Are exoplanetesimals differentiated?. (arXiv:2001.04499v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Bonsor_A/0/1/0/all/0/1">Amy Bonsor</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Carter_P/0/1/0/all/0/1">Philip J. Carter</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hollands_M/0/1/0/all/0/1">Mark Hollands</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gaensicke_B/0/1/0/all/0/1">Boris T. Gaensicke</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Leinhardt_Z/0/1/0/all/0/1">Zoe Leinhardt</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Harrison_J/0/1/0/all/0/1">John H. D. Harrison</a>
Metals observed in the atmospheres of white dwarfs suggest that many have
recently accreted planetary bodies. In some cases, the compositions observed
suggest the accretion of material dominantly from the core (or the mantle) of a
differentiated planetary body. Collisions between differentiated
exoplanetesimals produce such fragments. In this work, we take advantage of the
large numbers of white dwarfs where at least one siderophile (core-loving) and
one lithophile (rock-loving) species have been detected to assess how commonly
exoplanetesimals differentiate. We utilise N-body simulations that track the
fate of core and mantle material during the collisional evolution of planetary
systems to show that most remnants of differentiated planetesimals retain core
fractions similar to their parents, whilst some are extremely core-rich or
mantle-rich. Comparison with the white dwarf data for calcium and iron
indicates that the data are consistent with a model in which $66^{+4}_{-6}%$
have accreted the remnants of differentiated planetesimals, whilst
$31^{+5}_{-5}%$ have Ca/Fe abundances altered by the effects of heating
(although the former can be as high as $100%$, if heating is ignored). These
conclusions assume pollution by a single body and that collisional evolution
retains similar features across diverse planetary systems. These results imply
that both collisions and differentiation are key processes in exoplanetary
systems. We highlight the need for a larger sample of polluted white dwarfs
with precisely determined metal abundances to better understand the process of
differentiation in exoplanetary systems.
Metals observed in the atmospheres of white dwarfs suggest that many have
recently accreted planetary bodies. In some cases, the compositions observed
suggest the accretion of material dominantly from the core (or the mantle) of a
differentiated planetary body. Collisions between differentiated
exoplanetesimals produce such fragments. In this work, we take advantage of the
large numbers of white dwarfs where at least one siderophile (core-loving) and
one lithophile (rock-loving) species have been detected to assess how commonly
exoplanetesimals differentiate. We utilise N-body simulations that track the
fate of core and mantle material during the collisional evolution of planetary
systems to show that most remnants of differentiated planetesimals retain core
fractions similar to their parents, whilst some are extremely core-rich or
mantle-rich. Comparison with the white dwarf data for calcium and iron
indicates that the data are consistent with a model in which $66^{+4}_{-6}%$
have accreted the remnants of differentiated planetesimals, whilst
$31^{+5}_{-5}%$ have Ca/Fe abundances altered by the effects of heating
(although the former can be as high as $100%$, if heating is ignored). These
conclusions assume pollution by a single body and that collisional evolution
retains similar features across diverse planetary systems. These results imply
that both collisions and differentiation are key processes in exoplanetary
systems. We highlight the need for a larger sample of polluted white dwarfs
with precisely determined metal abundances to better understand the process of
differentiation in exoplanetary systems.
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