Research Papers in Physics and Astronomy

 

Date of this Version

1986

Document Type

Article

Citation

Bulletin of the American Astronomical Society, Vol. 18 (1986), p.964.

Comments

Copyright 1986 American Astronomical Society. Provided by the NASA Astrophysics Data System

Abstract

Consider a radially pulsating star. Expand the radius variation in a Fourier series: R = RO+Aicos(iwt+ϕi) [summation convention]. The velocity is v=--iwAisin(iwt+ϕi). The ratio of the radii at two phases of the cycle may be written

(R1/R2)2 = (L1 T24) / (L2 T14)/(L2 T14) = α

Setting R = Ro + Δr (Δr/Ro « 1), we obtain Ro = 2(αΔr2 - rΔl ) / (1-α). The radial excursion Δr at any phase of the pulsation may be determined from a Fourier fit to the observed velocity curve. Assuming highly accurate velocity data (e.g. CORAVEL data), this can be done very precisely. If we choose phase 2 to be that for which Δr2 = O, we have

α = (2/Ro) Δr1 + 1.

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