Wind morphology around cool evolved stars in binaries: the case of slowly accelerating oxygen-rich outflows. (arXiv:2001.04482v1 [astro-ph.SR])

Wind morphology around cool evolved stars in binaries: the case of slowly accelerating oxygen-rich outflows. (arXiv:2001.04482v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Mellah_I/0/1/0/all/0/1">I. El Mellah</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bolte_J/0/1/0/all/0/1">J. Bolte</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Decin_L/0/1/0/all/0/1">L. Decin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Homan_W/0/1/0/all/0/1">W. Homan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Keppens_R/0/1/0/all/0/1">R. Keppens</a>

The late stellar evolutionary phases of low and intermediate-mass stars are
strongly constrained by their mass-loss rates. The wind surrounding cool
evolved stars frequently shows non-spherical features, thought to be due to an
unseen companion orbiting the donor star. We study the morphology of the
circumbinary envelope, in particular around oxygen-rich asymptotic giant branch
(AGB) stars. We run a grid of 70 3D hydrodynamics simulations of a
progressively accelerating wind propagating in the Roche potential formed by a
mass-loosing evolved star in orbit with a main sequence companion. We resolve
the flow structure both in the immediate vicinity of the secondary, where bow
shocks, outflows and wind-captured disks form, and up to 40 orbital
separations, where spiral arms, arcs and equatorial density enhancements
develop. When the companion is deeply engulfed in the wind, the lower terminal
wind speeds and more progressive wind acceleration around oxygen-rich AGB stars
make them more prone than carbon-rich AGB stars to display more disturbed
outflows, a disk-like structure around the companion and a wind concentrated in
the orbital plane. In these configurations, a large fraction of the wind is
captured by the companion which leads to a significant shrinking of the orbit
over the mass-loss timescale, if the donor star is at least a few times more
massive than its companion. Provided the companion has a mass of at least a
tenth of the mass of the donor star, it can compress the wind in the orbital
plane up to large distances. Our grid of models covers a wide scope of
configurations function of the dust chemical content, the terminal wind speed
relative to the orbital speed, the extension of the dust condensation region
around the cool evolved star and the mass ratio. It provides a frame of
reference to interpret high-resolution maps of the outflows surrounding cool
evolved stars.

The late stellar evolutionary phases of low and intermediate-mass stars are
strongly constrained by their mass-loss rates. The wind surrounding cool
evolved stars frequently shows non-spherical features, thought to be due to an
unseen companion orbiting the donor star. We study the morphology of the
circumbinary envelope, in particular around oxygen-rich asymptotic giant branch
(AGB) stars. We run a grid of 70 3D hydrodynamics simulations of a
progressively accelerating wind propagating in the Roche potential formed by a
mass-loosing evolved star in orbit with a main sequence companion. We resolve
the flow structure both in the immediate vicinity of the secondary, where bow
shocks, outflows and wind-captured disks form, and up to 40 orbital
separations, where spiral arms, arcs and equatorial density enhancements
develop. When the companion is deeply engulfed in the wind, the lower terminal
wind speeds and more progressive wind acceleration around oxygen-rich AGB stars
make them more prone than carbon-rich AGB stars to display more disturbed
outflows, a disk-like structure around the companion and a wind concentrated in
the orbital plane. In these configurations, a large fraction of the wind is
captured by the companion which leads to a significant shrinking of the orbit
over the mass-loss timescale, if the donor star is at least a few times more
massive than its companion. Provided the companion has a mass of at least a
tenth of the mass of the donor star, it can compress the wind in the orbital
plane up to large distances. Our grid of models covers a wide scope of
configurations function of the dust chemical content, the terminal wind speed
relative to the orbital speed, the extension of the dust condensation region
around the cool evolved star and the mass ratio. It provides a frame of
reference to interpret high-resolution maps of the outflows surrounding cool
evolved stars.

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