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GCN Circular 3672

GRB 050724: Optical imaging/astrometry
2005-07-25T01:09:43Z (19 years ago)
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:

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.]
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