Study on Contact Binary Stars

A special issue of Galaxies (ISSN 2075-4434).

Deadline for manuscript submissions: 15 February 2026 | Viewed by 265

Special Issue Editors


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Guest Editor
Shandong Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, School of Space Science and Physics, Institute of Space Sciences, Shandong University, Weihai 264209, China
Interests: contact binary; mass ratio, short period cut-off; O’Connell effect; orbital period variation

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Guest Editor
LUX, Observatoire de Paris, CNRS, PSL, 61 Avenue de l’Observatoire, 75014 Paris, France
Interests: contact binary; light curve solutions; fundamental parameters; stellar evolution; observation process

Special Issue Information

Dear Colleagues,

In the Universe, more than half of the stars are in the binary star system. A contact binary is one type of close binary where both components fill their Roche lobes and share a common convective envelope. It is estimated that about one of every 500 F, G, and K main sequence stars is a contact binary in our galaxy. The orbital period of a contact binary is generally shorter than 0.5 days. They are very important tools for determining precise physical parameters of stars and for distance measurement. Decades of research on contact binaries have led to significant achievements in understanding stellar formation, evolution, and advancing astrophysics. There are many exciting and rewarding topics about contact binaries that are still controversial; these include, for example, the 0.22 day shortperiod cutoff, the minimum mass ratio, the O’Connell effect, and the thermal relaxation oscillation theory. To better understand these issues, a large number of contact binaries should be observed and analzyed. Due to ground- and space-based photometric surveys, more than one million contact binaries have been detected. This Special Issue aims to foster collaboration and drive collective progress in addressing some of these issues by analyzing a substantial number of contact binaries.

Dr. Kai Li
Dr. Atila Poro
Guest Editors

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Keywords

  • contact binary
  • O’Connell effect
  • shortperiod cutoff
  • minimum mass ratio
  • orbital period change
  • light curve analysis
  • radial velocity curve

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Published Papers (1 paper)

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Research

14 pages, 3536 KiB  
Article
The BSN Application-I: Photometric Light Curve Solutions of Contact Binary Systems
by Ehsan Paki, Atila Poro and Minoo Dokht Moosavi Rowzati
Galaxies 2025, 13(4), 74; https://doi.org/10.3390/galaxies13040074 - 30 Jun 2025
Abstract
Light curve analysis of W UMa-type contact binary systems using MCMC or MC methods can be time-consuming, primarily because the repeated generation of synthetic light curves tends to be relatively slow during the fitting process. Although various approaches have been proposed to address [...] Read more.
Light curve analysis of W UMa-type contact binary systems using MCMC or MC methods can be time-consuming, primarily because the repeated generation of synthetic light curves tends to be relatively slow during the fitting process. Although various approaches have been proposed to address this issue, their implementation is often challenging due to complexity or uncertain performance. In this study, we introduce the BSN application, whose name is taken from the BSN project. The application is designed for analyzing contact binary system light curves, supporting photometric data, and employing an MCMC algorithm for efficient parameter estimation. The BSN application generates synthetic light curves more than 40 times faster than PHOEBE during the MCMC fitting process. The BSN application enhances light curve analysis with an expanded feature set and a more intuitive interface while maintaining compliance with established scientific standards. In addition, we present the first light curve analyses of four contact binary systems based on the TESS data, utilizing the BSN application version 1.0. We also conducted a light curve analysis using the PHOEBE Python code and compared the resulting outputs. Two of the target systems exhibited asymmetries in the maxima of their light curves, which were appropriately modeled by introducing a cold starspot on one of the components. The estimated mass ratios of these total-eclipse systems place them within the category of low mass ratio contact binary stars. The estimation of the absolute parameters for the selected systems was carried out using the Pa empirical relationship. Based on the effective temperatures and masses of the components, three of the target systems were classified as A-subtype, while TIC 434222993 was identified as a W-subtype system. Full article
(This article belongs to the Special Issue Study on Contact Binary Stars)
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