A Super-Solar Metallicity for Stars With Hot Rocky Exoplanets

Mulders, Gijs D.; Pascucci, Ilaria; Apai, Dániel; Frasca, A.; Molenda-Żakowicz, J.

doi:10.3847/0004-6256/152/6/187

Cited by 127 publications

(135 citation statements)

References 56 publications

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“…When we first saw the apparent difference in planet host and field star velocities, we considered that we may be indirectly picking up on the relation between stellar metallicity and planet occurrence rate. The relation posits that planets are more common around metal-rich stars (Wang & Fischer 2015), though the relation is strongest for Jupiter-mass plan-ets and short-period planets (planets with periods shorter than 10 days) (Mulders et al 2016;Petigura et al 2018;Narang et al 2018). We thought we might be picking up on this relation because metal-poor stars are more common in the thick disk of the Milky Way, where stellar motion is also higher.…”

Section: Testing the Planet-metallicity Relationmentioning

confidence: 92%

Not gone with the wind: Planet occurrence is independent of stellar galactocentric velocity

McTier

Kipping

2019

Monthly Notices of the Royal Astronomical Society

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We demonstrate that planet occurrence does not depend on stellar galactocentric velocity in the Solar neighborhood. Using Gaia DR2 astrometry and radial velocity data, we calculate 3D galactocentric velocities for 197,090 Kepler field stars, 1647 of which are confirmed planet hosts. When we compare the galactocentric velocities of planet hosts to those of the entire field star sample, we observe a statistically significant (KS p-value = 10 −70 ) distinction, with planet hosts being apparently slower than field stars by ∼40 km/s. We explore some potential explanations for this difference and conclude that it is not a consequence of the planet-metallicity relation or distinctions in the samples' thin/thick disk membership, but rather an artefact of Kepler 's selection function. Non Kepler -host stars that have nearly identical distances, temperatures, surface gravities, and Kepler magnitudes to the confirmed planet hosts also have nearly identical velocity distributions. Using one of these identical non-host samples, we consider that the probability of a star with velocity v tot hosting a planet can be described by an exponential function proportional to e (−v tot /v 0 ) . Using a Markov Chain Monte Carlo sampler, we determine that v 0 >976 km/s to 99% confidence, which implies that planets in the Solar neighborhood are just as likely to form around highvelocity stars as they are around low-velocity stars. Our work highlights the subtle ways in which selection biases can create strong correlations without physical underpinnings.

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Section: Testing the Planet-metallicity Relationmentioning

confidence: 92%

Not gone with the wind: Planet occurrence is independent of stellar galactocentric velocity

McTier

Kipping

2019

Monthly Notices of the Royal Astronomical Society

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“…When studying the metallicity dependence of low-mass/small size planets it is very important to take into account the relation between orbital periods of planets and their host stars metallicities [116,139,161,192,[286][287][288][289]. In particular, Adibekyan et al [161] found that the super-Earth-like planets (M sin i < 10 M ⊕ ) orbiting metal-rich stars have orbital periods shorter than about 20 days, whereas planets orbiting metal-poor stars span a wide range of orbital periods [see also 116,287].…”

Section: Low-mass Planets and Metallicitymentioning

confidence: 99%

“…In particular, Adibekyan et al [161] found that the super-Earth-like planets (M sin i < 10 M ⊕ ) orbiting metal-rich stars have orbital periods shorter than about 20 days, whereas planets orbiting metal-poor stars span a wide range of orbital periods [see also 116,287]. However, these results were contested by Mulders et al [192] who argued that the observed trends might be due to selection effects. A systematic excess of short period ( 10 days) rocky planets (< 1.7 R ⊕ ) around metal-rich stars was reported in several works [139,192,288].…”

