- ID:
- ivo://CDS.VizieR/J/A+A/556/A150
- Title:
- SWEETCat I. Stellar parameters for host stars
- Short Name:
- J/A+A/556/A150
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we present new precise atmospheric parameters for stars with planets. We then take the opportunity to present a new catalogue of stellar parameters for FGK and M stars with planets detected by radial velocity, transit, and astrometry programs. Stellar atmospheric parameters and masses for the sample were derived assuming LTE and using high resolution and high signal-to-noise spectra. The methodology used is based on the measurement of equivalent widths for a list of iron lines and making use of iron ionization and excitation equilibrium principles. For the catalog, and whenever possible, we used parameters derived in previous works published by our team, using well defined methodologies for the derivation of stellar atmospheric parameters. This set of parameters amounts to over 65% of all planet host stars known, including more than 90% of all stars with planets discovered through radial velocity surveys. For the remaining targets, stellar parameters were collected from the literature.
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- ID:
- ivo://CDS.VizieR/J/A+A/650/A73
- Title:
- Synthetic XUV spectra of GJ 3470
- Short Name:
- J/A+A/650/A73
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Neptune-size exoplanets seem particularly sensitive to atmospheric evaporation, making it essential to characterize the stellar high-energy radiation that drives this mechanism. This is particularly important with M dwarfs, which emit a large and variable fraction of their luminosity in the ultraviolet and can display strong flaring behavior. The warm Neptune GJ 3470b, hosted by an M2 dwarf, was found to harbor a giant exosphere of neutral hydrogen thanks to three transits observed with the Hubble Space Telescope Imaging Spectrograph (HST/STIS). Here we report on three additional transit observations from the Panchromatic Comparative Exoplanet Treasury program, obtained with the HST Cosmic Origin Spectrograph. These data confirm the absorption signature from GJ 3470b's exosphere in the stellar Lyman-{alpha} line and demonstrate its stability over time. No planetary signatures are detected in other stellar lines, setting a 3{sigma} limit on GJ 3470b's far-ultraviolet (FUV) radius at 1.3 times its Roche lobe radius. We detect three flares from GJ 3470. They show different spectral energy distributions but peak consistently in the SiIII line, which traces intermediate-temperature layers in the transition region. These layers appear to play a particular role in GJ 3470's activity as emission lines that form at lower or higher temperatures than SiIII evolved differently over the long term. Based on the measured emission lines, we derive synthetic X-ray and extreme-ultraviolet (X+EUV, or XUV) spectra for the six observed quiescent phases, covering one year, as well as for the three flaring episodes. Our results suggest that most of GJ 3470's quiescent high-energy emission comes from the EUV domain, with flares amplifying the FUV emission more strongly. The neutral hydrogen photoionization lifetimes and mass loss derived for GJ 3470b show little variation over the epochs, in agreement with the stability of the exosphere. Simulations informed by our XUV spectra are required to understand the atmospheric structure and evolution of GJ 3470b and the role played by evaporation in the formation of the hot-Neptune desert.
- ID:
- ivo://CDS.VizieR/J/ApJ/803/90
- Title:
- {tau} Cet chemical composition
- Short Name:
- J/ApJ/803/90
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- {tau} Ceti (HD10700), a G8 dwarf with mass 0.78M_{sun}_, is a close (3.65pc) Sun-like star where five possibly terrestrial planet candidates (minimum masses of 2, 3.1, 3.5, 4.3, and 6.7M_{Earth}_) have recently been discovered. We report abundances of 23 elements using spectra from the MIKE spectrograph on Magellan. We find [Fe/H]=-0.49 and T_eff_=5387K. Using stellar models with the abundances determined here, we calculate the position of the classical habitable zone (HZ) with time. At the current best fit age, 7.63_-1.5_^+0.87^Gyr, up to two planets (e and f) may be in the HZ, depending on atmospheric properties. The Mg/Si ratio of the star is found to be 1.78, which is much greater than for Earth (~1.2). With a system that has such an excess of Mg/Si ratio it is possible that the mineralogical make-up of planets around {tau} Ceti could be significantly different from that of Earth, with possible oversaturation of MgO, resulting in an increase in the content of olivine and ferropericlase compared with Earth. The increase in MgO would have a drastic impact on the rheology of the mantles of the planets around {tau} Ceti.
