Astrophysics and Space Science

, Volume 210, Issue 1–2, pp 307–309 | Cite as

Nonlinear RR Lyrae models with new livermore opacities

  • J. A. Guzik
  • A. N. Cox
III. Models


A. N. Cox recently showed that a 20% opacity decrease in the 20,000-30,000 K region as indicated by the new Livermore OPAL opacities reconciles the discrepancy between pulsation and evolution masses of double-mode RR Lyrae variables. Nonlinear hydrodynamic calculations were performed for RR Lyrae models of mass 0.75M, 51L, andZ = 0.0001 (Osterhoff II type) including this opacity decrease. The Stellingwerf periodic relaxation method was used to converge the models to a limit cycle, and the Floquet matrix eigenvalues calculated to search for a tendency of the fundamental mode to grow from the full-amplitude overtone solution, and the overtone mode to grow from the full-amplitude fundamental solution, thereby predicting double-mode behavior. Models ofTeff < 7000 K with the opacity decrease have positive fundamental-mode growth rates in the overtone solution, in contrast to earlier results by Hodson and Cox (1982), and models withTeff > 7000 have positive 1st overtone growth rates in the fundamental-mode solution, but double-mode behavior was not found.


Growth Rate Early Result Fundamental Solution Fundamental Mode Relaxation Method 
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Copyright information

© Kluwer Academic Publishers 1993

Authors and Affiliations

  • J. A. Guzik
    • 1
  • A. N. Cox
    • 1
  1. 1.Los Alamos National LaboratoryUSA

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