High-eccentricity migration of planetesimals around polluted white dwarfs. (arXiv:2005.05977v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+OConnor_C/0/1/0/all/0/1">Christopher E. O'Connor</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lai_D/0/1/0/all/0/1">Dong Lai</a>
Several white dwarfs with atmospheric metal pollution have been found to host
small planetary bodies (planetesimals) orbiting near the tidal disruption
radius. We study the physical properties and dynamical origin of these bodies
under the hypothesis that they underwent high-eccentricity migration from
initial distances of several astronomical units. We examine two plausible
mechanisms for orbital migration and circularization: tidal friction and
ram-pressure drag in a compact disc. For each mechanism, we derive general
analytic expressions for the evolution of the orbit that can be rescaled for
various situations. We identify the physical parametres that determine whether
a planetesimal’s orbit can circularize within the appropriate time-scale and
constrain these parametres based on the properties of the observed systems. For
tidal migration to work, an internal viscosity similar to that of molten rock
is required, and this may be naturally produced by tidal heating. For disc
migration to operate, a minimal column density of the disc is implied; the
inferred total disc mass is consistent with estimates of the total mass of
metals accreted by polluted WDs.
Several white dwarfs with atmospheric metal pollution have been found to host
small planetary bodies (planetesimals) orbiting near the tidal disruption
radius. We study the physical properties and dynamical origin of these bodies
under the hypothesis that they underwent high-eccentricity migration from
initial distances of several astronomical units. We examine two plausible
mechanisms for orbital migration and circularization: tidal friction and
ram-pressure drag in a compact disc. For each mechanism, we derive general
analytic expressions for the evolution of the orbit that can be rescaled for
various situations. We identify the physical parametres that determine whether
a planetesimal’s orbit can circularize within the appropriate time-scale and
constrain these parametres based on the properties of the observed systems. For
tidal migration to work, an internal viscosity similar to that of molten rock
is required, and this may be naturally produced by tidal heating. For disc
migration to operate, a minimal column density of the disc is implied; the
inferred total disc mass is consistent with estimates of the total mass of
metals accreted by polluted WDs.
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