Astronomy and Astrophysics, volume 425, 519-527 (2004/10-2)
The nearest cool white dwarf (d∼4pc), the coolest M-type subdwarf (sdM9.5), and other high proper motion discoveries.
SCHOLZ R.-D., LEHMANN I., MATUTE I. and ZINNECKER H.
Abstract (from CDS):
We report the discovery of seven high proper motion stars with proper motions between about 0.7 and 2.2arcsec/yr, all at relatively low Galactic latitudes (13°<|b|<35°) and located in the southern sky. They were detected in a high proper motion search using multi-epoch positions in the optical SuperCOSMOS Sky Surveys and in the near-infrared sky surveys 2MASS and DENIS. Classification spectroscopy carried out for six of the objects reveals them to represent three different classes of cool objects in the solar neighbourhood: M dwarfs, M subdwarfs and cool white dwarfs. The star with the largest proper motion, SSSPM J1138-7722, is classified as a very nearby (d∼8pc) M 5.5 dwarf with Galactic thin disk kinematics. A second star with ∼2arcsec/yr proper motion, SSSPM J1358-3938, is still lacking spectroscopic confirmation but can be classified from photometry as a thick disk ∼M3.5 dwarf. Three objects turn out to be cool subdwarf members of the Galactic thick disk or halo, including the first sdM9.5 object, SSSPM J1013-1356, which represents the currently coolest known M subdwarf, another ultra-cool subdwarf, SSSPM J1930-4311, of spectral type sdM7.0 as well as an earlier type (sdM1.5) star. The latter, SSSPM J1530-8146, has an extremely large space velocity with clear halo kinematics (heliocentric (U,V,W)=(-534±78,-239±74,+188±23)km/s). Two objects show featureless spectra classifying them as cool white dwarfs with Teff<4500 K. One of them, SSSPM J1549-3544, is an extremely nearby (d∼4pc) thin disk object, the other one, SSSPM J1148-7458, has thick disk kinematics. SSSPM J1549-3544 is likely to be the nearest cool white dwarf and may be even the nearest isolated white dwarf, i.e. closer than van Maanen 2.
astrometry - surveys - stars: kinematics - stars: low-mass, brown dwarfs - stars: subdwarfs - stars: white dwarfs
SSSPM J2231-7415 is a misprint for SSSPM J2231-7515; in section 4.3, "LHS 337" should read "LHS 377".
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