The minimum mass ratio of W ursae majoris binaries

Frederic A. Rasio

doi:10.1086/187855

The minimum mass ratio of W ursae majoris binaries

Frederic A. Rasio^*

^*Corresponding author for this work

Physics and Astronomy

Research output: Contribution to journal › Article › peer-review

85 Scopus citations

Abstract

The minimum mass ratio for tidal stability of a contact binary containing two unevolved main-sequence stars is calculated to be q_min ≃ 0.09 in the case of a mostly radiative primary, and it is higher if an appreciable fraction of the mass lies in a convective envelope. At least one observed system, AW UMa, has a mass ratio just below this value (q = 0.075), implying that, if the system is stable, the primary must be slightly evolved and must have a very shallow convective envelope. Contact binaries with mass ratios significantly below that of AW UMa should not be observed, since they are tidally unstable and quickly merge into a single, rapidly rotating object, on a timescale ∼ 10³-10⁴ yr.

Original language	English (US)
Pages (from-to)	L41-L43
Journal	Astrophysical Journal
Volume	444
Issue number	1 PART 2
DOIs	https://doi.org/10.1086/187855
State	Published - May 1 1995

Keywords

Binaries: close
Blue stragglers
Hydrodynamics
Instabilities
Stars: evolution
Stars: rotation

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

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10.1086/187855

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abstract = "The minimum mass ratio for tidal stability of a contact binary containing two unevolved main-sequence stars is calculated to be qmin ≃ 0.09 in the case of a mostly radiative primary, and it is higher if an appreciable fraction of the mass lies in a convective envelope. At least one observed system, AW UMa, has a mass ratio just below this value (q = 0.075), implying that, if the system is stable, the primary must be slightly evolved and must have a very shallow convective envelope. Contact binaries with mass ratios significantly below that of AW UMa should not be observed, since they are tidally unstable and quickly merge into a single, rapidly rotating object, on a timescale ∼ 103-104 yr.",

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N2 - The minimum mass ratio for tidal stability of a contact binary containing two unevolved main-sequence stars is calculated to be qmin ≃ 0.09 in the case of a mostly radiative primary, and it is higher if an appreciable fraction of the mass lies in a convective envelope. At least one observed system, AW UMa, has a mass ratio just below this value (q = 0.075), implying that, if the system is stable, the primary must be slightly evolved and must have a very shallow convective envelope. Contact binaries with mass ratios significantly below that of AW UMa should not be observed, since they are tidally unstable and quickly merge into a single, rapidly rotating object, on a timescale ∼ 103-104 yr.

AB - The minimum mass ratio for tidal stability of a contact binary containing two unevolved main-sequence stars is calculated to be qmin ≃ 0.09 in the case of a mostly radiative primary, and it is higher if an appreciable fraction of the mass lies in a convective envelope. At least one observed system, AW UMa, has a mass ratio just below this value (q = 0.075), implying that, if the system is stable, the primary must be slightly evolved and must have a very shallow convective envelope. Contact binaries with mass ratios significantly below that of AW UMa should not be observed, since they are tidally unstable and quickly merge into a single, rapidly rotating object, on a timescale ∼ 103-104 yr.

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KW - Blue stragglers

KW - Hydrodynamics

KW - Instabilities

KW - Stars: evolution

KW - Stars: rotation

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The minimum mass ratio of W ursae majoris binaries

Abstract

Keywords

ASJC Scopus subject areas

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