- ID:
- ivo://CDS.VizieR/J/A+A/555/A150
- Title:
- Physical parameters of cool solar-type stars
- Short Name:
- J/A+A/555/A150
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Temperature, surface gravity, and metallicity are basic stellar atmospheric parameters necessary to characterize a star. There are several methods to derive these parameters and a comparison of their results often shows considerable discrepancies, even in the restricted group of solar-type FGK dwarfs. We want to check the differences in temperature between the standard spectroscopic technique based on iron lines and the infrared flux method (IRFM). We aim to improve the description of the spectroscopic temperatures especially for the cooler stars where the differences between the two methods are higher, as presented in a previous work. Our spectroscopic analysis was based on the iron excitation and ionization balance, assuming Kurucz model atmospheres in LTE. The abundance analysis was determined using the code MOOG. We optimized the line list using a cool star (HD 21749) with high resolution and high signal-to-noise spectrum, as a reference in order to check for weak, isolated lines. We test the quality of the new line list by re-deriving stellar parameters for 451 stars with high resolution and signal-to-noise HARPS spectra, that were analyzed in a previous work with a larger line list. The comparison in temperatures between this work and the latest IRFM for the stars in common shows that the differences for the cooler stars are significantly smaller and more homogeneously distributed than in previous studies for stars with temperatures below 5000K.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/412/1787
- Title:
- Physical parameters of 62 eclipsing binaries
- Short Name:
- J/MNRAS/412/1787
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed light-curve analysis of publicly available V-band observations of 62 binary stars, mostly contact binaries, obtained by the All Sky Automated Survey (ASAS)-3 project between 2000 and 2009. Eclipsing binaries are important astronomical targets for determining the physical parameters of component stars from the geometry of their orbits. They provide an independent direct method of measuring the radii of stars. We improved the ASAS determined periods and ephemerides, and obtained the Fourier parameters from the phased light curves of these 62 stars.
- ID:
- ivo://CDS.VizieR/J/A+A/531/A141
- Title:
- Physical parameters of PMS in open clusters
- Short Name:
- J/A+A/531/A141
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Our aims are twofold: To determine the physical parameters of PMS members in young open clusters (YOCs), and to check and compare the performances of different model isochrones. We compare UBVRI photometric observations of eleven YOCs to theoretical isochrones in the photometric diagrams. The comparison simultaneously provides membership assignments for MS and PMS stars and estimates for the masses, ages, and spatial distribution of the candidate members. The relations found between the different cluster parameters show that the procedure applied to assign cluster membership, and to measure physical parameters for the selected members, is well founded.
- ID:
- ivo://CDS.VizieR/V/41
- Title:
- Physical parameters of spectroscopic binaries
- Short Name:
- V/41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The catalogue contains all stars listed in the 7th Catalogue of Spectroscopic Binaries (Batten, 1967PDAO...13..119B), supplements by Pedoussaut et al.: 1971A&AS....4..253P (11), 1973A&AS...10..105P (12) and 1977A&AS...27...55P (13), and data picked up by the authors from current publications up to the beginning of 1978.
- ID:
- ivo://CDS.VizieR/J/A+A/533/A109
- Title:
- Pisa pre-main sequence tracks and isochrones
- Short Name:
- J/A+A/533/A109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In recent years new observations of pre-main sequence stars (pre-MS) with Z<Z_{sun}_ have been made available. To take full advantage of the continuously growing amount of data of pre-MS stars in different environments, we need to develop updated pre-MS models for a wide range of metallicity to assign reliable ages and masses to the observed stars. We present updated evolutionary pre-MS models and isochrones for a fine grid of mass, age, metallicity, and helium values. We use a standard and well-tested stellar evolutionary code (i.e. FRANEC), that adopts outer boundary conditions from detailed and realistic atmosphere models. In this code, we incorporate additional improvements to the physical inputs related to the equation of state and the low temperature radiative opacities essential to computing low-mass stellar models. We make available via internet a large database of pre-MS tracks and isochrones for a wide range of chemical compositions (Z=0.0002-0.03), masses (M=0.2-7.0M_{sun}_), and ages (1-100Myr) for a solar-calibrated mixing length parameter alpha (i.e. 1.68). For each chemical composition, additional models were computed with two different mixing length values, namely alpha=1.2 and 1.9. Moreover, for Z>=0.008, we also provided models with two different initial deuterium abundances. The characteristics of the models have been discussed in detail and compared with other work in the literature. The main uncertainties affecting theoretical predictions have been critically discussed. Comparisons with selected data indicate that there is close agreement between theory and observation.
