ON THE SPECTRUM OF THE LINEAR NONADIABATIC RADIAL STELLAR MODES

The growth rates of the radial vibrational modes display undulations whose physical origin is discussed. In radiative RR Lyrae models the 9th overtone can become almost unstable. The potential implications for astro-seismology are briefly discussed. It is shown how an existing Castor or Stellingwerf linear nonadiabatic (LNA) code can readily be modified to yield the eigenvalues of all the linear vibrational and thermal modes. It is also pointed out that unfortunate choices of the mass zoning can introduce unstable, unphysical, high order vibrational modes whose presence may have nefarious consequences in the numerical hydrodynamics.