Astronomy and Astrophysics – Astronomy
Scientific paper
Feb 1996
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996apj...458..327i&link_type=abstract
Astrophysical Journal v.458, p.327
Astronomy and Astrophysics
Astronomy
18
Accretion, Accretion Disks, Instabilities, Shock Waves, Stars: Oscillations, Stars: White Dwarfs
Scientific paper
The stability properties of two-temperature radiative shocks with power-law cooling functions and cooling functions appropriate to accretion onto nonmagnetic white dwarfs are studied. Two-temperature effects are important whenever the cooling is fast compared to the electron-ion, e-i, energy coupling because, in most astrophysical environments, the electrons dominate the cooling while the ions act simply as stores of the thermal energy. Two-temperature effects are usually important for the shocks encountered in compact X-ray binary systems. We find that: (1) two-temperature effects enhance the oscillatory instability of radiative shock waves. The weaker the e-i coupling through the shock transition and in the postshock cooling region, the stronger the destabilization due to two-temperature effects. For example, for radial oscillations, the fundamental mode (F), the lowest frequency mode, is stable in one-temperature flows dominated by bremsstrahlung. In two-temperature flows, the F mode is unstable if τbr/τei less than ˜1, where τbr and τei are the postshock bremsstrahlung and e-i energy equilibration timescales, if the e-i energy coupling through the shock transition is weak. By weak, we- mean shocks for which the electrons emerge from the shock transition with less than ˜40% of the thermal energy. When e-i coupling through the shock transition is strong, the radial F mode is stable regardless of the strength of the e-i coupling in the cooling region. This property of two-temperature flows means that observations of radial F mode oscillations in bremsstrahlung-dominated shocks could place constraints on the dissipation process at work in the strong shock waves encountered in astrophysical situations. (2) Radial oscillation modes behave as expected for realistic white dwarf functions (bremsstrahlung plus Compton cooling) in that Compton cooling strongly damps radial oscillations. However, for nonradial oscillations, Compton cooling actually enhances instability. This suggests that for weakly magnetic accretion flows where both bremsstrahlung and Compton cooling are important, shock oscillations could arise, contrary to expectations based on the effect Compton cooling has on the radial oscillations.
Aboasha Abdossalam
Imamura James N.
Wolff Michael Thomas
Wood Kent S.
No associations
LandOfFree
The Stability Properties of Two-Temperature White Dwarf Radiative Shock Waves does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The Stability Properties of Two-Temperature White Dwarf Radiative Shock Waves, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The Stability Properties of Two-Temperature White Dwarf Radiative Shock Waves will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1153808