Hydrodynamic Winds From Twin-Star Binaries. (arXiv:2007.07252v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+MacLeod_M/0/1/0/all/0/1">Morgan MacLeod</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Loeb_A/0/1/0/all/0/1">Abraham Loeb</a>
Stellar winds shape the evolution of stars through the loss of mass. In
binary systems, they also shape the stars’ evolution by modifying the orbit. In
this paper, we use hydrodynamic simulations to study the emergence of
nearly-isothermal winds from identical-twin binaries. We vary the degree to
which model stars fill their Roche lobes and the temperature of the wind.
Initialized at rest on the stellar surfaces, winds accelerate away from the
binary components through a sonic surface to supersonic outward velocities. In
cases where the binary fills its Roche lobe, a shared subsonic region surrounds
both components. We find that mass loss rates from close twin-star binaries are
enhanced relative to the expectation from two single-object winds. This binary
enhancement is best modeled as a function of the ratio of wind velocity to
orbital velocity. Similarly, we find that the specific angular momentum with
which winds emerge can vary between that of the binary components and that of
the outer Lagrange points depending on the ratio of wind velocity to orbital
velocity. Given that mass and angular momentum loss can be modeled as simple
functions of wind velocity, our results may be broadly applicable to the
evolution of close, equal-mass binaries. One particularly important potential
application is to massive, close binaries which may be progenitors of binary
black hole mergers through the chemically-homogeneous evolution channel.
Stellar winds shape the evolution of stars through the loss of mass. In
binary systems, they also shape the stars’ evolution by modifying the orbit. In
this paper, we use hydrodynamic simulations to study the emergence of
nearly-isothermal winds from identical-twin binaries. We vary the degree to
which model stars fill their Roche lobes and the temperature of the wind.
Initialized at rest on the stellar surfaces, winds accelerate away from the
binary components through a sonic surface to supersonic outward velocities. In
cases where the binary fills its Roche lobe, a shared subsonic region surrounds
both components. We find that mass loss rates from close twin-star binaries are
enhanced relative to the expectation from two single-object winds. This binary
enhancement is best modeled as a function of the ratio of wind velocity to
orbital velocity. Similarly, we find that the specific angular momentum with
which winds emerge can vary between that of the binary components and that of
the outer Lagrange points depending on the ratio of wind velocity to orbital
velocity. Given that mass and angular momentum loss can be modeled as simple
functions of wind velocity, our results may be broadly applicable to the
evolution of close, equal-mass binaries. One particularly important potential
application is to massive, close binaries which may be progenitors of binary
black hole mergers through the chemically-homogeneous evolution channel.
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