- ID:
- ivo://CDS.VizieR/J/MNRAS/496/5423
- Title:
- 4 planet-hosting stars asteroseismic masses
- Short Name:
- J/MNRAS/496/5423
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The study of planet occurrence as a function of stellar mass is important for a better understanding of planet formation. Estimating stellar mass, especially in the red giant regime, is difficult. In particular, stellar masses of a sample of evolved planet-hosting stars based on spectroscopy and grid-based modelling have been put to question over the past decade with claims they were overestimated. Although efforts have been made in the past to reconcile this dispute using asteroseismology, results were inconclusive. In an attempt to resolve this controversy, we study four more evolved planet-hosting stars in this paper using asteroseismology, and we revisit previous results to make an informed study of the whole ensemble in a self-consistent way. For the four new stars, we measure their masses by locating their characteristic oscillation frequency, numax, from their radial velocity time series observed by SONG. For two stars, we are also able to measure the large frequency separation, Delta nu, helped by extended SONG single-site and dual-site observations and new TESS observations. We establish the robustness of the numax-only-based results by determining the stellar mass from Delta nu, and from both Delta nu and numax. We then compare the seismic masses of the full ensemble of 16 stars with the spectroscopic masses from three different literature sources. We find an offset between the seismic and spectroscopic mass scales that is mass-dependent, suggesting that the previously claimed overestimation of spectroscopic masses only affects stars more massive than about 1.6M_{sun}_.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/495/3961
- Title:
- Planet-hosting stars chemical compositions
- Short Name:
- J/MNRAS/495/3961
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a line-by-line differential analysis of a sample of 16 planet-hosting stars and 68 comparison stars using high-resolution, high signal-to-noise ratio spectra gathered using Keck. We obtained accurate stellar parameters and high-precision relative chemical abundances with average uncertainties in Teff, logg, [Fe/H], and [X/H] of 15K, 0.034cm/s^2^, 0.012dex, and 0.025dex, respectively. For each planet host, we identify a set of comparison stars and examine the abundance differences (corrected for Galactic chemical evolution effect) as a function of the dust condensation temperature, Tcond, of the individual elements. While we confirm that the Sun exhibits a negative trend between abundance and Tcond, we also confirm that the remaining planet hosts exhibit a variety of abundance-Tcond trends with no clear dependence upon age, metallicity, or Teff. The diversity in the chemical compositions of planet-hosting stars relative to their comparison stars could reflect the range of possible planet-induced effects present in these planet hosts, from the sequestration of rocky material (refractory poor) to the possible ingestion of planets (refractory rich). Other possible explanations include differences in the time-scale, efficiency and degree of planet formation, or inhomogeneous chemical evolution. Although we do not find an unambiguous chemical signature of planet formation among our sample, the high-precision chemical abundances of the host stars are essential for constraining the composition and structure of their exoplanets.
- ID:
- ivo://CDS.VizieR/J/AJ/152/187
- Title:
- Planet occurrence and stellar metallicity for KOIs
- Short Name:
- J/AJ/152/187
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Host star metallicity provides a measure of the conditions in protoplanetary disks at the time of planet formation. Using a sample of over 20000 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]{simeq}0.15+/-0.05dex). 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<10days, the difference in host star metallicity is largest for hot rocky planets (<1.7R_{Earth}_), where the metallicity difference is [Fe/H]{simeq}0.25+/-0.07dex. 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.
