THE ROLE OF CORE MASS IN CONTROLLING EVAPORATION: THE KEPLER RADIUS DISTRIBUTION AND THE KEPLER-36 DENSITY DICHOTOMY

By E. Lopez, Jon Fortney. 2013

290 citations recorded by the source corpus.

We use models of coupled thermal evolution and photo-evaporative mass loss to understand the formation and evolution of the Kepler-36 system. We show that the large contrast in mean planetary density observed by Carter et al. can be explained as a natural consequence of photo-evaporation from planets that formed with similar initial compositions. However, rather than being due to differences in XUV irradiation between the planets, we find that this contrast is due to the difference in the masses of the planets' rock/iron cores and the impact that this has on mass-loss evolution. We explore in detail how our coupled models depend on irradiation, mass, age, composition, and the efficiency of mass loss. Based on fits to large numbers of coupled evolution and mass-loss runs, we provide analytic fits to understand threshold XUV fluxes for significant atmospheric loss, as a function of core mass and mass-loss efficiency. Finally we discuss these results in the context of recent studies of the radius distribution of Kepler candidates. Using our parameter study, we make testable predictions for the frequency of sub-Neptune-sized planets. We show that 1.8–4.0 R⊕ planets should become significantly less common on orbits within 10 days and discuss the possibility of a narrow “occurrence valley” in the radius–flux distribution. Moreover, we describe how photo-evaporation provides a natural explanation for the recent observations of Ciardi et al. that inner planets are preferentially smaller within the systems.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/500c0421ae2712d066fa6ecdd65d3d266069db8b

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. Jon Fortney
2. J. Owen
3. D. Charbonneau
4. N. Madhusudhan
5. C. Mordasini
6. Timothy Morton
7. J. Johnson
8. B. Fulton

In Instrumentation

1. J. Owen
2. Jon Fortney
3. Timothy Morton
4. D. Charbonneau
5. J. Johnson
6. E. Gaidos
7. J. Winn
8. E. Petigura

Citations in the corpus

• HOW ROCKY ARE THEY? THE COMPOSITION DISTRIBUTION OF KEPLER’S SUB-NEPTUNE PLANET CANDIDATES WITHIN 0.15 AU (2014, methodology): “In particular, we implement the mass loss threshold of Lopez & Fortney (2013), which is a scaling law for the incident flux a planet would need to have received from its host star to have lost half of its initial H+He envelope after several Gyr (Fthresh); it is based on the assumption of…”
• The California-Kepler Survey. III. A Gap in the Radius Distribution of Small Planets (2017, background): “For this reason, it has been suggested that the radii of sub-Neptune-size planets, along with knowledge of the irradiation history, would be sufficient to estimate bulk composition without additional information (Lopez & Fortney 2013; Wolfgang & Lopez 2015).”
• The California-Kepler Survey. VII. Precise Planet Radii Leveraging Gaia DR2 Reveal the Stellar Mass Dependence of the Planet Radius Gap (2018, background): “A gap in the radius distribution was predicted by several groups who considered the effect of photoevaporation on planetary envelopes by X-ray and extreme ultraviolet (XUV) radiation (Lopez & Fortney 2013; Owen & Wu 2013; Jin et al. 2014; Chen & Rogers 2016).”
• The Evaporation Valley in the Kepler Planets (2017, methodology): “For simplicity, we adopt a constant η = 0.1 (the so-called “energy-limited” approach, see e.g., Lopez & Fortney 2013).”
• A FRAMEWORK FOR CHARACTERIZING THE ATMOSPHERES OF LOW-MASS LOW-DENSITY TRANSITING PLANETS (2013, background): “He envelope with time (e.g., Lopez & Fortney 2013).”
• MAKE SUPER-EARTHS, NOT JUPITERS: ACCRETING NEBULAR GAS ONTO SOLID CORES AT 0.1 AU AND BEYOND (2014, background): “How can this system be accommodated within core accretion theory (see Owen & Wu 2013 and Lopez & Fortney 2013 for pioneering explorations)?”
• BREEDING SUPER-EARTHS AND BIRTHING SUPER-PUFFS IN TRANSITIONAL DISKS (2015, background): “By further color-coding these data by incident stellar flux, we observe that smaller GCRs correlate with larger irradiances, and deduce that evaporative winds powered by stellar irradiation may have eroded GCRs (e.g., Lopez & Fortney 2013; Owen & Wu 2013).”
• Revised Radii of Kepler Stars and Planets Using Gaia Data Release 2 (2018, background): “Even from this (likely contaminated) sample, we readily recover the previouslyreported gap in the radius distribution at ∼ 2R⊕ (Lopez & Fortney 2013; Owen & Wu 2013).”
• THE RADIUS DISTRIBUTION OF PLANETS AROUND COOL STARS (2013, background): “Understanding the shape of the planet radius distribution in detail inaccessible to histogram binning is especially important since it is known that the physical properties of planets likely change dramatically between ∼1 and ∼2 R⊕ (Weiss & Marcy 2014; Marcy et al. 2014; Lopez & Fortney 2013).”
• MOST 1.6 EARTH-RADIUS PLANETS ARE NOT ROCKY (2014, unknown): “1 Myr) (Rogers et al. 2011; Lopez & Fortney 2013).”
• Atmospheric Escape and the Evolution of Close-In Exoplanets (2018, methodology): “Figure taken from Lopez & Fortney (2013).”
• The California-Kepler Survey. IV. Metal-rich Stars Host a Greater Diversity of Planets (2017, background): “This gap was predicted by various groups who modeled the erosion erosion of envelopes (e.g. Lopez & Fortney 2013; Owen & Wu 2013; Jin et al. 2014; Chen & Rogers 2016).”
• Photoevaporation and high-eccentricity migration created the sub-Jovian desert (2018, result): “Owen & Wu (2013) and Lopez & Fortney (2013) studied the photoevaporation of low-mass planets that were present at short-periods at early times and showed that the shape of the lower-boundary in the radius-period plane was consistent with photoevaporation of the H/He atmospheres of an initially…”
• Compositional Imprints in Density–Distance–Time: A Rocky Composition for Close-in Low-mass Exoplanets from the Location of the Valley of Evaporation (2017, methodology): “They may also be erased or blurred if there are both rocky and icy cores at close-in orbits (Lopez & Fortney 2013).”
• THE IMPRINT OF EXOPLANET FORMATION HISTORY ON OBSERVABLE PRESENT-DAY SPECTRA OF HOT JUPITERS (2016, background): “For these relatively massive planets at 0.04 AU (i.e., not extremely close to the host star), mass loss is, as expected (e.g. Owen & Wu 2013; Lopez & Fortney 2013; Jin et al. 2014), not very important: the “dry Jupiter” looses only ≈ 1.3% of its initial envelope.”
• A STUDY OF THE SHORTEST-PERIOD PLANETS FOUND WITH KEPLER (2014, methodology): “Indeed, the levels of irradiation suffered by these planets (see Figure 6) are high enough to remove the entire envelope from a gaseous planet for a wide range of mass loss efficiencies and core masses (Lopez & Fortney 2013a).”
• HUBBLE SPACE TELESCOPE NEAR-IR TRANSMISSION SPECTROSCOPY OF THE SUPER-EARTH HD 97658B (2014, background): “…based on mod- 2 els of planet formation and atmospheric mass loss for close-in planets, this still leaves a wide range of plausible models (e.g., Rogers & Seager 2010b; Rogers et al. 2011; Nettelmann et al. 2011; Heng & Kopparla 2012; Lopez et al. 2012; Lopez & Fortney 2013; Fortney et al. 2013).”