K2-66b and K2-106b: Two Extremely Hot Sub-Neptune-size Planets with High Densities

Sinukoff, Evan; Howard, Andrew W.; Petigura, Erik A.; Fulton, Benjamin J.; Crossfield, Ian J. M.; Isaacson, Howard; Gonzales, Erica J.; Crepp, Justin R.; Brewer, John M.; Hirsch, Lea A.; Weiss, Lauren M.; Ciardi, David R.; Schlieder, Joshua E.; Benneke, Bjoern; Christiansen, Jessie L.; Dressing, Courtney D.; Hansen, Brad M. S.; Knutson, Heather A.; Kosiarek, Molly R.; Livingston, John H.; Greene, Thomas P.; Rogers, Leslie; Lépine, Sébastien

doi:10.3847/1538-3881/aa725f

Cited by 68 publications

(31 citation statements)

References 105 publications

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“…This type of interior structure is believed to be common among super-Earths and sub-Neptunes discovered by Kepler and K2 since RV observations have shown that most of these planets larger than about 1.6 Å R have densities too low to be explained by rocky compositions Weiss & Marcy 2014;Dressing et al 2015;Rogers 2015;Sinukoff et al 2017a). Due to its short (19 hr) orbital period, WASP-47 e is so highly irradiated that any hydrogen/helium envelope would quickly be lost via photoevaporation (Penz et al 2008;Sanz-Forcada et al 2011;Lopez et al 2012), so any envelope around WASP-47 e must be made of water or some other highmetallicity volatile material (Lopez 2017).…”

Section: Constraints On the Composition Of Wasp-47 Ementioning

confidence: 86%

Precise Masses in the WASP-47 System

Vanderburg

Becker

Buchhave

et al. 2017

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We present precise radial velocity observations of WASP-47, a star known to host a hot Jupiter, a distant Jovian companion, and, uniquely, two additional transiting planets in short-period orbits: a super-Earth in a ≈19 hr orbit, and a Neptune in a ≈9 day orbit. We analyze our observations from the HARPS-N spectrograph along with previously published data to measure the most precise planet masses yet for this system. When combined with new stellar parameters and reanalyzed transit photometry, our mass measurements place strong constraints on the compositions of the two small planets. We find that, unlike most other ultra-short-period planets, the inner planet, WASP-47 e, has a mass (6.83 ± 0.66 Å M ) and a radius (1.810 ± 0.027 Å R ) that are inconsistent with an Earth-like composition. Instead, WASP-47 e likely has a volatile-rich envelope surrounding an Earth-like core and mantle. We also perform a dynamical analysis to constrain the orbital inclination of WASP-47 c, the outer Jovian planet. This planet likely orbits close to the plane of the inner three planets, suggesting a quiet dynamical history for the system. Our dynamical constraints also imply that WASP-47 c is much more likely to transit than a geometric calculation would suggest. We calculate a transit probability for WASP-47 c of about 10%, more than an order of magnitude larger than the geometric transit probability of 0.6%.

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Section: Constraints On the Composition Of Wasp-47 Ementioning

confidence: 86%

Precise Masses in the WASP-47 System

Vanderburg

Becker

Buchhave

et al. 2017

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“…We felt a homogeneous analysis was warranted because the results in the literature were reported by different groups using different procedures to determine the stellar parameters and to mitigate the effects of timecorrelated noise in the radial-velocity data. For example, K2-106b was reported by Guenther et al (2017) to have an iron mass fraction of 80 +20 −30 %, while Sinukoff et al (2017) concluded that the composition was compatible with that of the Earth (35% iron). For this work, we combined all the previously published datasets, used the parallaxes from Gaia Data Release 2 (Gaia Collaboration et al 2018) to refine the stellar parameters, and employed a Gaussian Process framework to disentangle planetary radial velocity signals from cor-related noise.…”

