A theoretical study of problems in classical nova evolution

Thesis/Dissertation · Mon Jan 01 04:00:00 EST 1990

OSTI ID:6223909

Shankar, A

Three distinct issues in classical nova evolution are addressed with the aid of one- and two-dimensional numerical hydrodynamics. The effects of convection on nova outbursts are examined within the confines of the mixing length theory. It is found that increasing the efficiency of convection enhances the violence of the thermonuclear runaway (TNR). This also relates to the question of the feasibility of obtaining nova outbursts on magnetic white dwarfs among the AM Her systems. The effects of a strong magnetic field on the TNR are explored. The field interferes with the development of convection during the TNR, which results in lower ejection velocities. However, for field strengths typical of cataclysmic variables, the violence of strong outbursts is affected only moderately. The conditions necessary for the production of strong TNR's in the hibernation model of cataclysmic binary evolution are also examined. The feasibility of obtaining strong nova outbursts is investigated when the accretion rate during hibernation is decreased. It is found that a reduction (by a factor of 100) for periods of longer than a couple thousand years, is sufficient to ensure violent outbursts, even in the presence of large pre-outburst accretion rates. The effects of a common envelope phase (CEP) on the outburst are discussed. The motion of the secondary through an expanding common envelope is resisted by frictional drag. This dissipates both energy and angular momentum from the orbit inducing hydrodynamic motion. Significant departures are found to occur in the manner in which mass is lost when the effects of drag are taken into account. Specifically, a CEP is found to accelerate and enhance mass loss. Ejection is found to be concentrated in the orbital plane, with velocities of a few thousand km/sec.

• Research Organization: Illinois Univ., Urbana, IL (USA)
• OSTI ID: 6223909
• Country of Publication: United States
• Language: English

Related Subjects

640102* -- Astrophysics & Cosmology-- Stars & Quasi-Stellar
Radio & X-Ray Sources
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
BINARY STARS
DATA
DWARF STARS
ENERGY TRANSFER
ERUPTIVE VARIABLE STARS
FLUID MECHANICS
HEAT TRANSFER
HYDRODYNAMICS
INFORMATION
MAGNETIC FIELDS
MAGNETIC STARS
MATHEMATICAL MODELS
MECHANICS
NOVAE
NUCLEAR REACTIONS
NUCLEOSYNTHESIS
NUMERICAL DATA
STAR ACCRETION
STAR EVOLUTION
STAR MODELS
STARS
SYNTHESIS
THEORETICAL DATA
THERMONUCLEAR REACTIONS
VARIABLE STARS
WHITE DWARF STARS