Long-term tidal evolution of short-period planets with companions

By Rosemary A. Mardling. 2007

166 citations recorded by the source corpus.

Of the 14 transiting extrasolar planetary systems for which radii have been measured, at least three appear to be considerably larger than theoretical estimates suggest. It has been proposed by Bodenheimer, Lin & Mardling that undetected companions acting to excite the orbital eccentricity are responsible for these oversized planets, as they find new equilibrium radii in response to being tidally heated. In the case of HD 209458, this hypothesis has been rejected by some authors because there is no sign of such a companion at the 5 ms−1 level, and because it is difficult to say conclusively that the eccentricity is non-zero. Transit timing analysis as well as a direct transit search has further constrained the existence of very short period companions, especially in resonant orbits. Whether or not a companion is responsible for the large radius of HD 209458b, almost certainly some short-period systems have companions which force their eccentricities to non-zero values. This paper is dedicated to quantifying this effect. The eccentricity of a short-period planet will only be excited as long as its (non-resonant) companion's eccentricity is non-zero. Here, we show that the latter decays on a time-scale which depends on the structure of the interior planet, a time-scale which is often shorter than the lifetime of the system. This includes Earth-mass planets in the habitable zones of some stars. We determine which configurations are capable of sustaining significant eccentricity for at least the age of the system, and show that these include systems with companion masses as low as a fraction of an Earth mass. The orbital parameters of such companions are consistent with recent calculations which show that the migration process can induce the formation of low-mass planets external to the orbits of hot Jupiters. Systems with inflated planets are therefore good targets in the search for terrestrial planets.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/3ae245289f60c7f5f12c60217a93a67dd79f3539

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In Astronomy and Astrophysics

Citations in the corpus

The Habitability of Planets Orbiting M-dwarf Stars (2016, background): “For example, planets with companions will have orbital eccentricities that undergo oscillations (Mardling, 2007), while also experiencing a strong tidal interaction from the parent star that can fix the rotation rate as a function of eccentricity.”
HAT-P-16b: A 4 MJ PLANET TRANSITING A BRIGHT STAR ON AN ECCENTRIC ORBIT, (2010, background): “Most short–period TEPs have eccentricities consistent with zero, as is expected because of circularization driven by tidal dissipation within the planet with a typical timescale substantially less than 1 Gyr (see Jackson, Greenberg, & Barnes 2008; Mardling 2007).”
RESONANT POST-NEWTONIAN ECCENTRICITY EXCITATION IN HIERARCHICAL THREE-BODY SYSTEMS (2012, background): “It has been shown that the 1PN precession of the inner body may play an important role in secular evolution (e.g. Ford et al. 2000b; Miller & Hamilton 2002; Blaes et al. 2002; Mardling 2007; Fabrycky & Tremaine 2007; Zhang et al. 2013).”
The minimum-mass extrasolar nebula: in situ formation of close-in super-Earths (2012, background): “Tidal dissipation drives such a system to a fixed point for which the eccentricities cease to exhibit secular oscillations and the apsidal lines of the two planets precess at the same rate (Wu & Goldreich 2002; Mardling 2007).”
DISSIPATIVE DIVERGENCE OF RESONANT ORBITS (2012, background): “Through this secular interaction, tidal damping on e1 is translated to e2 as well (albeit on a longer timescale), even if there is no direct damping on e2 (i.e. τe2 = ∞; Wu & Goldreich (2002); Mardling (2007)).”
The Occurrence and Architecture of Exoplanetary Systems (2014, background): “Perhaps the innermost planets are being pulled closer to the star by tidal dissipation (Teitler & Königl 2014, Mardling 2007).”
MULTIPLE-PLANET SCATTERING AND THE ORIGIN OF HOT JUPITERS (2011, methodology): “Conversely, Wu & Lithwick (2011) used the equilibrium tide model (e.g. Hut 1981, Mardling 2007) which is strictly valid only for low-to-moderate eccentricities.”
Is tidal heating sufficient to explain bloated exoplanets? Consistent calculations accounting for finite initial eccentricity (2010, background): “– Presence of a third body: as proposed by Mardling (2007), a low mass terrestrial planet can drive the eccentricity of a massive giant planet during up to Gyr timescales.”
Tidal Heating of Extrasolar Planets (2008, background): “For example, Mardling (2007) proposed that an additional planet is needed to maintain the eccentricity.”