[vsnet-grb-info 15322] GRB 140716A: GROND confirmation of the afterglow

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  16614
SUBJECT: GRB 140716A: GROND confirmation of the afterglow
DATE:    14/07/20 14:54:05 GMT
FROM:    Sebastian Schmidl at TLS Tautenburg  <schmidl at tls-tautenburg.de>

J. Bolmer, F. Knust (both MPE Garching), S. Schmidl (TLS Tautenburg), and
J. Greiner (MPE Garching) report on behalf of the GROND team:

We re-observed the field of GRB 140716A (Swift trigger 604792; Cummings et
al., GCN 16596) simultaneously in g'r'i'z'JHK with GROND (Greiner et al.
2008, PASP 120, 405) mounted at the 2.2m MPG telescope at ESO La Silla
Observatory (Chile).

Observations started on July 20, 2014, at 09:47 UT, 3.97 days after the
GRB trigger. They were performed at an average seeing of 1.8" and at an
average airmass of 2.3.

Based on a total exposure of 1782 seconds in g'r'i'z', we measure for the
optical afterglow candidate reported by Knust et al. (GCN
#16601) the following preliminary magnitudes (all AB):

g' = 22.9 +/- 0.2 mag,
r' = 22.0 +/- 0.1 mag,
i' = 21.7 +/- 0.2 mag and
z' = 21.2 +/- 0.2 mag.

Compared to the first-epoch observations the source has faded in all
bands, confirming that this is the optical afterglow of GRB 140716A.

Given magnitudes are calibrated against GROND zeropoints and are not
corrected for the expected Galactic foreground extinction corresponding to
a reddening of E_(B-V) = 0.13 mag in the direction of the burst (Schlegel
et al. 1998).