• DOI:10.1051/0004-6361:20041059
• Corpus ID: 9352481

The nearest cool white dwarf (d ~ 4 pc), the coolest M-type subdwarf (sdM9.5), and other high proper motion discoveries

@article{Scholz2004TheNC,
  title={The nearest cool white dwarf (d ~ 4 pc), the coolest M-type subdwarf (sdM9.5), and other high proper motion discoveries},
  author={Ralf-Dieter Scholz and Ingo Lehmann and Israel Matute and H. Zinnecker Astrophysikalisches Institut Potsdam and Mpe Garching},
  journal={Astronomy and Astrophysics},
  year={2004},
  volume={425},
  pages={519-527}
}

• R. Scholz, I. Lehmann, +2 authors Mpe Garching
• Published 21 June 2004
• Physics
• Astronomy and Astrophysics

We report the discovery of seven high proper motion stars with proper motions between about 0.7 and 2.2 arcsec/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 differ- ent 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 ∼ 8 pc) M 5.5 dwarf with Galactic thin disk kinematics. A second star with ∼ 2a rcsec/yr proper motion, SSSPM J1358-3938, is still lacking spectroscopic confirmation but can be classified from photometry as a thick disk ∼M 3.5 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 (helio- centric (U,V,W) = (−534 ± 78, −239 ± 74, +188 ± 23) km s −1 ). 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 ∼ 4 pc) 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.