- ID:
- ivo://CDS.VizieR/J/A+A/624/A137
- Title:
- Stellar models and isochrones
- Short Name:
- J/A+A/624/A137
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Grids of stellar models are useful tools to derive the properties of stellar clusters, in particular young clusters hosting massive stars, and to provide information on the star formation process in various mass ranges. Because of their short evolutionary timescale, massive stars end their life while their low-mass siblings are still on the pre-main sequence (pre-MS) phase. Thus the study of young clusters requires consistent consideration of all the phases of stellar evolution. But despite the large number of grids that are available in the literature, a grid accounting for the evolution from the pre-MS accretion phase to the post-MS phase in the whole stellar mass range is still lacking. We build a grid of stellar models at solar metallicity with masses from 0.8M_{sun}_ to 120M_{sun}_, including pre-MS phase with accretion. We use the GENEC code to run stellar models on this mass range. The accretion law is chosen to match the observations of pre-MS objects on the Hertzsprung-Russell diagram. We describe the evolutionary tracks and isochrones of our models. The grid is connected to previous MS and post-MS grids computed with the same numerical method and physical assumptions, which provides the widest grid in mass and age to date.
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- ID:
- ivo://CDS.VizieR/J/A+AS/96/269
- Title:
- Stellar Models from 0.8 to 120 Msolar
- Short Name:
- J/A+AS/96/269
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New grids of stellar evolutionary models covering the range of 0.8 to 120 solar masses have been computed for metallicites Z=0.020 and Z=0.001. The models use the new opacities by Rogers and Iglesias (1992ApJS...79..507R) and by Kurucz (1991) at low T. The consequent changes in the solar helium content, in the mixing length ratio and in the overshooting parameter are taken into account after careful calibrations. Important physical ingredients as the nuclear reaction rates and the neutrino loss rates have been updated. The ionization of the main heavy elements is calculated in details. Results of the models are given in a compact way at corresponding evolutionary stages in each model. In addition to the tables, we shortly present some general results on the tracks in the HR diagrams, the lifetimes in the H-, He-, C-burning phases, and on massive and WR stars.
- ID:
- ivo://CDS.VizieR/J/A+A/628/A29
- Title:
- Stellar models grids (Z=0.0134-0.00134) 0.8-35Msun
- Short Name:
- J/A+A/628/A29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The theoretical apsidal motion constants are key tools to investigate the stellar interiors in close eccentric binary systems. In addition, these constants and the moment of inertia are also important to investigate the tidal evolution of close binary stars as well as of exo-planetary systems. The aim of the paper is to present new evolutionary models, based on the MESA package, that include the internal structure constants (k_2_, k_3_, and k_4_), the radius of gyration, and the gravitational potential energy for configurations computed from the pre-main-sequence (PMS) up to the first ascent giant branch or beyond. The calculations are available for the three metallicities [Fe/H] = 0.00, -0.50, and -1.00, which take the recent investigations in less metallic environments into account. This new set of models replaces the old ones, published about 15 years ago, using the code GRANADA. Core overshooting was taken into account using the mass-f_ov_ relationship, which was derived semi-empirically for models more massive than 1.2M_{sun}_. The differential equations governing the apsidal motion constants, moment of inertia, and the gravitational potential energy were integrated simultaneously through a fifth-order Runge-Kutta method with a tolerance level of 10^-7^. The resulting models (from 0.8 up to 35.0M_{sun}_) are presented in 54 tables for the three metallicities, containing the usual characteristics of an evolutionary model (age, initial masses, logT_eff_, logg, and logL), the constants of internal structure (k_2_, k_3_, and k_4_), the radius of gyration {beta} and the factor {alpha} that is related with the gravitational potential energy.
- ID:
- ivo://CDS.VizieR/J/A+A/424/919
- Title:
- Stellar models grids. Z=0.02, M=0.8 to 125
- Short Name:
- J/A+A/424/919
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new stellar models based on updated physics (opacities, expanded nuclear network and mass loss rates). We compute stellar models suitable for the mean solar neighborhood, i.e. for Z=0.02 and X=0.70. The covered mass range is from 0.8 up to 125M_{sun}_ and the models are followed until the exhaustion of carbon in the core, for the more massive ones. In addition, the effective temperatures of the more massive models are corrected for the effects of stellar winds, while models with lower effective temperatures are computed using a special treatment of the equation of state (CEFF). Convective core overshooting is assumed to be moderate and is modelled with alpha_ov_=0.20. Besides the classical ingredients of stellar models, we also provide the internal structure constants needed to investigate apsidal motion and tidal evolution in close binaries. The latter constants are made public for the first time. According to the current theories of tidal evolution, the time scales for synchronization and circularization for cool stars depend -- apart from the mass, radius and effective temperature -- on the depth of the convective envelope x_bf_ and on the radius of gyration {beta}. For stars with higher effective temperatures, these dependencies are mainly incorporated in the tidal torque constant E_2_. All these parameters are steep functions of mass and time, and thus require a special numerical treatment. The new mass loss formalism produces more mass concentrated configurations than previously, especially for more massive and more evolved stellar models. As the present grid is designed mainly for the study of double-lined eclipsing binaries, the gravity-darkening exponents necessary to calculate the surface brightness distribution in rotationally and/or tidally distorted stars are computed following the method described recently by Claret (1998, Cat. <J/A+AS/133/123>), and made available for each point of every evolutionary track.
