EDP Sciences
Free access
Volume 507, Number 3, December I 2009
Page(s) 1613 - 1616
Section Stellar structure and evolution
DOI http://dx.doi.org/10.1051/0004-6361/200912955
Published online 08 October 2009
A&A 507, 1613-1616 (2009)
DOI: 10.1051/0004-6361/200912955

The double degenerate LP 400-22 revisited

S. Vennes1, A. Kawka1, T. R. Vaccaro2, and N. M. Silvestri3

1  Astronomický ústav AV ČR, Fričova 298, 251 65 Ondřejov, Czech Republic
    e-mail: vennes, kawka@sunstel.asu.cas.cz
2  Department of Physics & Astronomy, Francis Marion University, Box 100547, Florence, SC 29501, USA
    e-mail: tvaccaro@fmarion.edu
3  Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195, USA
    e-mail: nms@astro.washington.edu

Received 22 July 2009 / Accepted 17 September 2009

We re-examine the properties of the high-velocity and extremely low-mass white dwarf LP 400-22 and its close companion. Based on an extended observation timeline, we determined a binary period of P = 1.01016 d, somewhat longer than the previously published period, and a mass function f(M2) = 0.180 $M_\odot$, implying a mass for the companion M2 > 0.41 $M_\odot$. We also re-appraised the mass and cooling age of the white dwarf using low-metallicity (Z = 0.001) evolutionary models appropriate for an old halo member, M1 = 0.19 $M_\odot$, and tcool$\approx$1.8 Gyr, and we infer a mass of 0.85–1.0 $M_\odot$ for the progenitor of the white dwarf. We discuss the likely origin of this system.

Key words: stars: binaries: close -- stars: individual: LP 400-22 -- white dwarfs

© ESO 2009