Precise Atmospheric Parameters for the Shortest-period Binary White Dwarfs: Gravitational Waves, Metals, and Pulsations
Abstract
We present a detailed spectroscopic analysis of 61 low-mass white dwarfs and provide precise atmospheric parameters, masses, and updated binary system parameters based on our new model atmosphere grids and the most recent evolutionary model calculations. For the first time, we measure systematic abundances of He, Ca, and Mg for metal-rich, extremely low mass white dwarfs and examine the distribution of these abundances as a function of effective temperature and mass. Based on our preliminary results, we discuss the possibility that shell flashes may be responsible for the presence of the observed He and metals. We compare stellar radii derived from our spectroscopic analysis to model-independent measurements and find good agreement except for white dwarfs with T eff <~ 10,000 K. We also calculate the expected gravitational wave strain for each system and discuss their significance to the eLISA space-borne gravitational wave observatory. Finally, we provide an update on the instability strip of extremely low mass white dwarf pulsators.
Based on observations obtained at the MMT Observatory, a joint facility of the Smithsonian Institution and the University of Arizona.- Publication:
-
The Astrophysical Journal
- Pub Date:
- October 2014
- DOI:
- 10.1088/0004-637X/794/1/35
- arXiv:
- arXiv:1408.3118
- Bibcode:
- 2014ApJ...794...35G
- Keywords:
-
- binaries: close;
- stars: abundances;
- stars: fundamental parameters;
- techniques: spectroscopic;
- white dwarfs;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 18 pages, 13 figures, 3 tables, accepted for publication in ApJ