Photometric and Spectroscopic Investigations of Three Large Amplitude Contact Binaries

TL;DR

This study combines photometric and spectroscopic analyses of three large amplitude contact binaries, revealing their physical properties, evolutionary states, and chromospheric activity, and comparing energy transfer efficiency among H-subtype systems.

Contribution

It provides detailed physical and evolutionary characterization of three large amplitude contact binaries using combined photometric and spectroscopic data, including new insights into energy transfer efficiency in H-subtype systems.

Findings

NSVS 7377875 is an A-subtype contact binary with high mass ratio.

Orbital period of NSVS 2418361 is increasing, indicating mass transfer.

H-subtype contact binaries have less efficient energy transfer rates.

Abstract

We performed photometric and spectroscopic studies of three large amplitude contact binaries, NSVS 2418361, ATLAS J057.1170+31.2384 and NSVS 7377875. The amplitudes of three systems' light curves are more than 0.7 magnitude. We analyzed the light curves using Wilson-Devinney code to yield physical parameters. The photometric solutions suggested that NSVS 7377875 belongs to an A-subtype contact binary, while the others are classified as W-subtype ones. Furthermore, the mass ratio of NSVS 7377875 is higher than 0.72, so it belongs to H-subtype contact binaries. Since their light curves have unequal height at two maxima which is called O'Connell effect, a dark spot on the primary component for each target was required to get a better fit of light curves. The orbital period investigation shows that the period of NSVS 2418361 is increasing, indicating a mass transfer from the less massive component to the more massive one, while the other targets exhibit no long-term variation. Our spectral subtraction analysis of LAMOST spectra revealed excess emissions in the $H_\alpha$ line, indicating chromospheric activity in all the three targets. The Gaia distance was applied to estimate the absolute parameters of the three targets, and we obtained their evolutionary state. The relationships between the energy transfer parameter of 76 H-subtype contact binaries and their bolometric luminosity ratios, as well as their contact degree, were presented. We discovered that H-subtype systems have less efficient energy transfer rate, which is corresponding to the conclusion proposed by Csizmadia \& Klagyivik.