[vsnet-grb-info 13569] GRB 130615A: GROND afterglow candidate

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  14898
SUBJECT: GRB 130615A: GROND afterglow candidate
DATE:    13/06/15 12:44:37 GMT
FROM:    Sebastian Schmidl at TLS Tautenburg  <schmidl at tls-tautenburg.de>

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).