Destruction of Jovian Planets around A-type Stars

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Destruction of Jovian Planets around A-type Stars

Post by Sirius_Alpha on 12th June 2018, 8:54 pm

A-type Stars, the Destroyers of Worlds: The lives and deaths of Jupiters in evolving stellar binaries

Hot Jupiters (HJs), gas giant planets orbiting their host stars with periods on the order of days, commonly occur in the Galaxy, including relatively massive (1.6−2.4 M⊙, i.e. A-type main sequence stars) and evolved stars. The majority of A-type main sequence stars have stellar binary companions, which can strongly affect the dynamical evolution of planets around either star. In this work we investigate the effects of gravitational perturbations by a far away stellar companion on the orbital evolution of gas giant planets orbiting A-type stars, the so-called Eccentric Kozai-Lidov (EKL) mechanism, including the effects of general relativity, post-main sequence stellar evolution, and tides. We find that only 0.15 % of all A-type stars will host HJs during their main sequence lifetime. However, we also find a new class of planets, Temporary Hot Jupiters (THJs), that form during the post-main sequence lifetime of a significant fraction (about 3.7 %) of all former A-type main sequence stars. These THJs orbit on periods of tens to a hundred days and only exist for a few 100,000 years before they are engulfed by their expanding host stars, but they reach the same temperatures as `classical' HJs due to the increased stellar luminosities. THJs' spin-orbit angles will mostly be misaligned. Tidal interactions between THJs and their expanding host stars will significantly influence the stellar envelopes, while the planets' eventual engulfment will lead to faster stellar spins and transient increased luminosity signals that should extend the possible time-frame to observe THJs far beyond the initial few 100,000 years. Overall we find that approximately 70 % of all gas giant planets orbiting A-type stars will eventually be destroyed or engulfed by their star, about 25 % during the main sequence lifetime and about 45 % during post-main sequence evolution.

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