Abstract
view Abstract Citations (29) References (30) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Properties of Quasi-periodic Oscillations in Accreting Magnetic White Dwarfs Wu, Kinwah ; Chanmugam, G. ; Shaviv, G. Abstract Previous studies of time-dependent accretion onto magnetic white dwarfs, in which the cooling was assumed to be due to bremsstrahlung emission, have shown that the accretion shock undergoes oscillations. However, when cyclotron cooling is also included, the oscillations are damped for sufficiently strong magnetic fields. Here we demonstrate that the oscillations can be sustained by accretion-fluctuation-induced excitations. The frequency of the QPOs are shown to increase quadratically with the magnetic field strength. We interpret the oscillations as a two-phase process in which bremsstrahlung cooling dominates in one half-cycle and cyclotron cooling in the other. Such a process may have very different consequences compared to a single-phase process where the functional form of the cooling is essentially the same throughout the cycle. If in the two-phase process damping occurs mainly in the cyclotron cooling half-cycle, there will be a universal effective damping factor which tends to suppress all oscillation modes indiscriminately. The oscillations of the accretion shock also could be a limit cycle process in which the system vacillates between two branches. Publication: The Astrophysical Journal Pub Date: September 1992 DOI: 10.1086/171782 Bibcode: 1992ApJ...397..232W Keywords: Accretion Disks; Bremsstrahlung; Stellar Magnetic Fields; Stellar Oscillations; White Dwarf Stars; Cyclotron Radiation; Harmonics; Luminosity; Stellar Mass Accretion; Astrophysics; ACCRETION; ACCRETION DISKS; HYDRODYNAMICS; STARS: MAGNETIC FIELDS; STARS: OSCILLATIONS; STARS: WHITE DWARFS full text sources ADS |
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