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On the Pulsation Amplitude of Cepheid Variables

  • Nikola Nikolov
  • Tsvetan Tsvetkov
Conference paper

Abstract

On the basis of more numerous data a relation log P ΔV/log Δ R (P is the period, ΔR is the amplitude of the radius variation and ΔV is the amplitude of the V-magnitude variation) for cepheid variables (Fernie, 1965) has been established. A linear relation between log ΔV and log ΔR for classical cepheids is found, which perhaps has a break at ΔR = 10 R.

In the log ΔR/log P diagram the s-cepheids (Efremov, 1968) form a distinct sequence. All s-cepheids present a relative variation of the radii ΔR/R≦0.075. Very probably this is in accordance with Efremov’s (1968) hypothesis that these cepheids cross for the first time the instability region in the HR-diagram.

On the basis of the log ΔR/log P diagram one could suppose that cepheids with log P≧1.1 pulsate in the first overtone whereas those with log P≦1.1 pulsate in the fundamental one. If these two groups of cepheids pulsate really differently, they would have a distinct P — L relation, as some investigators have found a break in the PL relation of cepheids near log P ≈ 1.

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Copyright information

© Springer-Verlag, Berlin, Heidelberg 1974

Authors and Affiliations

  • Nikola Nikolov
    • 1
  • Tsvetan Tsvetkov
    • 1
  1. 1.Department of Astronomy, Faculty of PhysicsUniversity of SofiaBulgaria

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