The dynamical history of the evaporating or disrupted ice giant planet around white dwarf WD J0914+1914. (arXiv:1912.02199v1 [astro-ph.EP])

The dynamical history of the evaporating or disrupted ice giant planet around white dwarf WD J0914+1914. (arXiv:1912.02199v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Veras_D/0/1/0/all/0/1">Dimitri Veras</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fuller_J/0/1/0/all/0/1">Jim Fuller</a>

Robust evidence of an ice giant planet shedding its atmosphere around the
white dwarf WD J0914+1914 represents a milestone in exoplanetary science,
allowing us to finally supplement our knowledge of white dwarf metal pollution,
debris discs and minor planets with the presence of a major planet. Here, we
discuss the possible dynamical origins of this planet, WD J0914+1914b. The very
young cooling age of the host white dwarf (13 Myr) combined with the currently
estimated planet-star separation of about 0.07 au imposes particularly
intriguing and restrictive coupled constraints on its current orbit and its
tidal dissipation characteristics. The planet must have been scattered from a
distance of at least a few au to its current location, requiring the current or
former presence of at least one more major planet in the system. We show that
WD J0914+1914b could not have subsequently shrunk its orbit through chaotic
f-mode tidal excitation (characteristic of such highly eccentric orbits) unless
the planet was or is highly inflated and had at least partially thermally
self-disrupted from mode-based energy release. We also demonstrate that if the
planet is currently assumed to reside on a near-circular orbit at 0.07 au, then
non-chaotic equilibrium tides impose unrealistic values for the planet’s tidal
quality factor. We conclude that WD J0914+1914b either resembles a disrupted
“Super-Puff” whose remains reside on a circular orbit, or a larger or denser
ice giant on a currently eccentric orbit. Distinguishing these two
possibilities strongly motivates follow-up observations.

Robust evidence of an ice giant planet shedding its atmosphere around the
white dwarf WD J0914+1914 represents a milestone in exoplanetary science,
allowing us to finally supplement our knowledge of white dwarf metal pollution,
debris discs and minor planets with the presence of a major planet. Here, we
discuss the possible dynamical origins of this planet, WD J0914+1914b. The very
young cooling age of the host white dwarf (13 Myr) combined with the currently
estimated planet-star separation of about 0.07 au imposes particularly
intriguing and restrictive coupled constraints on its current orbit and its
tidal dissipation characteristics. The planet must have been scattered from a
distance of at least a few au to its current location, requiring the current or
former presence of at least one more major planet in the system. We show that
WD J0914+1914b could not have subsequently shrunk its orbit through chaotic
f-mode tidal excitation (characteristic of such highly eccentric orbits) unless
the planet was or is highly inflated and had at least partially thermally
self-disrupted from mode-based energy release. We also demonstrate that if the
planet is currently assumed to reside on a near-circular orbit at 0.07 au, then
non-chaotic equilibrium tides impose unrealistic values for the planet’s tidal
quality factor. We conclude that WD J0914+1914b either resembles a disrupted
“Super-Puff” whose remains reside on a circular orbit, or a larger or denser
ice giant on a currently eccentric orbit. Distinguishing these two
possibilities strongly motivates follow-up observations.

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