GCN Circular 22701

P. Schady (MPE, Garching) reports:

We observed the field of GRB 180510B (Swift trigger 831816; Tohuvavohu et
al., GCN #22696
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 ) 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 23:14 UT on 10th May, 3.0 hours after the GRB
trigger. They were performed at an average seeing of 1.3" and at an
average airmass of 1.8.

A single point source is present within the 1.5" Swift-XRT error circle
reported by Beardmore et al. (GCN #22698
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 ) at

RA (J2000.0) = 05:11:52.66
DEC (J2000.0) = -62:19:26.4

with an uncertainty of 0.2" in each coordinate.

Based on 6.6 min of total exposures in g'r'i'z' and 6 min in JHK, the
estimated AB magnitudes are

g' = 20.5 +/- 0.1 mag
r' = 20.0 +/- 0.1 mag
i' = 19.8 +/- 0.1 mag
z' = 19.6 +/- 0.1 mag
J = 18.8 +/- 0.1 mag
H = 18.5 +/- 0.1 mag
K = 18.0 +/- 0.1 mag

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)=0.02 in the direction
of the burst (Schlafly & Finkbeiner 2011).

I would like to thank Markus Rabus for his excellent support from La Silla.