 23.9 s after the burst (6.7 s after the GCN notice
time). The unfiltered images are calibrated relative to USNO A2.0. We
detect a 14.1 magnitude source with coordinates:

19:35:58.65 +78:21:24.03    (J2000), with positional uncertainty of 1" or
better

start UT    	mag     mlim(of image)
----------------------------------
08:28:29.8     14.1	16.2

This source is not visible in DSS (second epoch), 2MASS or the MPChecker
database. Continuing observations are in progress.