GCN Circular 15052

V. Sudilovsky, K. Varela, and J. Greiner
(all MPE Garching) report on behalf of the GROND team:

We observed the field of GRB 130727A (Swift trigger 564342; Stroh et al.,
GCN #15046) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008,
PASP 120, 405) mounted at the 2.2 m MPG/ESO telescope at La
Silla Observatory (Chile).

Observations started at 23:40 UT on July 27, 2013, 7 hours after the
GRB trigger. They were performed at an average seeing of 2.3" and at
an average airmass of 2.2.

We detect the afterglow reported by Guidorzi et al. (GCN #15050), and
based on images with total exposures of 1500s in g'r'i'z'
and 1200s in JHK, we estimate preliminary magnitudes (all in AB) of

g' = 22.3 +/- 0.1 mag,
r' = 21.8 +/- 0.1 mag,
i' = 21.6 +/- 0.1 mag,
z' = 21.0 +/- 0.2 mag,
J = 20.4 +/- 0.3 mag,
H > 20.1 mag, and
K > 19.4 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) = 0.03 mag in
the direction of the burst (Schlegel et al. 1998).