[vsnet-grb-info 11250] GRB 111210A: GROND observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  12662
SUBJECT: GRB 111210A: GROND observations
DATE:    11/12/11 12:31:25 GMT
FROM:    Sylvio Klose at TLS Tautenburg  <klose at tls-tautenburg.de>

D. A. Kann, S. Klose (TLS Tautenburg), and J. Greiner, (MPE Garching)
report on behalf of the GROND team:

We observed the field of the Swift GRB 111210A (Swift trigger 509419; 
Siegel et al., GCN #12650) simultaneously in g'r'i'z'JHK with GROND 
(Greiner et al. 2008, PASP, 120, 405) mounted at the 2.2 m ESO/MPG 
telescope at La Silla Observatory (Chile). Observations started on 
December 11, 2011, at 08:06 UT, 0.73 days after the GRB trigger, during 
morning twilight and were partially performed only in the NIR. They were 
taken at an average seeing of 1".1 and at an airmass of 2 to 1.5.

At the position of the X-ray afterglow (Goad et al., GCN #12652) as well 
as the optical candidate (Tanvir et al., GCN #12657), we tentatively 
detect a source in the redder filters.

Based on co-added images of 743 s integration time in g'r'i'z' (centered 
0.7396 days after the trigger) and 2160 s in JHK (centered 0.7520 days 
after the trigger), the following magnitudes and limits (3 sigma, AB 
magnitude system) have been derived:

g' > 22.6,
r' > 23.2,
i' = 22.8 +/- 0.4,
z' = 22.4 +/- 0.3,
J =  21.4 +/ 0.3,
H =  21.4 +/- 0.4,
K >  20.5.

Our r'-band upper limit is not deep enough to check fading against the 
Gemini North candidate. If the faint detections actually represents a real 
object, this is likely the host galaxy of this GRB (Tanvir & Malesani, GCN 
12661).

Magnitudes were calibrated against the SDSS catalog in g'r'i'z' and 2MASS
field stars in JHK.