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GCN Circular 19693

GRB 160712A: GROND observations
2016-07-13T07:45:48Z (8 years ago)
Thomas Kruehler at MPE Garching <>
T. Kruehler and J. Greiner (all MPE Garching) report on behalf
of the GROND team:

We observed the field of GRB 160712A (Swift trigger 704155; Hagen et
al., GCN #19684) simultaneously in g'r'i'z'JHK with GROND (Greiner
et al. 2008, PASP 120, 405) mounted at the 2.2m MPG telescope at the
ESO La Silla Observatory (Chile).

Observations started at 03:18:21 UT on 2016-07-13, 7.4 hr after the GRB
trigger. They were performed at an average seeing of 2���.2, at an
average airmass of 1.1, and severely affected by passing clouds.

We found a single source sightly outside of the XRT errorcircle at:

RA (J2000.0) = 20:16:38.50
Dec. (J2000.0) = -26:57:30.7

with an uncertainty of 0".5 in each coordinate. The distance to the
center of the XRT error circle (90% confidence radius 1".5 arcsec)
is 2".2.

Based on images with 24.2 min of total exposure in g'r'i'z'
and 24.0 min in JHK at a mid-time of 03:57:19 UT on 2016-07-13,
we derive the following preliminary magnitudes and upper limits
(all in AB system):

g > 23.3 mag
r = 22.9 +- 0.3 mag
i = 21.7 +- 0.3 mag
z = 21.4 +- 0.3 mag
J = 20.5 +- 0.2 mag
H = 20.2 +- 0.2 mag
K = 20.0 +- 0.3 mag

Given magnitudes are calibrated against USNO as well as 2MASS
field stars and are not corrected for the expected Galactic foreground
extinction corresponding to a reddening of E_(B-V) = 0.065 mag in the
direction of the burst (Schlafly & Finkbeiner 2011).

No statement about variability can be made at this point. Given its
position somewhat outside of the XRT error circle, it is uncertain
whether this source is related to GRB 160712A.
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