GCN Circular 16099

K. Varela, C. Delvaux (both MPE Garching), A. Nicuesa Guelbenzu (TLS
Tautenburg), and J. Greiner (MPE Garching) report on behalf of the GROND
team:

We observed the field of GRB 140413A (Swift trigger 595616; D'Elia et al.,
GCN #16098) 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 La Silla Observatory
(Chile).

Observations started at 00:13 UT on 13 April 2014, less than 5 min after
the GRB trigger, and are continuing. They are performed at a mean airmass
of 1.9 and a mean seeing of 0.9".

We find a single point source within the 5.8" Swift/XRT error circle at
coordinates

   RA(J2000)  =  04:21:49.23
   Dec(J2000) = -51:10:58.0.

At a midtime of 00:17 UT we measure the following preliminary AB magnitudes:

r' = 20.2 +/- 0.1,
i' = 19.6 +/- 0.1,
z' = 19.3 +/- 0.1.

The source is also visible in g. At present we cannot decide if the source
is fading. Data processing is still ongoing, observations are continuing.

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)=0.02 mag in the
direction of the burst (Schlegel et al. 1998).