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- ID:
- ivo://CDS.VizieR/J/A+A/530/A33
- Title:
- Evolutionary tracks to estimate DLA depletions
- Short Name:
- J/A+A/530/A33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Silicates are an important component of interstellar dust that has been poorly investigated in high redshift galaxies. As a preliminary step to studying silicates at high redshift, we survey silicon depletions in damped Ly{alpha} (DLA) systems. Silicon depletion is mild in the Galactic interstellar medium (ISM) and is expected to be weaker in most DLA systems, so we introduce a method for improving the accuracy of DLA depletion measurements.
- ID:
- ivo://CDS.VizieR/J/MNRAS/502/32
- Title:
- Evolutionary traits for stellar phylogenie
- Short Name:
- J/MNRAS/502/32
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Since chemical abundances are inherited between generations of stars, we use them to trace the evolutionary history of our Galaxy. We present a robust methodology for creating a phylogenetic tree, a biological tool used for centuries to study heritability. Combining our phylogeny with information on stellar ages and dynamical properties, we reconstruct the shared history of 78 stars in the Solar Neighbourhood. The branching pattern in our tree supports a scenario in which the thick disk is an ancestral population of the thin disk. The transition from thick to thin disk shows an anomaly, which we attribute to a star formation burst. Our tree shows a further signature of the variability in stars similar to the Sun, perhaps linked to a minor star formation enhancement creating our Solar System. In this paper, we demonstrate the immense potential of a phylogenetic perspective and interdisciplinary collaboration, where with borrowed techniques from biology we can study key processes that have contributed to the evolution of the Milky Way.
- ID:
- ivo://CDS.VizieR/J/A+A/361/1023
- Title:
- Evolution models for {alpha}-enhanced stars
- Short Name:
- J/A+A/361/1023
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present four large sets of evolutionary tracks for stars with initial chemical compositions [Y=0.250, Z=0.008], [Y=0.2773, Z=0.019], [Y=0.320, Z=0.040] and [Y=0.390, Z=0.070] and enhancement of {alpha} elements with respect to the solar pattern. The major improvement with respect to previous similar calculations is that we use consistent opacities - i.e. computed with the same chemical composition as adopted in the stellar models - over the whole relevant range of temperatures. For the same initial chemical compositions [Y, Z] and otherwise identical input physics we present also new evolutionary sequences with solar-scaled mixtures of abundances. Based on these stellar models we calculate the corresponding sets of isochrones both in the Johnson-Cousins UBVRIJHK and HST/WFPC2 photometric systems. Furthermore, we derive integrated magnitudes, colours and mass-to-light ratios for ideal single stellar populations with total mass equal to 1M_{sun}_ Finally, the major changes in the tracks, isochrones, and integrated magnitudes and colours passing from solar-scaled to {alpha}-enhanced mixtures are briefly outlined. Retrieval of the complete data set is possible via the www page http://pleiadi.pd.astro.it .
- ID:
- ivo://CDS.VizieR/J/A+A/501/687
- Title:
- Evolutionnary models for solar twins
- Short Name:
- J/A+A/501/687
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze the non-standard mixing history of the solar twins HIP 55459, HIP 79672, HIP 56948, HIP 73815, and HIP 100963, to determine as precisely as possible their mass and age. We computed a grid of evolutionary models with non-standard mixing at several metallicities with the Toulouse-Geneva code for a range of stellar masses assuming an error bar of +/-50K in Teff. We choose the evolutionary model that reproduces accurately the observed low lithium abundances observed in the solar twins. Our best-fit model for each solar twin provides a mass and age solution constrained by their Li content and Teff determination. HIP 56 948 is the most likely solar-twin candidate at the present time and our analysis infers a mass of 0.994+/-0.004M_{sun}_ and an age of 4.71+/-1.39Gyr. Non-standard mixing is required to explain the low Li abundances observed in solar twins. Li depletion due to additional mixing in solar twins is strongly mass dependent. An accurate lithium abundance measurement and non-standard models provide more precise information about the age and mass more robustly than determined by classical methods alone.
- ID:
- ivo://CDS.VizieR/J/ApJS/155/651
- Title:
- Evolution of extremely metal-poor stars
- Short Name:
- J/ApJS/155/651
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Intermediate-mass stellar evolution tracks from the main sequence to the tip of the AGB for five initial masses (2-6M_{sun}_) and metallicity Z=0.0001 have been computed. The detailed one-dimensional structure and evolution models include exponential overshooting, mass loss, and a detailed nucleosynthesis network with updated nuclear reaction rates. The network includes a two-particle heavy neutron sink for approximating neutron density in the He-shell flash. It is shown how the neutron-capture nucleosynthesis is important in models of very low metallicity for the formation of light neutron-heavy species, like sodium or the heavy neon and magnesium isotopes. The models have high resolution, as required for modeling the third dredge-up. All sequences have been followed from the pre-main sequence to the end of the AGB when all envelope mass is lost. Detailed structural and chemical model properties as well as yields are presented. This set of stellar models is based on standard assumptions and updated input physics. It can be confronted with observations of extremely metal-poor stars and may be used to assess the role of AGB stars in the origin of abundance anomalies of some globular cluster members of correspondingly low metallicity.
