GCN Circular 18595

F. Knust, T.-W. Chen and J. Greiner (all MPE Garching) report on behalf of
the GROND team:

We observed the field of GRB 151112A (Swift trigger 663179; Malesani et
al., GCN #18588) simultaneously in g'r'i'z'JHK with GROND (Greiner et al.
2008, PASP 120, 405) mounted at the 2.2 m MPG telescope at the ESO La
Silla Observatory (Chile).

Observations started at 00:09 UT on 2015-11-13, 10.5hrs after the GRB
trigger, and are continuing. They were performed at an average seeing of
1.8" and at an average airmass of 1.2.

We found a single point source within the 1.4" Swift-XRT error circle
reported by Osborne et al. (GCN #18592) at

RA (J2000.0) = 00h 08m 12.77s

DEC (J2000.0) = -61d 39' 48.4"

with an uncertainty of 0.5" in each coordinate.

Based on 11.50 min of total exposures in g'r'i'z' and 12.00 min in JHK, we
estimate preliminary magnitudes (all in AB system) of

g' > 23.9 mag,
r' = 23.9 +/- 0.373 mag,
i' = 22.4 +/- 0.169 mag,
z' = 22.5 +/- 0.288 mag,
J  > 21.0 mag,
H  > 20.5 mag, and
K  > 19.0 mag.


Given magnitudes are calibrated against GROND zeropoints as well as 2MASS
field stars and are not corrected for the expected Galactic foreground
extinction corresponding to a reddening of E_(B-V)=0.01 mag in the
direction of the burst (Schlegel et al. 1998).