GCN Circular 3358
Subject
GRB050502b: Afterglow Confirmation: Correction to OT Coordinates
Date
2005-05-05T10:38:37Z (20 years ago)
From
Brian Schmidt at RSAA, ANU (MSSSO) <brian@mso.anu.edu.au>
S. Bradley Cenko, Derek B. Fox (Caltech), Joshua Rich, Brian Schmidt
(ANU), Jessie Christiansen (UNSW), and Edo Berger (Carnegie) report:
We have further analyzed our images of the field of GRB050502b (GCN
3330) taken with the 1-m ANU telescope (GCN 3338). Additionally, we
have imaged the field with the automated Palomar 60-inch telescope
(P60). Observations at the P60 consisted of 10 x 120 s exposures in the
Gunn i band taken at a mean epoch of 5:40 4 May 2005 UT (43.8 hours
after the burst).
Based on extrapolations from the 2MASS and USNO-B2 catalogs, we adopt
values of V=16.7, I=15.8, R=16.1 for the star located at RA =
09:30:12.616, Dec = +17:00:05.55 (J2000.0). We find the magnitude of
the afterglow candidate identified by Rich, Schmidt, and Christiansen
(GCN 3338) as follows:
Filter Facility UT Age Limit (3-sig) or measure
========================================================
V ANU1m 9:35 May 2 9.5 min V>20.7
V ANU1m 9:41 May 2 15 min V>20.2
V ANU1m 9:43 May 2 18 min V>20.8
V ANU1m 9:46 May 2 20 min V>21.8
I ANU1m 9:58 May 2 23 min I=19.84+/-0.09
i P60 5:40 May 4 43.8 hr i>21.7
We therefore identify this source as the afterglow of GRB050502b. To
reiterate the coordinates (J2000.0):
RA 09:30:10.024
DEC +16:59:48.07
Finally, we note the spectral slope at early times, beta > 2.9,
indicates that GRB050502b may be either highly extinguished or at
moderately high redshift.