Attributing the O'Connell effect in contact binaries to a cooling mass-transfer stream

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Autori principali: Fabry, Matthias, Prša, Andrej
Natura: Preprint
Pubblicazione: 2025
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author Fabry, Matthias
Prša, Andrej
author_facet Fabry, Matthias
Prša, Andrej
contents Contact binaries are very short-period systems that are continuously interacting by transferring mass and energy. Obtaining large, statistical samples of contact binaries from photometric surveys can put valuable constraints on the various processes involved in their evolution. Modeling those systems however present some challenges. In some contact-binary light curves, the O'Connell effect is visible, where the maxima at both quarter phases are unequal. In the literature, this effect is typically attributed to magnetic spots on the surface of the binary. In this work, we model contact-binary surfaces using PHOEBE, and include a parametric prescription for a lateral mass- and energy-transfer stream that travels from the hotter primary to the cooler secondary. We allow this stream to have a variable heat capacity. We fit a system from the Kepler sample with a strong O'Connell effect, and show that a low-heat capacity stream can explain the unequal maxima. This suggests that, in such systems, surface flows can play a significant role in transferring heat between components. Our methods can be used on larger samples of contact binaries from OGLE, Kepler, or TESS to advance our understanding of contact binary structure and evolution.
format Preprint
id arxiv_https___arxiv_org_abs_2510_17958
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Attributing the O'Connell effect in contact binaries to a cooling mass-transfer stream
Fabry, Matthias
Prša, Andrej
Solar and Stellar Astrophysics
Contact binaries are very short-period systems that are continuously interacting by transferring mass and energy. Obtaining large, statistical samples of contact binaries from photometric surveys can put valuable constraints on the various processes involved in their evolution. Modeling those systems however present some challenges. In some contact-binary light curves, the O'Connell effect is visible, where the maxima at both quarter phases are unequal. In the literature, this effect is typically attributed to magnetic spots on the surface of the binary. In this work, we model contact-binary surfaces using PHOEBE, and include a parametric prescription for a lateral mass- and energy-transfer stream that travels from the hotter primary to the cooler secondary. We allow this stream to have a variable heat capacity. We fit a system from the Kepler sample with a strong O'Connell effect, and show that a low-heat capacity stream can explain the unequal maxima. This suggests that, in such systems, surface flows can play a significant role in transferring heat between components. Our methods can be used on larger samples of contact binaries from OGLE, Kepler, or TESS to advance our understanding of contact binary structure and evolution.
title Attributing the O'Connell effect in contact binaries to a cooling mass-transfer stream
topic Solar and Stellar Astrophysics
url https://arxiv.org/abs/2510.17958