Gravity Modes in ZZ Ceti Stars. II. Eigenvalues and Eigenfunctions

Details Gravity Modes in ZZ Ceti Stars. II. Eigenvalues and Eigenfunctions Gravity Modes in ZZ Ceti Stars. II. Eigenvalues and Eigenfunctions

Jul 1999

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999apj...519..783w&link_type=abstract

The Astrophysical Journal, Volume 519, Issue 2, pp. 783-792.

Other

47

Stars: Oscillations, Stars: Variables: Other

Scientific paper

We report on numerical calculations of nonadiabatic eigenvalues and eigenfunctions for g-modes in ZZ Ceti variables. The spectrum of overstable l=1 modes delineates the instability strip. Its blue edge occurs where omegatau_c~1 for the n=1 mode. Here omega is radian frequency and tau_c is about 4 times the thermal time at the bottom of the surface convection zone. As a ZZ Ceti cools, its convection zone deepens, longer period modes become overstable, but the critical value of omegatau_c separating overstable and damped modes rises. The latter is a consequence of enhanced radiative damping for modes that propagate immediately below the convection zone. The critical value of omegatau_c is of observational significance, because modes with the smallest value of omegatau_c are most observable photometrically. Maximum periods for overstable modes predicted for our cooler model envelopes are about a factor of 2 longer than the observational upper limit of 1200 s. We assess a number of plausible resolutions for this discrepancy among which convective overshoot and nonlinear saturation look promising. The nonadiabatic eigenfunctions enable us to predict relative amplitudes and phases of photospheric variations of flux and velocity, quantities made accessible by recent observations. We also present asymptotic formula for damping rates of high-order modes, a result of consequence for future investigations of nonlinear saturation of the amplitudes of overstable modes.

Affiliated with

Also associated with

No associations

Rating

Gravity Modes in ZZ Ceti Stars. II. Eigenvalues and Eigenfunctions 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 Gravity Modes in ZZ Ceti Stars. II. Eigenvalues and Eigenfunctions, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Gravity Modes in ZZ Ceti Stars. II. Eigenvalues and Eigenfunctions will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1619539