Dearth of short-period Neptunian exoplanets: A desert in period-mass and period-radius planes

Mazeh, T.; Holczer, Tomer; Faigler, S.

doi:10.1051/0004-6361/201528065

Cited by 315 publications

(376 citation statements)

References 34 publications

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“…The gray colors show that the trend of higher host star metallicity at shorter orbital periods is also present in the data set from Buchhave et al (2014). consistent with the observed lack of hot Neptunes at very short orbital periods (  P 2.5 days) that can be explained by stripping of their gaseous envelopes (Lundkvist et al 2016;Mazeh et al 2016). However, while hot Jupiters are typically not found in multi-planet systems (Steffen et al 2012), hot rocky planets are.…”

Section: Discussionsupporting

confidence: 78%

A Super-Solar Metallicity for Stars With Hot Rocky Exoplanets

et al. 2016

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Host star metallicity provides a measure of the conditions in protoplanetary disks at the time of planet formation. Using a sample of over 20,000 Kepler stars with spectroscopic metallicities from the LAMOST survey, we explore how the exoplanet population depends on host star metallicity as a function of orbital period and planet size. We find that exoplanets with orbital periods less than 10 days are preferentially found around metal-rich stars ([Fe/ H] ; 0.15 ± 0.05 dex). The occurrence rates of these hot exoplanets increases to ∼30% for super-solar metallicity stars from ∼10% for stars with a sub-solar metallicity. Cooler exoplanets, which reside at longer orbital periods and constitute the bulk of the exoplanet population with an occurrence rate of 90%, have host star metallicities consistent with solar. At short orbital periods, < P 10 days, the difference in host star metallicity is largest for hot rocky planets (< Å R 1.7 ), where the metallicity difference is [Fe/H];0.25±0.07 dex. The excess of hot rocky planets around metal-rich stars implies they either share a formation mechanism with hot Jupiters, or trace a planet trap at the protoplanetary disk inner edge, which is metallicity dependent. We do not find statistically significant evidence for a previously identified trend that small planets toward the habitable zone are preferentially found around low-metallicity stars. Refuting or confirming this trend requires a larger sample of spectroscopic metallicities.

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Section: Discussionsupporting

confidence: 78%

A Super-Solar Metallicity for Stars With Hot Rocky Exoplanets

et al. 2016

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“…Mazeh et al (2016) present evidence for a profound lack of such planets in the population of known exoplanets. This cannot be explained by observational selection biases because close-in planets are easier to find than their longer period counterparts using both the RV and transit detection methods (see e.g.…”

Section: Introductionmentioning

confidence: 76%

Suppressed Far-UV Stellar Activity and Low Planetary Mass Loss in the WASP-18 System*

Fossati

Koskinen

Cubillos

et al. 2018

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WASP-18 hosts a massive, very close-in Jupiter-like planet. Despite its young age (<1 Gyr), the star presents an anomalously low stellar activity level: the measured log R ′ HK activity parameter lies slightly below the basal level; there is no significant time-variability in the log R ′ HK value; there is no detection of the star in the X-rays. We present results of far-UV observations of WASP-18 obtained with COS on board of Hubble Space Telescope aimed at explaining this anomaly. From the star's spectral energy distribution, we infer the extinction (E(B − V) ≈ 0.01 mag) and then the interstellar medium (ISM) column density for a number of ions, concluding that ISM absorption is not the origin of the anomaly. We measure the flux of the four stellar emission features detected in the COS spectrum (C II, C III, C IV, Si IV). Comparing the C II/C IV flux ratio measured for WASP-18 with that derived from spectra of nearby stars with known age, we see that the far-UV spectrum of WASP-18 resembles that of old (>5 Gyr), inactive stars, in stark contrast with its young age. We conclude that WASP-18 has an intrinsically low activity level, possibly caused by star-planet tidal interaction, as suggested by previous studies. Re-scaling the solar irradiance reference spectrum to match the flux of the Si IV line, yields an XUV integrated flux at the planet orbit of 10.2 erg s . For such high-mass planets, thermal escape is not energy limited, but driven by Jeans escape.

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“…WASP-49b is also 3× lighter than HD 189733b, and thus much closer to edge of the dearth of highly irradiated, intermediate-mass planets (Mazeh et al 2016). This desert, even more obvious in the mass-incident flux plane (Fig.…”

Section: Discussionmentioning

confidence: 99%

Hot Exoplanet Atmospheres Resolved with Transit Spectroscopy (HEARTS)

Wyttenbach

Lovis

Ehrenreich

et al. 2017

A&A

117

151

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High-resolution optical spectroscopy during the transit of HD 189733b, a prototypical hot Jupiter, allowed the resolution of the Na i D sodium lines in the planet, giving access to the extreme conditions of the planet upper atmosphere. We have undertaken HEARTS, a spectroscopic survey of exoplanet upper atmospheres, to perform a comparative study of hot gas giants and determine how stellar irradiation affect them. Here, we report on the first HEARTS observations of the hot Saturn-mass planet WASP-49b. We observed the planet with the HARPS high-resolution spectrograph at ESO 3.6m telescope. We collected 126 spectra of WASP-49, covering three transits of WASP-49b. We analyzed and modeled the planet transit spectrum, while paying particular attention to the treatment of potentially spurious signals of stellar origin. We spectrally resolve the Na i D lines in the planet atmosphere and show that these signatures are unlikely to arise from stellar contamination. The large contrasts of 2.0 ± 0.5% (D 2 ) and 1.8 ± 0.7% (D 1 ) require the presence of hot neutral sodium (2, 950 +400 −500 K) at high altitudes (∼1.5 planet radius or ∼45,000 km). From estimating the cloudiness index of WASP-49b, we determine its atmosphere to be cloud free at the altitudes probed by the sodium lines. WASP-49b is close to the border of the evaporation desert and exhibits an enhanced thermospheric signature with respect to a farther-away planet such as HD 189733b.

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Dearth of short-period Neptunian exoplanets: A desert in period-mass and period-radius planes

Cited by 315 publications

References 34 publications

A Super-Solar Metallicity for Stars With Hot Rocky Exoplanets

A Super-Solar Metallicity for Stars With Hot Rocky Exoplanets

Suppressed Far-UV Stellar Activity and Low Planetary Mass Loss in the WASP-18 System*

Hot Exoplanet Atmospheres Resolved with Transit Spectroscopy (HEARTS)

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