- ID:
- ivo://CDS.VizieR/J/MNRAS/419/L34
- Title:
- Surface gravity determination in late-type stars
- Short Name:
- J/MNRAS/419/L34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The frequency of maximum oscillation power measured in dwarfs and giants exhibiting solar-like pulsations provides a precise, and potentially accurate, inference of the stellar surface gravity. An extensive comparison for about 40 well-studied pulsating stars with gravities derived using classical methods (ionization balance, pressure-sensitive spectral features or location with respect to evolutionary tracks) supports the validity of this technique and reveals an overall remarkable agreement with mean differences not exceeding 0.05dex (although with a dispersion of up to ~0.2dex). It is argued that interpolation in theoretical isochrones may be the most precise way of estimating the gravity by traditional means in nearby dwarfs. Attention is drawn to the usefulness of seismic targets as benchmarks in the context of large-scale surveys.
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Search Results
- 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.
473. SWEET-Cat updated
- ID:
- ivo://CDS.VizieR/J/A+A/620/A58
- Title:
- SWEET-Cat updated
- Short Name:
- J/A+A/620/A58
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Exoplanets have now been proven to be very common. The number of its detections continues to grow following the development of better instruments and missions. One key step for the understanding of these worlds is their characterization, which mostly depend on their host stars. We perform a significant update of the Stars With ExoplanETs CATalog (SWEET-Cat), a unique compilation of precise stellar parameters for planet-host stars provided for the exoplanet community. We made use of high-resolution spectra for planet-host stars, either observed by our team or found in several public archives. The new spectroscopic parameters were derived for the spectra following the same homogeneous process (ARES+MOOG). The host star parameters were then merged together with the planet properties listed in exoplanet.eu to perform simple data analysis. We present new spectroscopic homogeneous parameters for 106 planet-host stars. Sixty-three planet hosts are also reviewed with new parameters. We also show that there is a good agreement between stellar parameters derived for the same star but using spectra obtained from different spectrographs. The planet-metallicity correlation is reviewed showing that the metallicity distribution of stars hosting low-mass planets (below 30M_{sun}_) is indistinguishable from that from the solar neighborhood sample in terms of metallicity distribution.
- ID:
- ivo://CDS.VizieR/J/ApJ/601/485
- Title:
- Synthetic Lick indices of alpha-enhanced stars
- Short Name:
- J/ApJ/601/485
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Synthetic Lick indices computed with solar scaled abundances and with {alpha}-element enhancement are presented and compared with predictions from both theoretical computations (Tripicco & Bell (1995AJ....110.3035T); Thomas, Maraston, & Bender (2003MNRAS.339..897T); Barbuy et al., 2003, Cat. <J/A+A/404/661>) and empirical fitting functions (de Freitas Pacheco, 1996MNRAS.278..841D). We propose selected combinations of indices capable of singling out {alpha}-enhanced stars without requiring previous knowledge of their main atmospheric parameters. By applying this approach to the 460 stars in the Worthey et al. (1994, Cat. <J/ApJS/94/687>) catalog, we detected a list of 82 candidate {alpha}-enhanced stars. The confirmation of {alpha}-enhancement was obtained by searching the literature for individual element abundance determinations from high-resolution spectroscopy for a subsample of 34 stars. Preliminary discussion of the properties of the detected {alpha}-enhanced stars with respect to their [Fe/H] values and kinematics is presented.
- ID:
- ivo://CDS.VizieR/J/ApJ/634/1319
- Title:
- Synthetic Lick indices of alpha-enhanced stars
- Short Name:
- J/ApJ/634/1319
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A sample of 119 F, G, and K solar neighborhood stars, selected under the condition [Fe/H]>0.00, is investigated in order to detect which of them, if any, present {alpha}-enhanced characteristics. According to the kinematics, the sample represents stars of the thin-disk component of the Galaxy.
- ID:
- ivo://CDS.VizieR/J/ApJ/613/312
- Title:
- Synthetic Lick indices of alpha-enhanced stars
- Short Name:
- J/ApJ/613/312
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of 402 F, G, and K solar neighborhood stars, with accurate estimates of [Fe/H] in the range -1.0 to +0.5dex, aimed at the detection of {alpha}-enhanced stars and at the investigation of their kinematical properties. The analysis is based on the comparison of 571 sets of spectral indices in the Lick/IDS system, coming from four different observational data sets, with synthetic indices computed with solar-scaled abundances and with {alpha}-element enhancement. We use selected combinations of indices to single out {alpha}-enhanced stars without requiring previous knowledge of their main atmospheric parameters. By applying this approach to the total data set, we obtain a list of 60 bona fide {alpha}-enhanced stars and of 146 stars with solar-scaled abundances. The properties of the detected {alpha}-enhanced and solar-scaled abundance stars with respect to their [Fe/H] values and kinematics are presented. A clear kinematic distinction between solar-scaled and {alpha}-enhanced stars was found, although a one-to-one correspondence to "thin disk" and "thick disk" components cannot be supported with the present data.
