Cephid Velocity Curves

Authors

Norman R. Simon, University of Nebraska - LincolnFollow
A.S. Lee, University of Nebraska-Lincoln
Terry J. Teays, University of Nebraska-LincolnFollow

Document Type

Article

Date of this Version

1980

Citation

Bulletin of the American Astronomical Society, Vol. 12 (1980), p. 862

Comments

Copyright 1980 American Astronomical Society.

Abstract

Fourier decompositions are made for~ number of observed velocity curves of classical Cepheids. The observations are fit with Fourier series of the form

v_obs = A₀ - A_i sin(iwt + ϕ_i) ,

where the index i runs from 1 to 4 or 1 to 8 depending upon the requirements of the data. Although the sample of stars is small, we show that the Hertzsprung progression expresses itself quantitatively in terms of the low-order Fourier coefficients, particularly the quantity ϕ₂₁ = ϕ₂ - 2ϕ₁. This result complements a similar finding for the light curves. When the Fourier decompositions of the velocity curves are compared with those of some theoretical models (Vermury and Stothers 1978, Ap. J. 225, 939), new evidence is uncovered favoring a resonance explanation for the "bump" sequence.