[vsnet-grb-info 7043] GRB 081204: GROND Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8627
SUBJECT: GRB 081204: GROND Observations
DATE:    08/12/06 11:45:59 GMT
FROM:    Adria C. Updike at Clemson U  <aupdike at clemson.edu>

A. Updike (Clemson University), C. Clemens, and J. Greiner (both MPE
Garching) report on behalf of the GROND team:

We observed the field of GRB 081204 (INTEGRAL trigger #5385; D. Gotz et
al., GCN #8614) for two epochs simultaneously in g'r'i'z'JHK with GROND
(Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m ESO/MPI
telescope at La Silla Observatory (Chile).

Observations began at 00:30 UT on Dec 5, 2008, 7.75 hr after the GRB
trigger, and consisted of 2.4 hours of exposures.  The second epoch began
at 00:31 UT on Dec 6, 31.75 hr after the trigger, and consisted of 1.3
hours of exposures. Observations were performed under favorable sky
conditions.

We detect two sources within the refined 5.3'' Swift-XRT error circle
reported by V. Mangano et al. (GCN #8620), at the astrometrically
corrected positions:

RA (J2000.0) 23h 19m 09.10s
Dec (J2000.0) -60d 13' 29.7"

and

RA (J2000.0) 23h 19m 09.37s
Dec (J2000.0) -60d 13' 31.2"

The second candidate agrees with the position reported by Berger & Rest
(GCN #8624).

We detect no evidence of fading in either source between the two epochs.
Therefore, we suggest that neither of the sources are the afterglow of
GRB 081204.

Our upper limits from the first epoch in g'r'i'z'JHK are as follows:

g' > 24.2
r' > 24.3
i' > 23.6
z' > 22.9
J  > 20.7
H  > 19.4
K  > 18.3

The given magnitudes are calibrated against GROND zeropoints as well as
2MASS field stars.