ON THE ANOMALOUS RADII OF THE TRANSITING EXTRASOLAR PLANETS

By Gregory Laughlin, M. Crismani, Fred C. Adams. 2011

141 citations recorded by the source corpus.

We present a systematic evaluation of the agreement between the observed radii of 90 well-characterized transiting extrasolar giant planets and their corresponding model radii. Our model radii are drawn from previously published calculations of coreless giant planets that have attained their asymptotic radii, and which have been tabulated for a range of planet masses and equilibrium temperatures. (We report a two-dimensional polynomial fitting function that accurately represents the models.) As expected, the model radii provide a statistically significant improvement over a null hypothesis that the sizes of giant planets are completely independent of mass and effective temperature. As is well known, however, fiducial models provide an insufficient explanation; the planetary radius anomalies, , are strongly correlated with planetary equilibrium temperature. We find that the radius anomalies have a best-fit dependence, , with α = 1.4 ± 0.6. Incorporating this relation into the model radii leads to substantially less scatter in the radius correlation. The extra temperature dependence represents an important constraint on theoretical models for hot Jupiters. Using simple scaling arguments, we find support for the hypothesis of Batygin & Stevenson that this correlation can be attributed to a planetary heating mechanism that is mediated by magnetohydrodynamic coupling between the planetary magnetic field and near-surface flow that is accompanied by ohmic dissipation at adiabatic depth. Additionally, we find that the temperature dependence is likely too strong to admit kinetic heating as the primary source of anomalous energy generation within the majority of the observed transiting planets.

Subfields: Astronomy and Astrophysics, Instrumentation, Statistical and Nonlinear Physics

View Paper: https://www.semanticscholar.org/paper/dbb0677ffbf8cba92315430cff49a6f18bcdc22f

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Citations in the corpus

LACK OF INFLATED RADII FOR KEPLER GIANT PLANET CANDIDATES RECEIVING MODEST STELLAR IRRADIATION (2011, background): “Laughlin et al. (2011) find support for this hypothesis from the set of transiting planets known in 2010 but also state that other processes should be contributing to account for the observed anomalies, such as the effects of heavy elements abundances (Batygin et al. 2011) or the internal heating…”
Photoevaporation and high-eccentricity migration created the sub-Jovian desert (2018, background): “…is largely independent of mass, as a result the competition between the degeneracy pressure and Coulomb pressure; furthermore, hot Jupiter inflation is believed to be correlated best with the equilibrium temperature (Teq, e.g. Laughlin et al. 2011; Thorngren & Fortney 2018; Sestovic et al. 2018).”
A Population Study of Gaseous Exoplanets (2017, background): “These results indicate that planetary surface gravity is a secondary factor in identifying inflated atmospheres (Laughlin et al. 2011; Weiss et al. 2013; Spiegel & Burrows 2013).”
A new vision of giant planet interiors: Impact of double diffusive convection (2012, background): “Indeed, it seems that invoking an extra source of (tidal, kinetic or magnetic) energy dissipation in these object interiors can not completely solve this “radius anomaly” puzzle and that an alternative or complementary process is necessary (Laughlin et al. 2011).”
Compositional Imprints in Density–Distance–Time: A Rocky Composition for Close-in Low-mass Exoplanets from the Location of the Valley of Evaporation (2017, background): “For giant planets, at a fixed planetary mass, those receiving high incident fluxes have a lower density (e.g., Laughlin et al. 2011).”
THE HEAVY-ELEMENT MASSES OF EXTRASOLAR GIANT PLANETS, REVEALED (2011, background): “Empirically, the unknown heating mechanism affects the close-in planets at high incident stellar flux (Kovács et al. 2010a) or planet Teff (Laughlin et al. 2011).”
Revised Radii of Kepler Stars and Planets Using Gaia Data Release 2 (2018, background): “Inflated Hot Jupiters Another feature revealed by Figure 9 is the wellknown trend of increasing giant planet radius with increasing stellar irradiance (e.g. Burrows et al. 2000; Demory & Seager 2011; Laughlin et al. 2011).”
PLANET OCCURRENCE WITHIN 0.25 AU OF SOLAR-TYPE STARS FROM KEPLER (2011, background): “Larger planets are typically young or close-in and inflated by one of several proposed mechanisms (e.g., Batygin & Stevenson 2010; Laughlin et al. 2011; Burrows et al. 2007).”