- ID:
- ivo://CDS.VizieR/J/A+A/644/A68
- Title:
- Abundance signature of M dwarf stars
- Short Name:
- J/A+A/644/A68
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Most of our current knowledge on planet formation is still based on the analysis of main-sequence, solar-type stars. Conversely, detailed chemical studies of large samples of M-dwarf planet hosts are still missing. We aim to test whether the correlations between the metallicity, individual chemical abundances, and mass of the star and the presence of different type of planets found for FGK stars still holds for the less massive M dwarf stars. Methods to determine in a consistent way stellar abundances of M dwarfs from high-resolution optical spectra are still missing. The present work is a first attempt to fill this gap. We analyse in a coherent and homogeneous way a large sample of M dwarfs with and without known planetary companions. We develop for the first time a methodology to determine stellar abundances of elements others than iron for M dwarf stars from high-resolution, optical spectra. Our methodology is based on the use of principal component analysis and sparse Bayesian's methods. We made use of a set of M dwarfs orbiting around an FGK primary with known abundances to train our methods. We applied our methods to derive stellar metallicities and abundances of a large sample of M dwarfs observed within the framework of current radial velocity surveys. We then used a sample of nearby FGK stars to cross-validate our technique by comparing the derived abundance trends in the M dwarf sample with those found on the FGK stars. The metallicity distribution of the different subsamples shows that M dwarfs hosting giant planets show a planet-metallicity correlation as well as a correlation with the stellar mass. M dwarfs hosting low-mass planets do not seem to follow the planet-metallicity correlation. We also found that the frequency of low-mass planets does not depend on the mass of the stellar host. These results seem in agreement with previous works. However, we note that for giant planet hosts our metallicities predict a weaker planet metallicity correlation but a stronger mass-dependency than photometric values. We show, for the first time, that there seems to be no differences in the abundance distribution of elements different from iron between M dwarfs with and without known planets. Our data shows that low-mass stars with planets follow the same metallicity, mass, and abundance trends than their FGK counterparts, which are usually explained within the framework of core-accretion models.
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- ID:
- ivo://CDS.VizieR/J/MNRAS/507/1847
- Title:
- A HARPS-N mass for the elusive Kepler-37d
- Short Name:
- J/MNRAS/507/1847
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To date, only 18 exoplanets with radial velocity (RV) semi-amplitudes <2m/s have had their masses directly constrained. The biggest obstacle to RV detection of such exoplanets is variability intrinsic to stars themselves, e.g. nuisance signals arising from surface magnetic activity such as rotating spots and plages, which can drown out or even mimic planetary RV signals. We use Kepler-37 - known to host three transiting planets, one of which, Kepler-37d, should be on the cusp of RV detectability with modern spectrographs - as a case study in disentangling planetary and stellar activity signals. We show how two different statistical techniques - one seeking to identify activity signals in stellar spectra, and another to model activity signals in extracted RVs and activity indicators - can enable detection of the hitherto elusive Kepler-37d. Moreover, we show that these two approaches can be complementary, and in combination, facilitate a definitive detection and precise characterisation of Kepler-37d. Its RV semi-amplitude of 1.22+/-0.31m/s (mass 5.4+/-1.4M_{Earth}_) is formally consistent with TOI-178b's 1.05^+0.25^_-0.30_m/s, the latter being the smallest detected RV signal of any transiting planet to date, though dynamical simulations suggest Kepler-37d's mass may be on the lower end of our 1{sigma} credible interval. Its consequent density is consistent with either a water-world or that of a gaseous envelope (~0.4% by mass) surrounding a rocky core. Based on RV modelling and a re-analysis of Kepler-37 TTVs, we also argue that the putative (non-transiting) planet Kepler-37e should probably be stripped of its 'confirmed' status.
