GCN Circular 20878

T.-W. Chen and P. Wiseman (both MPE Garching) report:

We observed the field of ATLAS17cck (Tonry et al., GCN #20877) 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 01:17 UT on 2017-03-16, 15 hours after the earliest
detection reported in Tonry et al. (GCN #20877). They were performed at an
average seeing of 1.4" and at an average airmass of 1.7.

Based on the 24.5 minutes (griz) and 21.3 minutes (JHK) of exposures, we do not
detect a source within the ATLAS17cck error circle of 2��� radius down to the
following 3 sigma limiting AB magnitudes:

g' > 23.9 mag,
r' > 23.9 mag,
i' > 23.3 mag,
z' > 23.1 mag,
J > 21.1 mag,
H > 20.6 mag, and
K > 18.8 mag

However, we note the detection of a bright, uncatalogued source located at RA,
Dec = 07:44:50.33, +24:45:54.8, equivalent to 116.22165, +24.76602, with an
r���-band magnitude of 16.2 mag. We believe this to be the same object as
ATLAS17cck, and that it corresponds to the asteroid (1056) Azalea, which is
expected at this location according to the IAU's Minor Planet Checker,
'http://www.minorplanetcenter.net/'.

The given limits are derived based on images calibrated against Pan-STARRS/2MASS
field stars, and are not corrected for the Galactic foreground extinction
corresponding to a reddening of E_(B-V)= 0.04 in the direction of the reported object
(Schlafly & Finkbeiner 2011).

We acknowledge the excellent support provided by the observer, Paula Sarkis, at
the telescope, and the support astronomer, Sam Kim, in obtaining these data. And
Ying-Tung Chen for checking the asteroid position.