TITLE:   GCN CIRCULAR
NUMBER:  22479
SUBJECT: GRB180314A: GROND detection of the afterglow
DATE:    18/03/14 01:17:19 GMT
FROM:    Jan Bolmer at MPE/Garching  <jan@bolmer.de>

J. Bolmer (ESO/MPE) reports:

I observed the field of GRB 180314A (Swift trigger 814129; P. D'Avanzo et al.,
GCN 22478) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008,
PASP 120, 405) mounted at the 2.2 m MPG telescope at ESO La Silla
Observatory (Chile).

Observations started at 00:47 UT on March 14, 2018, 4 minutes after
the GRB trigger. They were performed at an average seeing of 1".1 and at
an average airmass of 1.03.

We clearly detect the NIR/optical transient of GRB 180314A at
the position reported by P. D'Avanzo et al. (GCN 22478).
Based on total exposure of 200 seconds in g’r’i'z' at a midtime
of 00:50 UT, 7 minutes after the burst, we measure
the following preliminary magnitudes (AB magnitude
system):

g' = 17.87 +/- 0.01 mag,
r' = 17.57 +/- 0.02 mag,
i' = 17.36 +/- 0.03 mag,
z' = 17.25 +/- 0.03 mag

Magnitudes are calibrated against PanSTARRS field stars and are not
corrected for the Galactic foreground extinction corresponding to a
reddening of E_(B-V)= 0.07 mag in the direction of the burst (Schlegel et al. 1998).

Observations are continuing.