- ID:
- ivo://CDS.VizieR/J/AJ/162/211
- Title:
- APF radial velocity follow up of {iota} Draconis
- Short Name:
- J/AJ/162/211
- Date:
- 14 Mar 2022 06:38:23
- Publisher:
- CDS
- Description:
- Giant stars as known exoplanet hosts are relatively rare due to the potential challenges in acquiring precision radial velocities and the small predicted transit depths. However, these giant host stars are also some of the brightest in the sky and so enable high signal-to-noise ratio follow-up measurements. Here, we report on new observations of the bright (V~3.3) giant star {iota}Draconis ({iota}Dra), known to host a planet in a highly eccentric ~511 day period orbit. TESS observations of the star over 137days reveal asteroseismic signatures, allowing us to constrain the stellar radius, mass, and age to ~2%, ~6%, and ~28%, respectively. We present the results of continued radial-velocity monitoring of the star using the Automated Planet Finder over several orbits of the planet. We provide more precise planet parameters of the known planet and, through the combination of our radial-velocity measurements with Hipparcos and Gaia astrometry, we discover an additional long-period companion with an orbital period of ~68_-36_^+60^yr. Mass predictions from our analysis place this substellar companion on the border of the planet and brown dwarf regimes. The bright nature of the star combined with the revised orbital architecture of the system provides an opportunity to study planetary orbital dynamics that evolve as the star moves into the giant phase of its evolution.
- ID:
- ivo://CDS.VizieR/J/A+A/643/A112
- Title:
- CARMENES VIS RVs of 3 M dwarfs
- Short Name:
- J/A+A/643/A112
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We announce the discovery of two planets orbiting the M dwarfs GJ 251 (0.360+/-0.015M_{sun}_) and HD 238090 (0.578+/-0.021M_{sun}_) based on CARMENES radial velocity (RV) data. In addition, we independently confirm with CARMENES data the existence of Lalande 21185 b, a planet that has recently been discovered with the SOPHIE spectrograph. All three planets belong to the class of warm or temperate super-Earths and share similar properties. The orbital periods are 14.24d, 13.67d, and 12.95d and the minimum masses are 4.0+/-0.4M_{sun}_, 6.9+/-0.9M_{sun}_, and 2.7+/-0.3M_{sun}_ for GJ 251 b, HD 238090 b, and Lalande 21185 b, respectively. Based on the orbital and stellar properties, we estimate equilibrium temperatures of 351.0+/-1.4K for GJ 251 b, 469.6+/-2.6K for HD 238090 b, and 370.1+/-6.8K for Lalande 21185 b. For the latter we resolve the daily aliases that were present in the SOPHIE data and that hindered an unambiguous determination of the orbital period. We find no significant signals in any of our spectral activity indicators at the planetary periods. The RV observations were accompanied by contemporaneous photometric observations. We derive stellar rotation periods of 122.1+/-2.2d and 96.7+/-3.7d for GJ 251 and HD 238090, respectively. The RV data of all three stars exhibit significant signals at the rotational period or its first harmonic. For GJ 251 and Lalande 21185, we also find long-period signals around 600d, and 2900d, respectively, which we tentatively attribute to long-term magnetic cycles. We apply a Bayesian approach to carefully model the Keplerian signals simultaneously with the stellar activity using Gaussian process regression models and extensively search for additional significant planetary signals hidden behind the stellar activity. Current planet formation theories suggest that the three systems represent a common architecture, consistent with formation following the core accretion paradigm.
- ID:
- ivo://CDS.VizieR/J/AJ/160/239
- Title:
- Cluster difference imaging photometric survey. II.
- Short Name:
- J/AJ/160/239
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of TOI837b and its validation as a transiting planet. We characterize the system using data from the NASA Transiting Exoplanet Survey Satellite mission, the ESA Gaia mission, ground-based photometry from El Sauce and ASTEP400, and spectroscopy from CHIRON, FEROS, and Veloce. We find that TOI837 is a T=9.9mag G0/F9 dwarf in the southern open cluster IC2602. The star and planet are therefore 35_-5_^+11^ million years old. Combining the transit photometry with a prior on the stellar parameters derived from the cluster color-magnitude diagram, we find that the planet has an orbital period of 8.3days and is slightly smaller than Jupiter (R_p_=0.77_-0.07_^+0.09^R_Jup_). From radial velocity monitoring, we limit M_p_sin(i) to less than 1.20M_Jup_(3{sigma}). The transits either graze or nearly graze the stellar limb. Grazing transits are a cause for concern, as they are often indicative of astrophysical false-positive scenarios. Our follow-up data show that such scenarios are unlikely. Our combined multicolor photometry, high-resolution imaging, and radial velocities rule out hierarchical eclipsing binary scenarios. Background eclipsing binary scenarios, though limited by speckle imaging, remain a 0.2% possibility. TOI837b is therefore a validated adolescent exoplanet. The planetary nature of the system can be confirmed or refuted through observations of the stellar obliquity and the planetary mass. Such observations may also improve our understanding of how the physical and orbital properties of exoplanets change in time.
