The Structure and Stability of Extended, Inclined Circumplanetary Disk or Ring Systems. (arXiv:1912.00034v1 [astro-ph.EP])

The Structure and Stability of Extended, Inclined Circumplanetary Disk or Ring Systems. (arXiv:1912.00034v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Speedie_J/0/1/0/all/0/1">Jessica Speedie</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zanazzi_J/0/1/0/all/0/1">J. J. Zanazzi</a>

Large dips in the brightness for a number of stars have been observed, for
which the tentative explanation is occultation of the star by a transiting
circumplanetary disk or ring system. In order for the circumplanetary
disk/rings to block the host star’s light, the disk must be tilted out of the
planet’s orbital plane, which poses stability problems due to the radial extent
of the disk required to explain the brightness dip durations. This work uses
N-body integrations to study the structure and stability of circumplanetary
disk/ring systems tilted out of the planet’s orbital plane by the spinning
planet’s mass quadrupole. Simulating the disk as a collection of test particles
with orbits initialized near the Laplace surface (equilibrium between tidal
force from host star and force from planet’s mass quadrupole), we find that
many extended, inclined circumplanetary disks remain stable over the duration
of the integrations (~3-16 Myr). Two dynamical resonances/instabilities excite
the particle eccentricities and inclinations: the Lidov-Kozai effect which
occurs in the disk’s outer regions, and ivection resonance which occurs in the
disk’s inner regions. Our work places constraints on the maximum radial extent
of inclined circumplanetary disk/ring systems, and shows that gaps present in
circumplanetary disks do not necessarily imply the presence of exomoons.

Large dips in the brightness for a number of stars have been observed, for
which the tentative explanation is occultation of the star by a transiting
circumplanetary disk or ring system. In order for the circumplanetary
disk/rings to block the host star’s light, the disk must be tilted out of the
planet’s orbital plane, which poses stability problems due to the radial extent
of the disk required to explain the brightness dip durations. This work uses
N-body integrations to study the structure and stability of circumplanetary
disk/ring systems tilted out of the planet’s orbital plane by the spinning
planet’s mass quadrupole. Simulating the disk as a collection of test particles
with orbits initialized near the Laplace surface (equilibrium between tidal
force from host star and force from planet’s mass quadrupole), we find that
many extended, inclined circumplanetary disks remain stable over the duration
of the integrations (~3-16 Myr). Two dynamical resonances/instabilities excite
the particle eccentricities and inclinations: the Lidov-Kozai effect which
occurs in the disk’s outer regions, and ivection resonance which occurs in the
disk’s inner regions. Our work places constraints on the maximum radial extent
of inclined circumplanetary disk/ring systems, and shows that gaps present in
circumplanetary disks do not necessarily imply the presence of exomoons.

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