[vsnet-grb-info 10469] GRB 110407A: GROND Detection of the Optical Afterglow
GCN Circulars
gcncirc at capella2.gsfc.nasa.gov
Fri Apr 8 17:10:43 JST 2011
TITLE: GCN CIRCULAR
NUMBER: 11906
SUBJECT: GRB 110407A: GROND Detection of the Optical Afterglow
DATE: 11/04/08 08:10:39 GMT
FROM: Patricia Schady at MPE/Swift <pschady at mpe.mpg.de>
D. A. Kann (TLS Tautenburg), P. Schady and J. Greiner (both MPE
Garching) report on behalf of the GROND team:
We observed the field of GRB 110407A (Swift trigger 450884; Wolf et
al., GCN #11894) 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 00:50 UT on April 8, 11 hours after the GRB
trigger, and continued until ~03:30 UT. They were performed at a
seeing of 1.5-2.5" and at an average airmass of 1.5.
We detect a point source within the 1.7 arcsec enhanced Swift-XRT
error circle (Evans et al., GCN #11903), consistent with the optical
afterglow detection reported by Chuang et al. (GCN #11901) and
Malesani et al. (GCN #11904) in the g'r'i'z' bands. In an exposure of
102 mins at a mid-observing time of 02:31 UT (12.5 hours after the BAT
trigger), we estimate a preliminary r'-band magnitude (in the AB
system) of 23.9+/-0.1.
The r'-band magnitude is calibrated against SDSS field stars and has
not been corrected for the expected Galactic foreground extinction
corresponding to a reddening of E_(B-V)=0.03 mag in the direction of
the burst (Schlegel et al. 1998).
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