- ID:
- ivo://CDS.VizieR/J/ApJ/800/85
- Title:
- Teff, radii and luminosities of cool dwarfs
- Short Name:
- J/ApJ/800/85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Interferometric radius measurements provide a direct probe of the fundamental parameters of M dwarfs. However, interferometry is within reach for only a limited sample of nearby, bright stars. We use interferometrically measured radii, bolometric luminosities, and effective temperatures to develop new empirical calibrations based on low-resolution, near-infrared spectra. We find that H-band Mg and Al spectral features are good tracers of stellar properties, and derive functions that relate effective temperature, radius, and log luminosity to these features. The standard deviations in the residuals of our best fits are, respectively, 73K, 0.027R_{sun}_, and 0.049dex (an 11% error on luminosity). Our calibrations are valid from mid K to mid M dwarf stars, roughly corresponding to temperatures between 3100 and 4800K. We apply our H-band relationships to M dwarfs targeted by the MEarth transiting planet survey and to the cool Kepler Objects of Interest (KOIs). We present spectral measurements and estimated stellar parameters for these stars. Parallaxes are also available for many of the MEarth targets, allowing us to independently validate our calibrations by demonstrating a clear relationship between our inferred parameters and the stars' absolute K magnitudes. We identify objects with magnitudes that are too bright for their inferred luminosities as candidate multiple systems. We also use our estimated luminosities to address the applicability of near-infrared metallicity calibrations to mid and late M dwarfs. The temperatures we infer for the KOIs agree remarkably well with those from the literature; however, our stellar radii are systematically larger than those presented in previous works that derive radii from model isochrones. This results in a mean planet radius that is 15% larger than one would infer using the stellar properties from recent catalogs. Our results confirm the derived parameters from previous in-depth studies of KOIs 961 (Kepler-42), 254 (Kepler-45), and 571 (Kepler-186), the latter of which hosts a rocky planet orbiting in its star's habitable zone.
- ID:
- ivo://CDS.VizieR/J/ApJ/693/1084
- Title:
- Ten new and updated multiplanet systems
- Short Name:
- J/ApJ/693/1084
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the latest velocities for ten multiplanet systems, including a re-analysis of archival Keck and Lick data, resulting in improved velocities that supersede our previously published measurements. We derive updated orbital fits for 10 Lick and Keck systems, including two systems (HD 11964, HD 183263) for which we provide confirmation of second planets only tentatively identified elsewhere, and two others (HD 187123 and HD 217107) for which we provide a major revision of the outer planet's orbit. We compile orbital elements from the literature to generate a catalog of the 28 published multiple-planet systems around stars within 200pc.
- ID:
- ivo://CDS.VizieR/J/ApJ/761/166
- Title:
- Terrestrial exoplanet atmospheres. I.
- Short Name:
- J/ApJ/761/166
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a comprehensive photochemistry model for exploration of the chemical composition of terrestrial exoplanet atmospheres. The photochemistry model is designed from the ground up to have the capacity to treat all types of terrestrial planet atmospheres, ranging from oxidizing through reducing, which makes the code suitable for applications for the wide range of anticipated terrestrial exoplanet compositions. The one-dimensional chemical transport model treats up to 800 chemical reactions, photochemical processes, dry and wet deposition, surface emission, and thermal escape of O, H, C, N, and S bearing species, as well as formation and deposition of elemental sulfur and sulfuric acid aerosols. We validate the model by computing the atmospheric composition of current Earth and Mars and find agreement with observations of major trace gases in Earth's and Mars' atmospheres. We simulate several plausible atmospheric scenarios of terrestrial exoplanets and choose three benchmark cases for atmospheres from reducing to oxidizing. The most interesting finding is that atomic hydrogen is always a more abundant reactive radical than the hydroxyl radical in anoxic atmospheres. Whether atomic hydrogen is the most important removal path for a molecule of interest also depends on the relevant reaction rates. We also find that volcanic carbon compounds (i.e., CH_4_ and CO_2_) are chemically long-lived and tend to be well mixed in both reducing and oxidizing atmospheres, and their dry deposition velocities to the surface control the atmospheric oxidation states. Furthermore, we revisit whether photochemically produced oxygen can cause false positives for detecting oxygenic photosynthesis, and find that in 1 bar CO_2_-rich atmospheres oxygen and ozone may build up to levels that have conventionally been accepted as signatures of life, if there is no surface emission of reducing gases. The atmospheric scenarios presented in this paper can serve as the benchmark atmospheres for quickly assessing the lifetime of trace gases in reducing, weakly oxidizing, and highly oxidizing atmospheres on terrestrial exoplanets for the exploration of possible biosignature gases.