Section: Introductionmentioning

confidence: 99%

Homogeneous Analysis of Hot Earths: Masses, Sizes, and Compositions

Dai

Masuda

Winn

et al. 2019

ApJ

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Terrestrial planets have been found orbiting Sun-like stars with extremely short periods -some as short as 4 hours. These "ultra-short-period planets" or "hot Earths" are so strongly irradiated that any initial H/He atmosphere has probably been lost to photoevaporation. As such, the sample of hot Earths may give us a glimpse at the rocky cores that are often enshrouded by thick H/He envelopes on widerorbiting planets. However, the mass and radius measurements of hot Earths have been derived from a hodgepodge of different modeling approaches, and include several cases of contradictory results. Here, we perform a homogeneous analysis of the complete sample of 11 known hot Earths with an insolation exceeding 650 times that of the Earth. We combine all available data for each planet, incorporate parallax information from Gaia to improve the stellar and planetary parameters, and use Gaussian Process regression to account for correlated noise in the radial-velocity data. The homogeneous analysis leads to a smaller dispersion in the apparent composition of hot Earths, although there does still appear to be some intrinsic dispersion. Most of the planets are consistent with an Earth-like composition (35% iron and 65% rock), but two planets (K2-141b and K2-229b) show evidence for a higher iron fraction, and one planet (55 Cnc e) has either a very low iron fraction or an envelope of low-density volatiles. All of the planets are less massive than 8 M ⊕ , despite the selection bias towards more massive planets, suggesting that 8 M ⊕ is the critical mass for runaway accretion.

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“…Therefore the remnant cores of Neptunian or Jovian planets could be > 10M ⊕ . The possibility of very heavy cores is also supported by the discovery of rocky mega-Earths such as BD+20 594 b which has a mass and radius of 16.3 ± 6.0M ⊕ and 2.2 ± 0.1R ⊕ (Espinoza et al 2016) or K2-66 b with 21.3 ± 3.6M ⊕ and 2.50 ± 0.3R ⊕ (Sinukoff et al 2017) respectively. Therefore whilst the critical mass Υ β ∼ 10M ⊕ , the probabilistic function Γ γ could range from 10 − 25M ⊕ according to observations and theoretical predictions.…”

Section: Planetary Parametersmentioning

confidence: 92%

The Bimodal Distribution in Exoplanet Radii: Considering Varying Core Compositions and H₂ Envelope’s Sizes

Modirrousta-Galian

Locci

Micela

2020

ApJ

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Several models have been introduced in order to explain the radius distribution in exoplanet radii observed by Fulton et al. (2017) with one peak at ∼ 1.3R ⊕ the other at ∼ 2.4R ⊕ and the minimum at ∼ 1.75R ⊕ . In this paper we focus on the hypothesis that the exoplanet size distribution is caused by stellar XUV-induced atmospheric loss. We evolve 10 6 synthetic exoplanets by exposing them to XUV irradiation from synthetic ZAMS stars. For each planet we set a different interior composition which ranged from 100 wt% Fe (very dense) through 100 wt% MgSiO 3 (average density) and to 100 wt% H 2 O ice (low density) with varying hydrogen envelop sizes which varied from 0 wt% (a negligible envelop) to 100 wt% (a negligible core). Our simulations were able to replicate the bimodal distribution in exoplanet radii. We argue that in order to reproduce the distribution by Fulton et al. (2017) it is mandatory for there to be a paucity of exoplanets with masses above ∼ 8M ⊕ . Furthermore, our bestfit result predicts an initial flat distribution in exoplanet occurrence for M P 8M ⊕ with a strong deficiency for planets with 3M ⊕ . Our results are consistent with the ∼ 1.3R ⊕ radius peak mostly encompassing denuded exoplanets whilst the ∼ 2.4R ⊕ radius peak mainly comprising exoplanets with large hydrogen envelops.

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K2-66b and K2-106b: Two Extremely Hot Sub-Neptune-size Planets with High Densities

Cited by 68 publications

References 105 publications

Precise Masses in the WASP-47 System

Precise Masses in the WASP-47 System

Homogeneous Analysis of Hot Earths: Masses, Sizes, and Compositions

The Bimodal Distribution in Exoplanet Radii: Considering Varying Core Compositions and H₂ Envelope’s Sizes

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K2-66b and K2-106b: Two Extremely Hot Sub-Neptune-size Planets with High Densities

Cited by 68 publications

References 105 publications

Precise Masses in the WASP-47 System

Precise Masses in the WASP-47 System

Homogeneous Analysis of Hot Earths: Masses, Sizes, and Compositions

The Bimodal Distribution in Exoplanet Radii: Considering Varying Core Compositions and H2 Envelope’s Sizes

Contact Info

Product

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About

The Bimodal Distribution in Exoplanet Radii: Considering Varying Core Compositions and H₂ Envelope’s Sizes