New O-Cs for the Classical Cepheids RY Cas and V Lac over a Century (1873-2022)

TL;DR

This paper presents over a century of new O-C diagrams for the classical Cepheids RY Cas and V Lac, revealing their period variations and suggesting no binary system association.

Contribution

It provides the longest baseline O-C diagrams for these Cepheids, enabling precise period variation analysis over more than a hundred years.

Findings

RY Cas's period increases at +1.86 s/yr

V Lac's period decreases at -0.81 s/yr

No evidence of binary system association

Abstract

We give here new O-C diagrams of the two classical Cepheids RY Cas and V Lac, established on a large basis of times of maximum of light, which covers more than a century. These two Cepheids present a variation of their period for which it is possible to calculate an annual rate. This rate equals +1.86 s/yr for RY Cas and -0.81 s/yr for V Lac. Based on these two new O-C diagrams neither of them seems to show any association to a binary system.