- ID:
- ivo://CDS.VizieR/J/A+A/605/A102
- Title:
- Stellar models. 0.85<M<6, Z=0.0001-0.014
- Short Name:
- J/A+A/605/A102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent spectropolarimetric observations of otherwise ordinary (in terms e.g. of surface rotation and chemical properties) G, K, and M giants have revealed localized magnetic strips in the Hertzsprung-Russell diagram coincident with the regions where the first dredge-up and core helium burning occur. We seek to understand the origin of magnetic fields in such late-type giant stars, which is currently unexplained. In analogy with late-type dwarf stars, we focus primarily on parameters known to influence the generation of magnetic fields in the outer convective envelope. We compute the classical dynamo parameters along the evolutionary tracks of low- and intermediate-mass stars at various metallicities using stellar models that have been extensively tested by spectroscopic and asteroseismic observations. Specifically, these include convective turnover timescales and convective Rossby numbers, computed from the pre-main sequence (PMS) to the tip of the red giant branch (RGB) or the early asymptotic giant branch (AGB) phase. To investigate the effects of the very extended outer convective envelope, we compute these parameters both for the entire convective envelope and locally, that is, at different depths within the envelope. We also compute the turnover timescales and corresponding Rossby numbers for the convective cores of intermediate-mass stars on the main sequence. Our models show that the Rossby number of the convective envelope becomes lower than unity in the well-delimited locations of the Hertzsprung-Russell diagram where magnetic fields have indeed been detected. We show that {alpha}-{Omega} dynamo processes might not be continuously operating, but that they are favored in the stellar convective envelope at two specific moments along the evolution tracks, that is, during the first dredge-up at the base of the RGB and during central helium burning in the helium-burning phase and early-AGB. This general behavior can explain the so-called magnetic strips recently discovered by dedicated spectropolarimetric surveys of evolved stars.
- ID:
- ivo://CDS.VizieR/VI/118
- Title:
- Stellar Models until He burning
- Short Name:
- VI/118
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Grids of stellar evolutionary models published in the 4 papers referenced below are merged here. OPAL opacities with LS coupling and Grevesse composition were adopted, and Alexander's tables were used for lower temperatures. The models adopt a core overshooting with {alpha}_ov_=0.20, and mixing length parameter l/H_p_=1.52 that seems to represent well double-lined eclipsing binary stars. Mass loss during the main sequence and in the red giant phase were taken into account. The nuclear network treats 14 isotopes and optionally the lithium burning to study its depletion in less massive models during pre main sequence evolution. The initial parameters of the models are summarized in the file "grids.dat", with metal contents of Z=0.02 (solar), 0.01, 0.03 and 0.004 (Magellanic Clouds), with a wide range of initial hydrogen content around the solar composition. The mass range covered goes from 1 (0.6 for the solar composition) up to 40M_{sun}_ and the more massive models were followed until helium burning.
- ID:
- ivo://CDS.VizieR/J/A+AS/114/549
- Title:
- Stellar models until He burning - II.
- Short Name:
- J/A+AS/114/549
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Three new grids of stellar evolutionary models with Z=0.01 are presented for the following values of initial hydrogen content X_i_=0.80, 0.73 and 0.63. The latest set of radiative opacities with spin-orbit coupling provided by the Lawrence Livermore group are used. For the lower temperatures the results by Alexander were considered. The models were computed taking into account core overshooting and mass loss. The grids cover the mass range between 1 and 40M_{sun}_. The internal structure constants (k_j_,j=2, 3,4) and the moment of inertia are also computed. These parameters are needed to investigate apsidal motions and tidal interactions in double-lined eclipsing binaries. This paper is part of a project which aims to provide grids of stellar models for a wide range of metal and hydrogen content.
158. Stellar models VI.
- ID:
- ivo://CDS.VizieR/J/A+AS/115/339
- Title:
- Stellar models VI.
