Time dependent white dwarf radiative shocks
We study the oscillatory instability of white dwarf radiative accretion shocks discovered by Langer, Chanmugam, and Shaviv. We extend previous works by examining spherical shocks dominated by: (1) bremsstrahlung and Compton cooling; and (2) bremsstrahlung and Compton cooling when the effects of electron thermal conduction are not negligible. The results of our calculations allow us to delineate stability regimes as a function of the dwarf mass, M/sub d/, and the accretion rate, M/sup 0/. We parameterize M/sup 0/ in terms of the optical depth to electron scattering through the preshock flow, tau/sub es/. In the Compton cooling and bremsstrahlung case, the shocks are unstable to low order oscillation modes if M/sub d/ less than or equal to (0.7 +- 0.1) M/sub solar/ for tau/sub es/ = 14, and if M/sub d/ less than or equal to (0.9 +- 0.1) M/sub solar/ for tau/sub es/ = 1. When electron thermal conduction is added, low order oscillation modes are unstable only if M/sub d/ less than or equal to (0.3 +- 0.1) M/sub sun mass/. The unstable modes have approximate oscillation periods of 1.1 tau/sub br/ and 0.63 tau/sub br/, where tau/sub br/ is the bremsstrahlung cooling time scale of the postshock plasma. Our results can be scaled to magnetically funneled accretion flows as long as cyclotron emission contributes less than about 10% of the postshock cooling. 14 refs., 1 fig.
- Research Organization:
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Naval Research Lab. (NRL), Washington, DC (United States); Indiana Univ., Bloomington (USA). Dept. of Astronomy
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 5413361
- Report Number(s):
- LA-UR-85-2538; CONF-8506143-2; ON: DE85015698
- Resource Relation:
- Conference: 9. North American workshop on cataclysmic variables, Seattle, WA, USA, 24 Jun 1985; Other Information: Portions of this document are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
STAR ACCRETION
STAR MODELS
WHITE DWARF STARS
OSCILLATIONS
BREMSSTRAHLUNG
COMPTON EFFECT
MASS
SHOCK WAVES
STABILITY
VARIABLE STARS
BASIC INTERACTIONS
DWARF STARS
ELASTIC SCATTERING
ELECTROMAGNETIC INTERACTIONS
ELECTROMAGNETIC RADIATION
INTERACTIONS
MATHEMATICAL MODELS
RADIATIONS
SCATTERING
STAR EVOLUTION
STARS
640102* - Astrophysics & Cosmology- Stars & Quasi-Stellar
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