- ID:
- ivo://CDS.VizieR/J/A+A/576/A69
- Title:
- Li abundances in F stars
- Short Name:
- J/A+A/576/A69
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We aim, on the one hand, to study the possible differences of Li abundances between planet hosts and stars without detected planets at effective temperatures hotter than the Sun, and on the other hand, to explore the Li dip and the evolution of Li at high metallicities. We present lithium abundances for 353 main sequence stars with and without planets in the T_eff_ range 5900-7200K. We observed 265 stars of our sample with HARPS spectrograph during different planets search programs. We observed the remaining targets with a variety of high-resolution spectrographs. The abundances are derived by a standard local thermodynamic equilibrium analysis using spectral synthesis with the code MOOG and a grid of Kurucz ATLAS9 atmospheres. We find that hot jupiter host stars within the T_eff_ range 5900-6300K show lower Li abundances, by 0.14dex, than stars without detected planets. This offset has a significance at the level 7{sigma}, pointing to a stronger effect of planet formation on Li abundances when the planets are more massive and migrate close to the star. However, we also find that the average vsini of (a fraction of) stars with hot jupiters is higher on average than for single stars in the same T_eff_ region, suggesting that rotational-induced mixing (and not the presence of planets) might be the cause for a greater depletion of Li. We confirm that the mass-metallicity dependence of the Li dip is extended towards [Fe/H]~0.4dex (beginning at [Fe/H]~-0.4dex for our stars) and that probably reflects the mass-metallicity correlation of stars of the same T_eff_ on the main sequence. We find that for the youngest stars (<1.5Gyr) around the Li dip, the depletion of Li increases with vsini values, as proposed by rotationally-induced depletion models. This suggests that the Li dip consists of fast rotators at young ages whereas the most Li-depleted old stars show lower rotation rates (probably caused by the spin-down during their long lifes). We have also explored the Li evolution with [Fe/H] taking advantage of the metal-rich stars included in our sample. We find that Li abundance reaches its maximum around solar metallicity, but decreases in the most metal-rich stars, as predicted by some models of Li Galactic production.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/159/90
- Title:
- Li, C and O abundances of FGK stars
- Short Name:
- J/AJ/159/90
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Abundances of lithium, carbon, and oxygen have been derived using spectral synthesis for a sample of 249 bright F, G, and K Northern Hemisphere dwarf stars from the high-resolution spectra acquired with the Vilnius University Echelle Spectrograph (VUES) at the Moletai Astronomical Observatory of Vilnius University. The sample stars have metallicities, effective temperatures, and ages between -0.7-0.4dex, 5000-6900K, 1-12Gyr, accordingly. We confirm a so far unexplained lithium abundance decrease at supersolar metallicities --A(Li) in our sample stars, which drop by 0.7dex in the [Fe/H] range from +0.10 to +0.55dex. Furthermore, we identified stars with similar ages, atmospheric parameters, and rotational velocities, but with significantly different lithium abundances, which suggests that additional specific evolutionary factors should be taken into account while interpreting the stellar lithium content. Nine stars with predominantly supersolar metallicities, i.e., about 12% among 78 stars with C and O abundances determined, have the C/O number ratios larger than 0.65, thus may form carbon-rich rocky planets. Ten planet-hosting stars, available in our sample, do not show a discernible difference from the stars with no planets detected regarding their lithium content.
- ID:
- ivo://CDS.VizieR/J/ApJ/701/764
- Title:
- Light curves for five M-dwarf stars
- Short Name:
- J/ApJ/701/764
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have derived masses and radii for both components in five short-period single-lined eclipsing binary stars discovered by the TrES wide-angle photometric survey for transiting planets. All these systems consist of a visible F-star primary and an unseen M-star secondary (M_A_>=0.8M_{sun}_, M_B_<=0.45M_{sun}_). The spectroscopic orbital solution combined with a high-precision transit light curve for each system gives sufficient information to calculate the density of the primary star and the surface gravity of the secondary. The masses of the primary stars were obtained using stellar evolution models, which requires accurate determinations of metallicities and effective temperatures.
- ID:
- ivo://CDS.VizieR/J/A+A/614/A55
- Title:
- Lithium abundance in dwarfs & subgiants
- Short Name:
- J/A+A/614/A55
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We address the existence and origin of the lithium (Li) desert, a region in the Li-Teff plane sparsely populated by stars. Here we analyze some of the explanations that have been suggested for this region, including mixing in the late main sequence, a Li dip origin for stars with low Li abundances in the region, and a possible relation with the presence of planets. To study the Li desert, we measured the atmospheric parameters and Li abundance of 227 late-F dwarfs and subgiants, chosen to be in the Teff range of the desert and without previous Li abundance measurements. Subsequently, we complemented those with literature data to obtain a homogeneous catalog of 2318 stars, for which we compute masses and ages. We characterize stars surrounding the region of the Li desert. We conclude that stars with low Li abundances below the desert are more massive and more evolved than stars above the desert. Given the unexpected presence of low Li abundance stars in this effective temperature range, we concentrate on finding their origin. We conclude that these stars with low Li abundance do not evolve from stars above the desert: at a given mass, stars with low Li (i.e., below the desert) are more metal-poor. Instead, we suggest that stars below the Li desert are consistent with having evolved from the Li dip, discarding the need to invoke additional mixing to explain this feature. Thus, stars below the Li desert are not peculiar and are only distinguished from other subgiants evolved from the Li dip in that their combination of atmospheric parameters locates them in a range of effective temperatures where otherwise only high Li abundance stars would be found (i.e., stars above the desert).
