2MASS J06562998+3002455: Not a Cool White Dwarf Candidate, but a
  Population II Halo Star
  2MASS J06562998+3002455 or PSS 309-6 is a high proper-motion star that was
discovered during a survey with the 2.1 m telescope at Kitt Peak National
Observatory. Here, we reevaluate the status of this interesting star using Gaia
DR2. Our results strongly suggest that PSS 309-6 could be a Population II star
as the value of its V component is close to -220 km/s, which is typical for
halo stars in the immediate solar neighborhood. Kapteyn's star is the nearest
known halo star and PSS 309-6 exhibits similar kinematic and photometric
signatures. Its properties also resemble those of 2MASS J15484023-3544254,
which was once thought to be the nearest cool white dwarf but was later
reclassified as K-type subdwarf. Although it is virtually certain that PSS
309-6 is not a nearby white dwarf but a more distant Population II subdwarf,
further spectroscopic information, including radial velocity measurements, is
necessary to fully characterize this probable member of the Galactic halo.
