TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3672 SUBJECT: GRB 050724: Optical imaging/astrometry DATE: 05/07/25 01:09:43 GMT FROM: Josh Bloom at Harvard/CFA J. S. Bloom (UC Berkeley), A. Dupree (Smithsonian Astrophysical Observatory), H-W. Chen (MIT), & J. X. Prochaska (UC Santa Cruz) report: "Comparison of the 2MASS catalog with a short exposure with the unfiltered MIKE (Magellan II/Clay) guider CCD camera beginning on 2005-07-24 23:25:25 UTC shows faint sources near the XRT localizations (GCNs #3665 & #3669). We find the following positions (systematic error relative to the ICRS is 0.2" in both RA and DEC): A 16:24:44.964 -27:32:23.21 J2000 Source 1 in #3669 error circle B 16:24:44.912 -27:32:32.73 J2000 Source 1 in #3665 error circle, noted by Antonelli et al. #3666 C 16:24:45.303 -27:32:34.67 J2000 Source 2 in #3665 error circle D 16:24:44.398 -27:32:26.85 J2000 Bright galaxy to the West of XRT error circles Source D appears to be an extended galaxy and, while formally excluded by the 90% confidence regions of the various positions reported for the X-ray afterglow, is of interest nonetheless (especially given what appears to be an emerging trend of low-redshift galaxies associated with short bursts)." A finding chart may be found at: http://astro.berkeley.edu/~jbloom/grb050724.png Please email JSB if you would like to make use of the guider FITS image. This message may be cited. [GCN OPS NOTE 924jul05): Per author's request, hanged "astronomy" to "astrometry" in the Subject.]