The tidal quality of the hot Jupiter WASP-12b. (arXiv:2111.08273v2 [astro-ph.EP] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Efroimsky_M/0/1/0/all/0/1">Michael Efroimsky</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Makarov_V/0/1/0/all/0/1">Valeri V. Makarov</a>
WASP-12b stands out among the planets of its class of hot Jupiters because of
the observed fast orbital decay attributed to tidal dissipation. The measured
rate of the orbital period is $stackrel{bfcenterdot}{textstyle{P}}_{rm
orb},=,-,29pm3;mbox{ms/yr};$=$;(9.2pm1.0)times10^{-10};mbox{s/s}$.
In the literature heretofore, all attempts to explain this high rate were based
on the assumption that the orbital evolution is dominated by the tides in the
star. Since the modified tidal quality factor in yellow dwarfs is insufficient
to warrant such a decay rate, a hypothesis was put forward that the star may
actually be a subgiant. Using the latest data from the Gaia mission, we
estimate the mass of WASP-12 at $1.28,{M_{Sun}}$ and point out that it takes
at least $600~mbox{Myr}$ to evolve off the main sequence to its present state,
which is roughly 20 times the inferred dynamical lifetime of the planet. The
previous research neglected the tidal dissipation in the planet assuming it to
be negligible due to the likely synchronisation of its rotation and a presumed
high quality factor. We critically reassess this assumption in the light of
recent astrometric results for Jupiter and Saturn, also employing more advanced
theories of frequency-dependent tidal dissipation. Assuming that WASP-12b, like
our Jupiter and Saturn, has a solid core, we find that the observed orbital
decay is well explained by the tides in the planet. We calculate the exact
value of the modified quality factor from the observed orbital decay and the
upper bound eccentricity, which happens to coincide almost precisely with that
of our Jupiter.
WASP-12b stands out among the planets of its class of hot Jupiters because of
the observed fast orbital decay attributed to tidal dissipation. The measured
rate of the orbital period is $stackrel{bfcenterdot}{textstyle{P}}_{rm
orb},=,-,29pm3;mbox{ms/yr};$=$;(9.2pm1.0)times10^{-10};mbox{s/s}$.
In the literature heretofore, all attempts to explain this high rate were based
on the assumption that the orbital evolution is dominated by the tides in the
star. Since the modified tidal quality factor in yellow dwarfs is insufficient
to warrant such a decay rate, a hypothesis was put forward that the star may
actually be a subgiant. Using the latest data from the Gaia mission, we
estimate the mass of WASP-12 at $1.28,{M_{Sun}}$ and point out that it takes
at least $600~mbox{Myr}$ to evolve off the main sequence to its present state,
which is roughly 20 times the inferred dynamical lifetime of the planet. The
previous research neglected the tidal dissipation in the planet assuming it to
be negligible due to the likely synchronisation of its rotation and a presumed
high quality factor. We critically reassess this assumption in the light of
recent astrometric results for Jupiter and Saturn, also employing more advanced
theories of frequency-dependent tidal dissipation. Assuming that WASP-12b, like
our Jupiter and Saturn, has a solid core, we find that the observed orbital
decay is well explained by the tides in the planet. We calculate the exact
value of the modified quality factor from the observed orbital decay and the
upper bound eccentricity, which happens to coincide almost precisely with that
of our Jupiter.
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