Formation of planetary systems by pebble accretion and migration: Hot super-Earth systems from breaking compact resonant chains. (arXiv:1902.08772v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Izidoro_A/0/1/0/all/0/1">André Izidoro</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bitsch_B/0/1/0/all/0/1">Bertram Bitsch</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Raymond_S/0/1/0/all/0/1">Sean N. Raymond</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Johansen_A/0/1/0/all/0/1">Anders Johansen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Morbidelli_A/0/1/0/all/0/1">Alessandro Morbidelli</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lambrechts_M/0/1/0/all/0/1">Michiel Lambrechts</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jacobson_S/0/1/0/all/0/1">Seth A. Jacobson</a>
At least 30% of main sequence stars host planets with sizes between 1 and 4
Earth radii and orbital periods of less than 100 days. We use N-body
simulations including a model for gas-assisted pebble accretion and disk-planet
tidal interaction to study the formation of super-Earth systems. We show that
the integrated pebble mass reservoir creates a bifurcation between hot
super-Earths or hot-Neptunes ($lesssim15M_{oplus}$) and super-massive
planetary cores potentially able to become gas giant planets
($gtrsim15M_{oplus}$). Simulations with moderate pebble fluxes grow multiple
super-Earth-mass planets that migrate inwards and pile up at the disk’s inner
edge forming long resonant chains. We follow the long-term dynamical evolution
of these systems and use the period ratio distribution of observed planet-pairs
to constrain our model. Up to $sim$95% of resonant chains become dynamically
unstable after the gas disk dispersal, leading to a phase of late collisions
that breaks the resonant configuration. Our simulations match observations if
we combine a dominant fraction ($gtrsim95%$) of unstable systems with a
sprinkling ($lesssim5%$) of stable resonant chains (the Trappist-1 system
represents one such example). Our results demonstrate that super-Earth systems
are inherently multiple (${rm Ngeq2}$) and that the observed excess of
single-planet transits is a consequence of the mutual inclinations excited by
the planet-planet instability. In simulations in which planetary seeds are
initially distributed in the inner and outer disk, close-in super-Earths are
systematically ice-rich. This contrasts with the interpretation that most
super-Earths are rocky based on bulk density measurements of super-Earths and
photo-evaporation modeling of their bimodal radius distribution. We investigate
the conditions needed to form rocky super-Earths. The formation of rocky
super-Earths (abridged)
At least 30% of main sequence stars host planets with sizes between 1 and 4
Earth radii and orbital periods of less than 100 days. We use N-body
simulations including a model for gas-assisted pebble accretion and disk-planet
tidal interaction to study the formation of super-Earth systems. We show that
the integrated pebble mass reservoir creates a bifurcation between hot
super-Earths or hot-Neptunes ($lesssim15M_{oplus}$) and super-massive
planetary cores potentially able to become gas giant planets
($gtrsim15M_{oplus}$). Simulations with moderate pebble fluxes grow multiple
super-Earth-mass planets that migrate inwards and pile up at the disk’s inner
edge forming long resonant chains. We follow the long-term dynamical evolution
of these systems and use the period ratio distribution of observed planet-pairs
to constrain our model. Up to $sim$95% of resonant chains become dynamically
unstable after the gas disk dispersal, leading to a phase of late collisions
that breaks the resonant configuration. Our simulations match observations if
we combine a dominant fraction ($gtrsim95%$) of unstable systems with a
sprinkling ($lesssim5%$) of stable resonant chains (the Trappist-1 system
represents one such example). Our results demonstrate that super-Earth systems
are inherently multiple (${rm Ngeq2}$) and that the observed excess of
single-planet transits is a consequence of the mutual inclinations excited by
the planet-planet instability. In simulations in which planetary seeds are
initially distributed in the inner and outer disk, close-in super-Earths are
systematically ice-rich. This contrasts with the interpretation that most
super-Earths are rocky based on bulk density measurements of super-Earths and
photo-evaporation modeling of their bimodal radius distribution. We investigate
the conditions needed to form rocky super-Earths. The formation of rocky
super-Earths (abridged)
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