2MASS J06562998+3002455: Not a Cool White Dwarf Candidate, but a Population II Halo Star

TL;DR

This study reclassifies 2MASS J06562998+3002455 as a Population II halo star using Gaia DR2 data, challenging previous white dwarf classification and highlighting its kinematic and photometric similarities to known halo stars.

Contribution

The paper provides a re-evaluation of the star's classification, demonstrating it is a Population II halo star rather than a white dwarf, based on Gaia data analysis.

Findings

Star's velocity component suggests halo star membership

Properties resemble known halo stars like Kapteyn's star

Further spectroscopic data needed for confirmation

Abstract

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.