- ID:
- ivo://CDS.VizieR/J/ApJ/839/94
- Title:
- Abundances of solar twins from Keck/HIRES
- Short Name:
- J/ApJ/839/94
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The six planets of the Kepler-11 system are the archetypal example of a population of surprisingly low-density transiting planets revealed by the Kepler mission. We have determined the fundamental parameters and chemical composition of the Kepler-11 host star to unprecedented precision using an extremely high-quality spectrum from Keck-HIRES (R~67000, S/N per pixel ~260 at 600nm). Contrary to previously published results, our spectroscopic constraints indicate that Kepler-11 is a young main-sequence solar twin. The revised stellar parameters and new analysis raise the densities of the Kepler-11 planets by between 20% and 95% per planet, making them more typical of the emerging class of "puffy" close-in exoplanets. We obtain photospheric abundances of 22 elements and find that Kepler-11 has an abundance pattern similar to that of the Sun with a slightly higher overall metallicity. We additionally analyze the Kepler light curves using a photodynamical model and discuss the tension between spectroscopic and transit/TTV-based estimates of stellar density.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/423/122
- Title:
- Abundances of 93 solar-type Kepler targets
- Short Name:
- J/MNRAS/423/122
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed spectroscopic study of 93 solar-type stars that are targets of the NASA/Kepler mission and provide detailed chemical composition of each target. We find that the overall metallicity is well represented by Fe lines. Relative abundances of light elements (CNO) and {alpha} elements are generally higher for low-metallicity stars. Our spectroscopic analysis benefits from the accurately measured surface gravity from the asteroseismic analysis of the Kepler light curves. The accuracy on the log g parameter is better than 0.03dex and is held fixed in the analysis.
- ID:
- ivo://CDS.VizieR/J/A+A/640/A81
- Title:
- Abundances of 72 solar-type stars
- Short Name:
- J/A+A/640/A81
- Date:
- 29 Nov 2021 07:35:20
- Publisher:
- CDS
- Description:
- Previous high-precision studies of abundances of elements in solar twin stars are extended to a wider metallicity range to see how the trends of element ratios with stellar age depend on [Fe/H]. HARPS spectra with S/N>~600 at {lambda}~6000{AA} were analysed with MARCS model atmospheres to obtain 1D LTE abundances of C, O, Na, Mg, Al, Si, Ca, Ti, Cr, Fe, Ni, Sr, and Y in 72 solar-type stars including the binary star zeta Reticuli and ASTEC stellar models were used to determine stellar ages from effective temperatures, luminosities obtained via Gaia DR2 parallaxes, and heavy element abundances. The age-metallicity distribution appears to consist of the following two distinct populations: a sequence of old stars with a steep rise of [Fe/H] to ~+0.3 dex at an age of ~7Gyr and a younger sequence with [Fe/H] increasing from about -0.3dex to ~+0.2dex over the last 6Gyr. Furthermore, the trends of several abundance ratios, [O/Fe], [Na/Fe], [Ca/Fe], and [Ni/Fe], as a function of stellar age, split into two corresponding sequences. The [Y/Mg]-age relation, on the other hand, shows no offset between the two age sequences and has no significant dependence on [Fe/H], but the components of a visual binary star, {zeta} Reticuli, have a large and puzzling deviation. The split of the age-metallicity distribution into two sequences may be interpreted as evidence of two episodes of accretion of gas onto the Galactic disk with a quenching of star formation in between. Some of the [X/Fe]-age relations support this scenario but other relations are not so easy to explain, which calls for a deeper study of systematic errors in the derived abundances as a function of [Fe/H], in particular 3D non-LTE effects.
- ID:
- ivo://CDS.VizieR/J/A+A/327/587
- Title:
- Abundances of 9 solar-type stars
- Short Name:
- J/A+A/327/587
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Line identifications, measured equivalent widths and derived chemical abundances in 9 solar-type dwarf stars, which are identified by their Bright Star (HR, (Cat. <V/50>)) numbers.
