Detection of a cyclic period change in the contact binary TU UMi

TL;DR

This paper analyzes the orbital period of the contact binary TU UMi, revealing a cyclic oscillation and a continuous decrease, suggesting potential third body influence or magnetic activity effects.

Contribution

It presents the first detailed timing analysis combining literature, new observations, and TESS data to identify cyclic and secular period variations in TU UMi.

Findings

Detected a cyclic period oscillation with a 9.03-year period.

Found a continuous decrease in the orbital period at a rate of -1.12×10^{-7} d/yr.

Discussed possible causes including a third companion or magnetic activity cycle.

Abstract

This study aims at timing the eclipses of the binary star TU UMi. The times of minima are taken from the literature, from our observations in April 2004 and from TESS observations between 2019 and 2022. The orbital period analysis of the system indicates that there is a cyclic oscillation with an amplitude of 0.0081d and a period of 9.03 yr, accompanied by a continuous decrease at a rate of $dP/dt =-1.12 \times 10^{-7}\,\mathrm{d}\, \mathrm{yr}^{-1}$. We study the secular evolution of the orbital period of the system and the possibility of the existence of a third companion or the magnetic activity cycle of the primary component in the system.