Section: Low-mass Planets and Metallicitymentioning

confidence: 99%

Heavy Metal Rules. I. Exoplanet Incidence and Metallicity

Adibekyan

2019

Geosciences

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Discovery of only handful of exoplanets required to establish a correlation between giant planet occurrence and metallicity of their host stars. More than 20 years have already passed from that discovery, however, many questions are still under lively debate: What is the origin of that relation? what is the exact functional form of the giant planet -metallicity relation (in the metal-poor regime)?, does such a relation exist for terrestrial planets? All these question are very important for our understanding of the formation and evolution of (exo)planets of different types around different types of stars and are subject of the present manuscript. Besides making a comprehensive literature review about the role of metallicity on the formation of exoplanets, I also revisited most of the planet -metallicity related correlations reported in the literature using a large and homogeneous data provided by the SWEET-Cat catalog. This study lead to several new results and conclusions, two of which I believe deserve to be highlighted in the abstract: i) The hosts of sub-Jupiter mass planets (∼0.6 -0.9 M ) are systematically less metallic than the hosts of Jupiter-mass planets. This result might be related to the longer disk lifetime and higher amount of planet building materials available at high metallicities, which allow a formation of more massive Jupiter-like planets. ii) Contrary to the previous claims, our data and results do not support the existence of a breakpoint planetary mass at 4 M above and below which planet formation channels are different. However, the results also suggest that planets of the same (high) mass can be formed through different channels depending on the (disk) stellar mass i.e. environmental conditions.

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“…Host stars of planets with orbital periods greater than 10 days were more metal-poor than their short period counterparts. Mulders et al (2016) and Petigura et al (2018) showed that the occurrence rate of planets with periods less than 10 days was higher around metal-rich host stars than metal-poor host stars. 6.1.…”

Section: Host Star Metallicity and Planetsmentioning

confidence: 99%

“…One of the suggested explanations for this is that the hot super-Earths and Neptunes are the remnants of gas giants whose atmospheres have been eroded due to the extreme environment (Lopez et al 2012;Lundkvist et al 2016;Mazeh et al 2016). The other possible explanation is that these hot planets might have started off like hot Jupiters but were not able to accrete the gas quickly before the disk dissipated (Mulders et al 2016).…”

Section: Relationship Between Host Star Metallicity Andmentioning

confidence: 99%

Properties and Occurrence Rates for Kepler Exoplanet Candidates as a Function of Host Star Metallicity from the DR25 Catalog

Narang¹,

Manoj²,

Furlan

et al. 2018

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Correlations between the occurrence rate of exoplanets and their host star properties provide important clues about the planet formation processes. We studied the dependence of the observed properties of exoplanets (radius, mass, and orbital period) as a function of their host star metallicity. We analyzed the planetary radii and orbital periods of over 2800 Kepler candidates from the latest Kepler data release DR25 (Q1-Q17) with revised planetary radii based on Gaia DR2 as a function of host star metallicity (from the Q1-Q17 (DR25) stellar and planet catalog). With a much larger sample and improved radius measurements, we are able to reconfirm previous results in the literature. We show that the average metallicity of the host star increases as the radius of the planet increases. We demonstrate this by first calculating the average host star metallicity for different radius bins and then supplementing these results by calculating the occurrence rate as a function of planetary radius and host star metallicity. We find a similar trend between host star metallicity and planet mass: the average host star metallicity increases with increasing planet mass. This trend, however, reverses for masses > 4.0 M J : host star metallicity drops with increasing planetary mass. We further examined the correlation between the host star metallicity and the orbital period of the planet. We find that for planets with orbital periods less than 10 days, the average metallicity of the host star is higher than that for planets with periods greater than 10 days.

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A Super-Solar Metallicity for Stars With Hot Rocky Exoplanets

Cited by 127 publications

References 56 publications

Not gone with the wind: Planet occurrence is independent of stellar galactocentric velocity

Not gone with the wind: Planet occurrence is independent of stellar galactocentric velocity

Heavy Metal Rules. I. Exoplanet Incidence and Metallicity

Properties and Occurrence Rates for Kepler Exoplanet Candidates as a Function of Host Star Metallicity from the DR25 Catalog

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