Magnetic Chemically Peculiar Stars with Unsteady Periods

TL;DR

This paper investigates the unsteady rotational periods of certain chemically peculiar stars, analyzing their observed variations, potential causes, and the diversity of their period change behaviors.

Contribution

It provides a detailed analysis of period variations in several CP stars and discusses possible mechanisms behind these unsteady periods, highlighting their diversity and complexity.

Findings

Several CP stars exhibit significant period variations.

The period changes may be cyclic or chaotic.

Diverse behaviors observed in different stars.

Abstract

Photometrically and spectroscopically variable chemically peculiar (CP) stars are the optimum laboratories for testing the rotational evolution of main sequence stars. A vast majority of well-studied CP stars have quite steady rotational periods (e.g. SrCrEu star CQ UMa). However, there are several CP stars that exhibit apparent period variations. The origin of the period variations is unclear in many cases. We describe the observed period variations of several individual CP stars, especially V901 Ori, sigma Ori E, HR 7355, CU Vir, SX Ari, and EE Dra. The CP stars with unsteady periods now represent a very diverse group with dissimilar O-C diagrams and time scales. We also discuss the causes of the period changes found and a possible cyclicity or chaoticity of them.