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GCN Circular 10284

GRB 091221: ROTSE-III Detection of Optical Counterpart
2009-12-21T21:37:02Z (14 years ago)
Shashi Bhushan Pandey at ROTSE <>
GRB 091221: ROTSE-III Detection of Optical Counterpart

W. Zheng, F. Yuan and S. B. Pandey (U Mich), report on behalf of the ROTSE

ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia,
responded to GRB 091221 (Swift trigger 380311, GCN 10283 Krimm et al.). The
first image was at 20:53:18.1 UT, 25.8 s after the burst (9.1 s after the
GCN notice time). The unfiltered images are calibrated relative to USNO
A2.0. We detect a 17.4 magnitude, source with coordinates:

     03:43:11.47      +23:14:29.38    (J2000), with positional uncertainty
of 1" or better

start UT    	mag     mlim(of image)
20:54:49.5     17.4     18.0 

This source is not visible in DSS (second epoch), 2MASS or the MPChecker

A jpeg image is available at, the candidate is
marked as 110.

Continuing observations are in progress.
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