[vsnet-grb-info 7402] GRB 090308: GROND observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8966
SUBJECT: GRB 090308: GROND observations
DATE:    09/03/10 10:07:05 GMT
FROM:    Adria C. Updike at Clemson U  <aupdike at clemson.edu>

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

We observed the field of GRB 090308 (Swift trigger 345777; Evans et al.,
GCN #8948) 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 started at 00:01 UT on March 9th, 6 hours after the GRB
trigger for 2 hours, and were followed by a second epoch beginning at
07:44 UT and lasting 30 min. They were carried out at an average seeing of
1.7".

The red object just outside the enhanced XRT error circle noted by Cenko
et al. (GCN #8965) is detected in both epochs with no sign of fading.
Therefore, we conclude this is not the afterglow of GRB 090308.

Based on 30 min of our first epoch, we do not detect a source within the
Swift-XRT error circle reported by Evans & Page (GCN #8956) down to (all in
AB system)

 g' > 22.7,
 r' > 22.9,
 i' > 22.6,
 z' > 22.3,
 J > 21.1,
 H > 20.6 and
 K > 19.6

The given limits are derived based on calibrating the images against GROND
zeropoints and 2MASS field stars and are not corrected for the Galactic
foreground extinction corresponding to a reddening of E_(B-V)= 0.114 in the
direction of the burst (Schlegel et al. 1998).