Kozai Migration Naturally Explains the White Dwarf Planet WD1856b. (arXiv:2010.04724v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Munoz_D/0/1/0/all/0/1">Diego J. Muñoz</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Petrovich_C/0/1/0/all/0/1">Cristobal Petrovich</a>
The Jovian-sized object WD~1856~b transits a white dwarf (WD) in a compact
$1.4$-day orbit. Unlikely to have endured stellar evolution in its current
orbit, WD~1856~b is thought to have migrated from much wider separations.
Because the WD is old, and a member of a well-characterized hierarchical
multiple, the well-known Kozai mechanism provides an effective migration
channel for WD~1856~b. Moreover, the lack of tides in the star allows us to
directly connect the current semi-major axis to the pre-migration one, from
which we can infer the initial conditions of the system. By further demanding
that successful migrators survive all previous phases of stellar evolution, we
are able to constrain the mass of WD~1856~b to be $simeq0.7-3M_{rm J}$ and
its main sequence semi-major axis to be $simeq 2-2.5$ au. These properties
imply that WD~1856~b was born a typical gas giant. We further estimate the
occurrence rate of Kozai-migrated planets around WDs to be ${cal
O}(10^{-3}{-}10^{-4})$, suggesting that WD~1856~b is the only one in the {it
TESS} sample, but implying ${cal O}(10^2)$ future detections by LSST. In a
sense, WD~1856~b was an ordinary Jovian planet that underwent an extraordinary
dynamical history.
The Jovian-sized object WD~1856~b transits a white dwarf (WD) in a compact
$1.4$-day orbit. Unlikely to have endured stellar evolution in its current
orbit, WD~1856~b is thought to have migrated from much wider separations.
Because the WD is old, and a member of a well-characterized hierarchical
multiple, the well-known Kozai mechanism provides an effective migration
channel for WD~1856~b. Moreover, the lack of tides in the star allows us to
directly connect the current semi-major axis to the pre-migration one, from
which we can infer the initial conditions of the system. By further demanding
that successful migrators survive all previous phases of stellar evolution, we
are able to constrain the mass of WD~1856~b to be $simeq0.7-3M_{rm J}$ and
its main sequence semi-major axis to be $simeq 2-2.5$ au. These properties
imply that WD~1856~b was born a typical gas giant. We further estimate the
occurrence rate of Kozai-migrated planets around WDs to be ${cal
O}(10^{-3}{-}10^{-4})$, suggesting that WD~1856~b is the only one in the {it
TESS} sample, but implying ${cal O}(10^2)$ future detections by LSST. In a
sense, WD~1856~b was an ordinary Jovian planet that underwent an extraordinary
dynamical history.
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