- Short Name:
- J/A+AS/115/339
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New grids of models covering the evolution of low mass stars (0.8 to 1.7M{sun}) with metallicities Z=0.020 and 0.001 from the zero age main sequence up to the end of the early asymptotic giant branch are presented. The evolutionary tracks have been calculated with the new OPAL radiative opacities by Iglesias & Rogers (1992ApJ...397..717I) and Kurucz (1991). They complete the base of extensive grids of stellar models computed by the Geneva Group with up-to-date input physics (Schaller et al. 1992, Cat. J/A+AS/115/339; Schaerer et al. 1992, Cat. J/A+AS/98/523; Charbonnel et al. 1993, Cat. J/A+AS/101/415; Schaerer et al. 1993, Cat. J/A+AS/102/339; Meynet et al. 1994, Cat. J/A+AS/103/97).
- ID:
- ivo://CDS.VizieR/J/A+A/627/A24
- Title:
- Stellar models with rotation. 1.7<M<120, Z=0.0004
- Short Name:
- J/A+A/627/A24
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The effects of rotation on stellar evolution are particularly important at low metallicity, when mass loss by stellar winds diminishes and the surface enrichment due to rotational mixing becomes relatively more pronounced than at high metallicities. Here we investigate the impact of rotation and metallicity on stellar evolution. Using a similar physics as in our previous large grids of models at Z=0.002 and Z=0.014, we compute stellar evolution models with the Geneva code for rotating and non-rotating stars with initial masses (Mini) between 1.7 and 120M_{sun}_ and Z=0.0004 (1/35 solar). This is comparable to the metallicities of the most metal poor galaxies observed so far, such as I Zw 18. Concerning massive stars, both rotating and non-rotating models spend most of their core-helium burning phase with an effective temperature higher than 8000K. Stars become red supergiants only at the end of their lifetimes, and few RSGs are expected. Our models predict very few to no classical Wolf-Rayet stars as a results of weak stellar winds at low metallicity. The most massive stars end their lifetimes as luminous blue supergiants or luminous blue variables, a feature that is not predicted by models with higher metallicities. Interestingly, due to the behavior of the intermediate convective zone, the mass domain of stars producing pair-instability supernovae is smaller at Z=0.0004 than at Z=0.002. We find that during the main sequence phase, the ratio between nitrogen and carbon abundances (N/C) remains unchanged for non-rotating models. However, N/C increases by factors of 10-20 in rotating models at the end of the MS. Cepheids coming from stars with Mini>4-6M_{sun}_ are beyond the core helium burning phase and spend little time in the instability strip. Since they would evolve towards cooler effective temperatures, these Cepheids should show an increase of the pulsation period as a function of age.
- ID:
- ivo://CDS.VizieR/J/A+A/558/A103
- Title:
- Stellar models with rotation. 0.8<M<120, Z=0.002
- Short Name:
- J/A+A/558/A103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the impact of a subsolar metallicity on various properties of non-rotating and rotating stars, such as surface velocities and abundances, lifetimes, evolutionary tracks, and evolutionary scenarios. We provide a grid of single star models covering a mass range of 0.8 to 120M_{sun_} with an initial metallicity Z=0.002 with and without rotation. We discuss the impact of a change in the metallicity by comparing the current tracks with models computed with exactly the same physical ingredients but with a metallicity Z=0.014 (solar). We show that the width of the main-sequence (MS) band in the upper part of the Hertzsprung-Russell diagram (HRD), for luminosity above log(L/L_{sun}_)>5.5, is very sensitive to rotational mixing. Strong mixing significantly reduces the MS width. Here for the first time over the whole mass range, we confirm that surface enrichments are stronger at low metallicity provided that comparisons are made for equivalent initial mass, rotation, and evolutionary stage. We show that the enhancement factor due to a lowering of the metallicity (all other factors kept constant) increases when the initial mass decreases. Present models predict an upper luminosity for the red supergiants (RSG) of log (L/L_{sun}_) around 5.5 at Z=0.002 in agreement with the observed upper limit of RSG in the Small Magellanic Cloud. We show that models using shear diffusion coefficient, which is calibrated to reproduce the surface enrichments observed for MS B-type stars at Z=0.014, can also reproduce the stronger enrichments observed at low metallicity. In the framework of the present models, we discuss the factors governing the timescale of the first crossing of the Hertzsprung gap after the MS phase. We show that any process favouring a deep localisation of the H-burning shell (steep gradient at the border of the H-burning convective core, low CNO content), and/or the low opacity of the H-rich envelope favour a blue position in the HRD for the whole, or at least a significant fraction, of the core He-burning phase.