- ID:
- ivo://CDS.VizieR/J/ApJ/814/130
- Title:
- Planet occurrence rates calculated for KOIs
- Short Name:
- J/ApJ/814/130
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Trends in the planet population with host star mass provide an avenue to constrain planet formation theories. We derive the planet radius distribution function for Kepler stars of different spectral types, sampling a range in host star masses. We find that M dwarf stars have 3.5 times more small planets (1.0-2.8R_{Earth}_) than main-sequence FGK stars, but two times fewer Neptune-sized and larger (>2.8R_{Earth}_) planets. We find no systematic trend in the planet size distribution between spectral types F, G, and K to explain the increasing occurrence rates. Taking into account the mass-radius relationship and heavy-element mass of observed exoplanets, and assuming those are independent of spectral type, we derive the inventory of the heavy-element mass locked up in exoplanets at short orbits. The overall higher planet occurrence rates around M stars are not consistent with the redistribution of the same mass into more, smaller planets. At the orbital periods and planet radii where Kepler observations are complete for all spectral types, the average heavy-element mass locked up in exoplanets increases roughly inversely with stellar mass from 4M_{Earth}_ in F stars to 5M_{Earth}_in G and K stars to 7M_{Earth}_ in M stars. This trend stands in stark contrast with observed protoplanetary disk masses that decrease toward lower mass stars, and provides a challenge for current planet formation models. Neither models of in situ formation nor migration of fully formed planets are consistent with these results. Instead, these results are indicative of large-scale inward migration of planetary building blocks --either through type-I migration or radial drift of dust grains-- that is more efficient for lower mass stars, but does not result in significantly larger or smaller planets.
- ID:
- ivo://CDS.VizieR/J/ApJS/216/7
- Title:
- Planets Around Low-Mass Stars (PALMS). IV.
- Short Name:
- J/ApJS/216/7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from a high-contrast adaptive optics imaging search for giant planets and brown dwarfs (>~1M_Jup_) around 122 newly identified nearby (<~40pc) young M dwarfs. Half of our targets are younger than 135Myr and 90% are younger than the Hyades (620Myr). After removing 44 close stellar binaries (implying a stellar companion fraction of >35.4%+/-4.3% within 100AU), 27 of which are new or spatially resolved for the first time, our remaining sample of 78 single M dwarfs makes this the largest imaging search for planets around young low-mass stars (0.1-0.6M_{sun}_) to date. Our H- and K-band coronagraphic observations with Keck/NIRC2 and Subaru/HiCIAO achieve typical contrasts of 12-14mag and 9-13mag at 1", respectively, which correspond to limiting planet masses of 0.5-10M_Jup_ at 5-33AU for 85% of our sample. We discovered four young brown dwarf companions: 1RXS J235133.3+312720B (32+/-6M_Jup_; L0^+2^_-1_; 120+/-20AU), GJ 3629B (64^+30^_-23_M_Jup_; M7.5+/-0.5; 6.5+/-0.5AU), 1RXS J034231.8+121622B (35+/-8M_Jup_; L0+/-1; 19.8+/-0.9AU), and 2MASS J15594729+4403595B (43+/-9M_Jup_; M8.0+/-0.5; 190+/-20AU). Over 150 candidate planets were identified; we obtained follow-up imaging for 56% of these but all are consistent with background stars. Our null detection of planets enables strong statistical constraints on the occurrence rate of long-period giant planets around single M dwarfs.
- ID:
- ivo://CDS.VizieR/J/A+A/543/A45
- Title:
- Planets around metal-poor stars
- Short Name:
- J/A+A/543/A45
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The discovery of about 700 extrasolar planets, so far, has lead to the first statistics concerning extrasolar planets. The presence of giant planets seems to depend on stellar metallicity and mass. For example, they are more frequent around metal-rich stars, with an exponential increase in planet occurrence rates with metallicity. We analyzed two samples of metal-poor stars (-2.0<[Fe/H]<0.0) to see if giant planets are indeed rare around these objects. Radial velocity datasets were obtained with two different spectrographs (HARPS and HIRES). Detection limits for these data, expressed in minimum planetary mass and period, are calculated. These produce trustworthy numbers for the planet frequency. A general Lomb Scargle (GLS) periodogram analysis was used together with a bootstrapping method to produce the detection limits. Planet frequencies were calculated based on a binomial distribution function within metallicity bins. Almost all hot Jupiters and most giant planets should have been found in these data. Hot Jupiters around metal-poor stars have a frequency lower than 1.0% at one sigma. Giant planets with periods up to 1800 days, however, have a higher frequency of 2.63^+2.5^_-0.89_%. Taking into account the different metallicities of the stars, we show that giant planets appear to be very frequent (4.48^+4.04^_-1.38_%) around stars with [Fe/H]>-0.7, while they are rare around stars with [Fe/H]<-0.7. We conclude that giant planet frequency is indeed a strong function of metallicity, even in the low-metallicity tail. However, the frequencies are most likely higher than previously thought.
