Do Close-in Giant Planets Orbiting Evolved Stars Prefer Eccentric Orbits?

Grunblatt, Samuel K.; Huber, Daniel; Gaidos, Eric; Lopez, Eric; Barclay, Thomas; Chontos, Ashley; Sinukoff, Evan; Eylen, Vincent Van; Howard, Andrew W.; Isaacson, Howard

doi:10.3847/2041-8213/aacc67

Cited by 47 publications

(54 citation statements)

References 51 publications

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“…If confirmed, the mild eccentricity of HD 221416 b would be consistent with predictions of a population of planets around evolved stars for which orbital decay occurs faster than tidal circularization (Villaver et al 2014;Grunblatt et al 2018). Moreover, combining the asteroseismic age of the system with the possible nonzero eccentricity would allow constraints on the tidal Note.…”

Section: Discussionsupporting

confidence: 66%

A Hot Saturn Orbiting an Oscillating Late Subgiant Discovered by TESS

Huber

Chaplin

Chontos

et al. 2019

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We present the discovery of HD 221416 b, the first transiting planet identified by the Transiting Exoplanet Survey Satellite (TESS) for which asteroseismology of the host star is possible. HD 221416 b (HIP 116158, TOI-197) is a bright (V=8.2 mag), spectroscopically classified subgiant that oscillates with an average frequency of about 430 μHz and displays a clear signature of mixed modes. The oscillation amplitude confirms that the redder TESS bandpass compared to Kepler has a small effect on the oscillations, supporting the expected yield of thousands of solar-like oscillators with TESS 2 minute cadence observations. Asteroseismic modeling yields a robust determination of the host star radius (R å =2.943±0.064 R e), mass (M å =1.212±0.074 M e), and age (4.9±1.1 Gyr), and demonstrates that it has just started ascending the red-giant branch. Combining asteroseismology with transit modeling and radial-velocity observations, we show that the planet is a "hot Saturn" (R p =9.17±0.33 R ⊕) with an orbital period of ∼14.3 days, irradiance of F=343±24 F ⊕ , and moderate mass (M p =60.5±5.7 M ⊕) and density (ρ p =0.431±0.062 g cm −3). The properties of HD 221416 b show that the host-star metallicity-planet mass correlation found in sub-Saturns (4-8 R ⊕) does not extend to larger radii, indicating that planets in the transition between sub-Saturns and Jupiters follow a relatively narrow range of densities. With a density measured to ∼15%, HD 221416 b is one of the best characterized Saturn-size planets to date, augmenting the small number of known transiting planets around evolved stars and demonstrating the power of TESS to characterize exoplanets and their host stars using asteroseismology.

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Section: Discussionsupporting

confidence: 66%

A Hot Saturn Orbiting an Oscillating Late Subgiant Discovered by TESS

Huber

Chaplin

Chontos

et al. 2019

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“…Based on the study of three planetary systems, Grunblatt et al (2018) proposed that close-in planets orbiting evolved stars tend to reside on eccentric orbits. If this scenario is correct, the nearly circular orbits of EPIC 249893012 b, c, and d may be the result of the planets orbiting a star that is not evolved enough for a fair comparison to be made.…”

Section: Discussionmentioning

confidence: 99%

Three planets transiting the evolved star EPIC 249893012: a hot 8.8-M_⊕ super-Earth and two warm 14.7 and 10.2-M_⊕ sub-Neptunes

Hidalgo

Πάλλη

Alonso

et al. 2020

A&A

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We report the discovery of a new planetary system with three transiting planets, one super-Earth and two sub-Neptunes, that orbit EPIC 249893012, a G8 IV-V evolved star (M⋆ = 1.05 ± 0.05 M⊙, R⋆ = 1.71 ± 0.04 R⊙, Teff = 5430 ± 85 K). The star is just leaving the main sequence. We combined K2 photometry with IRCS adaptive-optics imaging and HARPS, HARPS-N, and CARMENES high-precision radial velocity measurements to confirm the planetary system, determine the stellar parameters, and measure radii, masses, and densities of the three planets. With an orbital period of 3.5949−0.0007+0.0007 days, a mass of 8.75−1.08+1.09 M⊕, and a radius of 1.95−0.08+0.09 R⊕, the inner planet b is compatible with nickel-iron core and a silicate mantle (ρb = 6.39−1.04+1.19 g cm−3). Planets c and d with orbital periods of 15.624−0.001+0.001 and 35.747−0.005+0.005 days, respectively, have masses and radii of 14.67−1.89+1,84 M⊕ and 3.67−0.14+0.17 R⊕ and 10.18−2.42+2.46 M⊕ and 3.94−0.12+0.13 R⊕, respectively, yielding a mean density of 1.62−0.29+0.30 and 0.91−0.23+0.25 g cm−3, respectively. The radius of planet b lies in the transition region between rocky and gaseous planets, but its density is consistent with a rocky composition. Its semimajor axis and the corresponding photoevaporation levels to which the planet has been exposed might explain its measured density today. In contrast, the densities and semimajor axes of planets c and d suggest a very thick atmosphere. The singularity of this system, which orbits a slightly evolved star that is just leaving the main sequence, makes it a good candidate for a deeper study from a dynamical point of view.

