Limits on eccentricity excitation by tidally enhanced mass loss in Wolf-Rayet binaries
Abstract
Wolf--Rayet (WR) binaries frequently display high orbital eccentricities, and their eccentricity distributions are inconsistent with that of high-mass Galactic field binaries at high significance. This raises the question of whether these eccentricities are primordial or generated during the WR phase. We test whether a tidal enhancement of the mass-loss rate can pump the eccentricity of a WR binary on a sample of 14 WR systems. We model each system as a variable-mass two-body problem and integrate the orbital evolution over the WR lifetime under three prescriptions: i) adiabatic isotropic mass loss, ii) equilibrium-tide circularization, and iii) a tidally enhanced, pericenter-focused mass loss in which the companion-facing reduction of the effective surface gravity raises the local Eddington parameter. Adiabatic mass loss can not change eccentricity and affects only the orbital separation, which increases by up to a factor of ~20. Tidal circularization is effective only in the tightest orbits, which are compatible with the observed systems only for high mass-loss rates, a regime in which any primordial eccentricity is erased. The tidally enhanced mass loss channel pumps the eccentricity by only ≤10−4, three to four orders of magnitude below the observed values, and therefore cannot be the responsible mechanism. We conclude that the high eccentricities of WR binaries are predominantly primordial rather than generated by mass loss during the WR phase.
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BibTeX
@misc{frohlich2026limits,
title = {{Limits on eccentricity excitation by tidally enhanced mass loss in Wolf-Rayet binaries}},
author = {Viktória Fröhlich and Zsolt Regály},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.34726},
eprint = {2609.34726},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.34726},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Limits on eccentricity excitation by tidally enhanced mass loss in Wolf-Rayet binaries
AU - Viktória Fröhlich
AU - Zsolt Regály
PY - 2026
DA - 2026/09/28
PB - arXiv
DO - 10.48550/arxiv.2609.34726
UR - https://arxiv.org/abs/2609.34726
AB - Wolf--Rayet (WR) binaries frequently display high orbital eccentricities, and their eccentricity distributions are inconsistent with that of high-mass Galactic field binaries at high significance. This raises the question of whether these eccentricities are primordial or generated during the WR phase. We test whether a tidal enhancement of the mass-loss rate can pump the eccentricity of a WR binary on a sample of 14 WR systems. We model each system as a variable-mass two-body problem and integrate the orbital evolution over the WR lifetime under three prescriptions: i) adiabatic isotropic mass loss, ii) equilibrium-tide circularization, and iii) a tidally enhanced, pericenter-focused mass loss in which the companion-facing reduction of the effective surface gravity raises the local Eddington parameter. Adiabatic mass loss can not change eccentricity and affects only the orbital separation, which increases by up to a factor of ~20. Tidal circularization is effective only in the tightest orbits, which are compatible with the observed systems only for high mass-loss rates, a regime in which any primordial eccentricity is erased. The tidally enhanced mass loss channel pumps the eccentricity by only ≤10^−4, three to four orders of magnitude below the observed values, and therefore cannot be the responsible mechanism. We conclude that the high eccentricities of WR binaries are predominantly primordial rather than generated by mass loss during the WR phase.
ER -