Mass Transfer and Intrinsic Light Variability in the Contact Binary MT Cas

Haifeng Dai,Huiyu Yuan,Yuangui Yang

doi:10.1155/2019/4593092

Abstract

First CCD photometry for the contact binary MT Cas is performed in 2013 in December. The spectral type of F8V is determined from the low-precision spectrum observed on 2018 Oct 22. With Wilson-Devinney code, the photometric solutions are deduced from VRc light curves (LCs) and AAVSO’s and ASAS-SN’s data, respectively. The results imply that MT Cas is a W-type weak-contact binary with a mass ratio of q=2.365(±0.005) and a fill-out factor of f=16.6(±1.2)%, respectively. The asymmetric LCs in 2013 are modeled by a dark spot on the more massive component. By analyzing the (O-C) curve, it is discovered that the orbital period may be undergoing a secular increase at a rate of dP/dt=1.12(±0.09)×10-8d yr-1, which may result from mass transfer from the less massive component to the more massive one. With mass transferring, MT Cas may evolve into a broken-contact configuration as predicted by TRO theory.

Highlights

W Ursae Majoris binary contains two components, which are embedded in a common envelope [1, 2]
Except for some photometric data performed by several amateur observers of AAVSO and ASASSN database [15], no additional observations for this binary have been presented up to now
The low-precision spectrum for MT Cas was obtained by using the Yunnan Faint Object Spectrograph and Camera (YFOSC), which is attached to the 2.4-m telescope at Lijiang station (LJs) of Yunnan Astronomical Observatory of China (YNAO) at UT 15:50:13 of 2018 October 22

Summary

Introduction

W Ursae Majoris binary contains two components, which are embedded in a common envelope [1, 2]. Models for contact binary have been recently constructed by several investigators (e.g., see [3,4,5]). Their evolutionary status still remains unclear because the spectra cannot be analyzed for abundances due to the extreme broadening and blending of spectral lines. Except for some photometric data performed by several amateur observers of AAVSO (https://www.aavso.org/data-download) and ASASSN database [15] (https://asas-sn.osu.edu/database/light curves/335960), no additional observations for this binary have been presented up to now.

New Observations

Eclipse Times and Period Analysis

Method

Modeling Light Curves

Results and Discussions