BSN-VI: Multiband Light Curve Modeling of Four W UMa-Type Contact Binaries I. Revisiting Energy Transfer Mechanisms and Luminosity Behavior

TL;DR

This paper delivers high-precision multiband photometry and comprehensive light-curve modeling for four W UMa-type contact binaries, augmented by TESS data for DM Cir and Gaia DR3-based absolute parameter estimation. Through PHOEBE/BSN with MCMC, the authors obtain tight constraints on temperatures, mass ratios, and orbital geometries, revealing near-thermal contact ($|\Delta T|$ of only a few tens to a few hundred kelvin) and no significant third-light contribution. They update the ephemerides, derive robust absolute parameters (masses, radii, luminosities, and separations), and classify the systems as two W-subtypes and two A-subtypes, confirming dynamical stability. An energy-transfer analysis across 411 W UMa systems shows general agreement with theoretical expectations (Mochnacki 1981; Jiang 2009) and highlights varying transfer efficiency among the targets, influenced by mass ratio and evolutionary state. The results support an AML-driven formation scenario with past mass transfer and provide a solid, Gaia-grounded benchmark for the structure and evolution of contact binaries.

Abstract

We presented the first high-precision, detailed photometric analysis of four W Ursae Majoris (W UMa)-type contact binaries, Linear 10772300, Linear 11150338, Linear 20372537 and DM Cir. In addition to ground-based multiband photometric observations, data from the Transiting Exoplanet Survey Satellite (TESS) were employed for the analysis of the DM Cir system. New ephemeris and linear fit to the O-C diagrams were derived using extracted times of minima and additional literature. The light curve modeling was performed using the PHysics Of Eclipsing BinariEs (PHOEBE) Python code and the BSN application, employing a Markov Chain Monte Carlo approach. In each systems, the two stellar components exhibited minimal temperature differences ($ΔT<150$ K), confirming efficient energy exchange within their common convective envelopes. Absolute parameters were estimated using the Gaia Data Release 3 (Gaia DR3) parallax and astrophysical equations. Based on effective temperatures and component masses, two systems were classified as W-subtype systems, while others belonged to the A-subtype. We computed the initial masses of the primary ($M_{1i}$) and secondary ($M_{2i}$) components for four target systems using a method based on the observational properties of overluminous secondary components. We found initial primary masses in the range 0.6-1.0$M_\odot$ and initial secondary masses in the range 0.9-1.7$M_\odot$ with mass loss $<1.0M_{\odot}$. We investigated the relative energy transfer rates ($U_{1}$ and $U_{2}$) and nuclear luminosities ($L_{10}$ and $L_{20}$) based on the physical parameters of 411 W UMa-type contact binaries, including the four systems analyzed in this study, through wide range of mass ratios. The results for all systems provided a comprehensive view of energy transfer behavior throughout different evolutionary stages of contact binaries.

Figures (7)

• Figure 1: O–C diagrams illustrating the period variations of the targets.
• Figure 2: Sum of the squared residuals as a function of the mass ratio.
• Figure 3: Corner plots based on the heat-map of the target contact binary systems were determined through MCMC modeling by the BSN application.
• Figure 4: The colored dots represent the observed light curves of the systems in different filters, and the synthetic light curves, generated using the light curve solutions, are also shown. Residuals are shown at the bottom of each panel.
• Figure 5: 3D view of the stellar components in the four target binary systems at orbital phases 0, 0.25, 0.50, and 0.75, respectively.