- ID:
- ivo://CDS.VizieR/J/A+A/578/A46
- Title:
- Evolution of galaxy clusters metal abundance
- Short Name:
- J/A+A/578/A46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the combined analysis of the metal content of 83 objects in the redshift range 0.09-1.39, and spatially-resolved in the 3 bins (0-0.15, 0.15-0.4, >0.4)R_500_, as obtained with similar analysis using XMM-Newton data in Leccardi & Molendi (2008A&A...487..461L) and Baldi et al. (2012A&A...537A.142B). By combining these two large datasets, we investigate the relations between abundance, temperature, radial position and redshift holding in the Intra-Cluster Medium. We fit functional forms to the combination of the different physical quantities of interest, i.e. ICM metal abundance, radius, and redshift. We use the pseudo-entropy ratio to separate the Cool-Core (CC) cluster population, where the central gas density tends to be relatively higher, cooler and more metal rich, from the Non-Cool-Core systems.
- ID:
- ivo://CDS.VizieR/J/A+A/654/A137
- Title:
- Evolution of Li in FGK dwarf stars
- Short Name:
- J/A+A/654/A137
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We investigate two topics regarding solar mass FGK-type stars, the lithium rotation connection (LRC) and the existence of the "lithium desert". We determine the minimum critical rotation velocity (vsini) related with the LRC separating slow from rapid stellar rotators, as being 5km/s. This value also split different stellar properties. For the first time we explore the behaviour of the LRC for some stellar associations with ages between 45Myr and 120Myr. This allows us to study the LRC age dependence at the beginning of the general spin down stage for low mass stars, which starts at ~30-40Myr. We find that each stellar group presents a characteristic minimum lithium (Li) depletion connected to a specific large rotation velocity and that this minimum changes with age. For instance, this minimum changes from ~50km/s to less than 20km/s in 200Myr. Regarding the lithium desert, it was described as a limited region in the A(Li)-Teff map containing no stars. Using Teff from Gaia DR2 we detect 30 stars inside and/or near the same box defined originally as the Li desert. Due to their intrinsic Teff errors some of these stars may be inside or outside the box, implying a large probability that the box contains several stars. Considering this last fact the "lithium desert" appears to be more a statistical distribution fluctuation than a real problem.
- ID:
- ivo://CDS.VizieR/J/A+A/573/A71
- Title:
- Evolution of rotating very massive LC stars
- Short Name:
- J/A+A/573/A71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- With growing evidence for the existence of very massive stars at subsolar metallicity, there is an increased need for corresponding stellar evolution models. We present a dense model grid with a tailored input chemical composition appropriate for the Large Magellanic Cloud (LMC).
- ID:
- ivo://CDS.VizieR/J/A+A/557/A70
- Title:
- Evolved planet hosts - stellar parameters
- Short Name:
- J/A+A/557/A70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- It is still being debated whether the well-known metallicity - giant planet correlation for dwarf stars is also valid for giant stars. For this reason, having precise metallicities is very important. Precise stellar parameters are also crucial to planetary research for several other reasons. Different methods can provide different results that lead to discrepancies in the analysis of planet hosts. To study the impact of different analyses on the metallicity scale for evolved stars, we compare different iron line lists to use in the atmospheric parameter derivation of evolved stars. Therefore, we use a sample of 71 evolved stars with planets. With these new homogeneous parameters, we revisit the metallicity - giant planet connection for evolved stars. A spectroscopic analysis based on Kurucz models in local thermodynamic equilibrium (LTE) was performed through the MOOG code to derive the atmospheric parameters. Two different iron line list sets were used, one built for cool FGK stars in general, and the other for giant FGK stars. Masses were calculated through isochrone fitting, using the Padova models. Kolmogorov-Smirnov tests (K-S tests) were then performed on the metallicity distributions of various different samples of evolved stars and red giants. All parameters compare well using a line list set, designed specifically for cool and solar-like stars to provide more accurate temperatures. All parameters derived with this line list set are preferred and are thus adopted for future analysis. We find that evolved planet hosts are more metal-poor than dwarf stars with giant planets. However, a bias in giant stellar samples that are searched for planets is present. Because of a colour cut-off, metal-rich low-gravity stars are left out of the samples, making it hard to compare dwarf stars with giant stars. Furthermore, no metallicity enhancement is found for red giants with planets (logg<3.0dex) with respect to red giants without planets.