- ID:
- ivo://CDS.VizieR/V/81
- Title:
- Taxonomy of Barium Stars
- Short Name:
- V/81
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Image-tube spectra and photometric observations for 389 bariums stars have been used to determine spectral classification, barium intensity, radial velocity, luminosity, and kinematical properties. The objective of this study is to obtain a homogeneous dataset for analyzing barium characteristics in uniform fashion.
- ID:
- ivo://CDS.VizieR/J/ApJ/743/141
- Title:
- T dwarf companions around M, L, T dwarfs in IR
- Short Name:
- J/ApJ/743/141
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report observational techniques, results, and Monte Carlo population analyses from a Spitzer Infrared Array Camera imaging survey for substellar companions to 117 nearby M, L, and T dwarf systems (median distance of 10pc, mass range of 0.6 to ~0.05M_{sun}_). The two-epoch survey achieves typical detection sensitivities to substellar companions of [4.5um]<=17.2mag for angular separations between about 7" and 165". Based on common proper motion analysis, we find no evidence for new substellar companions. Using Monte Carlo orbital simulations (assuming random inclination, random eccentricity, and random longitude of pericenter), we conclude that the observational sensitivities translate to an ability to detect 600-1100K brown dwarf companions at semimajor axes >~35AU and to detect 500-600 K companions at semimajor axes >~60AU. The simulations also estimate a 600-1100K T dwarf companion fraction of <3.4% for 35-1200AU separations and <12.4% for the 500-600K companions for 60-1000AU separations.
- ID:
- ivo://CDS.VizieR/J/MNRAS/433/457
- Title:
- 76 T dwarfs from the UKIDSS LAS
- Short Name:
- J/MNRAS/433/457
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of 76 new T dwarfs from the UKIRT Infrared Deep Sky Survey (UKIDSS) Large Area Survey (LAS). Near-infrared broad- and narrow-band photometry and spectroscopy are presented for the new objects, along with Wide-field Infrared Survey Explorer (WISE) and warm-Spitzer photometry. Proper motions for 128 UKIDSS T dwarfs are presented from a new two epoch LAS proper motion catalogue. We use these motions to identify two new benchmark systems: LHS 6176AB, a T8p+M4 pair and HD 118865AB, a T5.5+F8 pair. Using age constraints from the primaries and evolutionary models to constrain the radii, we have estimated their physical properties from their bolometric luminosity. We compare the colours and properties of known benchmark T dwarfs to the latest model atmospheres and draw two principal conclusions. First, it appears that the H-[4.5] and J-W2 colours are more sensitive to metallicity than has previously been recognized, such that differences in metallicity may dominate over differences in Teff when considering relative properties of cool objects using these colours. Secondly, the previously noted apparent dominance of young objects in the late-T dwarf sample is no longer apparent when using the new model grids and the expanded sample of late-T dwarfs and benchmarks. This is supported by the apparently similar distribution of late-T dwarfs and earlier type T dwarfs on reduced proper motion diagrams that we present. Finally, we present updated space densities for the late-T dwarfs, and compare our values to simulation predictions and those from WISE.
- ID:
- ivo://CDS.VizieR/J/AN/328/938
- Title:
- Teff/line-depth ratio for ELODIE spectra
- Short Name:
- J/AN/328/938
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The dependence on the temperature of photospheric line-depth ratios (LDRs) in the spectral range 619.0-628.0nm is investigated by using a sample of 174 ELODIE Archive stellar spectra of luminosity class from V to III. The rotational broadening effect on LDRs is also studied. We provide useful calibrations of effective temperature versus LDRs for giant and main sequence stars with 3800<~T_eff_<~6000K and vsini in the range 0-30km/s. We found that, with the exception of very few line pairs, LDRs, measured at a spectral resolution as high as 42000, depend on vsini and that, by neglecting the rotational broadening effect, the T_eff_ determination can be wrong by ~100K in the worst cases.
