Basic relations for the period variation models of variable stars

TL;DR

This paper introduces fundamental relations and models for analyzing period variations in variable stars, including phase functions and instant periods, to improve understanding of their behavior.

Contribution

It presents new basic relations and equations connecting phase functions and instant periods in variable star models, along with simple period models.

Findings

Introduced phase function and instant period concepts.

Formulated basic relations among period variation parameters.

Presented simple models for period variations.

Abstract

Models of period variations are basic tools for period analyzes of variable stars. We introduce phase function and instant period and formulate basic relations and equations among them. Some simple period models are also presented.