GCN Circular 15107

K. Varela (MPE Garching), S. Klose (TLS Tautenburg)
and J. Greiner (both MPE Garching) report on behalf of the GROND team:

We observed the field of GRB 130816B (Stamatikos et al., GCN #15099)
simultaneously in g'r'i'z'JHKs 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 23:12 UT on 16 August 2013, 18.3 hours after the
GRB trigger. They were performed at an average seeing of 1.6" and at and
average airmass of 2.20. We find a source inside the 1.9" Swift-XRT error
circle (Osborne et al., GCN #15102) at coordinates

RA(J2000.0) = 11:20:03.96
DEC (J200.0) = -57:33:27.1

with an uncertainty of 0.5" in each coordinate.

Based on the first 460 sec g'r'i'z and 480 sec JHK exposure,
we estimate preliminary magnitudes (all in AB) of

g' > 23.5 mag
r' = 23.1 +/- 0.2 mag,
i' = 22.5 +/- 0.2 mag,
z' = 21.6 +/- 0.1 mag,
J = 20.5 +/- 0.3 mag,
H = 20.5 +/- 0.3 mag,
K = 19.9 +/- 0.4 mag,

calibrated against GROND zero points (griz) and 2MASS (JHK) and
are not corrected for the Galactic foreground extinction corresponding to
a reddening of E_(B-V)= 0.56 mag in the direction of the burst
(Schlegel et al. 1998).