- ID:
- ivo://CDS.VizieR/J/ApJ/809/8
- Title:
- Terrestrial planet occurrence rates for KOI stars
- Short Name:
- J/ApJ/809/8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We measure planet occurrence rates using the planet candidates discovered by the Q1-Q16 Kepler pipeline search. This study examines planet occurrence rates for the Kepler GK dwarf target sample for planet radii, 0.75<=Rp<=2.5R_{Earth}_, and orbital periods, 50<=Porb<=300days, with an emphasis on a thorough exploration and identification of the most important sources of systematic uncertainties. Integrating over this parameter space, we measure an occurrence rate of F_0_=0.77 planets per star, with an allowed range of 0.3<=F0<=1.9. The allowed range takes into account both statistical and systematic uncertainties, and values of F_0_ beyond the allowed range are significantly in disagreement with our analysis. We generally find higher planet occurrence rates and a steeper increase in planet occurrence rates toward small planets than previous studies of the Kepler GK dwarf sample. Through extrapolation, we find that the one year orbital period terrestrial planet occurrence rate {zeta}_1.0_=0.1, with an allowed range of 0.01<={zeta}_1.0_<=2, where {zeta}_1.0_ is defined as the number of planets per star within 20% of the Rp and Porb of Earth. For G dwarf hosts, the {zeta}_1.0_ parameter space is a subset of the larger {eta}_{Earth}_ parameter space, thus {zeta}_1.0_ places a lower limit on {eta}_{Earth}_ for G dwarf hosts. From our analysis, we identify the leading sources of systematics impacting Kepler occurrence rate determinations as reliability of the planet candidate sample, planet radii, pipeline completeness, and stellar parameters.
- ID:
- ivo://CDS.VizieR/J/A+A/633/A53
- Title:
- TESS planet candidates classification
- Short Name:
- J/A+A/633/A53
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Accurately and rapidly classifying exoplanet candidates from transit surveys is a goal of growing importance as the data rates from space-based survey missions increase. This is especially true for NASA's TESS mission which generates thousands of new candidates each month. Here we created the first deep learning model capable of classifying TESS planet candidates. We adapted the neural network model of Ansdell et al (2018) to TESS data. We then trained and tested this updated model on 4 sectors of high-fidelity, pixel-level simulations data created using the Lilith simulator & processed using the full TESS pipeline. With the caveat that direct transfer of the model to real data will not perform as accurately, we also applied this model to four sectors of TESS candidates. We find our model performs very well on our simulated data, with 97% average precision and 92% accuracy on planets in the 2-class model. This accuracy is also boosted by another ~4% if planets found at the wrong periods are included. We also performed 3- and 4-class classification of planets, blended & target eclipsing binaries, and non-astrophysical false positives, which have slightly lower average precision and planet accuracies, but are useful for follow-up decisions. When applied to real TESS data, 61% of Threshold Crossing Events (TCEs) coincident with currently published TOIs are recovered as planets, 4% more are suggested to be Eclipsing Binaries, and we propose a further 200 TCEs as planet candidates.
- ID:
- ivo://CDS.VizieR/J/A+A/653/A66
- Title:
- TEXES spectra of Saturn from February 03 2013
- Short Name:
- J/A+A/653/A66
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- The abundance of deuterium in giant planet atmospheres provides constraints on the reservoirs of ices incorporated into these worlds during their formation and evolution. Motivated by discrepancies in the measured deuterium-hydrogen ratio (D/H) on Jupiter and Saturn, we present a new measurement of the D/H ratio in methane for Saturn from ground-based measurements. We analysed a spectral cube (covering 1151-1160cm^-1^ from 6 February 2013) from the Texas Echelon Cross Echelle Spectrograph (TEXES) on NASA's Infrared Telescope Facility (IRTF) where emission lines from both methane and deuterated methane are well resolved. Our estimate of the D/H ratio in stratospheric methane, 1.65(-0.21/+0.27)*10^-5^ is in agreement with results derived from Cassini CIRS and ISO/SWS observations, confirming the unexpectedly low CH3D abundance. Assuming a fractionation factor of 1.34(+/-0.19) we derive a hydrogen D/H of 1.23(-0.23/+0.27)*10^-5^. This value remains lower than previous tropospheric hydrogen D/H measurements of (i) Saturn 2.10(+/-0.13)*10^-5^, (ii) Jupiter 2.6(+/-0.7)*10^-5^ and (iii) the proto-solar hydrogen D/H of 2.1(+/-0.5)*10^-5^, suggesting that the fractionation factor may not be appropriate for stratospheric methane, or that the D/H ratio in Saturn's stratosphere is not representative of the bulk of the planet.
- ID:
- ivo://CDS.VizieR/J/A+A/392/215
- Title:
- The CORALIE survey for extrasolar planets. IX.
- Short Name:
- J/A+A/392/215
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Table 1 contains the CORALIE radial-velocity measurements for the stellar system HD41004. CORALIE is a fiber-fed echelle spectrograph designed for high-precision radial-velocity measurements. It is mounted on the 1.2-m "Leonard Euler" Swiss Telescope at ESO-La Silla Observatory (Chile).