GCN Circular 14898

J. Elliott (MPE Garching), S. Schmidl (TLS Tautenburg), J.Greiner
(MPE Garching), D. A. Kann (TLS Tautenburg), S. Ciceri and L. Mancini
(both MPIA) report on behalf of the GROND team:

We observed the field of GRB 130615A (Swift trigger 558271, Sonbas et al.,
GCN #14897) 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 on June 15, 2013, at 10:17:21 UT, 0.54 hrs after the
GRB trigger. They were performed at an average seeing of 1".1 and at an
average airmass of 1.9.

We find a source inside the enhanced 2".1 SWIFT/XRT error circle
(http://www.swift.ac.uk/sper/558271/) at

RA (J2000.0) = 18:19:19.11

DEC (J2000.0) = -68:09:40.5

with an uncertainty of 0".5 in each coordinate.

Based on a total exposure time of 263 s in g'r'i'z' and 240 s in JHK, at a
midtime of 0.82 hrs after the burst, we measure the following preliminary
AB magnitudes:

g' = 21.3 +/- 0.1 mag,
r' = 20.7 +/- 0.1 mag,
i' = 20.6 +/- 0.1 mag,
z' = 20.5 +/- 0.1 mag,
J = 20.2 +/- 0.3 mag,
H = 19.8 +/- 0.3 mag and
K > 19.1 mag

Considering the galactic foreground extinction, the fit to the spectral
energy distribution indicates a redshift <~ 3.

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)=0.12 mag
in the direction of the burst (Schlegel et al. 1998).