- ID:
- ivo://CDS.VizieR/J/A+A/631/A136
- Title:
- 7 CMa system velocity curves
- Short Name:
- J/A+A/631/A136
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of a second planet orbiting the K giant star 7 CMa based on 166 high-precision radial velocities obtained with Lick, HARPS, UCLES and SONG. The periodogram analysis reveals two periodic signals of approximately 745 and 980d, associated to planetary companions. A double-Keplerian orbital fit of the data reveals two Jupiter-like planets with minimum masses M_b_sini~1.9Mj and M_c_sini~0.9Mj, orbiting at semi-major axes of a_b_~1.75au and a_c_~2.15au, respectively. Given the small orbital separation and the large minimum masses of the planets close encounters may occur within the time baseline of the observations, thus, a more accurate N-body dynamical modeling of the available data is performed. The dynamical best-fit solution leads to collision of the planets and we explore the long-term stable configuration of the system in a Bayesian framework, confirming that 13% of the posterior samples are stable for at least 10Myr. The result from the stability analysis indicates that the two-planets are trapped in a low-eccentricity 4:3 mean-motion resonance. This is only the third discovered system to be inside a 4:3 resonance, making it very valuable for planet formation and orbital evolution models.
- ID:
- ivo://CDS.VizieR/J/A+A/619/A1
- Title:
- 55 Cnc radial velocities and photometry
- Short Name:
- J/A+A/619/A1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Orbiting a bright, nearby star the 55 Cnc system offers a rare opportunity to study a multiplanet system that has a wide range of planetary masses and orbital distances. Using two decades of photometry and spectroscopy data, we have measured the rotation of the host star and its solar-like magnetic cycle. Accounting for this cycle in our velocimetric analysis of the system allows us to revise the properties of the outermost giant planet and its four planetary companions. The innermost planet 55 Cnc e is an unusually close-in super-Earth, whose transits have allowed for detailed follow-up studies. Recent observations favor the presence of a substantial atmosphere yet its composition, and the nature of the planet, remain unknown. We combined our derived planet mass (Mp=8.0+/-0.3M_{Earth}_) with refined measurement of its optical radius derived from HST/STIS observations (Rp=1.88+/-0.03R_{Earth}_ over 530-750nm) to revise the density of 55 Cnc e (rho=6.7+/-0.4g/cm^3^). Based on these revised properties we have characterized possible interiors of 55 Cnc e using a generalized Bayesian model. We confirm that the planet is likely surrounded by a heavyweight atmosphere, contributing a few percents of the planet radius. While we cannot exclude the presence of a water layer underneath the atmosphere, this scenario is unlikely given the observations of the planet across the entire spectrum and its strong irradiation. Follow-up observations of the system in photometry and in spectroscopy over different time-scales are needed to further investigate the nature and origin of this iconic super-Earth.
- ID:
- ivo://CDS.VizieR/J/AJ/160/96
- Title:
- CORALIE and PFS radial velocities of HD 86226
- Short Name:
- J/AJ/160/96
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Transiting Exoplanet Survey Satellite (TESS) mission was designed to find transiting planets around bright, nearby stars. Here, we present the detection and mass measurement of a small, short-period (~4days) transiting planet around the bright (V=7.9), solar-type star HD86226 (TOI-652, TIC22221375), previously known to host a long-period (~1600days) giant planet. HD86226c (TOI-652.01) has a radius of 2.16{+/-}0.08R_{Earth}_ and a mass of 7.25_-1.12_^+1.19^M_{Earth}_, based on archival and new radial velocity data. We also update the parameters of the longer-period, not-known-to-transit planet, and find it to be less eccentric and less massive than previously reported. The density of the transiting planet is 3.97g/cm^3^, which is low enough to suggest that the planet has at least a small volatile envelope, but the mass fractions of rock, iron, and water are not well- constrained. Given the host star brightness, planet period, and location of the planet near both the "radius gap" and the "hot Neptune desert," HD86226c is an interesting candidate for transmission spectroscopy to further refine its composition.