- ID:
- ivo://CDS.VizieR/J/ApJ/790/146
- Title:
- Planets in Kepler's multi-transiting systems
- Short Name:
- J/ApJ/790/146
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the orbital architectures of Kepler systems having multiple-planet candidates identified in the analysis of data from the first six quarters of Kepler data and reported by Batalha et al. (2013, J/ApJS/204/24). These data show 899 transiting planet candidates in 365 multiple-planet systems and provide a powerful means to study the statistical properties of planetary systems. Using a generic mass-radius relationship, we find that only two pairs of planets in these candidate systems (out of 761 pairs total) appear to be on Hill-unstable orbits, indicating ~96% of the candidate planetary systems are correctly interpreted as true systems. We find that planet pairs show little statistical preference to be near mean-motion resonances. We identify an asymmetry in the distribution of period ratios near first-order resonances (e.g., 2:1, 3:2), with an excess of planet pairs lying wide of resonance and relatively few lying narrow of resonance. Finally, based upon the transit duration ratios of adjacent planets in each system, we find that the interior planet tends to have a smaller transit impact parameter than the exterior planet does. This finding suggests that the mode of the mutual inclinations of planetary orbital planes is in the range 1.{deg}0-2.{deg}2, for the packed systems of small planets probed by these observations.
- ID:
- ivo://CDS.VizieR/J/AJ/155/136
- Title:
- Planets orbiting bright stars in K2 campaigns 0-10
- Short Name:
- J/AJ/155/136
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Since 2014, NASA's K2 mission has observed large portions of the ecliptic plane in search of transiting planets and has detected hundreds of planet candidates. With observations planned until at least early 2018, K2 will continue to identify more planet candidates. We present here 275 planet candidates observed during Campaigns 0-10 of the K2 mission that are orbiting stars brighter than 13 mag (in Kepler band) and for which we have obtained high-resolution spectra (R=44000). These candidates are analyzed using the vespa package in order to calculate their false-positive probabilities (FPP). We find that 149 candidates are validated with an FPP lower than 0.1%, 39 of which were previously only candidates and 56 of which were previously undetected. The processes of data reduction, candidate identification, and statistical validation are described, and the demographics of the candidates and newly validated planets are explored. We show tentative evidence of a gap in the planet radius distribution of our candidate sample. Comparing our sample to the Kepler candidate sample investigated by Fulton et al. (2017, J/AJ/154/109), we conclude that more planets are required to quantitatively confirm the gap with K2 candidates or validated planets. This work, in addition to increasing the population of validated K2 planets by nearly 50% and providing new targets for follow-up observations, will also serve as a framework for validating candidates from upcoming K2 campaigns and the Transiting Exoplanet Survey Satellite, expected to launch in 2018.
- ID:
- ivo://CDS.VizieR/J/A+A/552/A119
- Title:
- Planet-star and moon-planet interaction
- Short Name:
- J/A+A/552/A119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Electromagnetic coupling of planetary moons with their host planets is well observed in our solar system. Similar couplings of extrasolar planets with their central stars have been studied observationally on an individual as well as on a statistical basis. We aim to model and to better understand the energetics of planet star and moon planet interactions on an individual and as well as on a statistical basis.
- ID:
- ivo://CDS.VizieR/J/MNRAS/441/3543
- Title:
- Possible planets around A stars
- Short Name:
- J/MNRAS/441/3543
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Kepler photometry of A stars shows that a considerable fraction (about 19 per cent) have a peculiar feature in the periodogram. This feature consists of a broad peak, thought to be due to differential rotation in a spotted star, and a sharp peak at slightly higher frequency. The pattern clearly involves some widespread stellar property and the sharp peak implies a strictly coherent periodicity. We investigate the possibility that the periodicity is due to rotation, pulsation or an orbital effect. We argue that neither rotation nor pulsation can provide a suitable, testable, explanation. We suggest that the sharp feature could be due to a planet in synchronous orbit around the rapidly rotating, spotted A star, not necessarily in transit. Spectroscopic observations of sufficient precision are required to falsify this hypothesis.