- ID:
- ivo://CDS.VizieR/J/AJ/156/22
- Title:
- Planetary candidates from K2 Campaign 16
- Short Name:
- J/AJ/156/22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Given that Campaign 16 of the K2 mission is one of just two K2 campaigns observed so far in "forward-facing" mode, which enables immediate follow-up observations from the ground, we present a catalog of interesting targets identified through photometry alone. Our catalog includes 30 high-quality planet candidates (showing no signs of being non-planetary in nature), 48 more ambiguous events that may be either planets or false positives, 164 eclipsing binaries, and 231 other regularly periodic variable sources. We have released light curves for all targets in C16 and have also released system parameters and transit vetting plots for all interesting candidates identified in this paper. Of particular interest is a candidate planet orbiting the bright F dwarf HD 73344 (V=6.9, K=5.6) with an orbital period of 15 days. If confirmed, this object would correspond to a 2.56+/-0.18 R_{Earth}_ planet and would likely be a favorable target for radial velocity characterization. This paper is intended as a rapid release of planet candidates, eclipsing binaries, and other interesting periodic variables to maximize the scientific yield of this campaign, and as a test run for the upcoming TESS mission, whose frequent data releases call for similarly rapid candidate identification and efficient follow up.
- ID:
- ivo://CDS.VizieR/J/ApJS/226/7
- Title:
- Planet candidates discovered using K2's 1st yr
- Short Name:
- J/ApJS/226/7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 197 planet candidates discovered using data from the first year of the NASA K2 mission (Campaigns 0-4), along with the results of an intensive program of photometric analyses, stellar spectroscopy, high-resolution imaging, and statistical validation. We distill these candidates into sets of 104 validated planets (57 in multi-planet systems), 30 false positives, and 63 remaining candidates. Our validated systems span a range of properties, with median values of R_P_=2.3R_{Earth}_, P=8.6 days, Teff=5300K, and Kp=12.7mag. Stellar spectroscopy provides precise stellar and planetary parameters for most of these systems. We show that K2 has increased by 30% the number of small planets known to orbit moderately bright stars (1-4R_{Earth}_, Kp=9-13mag). Of particular interest are 76 planets smaller than 2R_{Earth}_, 15 orbiting stars brighter than Kp=11.5mag, 5 receiving Earth-like irradiation levels, and several multi-planet systems-including 4 planets orbiting the M dwarf K2-72 near mean-motion resonances. By quantifying the likelihood that each candidate is a planet we demonstrate that our candidate sample has an overall false positive rate of 15%-30%, with rates substantially lower for small candidates (<2R_{Earth}_) and larger for candidates with radii >8R_{Earth}_ and/or with P<3days. Extrapolation of the current planetary yield suggests that K2 will discover between 500 and 1000 planets in its planned four-year mission, assuming sufficient follow-up resources are available. Efficient observing and analysis, together with an organized and coherent follow-up strategy, are essential for maximizing the efficacy of planet-validation efforts for K2, TESS, and future large-scale surveys.
- ID:
- ivo://CDS.VizieR/J/AJ/155/21
- Title:
- Planet candidates from K2 campaigns 5-8
- Short Name:
- J/AJ/155/21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 151 planet candidates orbiting 141 stars from K2 campaigns 5-8 (C5-C8), identified through a systematic search of K2 photometry. In addition, we identify 16 targets as likely eclipsing binaries, based on their light curve morphology. We obtained follow-up optical spectra of 105/141 candidate host stars and 8/16 eclipsing binaries to improve stellar properties and to identify spectroscopic binaries. Importantly, spectroscopy enables measurements of host star radii with ~10% precision, compared to ~40% precision when only broadband photometry is available. The improved stellar radii enable improved planet radii. Our curated catalog of planet candidates provides a starting point for future efforts to confirm and characterize K2 discoveries.
- 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}_.
- ID:
- ivo://CDS.VizieR/J/AJ/159/194
- Title:
- Planets around main sequence stars in GALEX UV
- Short Name:
- J/AJ/159/194
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Most (~82%) of the over 4000 confirmed exoplanets known today orbit very close to their host stars, within 0.5au. Planets at such small orbital distances can result in significant interactions with their host stars, which can induce increased activity levels in them. In this work, we have searched for statistical evidence for star-planet interactions in the ultraviolet (UV) using the largest sample of 1355 Galaxy Evolution Explorer (GALEX) detected host stars with confirmed exoplanets and making use of the improved host-star parameters from Gaia DR2. From our analysis, we do not find any significant correlation between the UV activity of the host stars and their planetary properties. We further compared the UV properties of planet host stars to that of chromospherically active stars from the RAdial Velocity Experiment (RAVE) survey. Our results indicate that the enhancement in chromospheric activity of host stars due to star-planet interactions may not be significant enough to reflect in their near and far V broadband flux.