- ID:
- ivo://CDS.VizieR/J/A+A/635/A122
- Title:
- CoRoT-30b and CoRoT-31b radial velocity curves
- Short Name:
- J/A+A/635/A122
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery as well as the orbital and physical characterizations of two new transiting giant exoplanets, CoRoT-30 b and CoRoT-31 b, with the CoRoT space telescope. We analyzed two complementary data sets: photometric transit light curves measured by CoRoT, and radial velocity curves measured by the HARPS spectrometer. To derive the absolute masses and radii of the planets, we modeled the stars from available magnitudes and spectra. We find that CoRoT-30 b is a warm Jupiter on a close-to-circular 9.06-day orbit around a G3V star with a semi-major axis of about 0.08AU. It has a radius of 1.01+/-0.08R_Jup_, a mass of 2.90+/-0.22M_Jup_, and therefore a mean density of 3.45+/-0.65g/cm^3^. The hot Jupiter CoRoT-31 b is on a close to circular 4.63-day orbit around a G2 IV star with a semi-major axis of about 0.05AU. It has a radius of 1.46+/-0.30R_Jup_, a mass of 0.84+/-0.34M_Jup_, and therefore a mean density of 0.33+/-0.18g/cm^3^. Neither system seems to support the claim that stars hosting planets are more depleted in lithium. The radii of both planets are close to that of Jupiter, but they differ in mass; CoRoT-30 b is ten times denser than CoRoT-31 b. The core of CoRoT-30 b would weigh between 15 and 75 Earth masses, whereas relatively weak constraints favor no core for CoRoT-31 b. In terms of evolution, the characteristics of CoRoT-31 b appear to be compatible with the high-eccentricity migration scenario, which is not the case for CoRoT-30 b. The angular momentum of CoRoT-31 b is currently too low for the planet to evolve toward synchronization of its orbital revolution with stellar rotation, and the planet will slowly spiral-in while its host star becomes a red giant. CoRoT-30 b is not synchronized either: it looses angular momentum owing to stellar winds and is expected reach steady state in about 2Gyr. CoRoT-30 and 31, as a pair, are a truly remarkable example of diversity in systems with hot Jupiters.
- ID:
- ivo://CDS.VizieR/J/A+A/645/A7
- Title:
- Determining true mass of RV exoplanets with Gaia
- Short Name:
- J/A+A/645/A7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Mass is one of the most important parameters for determining the true nature of an astronomical object. Yet, many published exoplan- ets lack a measurement of their true mass, in particular those detected as a result of radial-velocity (RV) variations of their host star. For those examples, only the minimum mass, or msini, is known, owing to the insensitivity of RVs to the inclination of the detected orbit compared to the plane of the sky. The mass that is given in databases is generally that of an assumed edge-on system (~90{deg}), but many other inclinations are possible, even extreme values closer to 0{deg} (face-on). In such a case, the mass of the published object could be strongly underestimated by up to two orders of magnitude. In the present study, we use GASTON, a recently developed tool taking advantage of the voluminous Gaia astrometric database to constrain the inclination and true mass of several hundreds of published exoplanet candidates. We find 9 exoplanet candidates in the stellar or brown dwarf (BD) domain, among which 6 were never characterized. We show that 30 Ari B b, HD 141937 b, HD 148427 b, HD 6718 b, HIP 65891 b, and HD 16760 b have masses larger than 13.5 M_J_ at 3{sigma}. We also confirm the planetary nature of 27 exoplanets, including HD 10180 c, d and g. Studying the orbital periods, eccentricities, and host-star metallicities in the BD domain, we found distributions with respect to true masses consistent with other publications. The distribution of orbital periods shows of a void of BD detections below ~100d, while eccentricity and metallicity distributions agree with a transition between BDs similar to planets and BDs similar to stars in the range 40-50M_J_.
