White Dwarf Photospheres in the Laboratory: A Testbed for Fundamental Atomic Processes
While the spectrum of pure hydrogen plasmas at low densities seems well understood, at higher densities this is not the case. In this domain the line broadening can be extreme and the lines overlap, making the determination of the continuum problematic. The surfaces of white dwarf stars (WDs) fall into this high-density category. Observationally, we find a systematic offset between the masses of WDs derived using the gravitational-redshift method and those using the spectral line-shape fitting method (Falcon et al. 2010, ApJ, 712,585). Given the straightforward nature of the gravitational-redshift method, this discrepancy points toward incompleteness in the modeling of the broadening of hydrogen lines. The resulting uncertainty in mass hinders the many uses of WDs in astronomy and physics: for example, as Galactic chronometers (Winget et al. 1987, ApJL, 315, 77), tracers of stellar evolution, and probes of dense Coulomb plasmas (Winget et al. 2009, ApJL, 693, 6). This has motivated recent attempts to improve the theoretical line profiles used in white dwarf atmosphere models by independent groups, including us. Laboratory benchmarks are essential for assessing the viability of these new theories (Falcon et al. 2013, HEDP, 9, 82). Therefore, our goal is to make laboratory benchmark measurements of atomic line shapes in H – eventually He and C and O as well--for comparison with the lines observed in the photospheres of white dwarf stars.
- Research Organization:
- Univ. of Texas, Austin, TX (United States)
- Sponsoring Organization:
- USDOE National Nuclear Security Administration (NNSA)
- Contributing Organization:
- Sandia National Laboratories, Albuquerque, NM
- DOE Contract Number:
- SC0010623
- OSTI ID:
- 1421934
- Report Number(s):
- DOE-UTEX-10623
- Resource Relation:
- Related Information: N/A
- Country of Publication:
- United States
- Language:
- English
Similar Records
Experimental methods for laboratory measurements of helium spectral line broadening in white dwarf photospheres
Simulation of Stark-broadened Hydrogen Balmer-line Shapes for DA White Dwarf Synthetic Spectra