[vsnet-grb-info 15309] GRB 140716A: GROND afterglow candidate

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  16601
SUBJECT: GRB 140716A: GROND afterglow candidate
DATE:    14/07/17 12:21:55 GMT
FROM:    Sebastian Schmidl at TLS Tautenburg  <schmidl at tls-tautenburg.de>

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

We 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 at 10:16 UT on July 17, 2014, 23.8 hrs after
the GRB trigger. They were performed at an average seeing of 1.8" and at
an average airmass of 2.3.

We find a faint source inside the XRT error circle given in Page et al.
(GCN 16600) at coordinates

RA  (J2000.0) =  07:12:41.20
DEC (J2000.0) = -60:10:35.3

with an uncertainty of 0.5" in each coordinate.

Based on a total exposures of 264 seconds in g'r'i'z' and 240 seconds in
JHK, at a mid-time of 23.9 hrs after the burst, we measure the following
preliminary magnitudes (all in AB):

g' = 21.5 +/- 0.1,
r' = 21.0 +/- 0.1,
i' = 20.9 +/- 0.1,
z' = 20.6 +/- 0.1,
J > 20.1,
H > 19.6 and
K > 18.7.

At present we cannot decide if the source is fading.

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) = 0.13 mag
in the direction of the burst (Schlegel et al. 1998).