Photometric and Spectroscopic Studies of Four Low Mass-ratio Contact Binaries with Period Longer than 0.7 days

TL;DR

This study analyzes four long-period low-mass-ratio contact binaries using photometric and spectroscopic data, revealing their contact types, magnetic activity, stability, and comparing their properties with other binaries based on period.

Contribution

It provides detailed characterization of four long-period low-mass-ratio contact binaries and compares their properties with short-period systems, highlighting differences in activity and structure.

Findings

V0508 And, V0844 Aur, V0699 Cep are medium-contact binaries; NSVS 6259046 is a deep-contact binary.

V0844 Aur shows no long-term period variation; others have increasing periods.

V0699 Cep exhibits chromospheric activity and is an early-type contact binary.

Abstract

Photometric and spectroscopic studies of four long-period low mass-ratio contact binaries, V0508 And, V0844 Aur, V0699 Cep, and NSVS 6259046, are performed. V0508 And, V0844 Aur, and V0699 Cep are found to be A-type low-mass-ratio medium-contact binaries, while NSVS 6259046 is found to be an A-type deep-contact binary. O - C analysis indicates no long-term variation in V0844 Aur. However, the orbital periods of the other three targets are increasing. We conclude that V0844 Aur, V0699 Cep and NSVS 6259046 are magnetically active, as evidenced by the presence and variable nature of the O'Connell effect in these systems. By analyzing the LAMOST spectroscopic data, we find out that NSVS 6259046 and V0508 And exhibit no chromospheric activity on the dates the LAMOST spectra were taken, while the low signal-to-noise ratio in LAMOST data for V0844 Aur prevents us from obtaining reliable results. We discover that V0699 Cep is an early-type contact binary with chromospheric activity. Their initial masses and ages are calculated. All four systems are determined to be currently stable. We collect 217 contact binaries with both spectroscopic and photometric observations, and compare the differences between short-period and long-period systems in terms of mass-luminosity relation and mass-radius relation, using 0.7 days as the period boundary.