ON THE SPECTRUM OF THE LINEAR NONADIABATIC RADIAL STELLAR MODES

The growth rates of the radial vibrational modes display undulations w hose physical origin is discussed. In radiative RR Lyrae models the 9t h overtone can become almost unstable. The potential implications for astro-seismology are briefly discussed. It is shown how an existing Ca stor or Stellingwerf linear nonadiabatic (LNA) code can readily be mod ified to yield the eigenvalues of all the linear vibrational and therm al modes. It is also pointed out that unfortunate choices of the mass zoning can introduce unstable, unphysical, high order vibrational mode s whose presence may have nefarious consequences in the numerical hydr odynamics.