- ID:
- ivo://CDS.VizieR/J/AJ/156/27
- Title:
- Masses & radii of 4 VLM stars in EB systems
- Short Name:
- J/AJ/156/27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Eclipsing binaries (EBs) with one of the companions as very low-mass stars (VLMSs; or M dwarfs) are testbeds to substantiate stellar models and evolutionary theories. Here we present four EB candidates with F-type primaries, namely, SAO 106989, HD 24465, EPIC 211682657, and HD 205403, identified from different photometry missions, SuperWASP, Kilodegree Extremely Little Telescope (KELT), Kepler 2 (K2), and Solar Terrestrial Relations Observatory (STEREO). Using the high-resolution spectrograph PRL Advanced Radial velocity Abu-sky Search at the 1.2 m telescope at Mount Abu, Rajasthan, India, we hereby report the detection of four VLMSs as companions to the four EBs. We performed spectroscopic analysis and found the companion masses to be 0.256+/-0.005, 0.233+/-0.002, 0.599+/-0.017, and 0.406+/-0.005 M_{sun}_ for SAO 106989, HD 24465, EPIC 211682657, and SAO 106989B, respectively. We determined orbital periods of 4.39790+/-0.00001, 7.19635+/-0.00002, 3.142023+/-0.000003, and 2.444949+/-0.000001 days and eccentricities of 0.248+/-0.005, 0.208+/-0.002, 0.0097+/- 0.0008, and 0.002+/-0.002 for EBs SAO 106989, HD 24465, EPIC 211682657, and HD 205403, respectively. The radii derived by modeling the photometry data are 0.326+/-0.012 R_{sun}_ for SAO 106989, 0.244+/-0.001 R_{sun}_ for HD 24465B, 0.566+/-0.005 R_{sun}_ for EPIC 211682657B, and 0.444+/-0.014 R_{sun}_ for HD 205403B. The radii of HD 24465B and EPIC 211682657B have been measured by precise Kepler photometry and are consistent with theory within the error bars. However, the radii of SAO 106989B and HD 205403B, measured by KELT and STEREO photometry, are 17%-20% higher than those predicted by theory. A brief comparison of the results of the current work is made with the M dwarfs already studied in the literature.
- ID:
- ivo://CDS.VizieR/J/MNRAS/445/2223
- Title:
- Mass estimation for FGK stars
- Short Name:
- J/MNRAS/445/2223
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stellar evolutionary models simulate well binary stars when individual stellar mass and system metallicity are known. The mass can be derived directly from observations only in the case of multiple stellar systems, mainly binaries. Yet, the number of such stars for which accurate stellar masses are available is rather small. The main goal of this project is to provide realistic mass estimates for a homogeneous sample of about a thousand FGK single stars, using four different methods and techniques. We present the masses inferred according to each one of these methods as well as a final mass estimate consisting in the median of the four mass estimates. The procedures evaluated here include the use of stellar evolutionary models, mass-luminosity relation and surface gravity spectroscopic observations. By combining the results obtained with different methods, we determine the best mass value for each individual star, as well as the associated error budget. Our results confirm the expected consistency between the different mass estimation methods. None the less, for masses above 1.2M_{sun}_, the spectroscopic surface gravities seem to overestimate the mass. This result may be a consequence of the spectroscopic surface gravities used in this analysis. Nevertheless, this problem is minimized by the fact that we have several approaches available for deriving stellar masses. Moreover, we suggest an empirical procedure to overcome this issue.
