Variable stars, distance scale, globular clusters

TL;DR

This paper reviews variable star research, discusses the universal distance scale, and introduces a new approach to calculating the projection factor for pulsating stars, improving radius estimates.

Contribution

It proposes a novel method for calculating the projection factor that accounts for limb darkening, photosphere velocity, and spectrograph line width, enhancing pulsating star analysis.

Findings

New analytic approximation for projection factor

Improved radius estimation for pulsating variables

Enhanced understanding of variable stars in globular clusters

Abstract

Current state of the variable stars studies, including halo and globular-cluster variables is briefly discussed, as well as the halo kinematics and modern problems of the Universal distance scale. I propose new approach to the projection factor (PF) calculation which takes into account its variation with limb darkening, photosphere velocity and the intrinsic line width of the spectrograph used for radial velocity measurements. Simple analytic approximation for PF is given, useful for estimates of the pulsating variables radii via Baade-Wesselink-Balona technique.