TITLE:   GCN CIRCULAR
NUMBER:  16257
SUBJECT: GRB140512A : GROND observations
DATE:    14/05/13 09:52:24 GMT
FROM:    Karla Varela at MPE  <kvarela@mpe.mpg.de>

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

We observed the field of GRB 140512A (Pagani et al., GCN 16249)
simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120,
405) mounted at the 2.2m MPG telescope at La Silla Observatory (Chile).

Observations started at 03:36 UT on May 13, about 8.0 hrs after the GRB
trigger. They were performed at an average seeing of 1.7" and at an
average airmass
of 2.3.

The afterglow discovered by Gorbovskoy et al. (GCN 16250)
is detected in all optical bands and the JH bands. At a mean time of 04:02
UT, with
a 264 s exposure in g’r’i’z’ bands and 240 s in JHK, we measure the following
preliminary AB magnitudes:

g'= 20.3 +/- 0.1 mag,
r'= 19.7 +/- 0.1 mag,
i'= 19.5 +/- 0.1 mag,
z'= 19.3 +/- 0.1 mag,
J = 19.0 +/- 0.1 mag,
H = 18.6 +/- 0.1 mag, and
K > 18.2 mag.

The given optical and NIR magnitudes are calibrated against GROND
zeropoints and
2MASS field stars in g'r'i'z and JHK respectively, and are not corrected
for the
Galactic foreground extinction corresponding to a reddening of E(B-V)=0.16
in the
direction of the burst (Schlegel et al. 1998).