Pebble-driven Planet Formation around Very Low-mass Stars and Brown Dwarfs. (arXiv:2004.07239v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Liu_B/0/1/0/all/0/1">Beibei Liu</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:+Johansen_A/0/1/0/all/0/1">Anders Johansen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pascucci_I/0/1/0/all/0/1">Ilaria Pascucci</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Henning_T/0/1/0/all/0/1">Thomas Henning</a>
We conduct a pebble-driven planet population synthesis study to investigate
the formation of planets around very low-mass stars and brown dwarfs, in the
(sub)stellar mass range between $0.01 M_{odot}$ and $0.1 M_{odot}$. Based
on the extrapolation of numerical simulations of planetesimal formation by the
streaming instability, we obtain the characteristic mass of the planetesimals
and the initial masses of the protoplanets (largest bodies from the
planetesimal size distributions), in either the early self-gravitating phase or
the later non-self-gravitating phase of the protoplanetary disk evolution. We
find that the initial protoplanets form with masses that increase with host
mass, orbital distance and decrease with disk age. Around late M-dwarfs of $0.1
M_{odot}$, these protoplanets can grow up to Earth-mass planets by pebble
accretion. However, around brown dwarfs of $0.01 M_{odot}$, planets do not
grow larger than Mars mass when the initial protoplanets are born early in
self-gravitating disks, and their growth stalls at around $0.01$ Earth-mass
when they are born late in non-self-gravitating disks. Around these low mass
stars and brown dwarfs, we find no channel for gas giant planet formation
because the solid cores remain too small. When the initial protoplanets form
only at the water-ice line, the final planets typically have ${gtrsim} 15%$
water mass fraction. Alternatively, when the initial protoplanets form
log-uniformly distributed over the entire protoplanetary disk, the final
planets are either very water-rich (water mass fraction ${gtrsim}15%$) or
entirely rocky (water mass fraction ${lesssim}5%$).
We conduct a pebble-driven planet population synthesis study to investigate
the formation of planets around very low-mass stars and brown dwarfs, in the
(sub)stellar mass range between $0.01 M_{odot}$ and $0.1 M_{odot}$. Based
on the extrapolation of numerical simulations of planetesimal formation by the
streaming instability, we obtain the characteristic mass of the planetesimals
and the initial masses of the protoplanets (largest bodies from the
planetesimal size distributions), in either the early self-gravitating phase or
the later non-self-gravitating phase of the protoplanetary disk evolution. We
find that the initial protoplanets form with masses that increase with host
mass, orbital distance and decrease with disk age. Around late M-dwarfs of $0.1
M_{odot}$, these protoplanets can grow up to Earth-mass planets by pebble
accretion. However, around brown dwarfs of $0.01 M_{odot}$, planets do not
grow larger than Mars mass when the initial protoplanets are born early in
self-gravitating disks, and their growth stalls at around $0.01$ Earth-mass
when they are born late in non-self-gravitating disks. Around these low mass
stars and brown dwarfs, we find no channel for gas giant planet formation
because the solid cores remain too small. When the initial protoplanets form
only at the water-ice line, the final planets typically have ${gtrsim} 15%$
water mass fraction. Alternatively, when the initial protoplanets form
log-uniformly distributed over the entire protoplanetary disk, the final
planets are either very water-rich (water mass fraction ${gtrsim}15%$) or
entirely rocky (water mass fraction ${lesssim}5%$).
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