Photometric study and period analysis of the contact binary XZ Leonis

TL;DR

This study presents detailed photometric and period analysis of the contact binary XZ Leo, revealing its physical parameters, orbital period increase, and evolutionary status, supporting the Thermal Relaxation Oscillation theory.

Contribution

It provides a comprehensive photometric and orbital analysis of XZ Leo, including new light curves, revised system parameters, and long-term period behavior, which was not previously studied in detail.

Findings

XZ Leo is an A-type contact binary with 24% contact degree.

The orbital period is increasing at a rate of 6.12×10^{-8} days/year.

The system is likely to evolve into a broken-contact stage in 1.56 million years.

Abstract

We present multi-color CCD photometry of the neglected contact binary XZ Leo. Completely covered VRI band light curves and four times of minimum light were obtained. Combining the photometric and previously published radial velocity data, a revised photometric analysis was carried out for the binary system by applying the Wilson-Devinney code. With a hot spot placed on the massive primary component near the neck region of the common envelope, the light curves were satisfactorily modeled. The photometric solution combined with the radial velocity solution reveals that XZ Leo is an A-type contact binary with a degree of contact of 24($\pm1)\%$. The absolute parameters of the components were determined as M_1 = 1.74($\pm$0.06)M_\odot, M_2 = 0.61($\pm$0.02)M_\odot, R_1 = 1.69($\pm$0.01)R_\odot, R_2 = 1.07($\pm0.01$)R_\odot, L_1 = 6.73($\pm0.08$) L_\odot, L_2 = 2.40($\pm$0.04)L_\odot. Based on all the available data, the long-term orbital period behavior of the system was investigated. It indicates that the binary system was undergoing continuous orbital period increase in the past three decades with a rate of dP/dt = + 6.12 \times {10^{-8}} days yr^{-1}, which suggests a probable mass transfer from the secondary to the primary component at a rate of dM/dt= 3.92\times 10^{-8} M_\odot yr^{-1}. The binary system is expected to evolve into the broken-contact stage in $1.56 \times 10^6$ years. This could be evidence supporting the Thermal Relaxation Oscillation theory.