- ID:
- ivo://CDS.VizieR/J/ApJ/629/1055
- Title:
- Evolution of close binary systems
- Short Name:
- J/ApJ/629/1055
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We collect data on the masses, radii, etc., of three classes of close binary stars: low-temperature contact binaries (LTCBs), near-contact binaries (NCBs), and detached close binaries (DCBs). We restrict ourselves to systems in which (1) both components are, at least arguably, near the main sequence, (2) the periods are less than a day, and (3) there is both spectroscopic and photometric analysis leading to reasonably reliable data. We discuss the possible evolutionary connections between these three classes, emphasizing the roles played by mass loss and angular momentum loss in rapidly rotating cool stars. We describe a new mechanism, differential rotation as observed in the Sun, which can explain the remarkable efficiency of heat transport in the outer envelopes of contact binaries.
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- 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/592/A111
- Title:
- Evolution of long-lived globular cluster stars
- Short Name:
- J/A+A/592/A111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Globular clusters host multiple populations of long-lived low-mass stars whose origin remains an open question. Several scenarios have been proposed to explain the associated photometric and spectroscopic peculiarities. They differ, for instance, in the maximum helium enrichment they predict for stars of the second population, which these stars can inherit at birth as the result of the internal pollution of the cluster by different types of stars of the first population. We present the distribution of helium-rich stars in present-day globular clusters as it is expected in the original framework of the fast-rotating massive stars scenario (FRMS) as first-population polluters. We focus on NGC 6752. We completed a grid of 330 stellar evolution models for globular cluster low-mass stars computed with different initial chemical compositions corresponding to the predictions of the original FRMS scenario for [Fe/H]=-1.75. Starting from the initial helium-sodium relation that allows reproducing the currently observed distribution of sodium in NGC 6752, we deduce the helium distribution expected in that cluster at ages equal to 9 and 13Gyr. We distinguish the stars that are moderately enriched in helium from those that are very helium-rich (initial helium mass fraction below and above 0.4, respectively), and compare the predictions of the FRMS framework with other scenarios for globular cluster enrichment.
- ID:
- ivo://CDS.VizieR/J/A+A/512/A10
- Title:
- Evolution of massive AGB stars. III.
- Short Name:
- J/A+A/512/A10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first simulations of the full evolution of super-AGB stars through the entire thermally pulsing AGB phase. We analyse their structural and evolutionary properties and determine the first SAGB yields. Stellar models of various initial masses and metallicities were computed using standard physical assumptions which prevents the third dredge-up. A postprocessing nucleosynthesis code was used to compute the SAGB yields, to quantify the effect of the third dredge-up (3DUP) and to assess the uncertainties associated with the treatment of convection. Owing to their massive oxygen-neon core, SAGB stars suffer weak thermal pulses, have very short interpulse periods and develop very high temperatures at the base of their convective envelope (up to 140x10^8^K), leading to very efficient hot bottom burning. SAGB stars are consequently heavy manufacturers of ^4^He, ^13^C, and ^14^N. They are also able to inject significant amounts of ^7^Li, ^17^O, ^25^Mg, and ^26,27^Al in the interstellar medium. The 3DUP mainly affects the CNO yields, especially in the lower metallicity models. Our post-processing simulations also indicate that changes in the temperature at the base of the convective envelope, which would result from a change in the efficiency of convective energy transport, have a dramatic impact on the yields and represent another major source of uncertainty.
- ID:
- ivo://CDS.VizieR/J/ApJ/611/452
- Title:
- Evolution of massive stars
- Short Name:
- J/ApJ/611/452
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed study of the evolution of massive stars of masses 15, 20, 25, and 30M_{Sun}_ assuming solar-like initial chemical composition. The stellar sequences were evolved through the advanced burning phases up to the end of core oxygen burning. We present a careful analysis of the physical characteristics of the stellar models. In particular, we investigate the effect of the still-unsettled reaction ^12^C({alpha},{gamma})^16^O on the advanced evolution by using recent compilations of this rate.
- ID:
- ivo://CDS.VizieR/J/ApJ/825/7
- Title:
- Evolution of ~6Ms CDF-S galaxies
- Short Name:
- J/ApJ/825/7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present measurements of the evolution of normal-galaxy X-ray emission from z~0-7 using local galaxies and galaxy samples in the ~6Ms Chandra Deep Field-South (CDF-S) survey. The majority of the CDF-S galaxies are observed at rest-frame energies above 2keV, where the emission is expected to be dominated by X-ray binary (XRB) populations; however, hot gas is expected to provide small contributions to the observed-frame <~1keV emission at z<~1. We show that a single scaling relation between X-ray luminosity (L_X_) and star-formation rate (SFR) literature, is insufficient for characterizing the average X-ray emission at all redshifts. We establish that scaling relations involving not only SFR, but also stellar mass (M_*_) and redshift, provide significantly improved characterizations of the average X-ray emission from normal galaxy populations at z~0-7. We further provide the first empirical constraints on the redshift evolution of X-ray emission from both low-mass XRB (LMXB) and high-mass XRB (HMXB) populations and their scalings with M_*_ and SFR, respectively.
- ID:
- ivo://CDS.VizieR/J/MNRAS/275/1102
- Title:
- Evolution of quasar luminosity function
- Short Name:
- J/MNRAS/275/1102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In an earlier paper (Hawkins & Veron, 1993MNRAS.260..202H) we presented quasar luminosity functions in three redshift bins, derived from a variability selected sample. Here we provide a major extension to this survey, with a view to improving statistics and completeness, and extending the redshift range. The luminosity functions for redshifts of less than 2.2 show a featureless power law of the form {phi}=10^{beta}(M-M_0_)^, with no sign of a 'break'. The quasar luminosity function is also derived by the redshift range 2.2<z<3.2, which again shows a featureless power law, but with a steeper slope. When the data are combined with a new sample of bright quasars, the quasar luminosity functions in all four redshift ranges are consistent with a single power law of index {beta}=0.63. Plots of quasar space density as a function of redshift in three luminosity bins are also presented and show strong evolution at low redshift but nearly constant space density beyond a redshift of 2.
- 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).