The Baade-Becker-Wesselink technique and the fundamental astrophysical parameters of Cepheids

TL;DR

This paper introduces a new version of the Baade-Becker-Wesselink method that independently determines reddening, intrinsic color, radius, luminosity, and distance of Cepheids, enhancing astrophysical parameter estimation.

Contribution

It generalizes existing techniques by allowing independent reddening and intrinsic color determination, improving accuracy in Cepheid parameter estimation.

Findings

Successfully applied to classical Cepheids with precise light and radial-velocity data.

Enables calibration of the F(CI_0) function for pulsating stars.

Potential application to other pulsating variables like RR Lyraes.

Abstract

The BBW method remains one of most demanded tool to derive full set of Cepheid astrophysical parameters. Surface brightness version of the BBW technique was preferentially used during last decades to calculate Cepheid radii and to improve PLC relations. Its implementation requires a priory knowledge of Cepheid reddening value. We propose a new version of the Baade--Becker--Wesselink technique, which allows one to independently determine the colour excess and the intrinsic colour of a radially pulsating star, in addition to its radius, luminosity, and distance. It is considered to be a generalization of the Balona light curve modelling approach. The method also allows the function F(CI_0) = BC + 10 log Teff for the class of pulsating stars considered to be calibrated. We apply this technique to a number of classical Cepheids with very accurate light and radial-velocity curves. The new technique can also be applied to other pulsating variables, e.g. RR Lyraes. We discuss also possible dependence of the projection factor on the pulsation phase.