- ID:
- ivo://CDS.VizieR/J/A+A/624/A10
- Title:
- Normalized Halpha line profiles of FGK stars
- Short Name:
- J/A+A/624/A10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The determination of stellar effective temperature (T_eff_) in F, G, and K stars using Halpha profile fitting is a quite remarkable and powerful tool because it does not depend on reddening and is only slightly sensitive to other atmospheric parameters. Nevertheless, this technique is not frequently used because of the complex procedure needed to recover the profile of broad lines in echelle spectra. As a consequence, tests performed on different models have sometimes provided ambiguous results. The main aim of this work is to test the ability of the Halpha profile fitting technique to derive T_eff. We also aim to improve the applicability of this technique to echelle spectra and to test how well 1D+LTE models perform on a variety of F-K stars. We also apply the technique to HARPS spectra and test the reliability and the stability of the HARPS response over several years using the Sun. We have developed a normalization method for recovering undistorted Halpha profiles and we have first applied it to spectra acquired with the single-order coude instrument (resolution R=45000) at do Pico dos Dias Observatory to avoid the problem of blaze correction. The continuum location around Halpha is optimised using an iterative procedure, where the identification of minute telluric features is performed. A set of spectra was acquired with the MUSICOS echelle spectrograph (R=40000) to independently validate the normalization method. The accuracy of the method and of the 1D+LTE model is determined using coude/HARPS/MUSICOS spectra of the Sun and coude-only spectra of a sample of ten Gaia Benchmark Stars with T_eff_ determined from interferometric measurements. HARPS, coude, and MUSICOS spectra are used to determine T_eff_ of 43 sample stars. We find that a proper choice of spectral windows of fits plus the identification of telluric features allow for a very careful normalization of the spectra and produce reliable H{alpha} profiles. We also find that the most used solar atlases cannot be used as templates for Halpha temperature diagnostics without renormalization. The comparison with the Sun shows that H{alpha} profiles from 1D+LTE models underestimate the solar T_eff_ by 28K. We find the same agreement between Halpha and interferometry and between Halpha and Infrared Flux Method: a shallow dependency on metallicity according to the relation T_eff_=T_eff_^Halpha^-159[Fe/H]+28K within the metallicity range -0.70 to +0.40dex. The comparison with the Infrared Flux Method shows a scatter of 59K dominated by photometric errors (52K). In order to investigate the origin of this dependency, we analysed spectra from 3D models and found that they produce hotter temperatures, and that their use largely improves the agreement with the interferometric and Infrared Flux Method measurements. Finally, we find HARPS spectra to be fully suitable for Halpha profile temperature diagnostics; they are perfectly compatible with the coude spectra, and lead to the same T_eff_ for the Sun as that found when analysing HARPS spectra over a timespan of more than 7 years.
- ID:
- ivo://CDS.VizieR/J/AJ/159/255
- Title:
- Observation & radial velocity of WASP-150 & WASP-176
- Short Name:
- J/AJ/159/255
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of two transiting exoplanets from the Wide Angle Search for Planets (WASP) survey, WASP-150b and WASP-176b. WASP-150b is an eccentric (e=0.38) hot Jupiter on a 5.6day orbit around a V=12.03, F8 main-sequence host. The host star has a mass and radius of 1.4M_{sun}_ and 1.7R_{sun}_ respectively. WASP-150b has a mass and radius of 8.5M_J_ and 1.1R_J_, leading to a large planetary bulk density of 6.4{rho}_J_. WASP-150b is found to be ~3Gyr old, well below its circularization timescale, supporting the eccentric nature of the planet. WASP-176b is a hot Jupiter planet on a 3.9day orbit around a V=12.01, F9 sub-giant host. The host star has a mass and radius of 1.3M{sun} and 1.9R{sun}. WASP-176b has a mass and radius of 0.86M_J_ and 1.5R_J_, respectively, leading to a planetary bulk density of 0.23{rho}_J_.
- ID:
- ivo://CDS.VizieR/J/AJ/160/235
- Title:
- Optical photometry and RVs of TOI-481b and TOI-892b
- Short Name:
- J/AJ/160/235
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the discovery of two new 10 day period giant planets from the Transiting Exoplanet Survey Satellite mission, whose masses were precisely determined using a wide diversity of ground-based facilities. TOI-481b and TOI-892b have similar radii (0.99{+/-}0.01R_Jup_ and 1.07{+/-}0.02R_Jup_, respectively), and orbital periods (10.3311days and 10.6266days, respectively), but significantly different masses (1.53{+/-}0.03M_Jup versus 0.95{+/-}0.07M_Jup_, respectively). Both planets orbit metal-rich stars ([Fe/H]=+0.26{+/-}0.05dex and [Fe/H]=+0.24{+/-}0.05 for TOI-481 and TOI-892, respectively) but at different evolutionary stages. TOI-481 is a M_*_=1.14{+/-}0.02M_{odot}_, R_*_=1.66{+/-}0.02R_{odot}_ G-type star (Teff=5735{+/-}72K), that with an age of 6.7Gyr, is in the turn-off point of the main sequence. TOI-892 on the other hand, is a F-type dwarf star (Teff=6261{+/-}80K), which has a mass of M_*_=1.28{+/-}0.03M_{odot}_ and a radius of R_*_=1.39{+/-}0.02R_{odot}_. TOI-481b and TOI-892b join the scarcely populated region of transiting gas giants with orbital periods longer than 10days, which is important to constrain theories of the formation and structure of hot Jupiters.
- ID:
- ivo://CDS.VizieR/J/A+A/587/A51
- Title:
- Overlooked wide companions of nearby F stars
- Short Name:
- J/A+A/587/A51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We checked a sample of 545 F stars within 50pc for wide companions using existing near-infrared and optical sky surveys.
