Why DA and DB white dwarfs do not show coronal activity and p-mode oscillations

Details Why DA and DB white dwarfs do not show coronal activity and p-mode oscillations Why DA and DB white dwarfs do not show coronal activity and p-mode oscillations

Nov 1989

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1989apj...346..435m&link_type=abstract

Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 346, Nov. 1, 1989, p. 435-443. Research supported by the Universities Space

Computer Science

Sound

8

Stellar Atmospheres, Stellar Coronas, Stellar Oscillations, Wave Propagation, White Dwarf Stars, Sound Waves, Stellar Activity, Vibration Mode

Scientific paper

The problems of nonradiative heating of outer atmospheric layers and p-mode oscillations in white dwarfs caused by acoustic waves generated in convective zones are discussed. These effects have been studied by calculating the cutoff periods for adiabatic and isothermal waves propagating in atmospheres of DA and DB stars with Teff greater than or equal 20,000 K and log g = 6-9. The obtained cutoff periods are approximately bounded by 0.01 and 40 sec for high- and low-gravity white dwarfs, respectively. Expected amplitudes of p-mode oscillations corresponding to trapped acoustic waves with small angular wave numbers are estimated, indicating that the amplitudes could be observed as Doppler shifts of spectral lines which might be detectable if adequate spectral resolution were available. The luminosity variations corresponding to these amplitudes are unlikely to be observable when all damping processes are accounted for. Results also indicate that the present theory of convection predicts some irregularities in the behavior of physical parameters.

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