T. Schweyer (MPE Garching), D. A. Kann (TLS Tautenburg), and J. Greiner
(MPE Garching) report on behalf of the GROND team:
We observed the field of GRB 150430A (Swift trigger 639433; D'Elia et al.,
GCN # 17789) 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
Observations started at 07:09 UT on 2015-04-30, 6.8 hrs after the GRB
trigger. They were performed at an average seeing of 0.9" and at an
average airmass of 1.6.
Inside the 1.4" enhanced XRT error circle (Burrows et al., GCN # 17792)
and in the nearby surroundings we detect no sources.
Based on 27 min of total exposure time in g'r'i'z' and 20 min in JHK
centered 7.56 hrs after the GRB, we estimate the following preliminary
upper limits (AB magnitudes):
g' > 24.3 mag,
r' > 24.3 mag,
i' > 23.8 mag,
z' > 23.5 mag,
J > 21.5 mag,
H > 20.8 mag, and
K > 19.5 mag.
Given magnitudes are calibrated against GROND zero points (g'r'i'z') as
well as 2MASS field stars (JHK) and are not corrected for the expected
Galactic foreground extinction corresponding to a reddening of
E_(B-V)=0.03 mag in the direction of the burst (Schlegel et al. 1998)