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GCN Circular 12988

Subject
GRB 120224A: GROND detection of the afterglow candidate
Date
2012-02-27T01:33:33Z (12 years ago)
From
Jonny Elliott at MPE/GROND <jonnyelliott@mpe.mpg.de>
J. Elliott (MPE Garching), S. Klose (TLS Tautenburg) and J. Greiner (MPE
Garching) report on behalf of the GROND team:

We observed the field of GRB120224A (Swift trigger 515976; Saxton et al.,
GCN #12980) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008,
PASP 120, 405) mounted at the 2.2 m MPG/ESO telescope at La Silla
Observatory (Chile).

First observations started at 00:14 UT on 25 February 2012, 19.58 hrs
after the GRB trigger. They were perfomed at an average seeing of 1".27
and at an average airmass of 1.4.

After an exposure time of 4.72 min in g'r'i'z' and 8 min JHK, no source was
detected.

Second observations started at 00:48 UT on 26 February 2012, 1.84 days
after the GRB trigger. They were performed at an average seeing of 0".96
and at an average airmass of 2.0.

We find a single point source within the 1".8 refined Swift-XRT error circle
reported by Osborne et al. (GCN #12981) at

RA (J2000.0) = 02:43:46.15 = 40.94230

Dec. (J2000.0) = -17:45:42.0 = -17.76169

with an uncertainty of 0".5 in each coordinate.

Based on total exposures of 36 min in JHK, we estimate preliminary
magnitude (AB) of,

J = 20.9 +/- 0.2

The given magnitude is calibrated against 2MASS field stars and is not
corrected for the expected Galactic foreground extinction corresponding to
a reddening of E(B-V)=0.04 in the direction of the burst (Schlegel et al.
1998).
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