The double degenerate system NLTT 11748

0354849 - ASÚ 2011 RIV FR eng J - Journal Article
Kawka, Adela - Vennes, Stephane - Vaccaro, T.R.
The double degenerate system NLTT 11748.
Astronomy & Astrophysics. Roč. 516, Jun-Jul (2010), L7/1-L7/4. ISSN 0004-6361. E-ISSN 1432-0746
R&D Projects: GA AV ČR(CZ) IAA300030908; GA ČR GAP209/10/0967
Grant - others:GA AV ČR(CZ) IAA301630901
Program: IA
Institutional research plan: CEZ:AV0Z10030501
Keywords : close binaries * white dwarfs
Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics
Impact factor: 4.410, year: 2010

We show that the extremely low-mass white dwarf NLTT 11748 (0.17 of solar mass) is in a close binary with a fainter companion. We obtained a series of radial velocity measurements of the low-mass white dwarf using the Halpha core and determined an orbital period of 5.64 h. The velocity semi-amplitude (K = 274.8 km/s) and orbital period imply that it is a degenerate star, and that the minimum mass for the companion is 0.75 of solar mass (assuming a mass of 0.167 of solar mass for the primary). Our analysis of Balmer line profiles shows that a 0.75 of solar mass white dwarf companion does not contribute more than 2% or 5% of the flux (V-band) for helium-or hydrogen-rich surfaces, respectively. The kinematics of the system suggest that it belongs to the Galactic halo.
Permanent Link: http://hdl.handle.net/11104/0193761