GCN Circular 8849
Subject
GRB 090123: GROND detection
Event
Date
2009-01-24T11:09:19Z (17 years ago)
From
Jochen Greiner at MPI <jcg@mpe.mpg.de>
A. Rossi (Tautenburg Obs.) and J. Greiner (MPE Garching) report on behalf
of the GROND team:
GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2m ESO/MPI
telescope at La Silla Observatory (Chile) imaged the field of GRB 090123
(Swift trigger 340895, Grupe et al. 2009, GCN #8842) simultaneously in
g'r'i'z'JHK. Observation started on 2009-01-24 at 01:22 UTC, about 17 hours
after the burst. The total exposure time was 25 minutes, the average seeing
1.3 at airmass 2.5.
We detect the afterglow at the position reported by SWIFT UVOT (Marshall
et al 2009, GCN #8846) in g'r'i'z', but not in JHK. We estimate the following
observed magnitudes and upper limits (all in AB system):
g' = 22.77 +- 0.05
r' = 22.45 +- 0.05
i' = 21.95 +- 0.08
z' = 22.09 +- 0.12
J > 21.5
H > 21.0
K > 20.5
calibrated against GROND zeropoints and 2MASS field stars.