A new wide pair of cool white dwarfs in the solar neighborhood

R. D. Scholz, G. Szokoly, M. Andersen, R. Ibata, M. J. Irwin

Research output: Contribution to journalArticle

30 Citations (Scopus)

Abstract

We report the discovery of a wide pair (93″ angular separation) of extremely cool (Teff <4000 K) white dwarfs with a very large common proper motion (∼1″.9 yr-1). The objects were discovered in a high proper motion survey in the poorly investigated southern sky region with δ <-60° using Super-COSMOS Sky Survey (SSS) data. Both objects, SSSPM J2231-7514 and SSSPM J2231-7515, show featureless optical spectra. Fits of blackbody models to the spectra yield effective temperatures of 3810 and 3600 K, respectively, for the bright (V = 16.60) and faint (V = 16.87) components. Both degenerates are much brighter than other recent discoveries of cool white dwarfs with comparable effective temperatures and/or BJ-R colors. Therefore, they should be relatively nearby objects. The comparison with other cool white dwarfs and a photometric distance determination yield distance estimates between 9 and 14 pc. The latter seems to be more realistic since the good agreement of the proper motion of both components within the errors of about 8 mas yr-1 and the angular separation between the two stars support a distance of about 15 pc, with relatively small masses of the components. With a smaller distance we should be able to measure a differential proper motion due to orbital motion if the orbital plane is not strongly inclined and if the present orbital velocity vector is not close to the line of sight. The space velocity based on that distance and assumptions on radial velocity make the new pair of extremely cool white dwarfs probably some of the oldest members of the Galactic disk population, although the possibility that these objects are part of a Galactic halo dark matter component also cannot yet be ruled out.

Original languageEnglish
Pages (from-to)539-544
Number of pages6
JournalAstrophysical Journal
Volume565
Issue number1 I
DOIs
Publication statusPublished - Jan 20 2002

Fingerprint

solar neighborhood
proper motion
Southern sky
orbital velocity
temperature
galactic halos
radial velocity
line of sight
optical spectrum
dark matter
orbits
color
stars
orbitals
estimates

Keywords

  • Astrometry
  • Binaries: general
  • Dark matter
  • Galaxy: halo
  • Solar neighborhood
  • White dwarfs

ASJC Scopus subject areas

  • Space and Planetary Science
  • Nuclear and High Energy Physics

Cite this

Scholz, R. D., Szokoly, G., Andersen, M., Ibata, R., & Irwin, M. J. (2002). A new wide pair of cool white dwarfs in the solar neighborhood. Astrophysical Journal, 565(1 I), 539-544. https://doi.org/10.1086/324477

A new wide pair of cool white dwarfs in the solar neighborhood. / Scholz, R. D.; Szokoly, G.; Andersen, M.; Ibata, R.; Irwin, M. J.

In: Astrophysical Journal, Vol. 565, No. 1 I, 20.01.2002, p. 539-544.

Research output: Contribution to journalArticle

Scholz, RD, Szokoly, G, Andersen, M, Ibata, R & Irwin, MJ 2002, 'A new wide pair of cool white dwarfs in the solar neighborhood', Astrophysical Journal, vol. 565, no. 1 I, pp. 539-544. https://doi.org/10.1086/324477
Scholz, R. D. ; Szokoly, G. ; Andersen, M. ; Ibata, R. ; Irwin, M. J. / A new wide pair of cool white dwarfs in the solar neighborhood. In: Astrophysical Journal. 2002 ; Vol. 565, No. 1 I. pp. 539-544.
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