TITLE:   GCN CIRCULAR
NUMBER:  18694
SUBJECT: GRB 151215A: GROND Detection of the Optical/NIR Afterglow
DATE:    15/12/15 05:03:48 GMT
FROM:    Philip Wiseman at MPE/Swift  <wiseman@mpe.mpg.de>

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

We observed the field of GRB 151215A (Swift trigger 667392; Gibson et al.,
GCN #18691) 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 04:04 UT on 15/12/2015, 63 minutes after the GRB
trigger, and are continuing. They were performed at an average seeing of
1.40" and at an average airmass of 2.5.

We found a single point source within the 2.2" Swift-XRT error circle
reported by Evans et al. (GCN #18693) and consistent with that of Cenko
GCN #18692), at:

RA (J2000.0) = 93.58416 = 06:14:20.2

Dec. (J2000.0) = +35.51596 = +35:30:57.5

with an uncertainty of 0.3" in each coordinate.

Based on the first 3.3 min of total exposures in g'r'i'z' and 3.0 min in
JHK, we estimate preliminary magnitudes (AB system) of

g' = 21.81 +/- 0.09 mag,
r' = 20.80 +/- 0.05 mag,
i' = 20.44 +/- 0.05 mag,
z' = 20.36 +/- 0.07 mag,
J = 19.6 +/- 0.2 mag,
H = 19.8 +/- 0.5 mag, and
K = 18.4 +/- 0.4 mag.

Given magnitudes are calibrated against SDSS as well as 2MASS field stars
and are not corrected for the expected Galactic foreground extinction
corresponding to a reddening of E_(B-V)=0.34 mag in the direction of the
burst (Schlafly & Finkbeiner et al. 2011).