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GCN Circular 12679

GRB 111212A: GROND observations
2011-12-14T09:11:29Z (12 years ago)
Alexander Kann at TLS Tautenburg <>
D. A. Kann, A. Rossi (TLS Tautenburg), V. Sudilovsky, P. Schady and J.
Greiner, (MPE Garching) report on behalf of the GROND team:

We observed the field of the Swift GRB 111212A (Swift trigger 509543;
Campana et al., GCN #12667) 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 13, 2011, at 00:35 UT, in twilight, and are centered 0.658 days
after the GRB trigger. They were taken at an average seeing of 1".2 and at
an airmass of 2. Integration times were 1734 sec in the optical and 2640
sec in the NIR. These observations were obtained under challenging
conditions, with thick cirrus preventing guiding.

A second epoch was obtained on December 14, 2011, starting at 00:57 UT and
centered at 1.667 days after the GRB. It was taken at an average seeing of
1".2 and at an airmass of 2. Integration times were 2420 sec in the
optical and 2160 sec in the NIR. Conditions were much better, with clear,
moonless skies.

At the position of the X-ray afterglow (Osborne et al., GCN #12670), we do
not detect any significant sources in any bands. We derive the following
limits (3 sigma, AB magnitude system):

0.658 days after the trigger:

g' > 24.1
r' > 24.2
i' > 23.4
z' > 22.8
J > 20.5
H > 20.0
K > 18.1

1.667 days after the trigger:

g' > 24.8
r' > 24.8
i' > 23.8
z' > 23.4
J > 21.6
H > 21.0
K > 19.3

Magnitudes were calibrated against GROND zero points in g'r'i'z' and 2MASS
field stars in JHK.
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