Hot Stuff for One Year (HSOY) - A 583 million star proper motion
  catalogue derived from Gaia DR1 and PPMXL
  Recently, the first installment of data from ESA's Gaia astrometric satellite
mission (Gaia-DR1) was released, containing positions of more than 1 billion
stars with unprecedented precision, as well as only proper motions and
parallaxes, however only for a subset of 2 million objects. The second release,
due in late 2017 or early 2018, will include those quantities for most objects.
In order to provide a dataset that bridges the time gap between the Gaia-DR1
and Gaia-DR2 releases and partly remedies the lack of proper motions in the
former, HSOY ("Hot Stuff for One Year") was created as a hybrid catalogue
between Gaia-DR1 and ground-based astrometry, featuring proper motions (but no
parallaxes) for a large fraction of the DR1 objects. While not attempting to
compete with future Gaia releases in terms of data quality or number of
objects, the aim of HSOY is to provide improved proper motions partly based on
Gaia data, allowing some studies to be carried out just now or as pilot studies
for later larger projects requiring higher-precision data. The HSOY catalogue
was compiled using the positions taken from Gaia-DR1 combined with the input
data from the PPMXL catalogue, employing the same weighted least-squares
technique that was used to assemble the PPMXL catalogue itself. Results. This
effort resulted in a four-parameter astrometric catalogue containing
583,000,000 objects, with Gaia-DR1 quality positions and proper motions with
precisions from significantly less than 1 mas/yr to 5 mas/yr, depending on the
object's brightness and location on the sky.