- ID:
- ivo://CDS.VizieR/J/PAZh/37/781
- Title:
- Abundances of 7 southern-hemisphere Cepheids
- Short Name:
- J/PAZh/37/781
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- For seven faint southern Cepheids (WW Car, SX Car, UZ Car, UY Car, GX Car, HW Car, YZ Car), we have determined their atmospheric parameters and chemical composition for the first time based on ten high-resolution (R=50000) spectra taken with the 1.5-m Hexapod telescope at the Joint Observatory of the Northern Catholic University (Antofagasta, Chile) and the Ruhr University (Bochum, Germany). Six objects from the list demonstrate atmospheric parameters and chemical composition typical of Cepheids that have passed through the first dredge-up phase, while WW Car is probably an anomalous Cepheid. According to our preliminary estimates, it has an overabundance of CNO, a deficit of sodium and aluminium, and a slight deficit of magnesium, with iron and other elements being underabundant relative to the Sun.
- ID:
- ivo://CDS.VizieR/J/AZh/84/997
- Title:
- Abundances of Sr, Y, Zr, Ce and Ba
- Short Name:
- J/AZh/84/997
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Sr, Y, Zr, and Ce abundances are derived for the sample of 74 cool dwarfs and subgiants with the iron abundance [Fe/H] ranged between -2.43 and 0.25. The results are based on LTE (Y, Zr and Ce) and non-LTE (Sr) line formation and line profile analysis of high resolution (40000 and 60000) spectra that have a typical S/N of 50-200. The Zr/Y, Sr/Y, and Sr/Zr ratios in the halo stars form nearly a plateau over the wide metallicity range, -2.43<=[Fe/H]<=0.90, indicating a common origin of Sr, Y, and Zr at the epoch of the halo formation. We find a steep decline of [Zr/Y] in the thick disk stars with increasing Ba abundance. This suggests the reduction of the production rate of Zr compared to that for Y at the active phase of the thick disk formation. The halo and thick disk stars reveal an overabundance of Zr relative to barium that grows with decreasing Ba abundance. There is a clear correlation of the [Zr/Ba] and [Eu/Ba] abundance ratios. Our observational findings for the halo and thick disk do not support the Galaxy chemical evolution models available in the literature and require to improve their predictions. The thin disk stars reveal, on average, solar abundance ratios for (Y,Zr)/Fe, (Y,Zr)/Ba, and Zr/Y. We note a slight decline of Zr/Ba and Zr/Y in these stars with increasing Ba abundance. Our results favour a dominance of the asymptotic giant branch stars in the heavy element enrichment of the interstellar gas over the epoch of the thin disk existence, in agreement with the theory of the main s-process nucleosynthesis.
- ID:
- ivo://CDS.VizieR/J/A+A/530/A15
- Title:
- Abundances of 94 stars
- Short Name:
- J/A+A/530/A15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Abundances of Mn, Cu, Zn, Y, and Ba are determined for a sample of stars previously studied by Nissen & Schuster (2010, Cat. J/A+A/511/L10). Equivalent widths of atomic lines are measured from high resolution VLT/UVES and NOT/FIES spectra and used to derive abundance ratios from an LTE analysis based on MARCS model atmospheres. The analysis is made relative to two thick-disk stars, HD22879 and HD76932, such that very precise differential values are obtained.
