TITLE:   GCN CIRCULAR
NUMBER:  11756
SUBJECT: GRB 110223B: GROND Detection of Optical Afterglow Candidate
DATE:    11/02/24 01:49:21 GMT
FROM:    Felipe Olivares Estay at MPE  <felipe@mpe.mpg.de>

V. Sudilovsky, J. Elliott, F. Olivares E., and J. Greiner (MPE
Garching) report on behalf of the GROND team:

We observed the field of GRB 110223B (Swift trigger 446677; Stamatikos
et al., GCN #11754) simultaneously in g'r'i'z'JHK with GROND (Greiner
et al. 2008, PASP 120, 405) mounted at the 2.2 m MPI/ESO telescope at
La Silla Observatory (Chile).

Observations started at 00:05 UT on February 24th, 2.7 hours after the
GRB trigger, and are continuing. They were performed at an average
seeing of 1.4" and at an average airmass of 1.6.

We found a single point source within the 2.1" Swift/XRT error circle
reported by Stamatikos et al. (GCN #11754) at

�RA (J2000.0) = 10h 00m 55.98s
�DEC (J2000.0) = -68d 18' 06.0"

with an uncertainty of 0.3" in each coordinate.

Based on 7.7 min exposure started at 00:30 UT, we estimate a
preliminary r'-band magnitude of 22.1 +/- 0.1 calibrated against GROND
zero points (AB system). No statements about the variability can be
made at this stage. This measurement is not corrected for the
considerable Galactic foreground extinction corresponding to a
reddening of E(B-V)=0.226 mag in the direction of the burst (Schlegel
et al. 1998).