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“…These studies suggest that hot Jupiters undergo tidal orbital decay when a star begins evolving into a subgiant (Schlaufman & Winn 2013). The planets around these "retired A stars" tend to be in longer period and more circular orbits than those found around main-sequence stars (Jones et al 2014), although recent discoveries have unveiled numerous hot Jupiters in close-in orbits about evolved stars (Grunblatt et al 2018). These issues inspired us to look into the hot Jupiter occurrence rate around main-sequence A stars.…”

Section: Occurrence Rate Of Hot Jupiters From Tessmentioning

confidence: 99%

Two New HATNet Hot Jupiters around A Stars and the First Glimpse at the Occurrence Rate of Hot Jupiters from TESS^∗

et al. 2019

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Wide-field surveys for transiting planets are well suited to searching diverse stellar populations, enabling a better understanding of the link between the properties of planets and their parent stars. We report the discovery of HAT-P-69 b (TOI 625.01) and HAT-P-70 b (TOI 624.01), two new hot Jupiters around A stars from the Hungarian-made Automated Telescope Network (HATNet) survey that have also been observed by the Transiting Exoplanet Survey Satellite. HAT-P-69 b has a mass of-+ 3.58 0.58 0.58 M Jup and a radius of-+ 1.676 0.033 0.051 R Jup and resides in a prograde 4.79 day orbit. HAT-P-70 b has a radius of-+ 1.87 0.10 0.15 R Jup and a mass constraint of s <6.78 3 ()M Jup and resides in a retrograde 2.74 day orbit. We use the confirmation of these planets around relatively massive stars as an opportunity to explore the occurrence rate of hot Jupiters as a function of stellar mass. We define a sample of 47,126 main-sequence stars brighter than T mag =10 that yields 31 giant planet candidates, including 18 confirmed planets, 3 candidates, and 10 false positives. We find a net hot Jupiter occurrence rate of 0.41±0.10% within this sample, consistent with the rate measured by Kepler for FGK stars. When divided into stellar mass bins, we find the occurrence rate to be 0.71±0.31% for G stars, 0.43±0.15% for F stars, and 0.26±0.11% for A stars. Thus, at this point, we cannot discern any statistically significant trend in the occurrence of hot Jupiters with stellar mass.

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Do Close-in Giant Planets Orbiting Evolved Stars Prefer Eccentric Orbits?

Cited by 47 publications

References 51 publications

A Hot Saturn Orbiting an Oscillating Late Subgiant Discovered by TESS

A Hot Saturn Orbiting an Oscillating Late Subgiant Discovered by TESS

Three planets transiting the evolved star EPIC 249893012: a hot 8.8-M_⊕ super-Earth and two warm 14.7 and 10.2-M_⊕ sub-Neptunes

Two New HATNet Hot Jupiters around A Stars and the First Glimpse at the Occurrence Rate of Hot Jupiters from TESS^∗

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Do Close-in Giant Planets Orbiting Evolved Stars Prefer Eccentric Orbits?

Cited by 47 publications

References 51 publications

A Hot Saturn Orbiting an Oscillating Late Subgiant Discovered by TESS

A Hot Saturn Orbiting an Oscillating Late Subgiant Discovered by TESS

Three planets transiting the evolved star EPIC 249893012: a hot 8.8-M⊕ super-Earth and two warm 14.7 and 10.2-M⊕ sub-Neptunes

Two New HATNet Hot Jupiters around A Stars and the First Glimpse at the Occurrence Rate of Hot Jupiters from TESS∗

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Three planets transiting the evolved star EPIC 249893012: a hot 8.8-M_⊕ super-Earth and two warm 14.7 and 10.2-M_⊕ sub-Neptunes

Two New HATNet Hot Jupiters around A Stars and the First Glimpse at the Occurrence Rate of Hot Jupiters from TESS^∗