GCN Circular 17248

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

We observed the field of GRB 141225A (Swift trigger 622476; D'Avanzo et
al., GCN #17229) 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 ESO La Silla
Observatory (Chile).

Observations started at 05:58 UT on 26 December 2014, around 7 hours after
the  GRB trigger. They were performed at an average seeing of 1".4 and at
an average airmass of 2.3.

Based on images with exposure times of 2640 s in g'r'i'z' and 2400 s in
JHK, we detect the afterglow (Gorosabel et al., GCN #17230, Guidorzi et
al., GCN #17231) at the following AB magnitudes:

g' = 22.56 +/- 0.07 mag,
r' = 22.31 +/- 0.07 mag,
i' = 22.34 +/- 0.14 mag,
z' = 21.74 +/- 0.12 mag,
J  > 21.5 mag,
H  > 21.0 mag, and
K  > 17.3 mag.

The colors do not point to a strongly extinguished afterglow, implying it
is intrinsically faint.

The given magnitudes and limits are derived based on calibrating the
images against SDSS (g'r'i'z') and 2MASS field stars (JHK) and are not
corrected for the Galactic foreground extinction corresponding to a
reddening of E_(B-V)= 0.017 in the direction of the burst (Schlegel et al.
1998).