Excitation of post-AGB Star Binary Eccentricity by Massive Polar-Aligned Circumbinary Disks

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Hauptverfasser: Huang, Shunquan, Martin, Rebecca G., Lubow, Stephen H.
Format: Preprint
Veröffentlicht: 2025
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author Huang, Shunquan
Martin, Rebecca G.
Lubow, Stephen H.
author_facet Huang, Shunquan
Martin, Rebecca G.
Lubow, Stephen H.
contents Many post-AGB star binaries are observed to have relatively high orbital eccentricities (up to 0.6). Recently, AC Her was observed to have a polar-aligned circumbinary disk. We perform hydrodynamic simulations to explore the impact of a polar-aligned disk on the eccentricity of a binary. For a binary system with central masses of 0.73 M_sun and 1.4 M_sun, we find that a disk with a total mass of 0.1 M_sun can enhance the binary eccentricity from 0.2 to 0.7 within 5000 years, or from 0.01 to 0.65 within 15000 years. Even if the disk mass is as low as 0.01 M_sun, the binary eccentricity grows within our simulation time while the system remains stable. These eccentricity variations are associated with the variations of the inclination between the disk and the binary orbit due to von Zeipel-Kozai-Lidov oscillations. The oscillations eventually damp and leave the binary eccentricity at a high value. The numerical results are in good agreement with analytical estimates. In addition, we examine the AC-Her system and find that the disk mass should be on the order of 10^(-3)M_sun for the disk to remain polar.
format Preprint
id arxiv_https___arxiv_org_abs_2504_17125
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Excitation of post-AGB Star Binary Eccentricity by Massive Polar-Aligned Circumbinary Disks
Huang, Shunquan
Martin, Rebecca G.
Lubow, Stephen H.
Solar and Stellar Astrophysics
Many post-AGB star binaries are observed to have relatively high orbital eccentricities (up to 0.6). Recently, AC Her was observed to have a polar-aligned circumbinary disk. We perform hydrodynamic simulations to explore the impact of a polar-aligned disk on the eccentricity of a binary. For a binary system with central masses of 0.73 M_sun and 1.4 M_sun, we find that a disk with a total mass of 0.1 M_sun can enhance the binary eccentricity from 0.2 to 0.7 within 5000 years, or from 0.01 to 0.65 within 15000 years. Even if the disk mass is as low as 0.01 M_sun, the binary eccentricity grows within our simulation time while the system remains stable. These eccentricity variations are associated with the variations of the inclination between the disk and the binary orbit due to von Zeipel-Kozai-Lidov oscillations. The oscillations eventually damp and leave the binary eccentricity at a high value. The numerical results are in good agreement with analytical estimates. In addition, we examine the AC-Her system and find that the disk mass should be on the order of 10^(-3)M_sun for the disk to remain polar.
title Excitation of post-AGB Star Binary Eccentricity by Massive Polar-Aligned Circumbinary Disks
topic Solar and Stellar Astrophysics
url https://arxiv.org/abs/2504.17125