A new extremely low-mass white dwarf in the NLTT catalogue
Abstract
We report on the discovery of the extremely low-mass, hydrogen-rich white dwarf, NLTT 11748. Based on measurements of the effective temperature (8540 ± 50 K) and surface gravity (log g = 6.20 ± 0.15) obtained by fitting the observed Balmer line profiles with synthetic spectra, we derive a mass of 0.167 ± 0.005 M_⊙. This object is one of only a handful of white dwarfs with masses below 0.2 M_⊙ that are believed to be the product of close binary evolution with an episode of Roche lobe overflow onto a degenerate companion (neutron star or white dwarf). Assuming membership in the halo population, as suggested by the kinematics and adopting a cooling age of 4.0{-}6.3 Gyr for the white dwarf, we infer a progenitor mass of 0.87-0.93 M_⊙. The likely companion has yet to be identified, but a search for radial velocity variations may help constrain its nature.
Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile under programme ID 82.D-0750.- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- November 2009
- DOI:
- 10.1051/0004-6361/200912954
- arXiv:
- arXiv:0909.3249
- Bibcode:
- 2009A&A...506L..25K
- Keywords:
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- white dwarfs;
- stars: individual: NLTT 11748;
- stars: atmospheres;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- Accepted for publication in A&