- ID:
- ivo://CDS.VizieR/J/ApJ/720/1290
- Title:
- Abundances of stars hosting planets
- Short Name:
- J/ApJ/720/1290
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The metal content of planet-hosting stars is an important ingredient that may affect the formation and evolution of planetary systems. Accurate stellar abundances require the determinations of reliable physical parameters, namely, the effective temperature, surface gravity, microturbulent velocity, and metallicity. This work presents the homogeneous derivation of such parameters for a large sample of stars hosting planets (N=117), as well as a control sample of disk stars not known to harbor giant, closely orbiting planets (N=145). Stellar parameters and iron abundances are derived from an automated analysis technique developed for this work. As previously found in the literature, the results in this study indicate that the metallicity distribution of planet-hosting stars is more metal rich by ~0.15 dex when compared to the control sample stars. A segregation of the sample according to planet mass indicates that the metallicity distribution of stars hosting only Neptunian-mass planets (with no Jovian-mass planets) tends to be more metal poor in comparison with that obtained for stars hosting a closely orbiting Jovian planet. The significance of this difference in metallicity arises from a homogeneous analysis of samples of FGK dwarfs which do not include the cooler and more problematic M dwarfs.
- ID:
- ivo://CDS.VizieR/J/ApJ/889/27
- Title:
- Abundances of 11 stars in Carina II and III
- Short Name:
- J/ApJ/889/27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first detailed elemental abundances in the ultra-faint Magellanic satellite galaxies Carina II (Car II) and Carina III (CarIII). With high-resolution Magellan/MIKE spectroscopy, we determined the abundances of nine stars in Car II, including the first abundances of an RR Lyrae star in an ultra-faint dwarf galaxy (UFD), and two stars in Car III. The chemical abundances demonstrate that both systems are clearly galaxies and not globular clusters. The stars in these galaxies mostly display abundance trends matching those of other similarly faint dwarf galaxies: enhanced but declining [{alpha}/Fe] ratios, iron-peak elements matching the stellar halo, and unusually low neutron-capture element abundances. One star displays a low outlying [Sc/Fe]=-1.0. We detect a large Ba scatter in Car II, likely due to inhomogeneous enrichment by low-mass asymptotic giant branch star winds. The most striking abundance trend is for [Mg/Ca] in Car II, which decreases from +0.4 to -0.4 and indicates clear variation in the initial progenitor masses of enriching core-collapse supernovae. So far, the only UFDs displaying a similar [Mg/Ca] trend are likely satellites of the Large Magellanic Cloud. We find two stars with [Fe/H]<=-3.5 whose abundances likely trace the first generation of metal-free Population III stars and are well fit by Population III core-collapse supernova yields. An appendix describes our new abundance uncertainty analysis that propagates line-by-line stellar parameter uncertainties.
- ID:
- ivo://CDS.VizieR/J/A+A/489/923
- Title:
- Abundances of stars in lower main sequence
- Short Name:
- J/A+A/489/923
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The aim of this paper is to provide fundamental parameters and abundances with a high accuracy for a large sample of cool main sequence stars. This study is part of wider project, in which the metallicity distribution of the local thin disc is investigated from a complete sample of G and K dwarfs within 25pc. The stars were observed at high resolution and a high signal-to-noise ratio with the ELODIE echelle spectrograph. The Vsini were obtained with a calibration of the cross-correlation function. Effective temperatures were estimated by the line depth ratio method. Surface gravities (logg) were determined by two methods: parallaxes and ionization balance of iron. The Mg and Na abundances were derived using a non-LTE approximation. Abundances of other elements were obtained by measuring equivalent widths. Rotational velocities, atmospheric parameters Teff, logg, [Fe/H], Vt, and Li, O, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Co, Ni, and Zn abundances are provided for 131 stars. Among them, more than 30 stars are active stars with a fraction of BY Dra and RS CVn type stars for which spectral peculiarities were investigated. We find the mean abundances of the majority of elements in active and non-active stars to be similar, except for Li, and possibly for Zn and Co. The lithium is reliably detected in 54% of active stars but only in 20% of non -active stars. No correlation is found between Li abundances and rotational velocities. A possible anticorrelation of log A(Li) with the index of chromospheric activity GrandS is observed. Active and non active cool dwarfs show similar dependencies of most elemental ratios vs [Fe/H]. This allows us to use such abundance ratios to study the chemical and dynamical evolution of the Galaxy. Among active stars, no clear correlation has been found between different indicators of activity for our sample stars.
