[vsnet-grb-info 14896] GRB 140428A: GROND observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  16191
SUBJECT: GRB 140428A: GROND observations
DATE:    14/04/30 22:02:44 GMT
FROM:    Karla Varela at MPE  <kvarela at mpe.mpg.de>

F. Knust, K. Varela, J. Greiner (MPE Garching), and D. A. Kann
(TLS Tautenburg) report on behalf of the GROND team:

We observed the field of GRB 140428A (Swift trigger 597519; Kocevski et
al., GCN #16177) 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 La Silla
Observatory (Chile).

Observations started at 00:43 UT on 2014-04-29, 2 hours after the GRB
trigger. They were performed at an average seeing of 1.4" and at an
average airmass of 1.9.

We found a single point source within the 1.7" Swift-XRT error circle
reported by Page et al. (GCN #16178) at

RA (J2000.0) = 12h 57m 28.39s
DEC (J2000.0) = + 28d 23' 06.4"

with an uncertainty of 0.5" in each coordinate.

This source is consistent with the one reported by Perley (GCN #16180).

Based on the first 1133 s of total exposures in g'r'i'z' and 1920 s in
JHK, we estimate preliminary magnitudes (all in AB system) of

g' > 24.4 mag,
r' = 23.6 +/- 0.2 mag,
i' = 21.7 +/- 0.1 mag,
z' = 21.5 +/- 0.1 mag,
J > 19.7 mag,
H > 20.6 mag, and
K > 19.1mag.