- 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.
Number of results to display per page
Search Results
- 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.
18013. 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.
- ID:
- ivo://CDS.VizieR/J/A+A/537/A146
- Title:
- Stellar models with rotation. 0.8<M<120, Z=0.014
- Short Name:
- J/A+A/537/A146
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Many topical astrophysical research areas, such as the properties of planet host stars, the nature of the progenitors of different types of supernovae and gamma ray bursts, and the evolution of galaxies, require complete and homogeneous sets of stellar models at different metallicities in order to be studied during the whole of cosmic history. We present here a first set of models for solar metallicity, where the effects of rotation are accounted for in a homogeneous way. We computed a grid of 48 different stellar evolutionary tracks, both rotating and non-rotating, at Z=0.014, spanning a wide mass range from 0.8 to 120M_{sun}_. For each of the stellar masses considered, electronic tables provide data for 400 stages along the evolutionary track and at each stage, a set of 43 physical data are given. These grids thus provide an extensive and detailed data basis for comparisons with the observations. The rotating models start on the ZAMS with a rotation rate v_ini_/v_crit_=0.4. The evolution is computed until the end of the central carbon-burning phase, the early AGB phase, or the core helium-flash for, respectively, the massive, intermediate, and both low and very low mass stars. The initial abundances are those deduced by Asplund et collaborators, which best fit the observed abundances of massive stars in the solar neighbourhood. We update both the opacities and nuclear reaction rates, and introduce new prescriptions for the mass-loss rates as stars approach the Eddington and/or the critical velocity. We account for both atomic diffusion and magnetic braking in our low-mass star models. The present rotating models provide a good description of the average evolution of non-interacting stars. In particular, they reproduce the observed MS width, the positions of the red giant and supergiant stars in the HR diagram, the observed surface compositions and rotational velocities. Very interestingly, the enhancement of the mass loss during the RSG stage, when the luminosity becomes supra-Eddington in some outer layers, help models above 15-20 Msun to lose a significant part of their hydrogen envelope and evolve back into the blue part of the HR diagram. This result has interesting consequences for the blue to red supergiant ratio, the minimum mass for stars to become WR stars, and the maximum initial mass of stars that explode as type II-P supernovae.
- ID:
- ivo://CDS.VizieR/J/MNRAS/449/3160
- Title:
- Stellar multiplicity and debris discs
- Short Name:
- J/MNRAS/449/3160
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Circumstellar dust discs have been observed around many nearby stars. However, many stars are part of binary or multiple stellar systems. A natural question arises regarding the presence and properties of such discs in systems with more than one star. To address this, we consider a sample of 449 systems (spectral types A-M) observed with the Herschel Space Observatory as part of the DEBRIS (Disc Emission via a Bias-free Reconnaissance in the Infrared/Submillimetre) programme. We have examined the stellar multiplicity of this sample by gathering information from the literature and performing an adaptive optics imaging survey at Lick Observatory. Five new companions were revealed with our programme. In total, we identify 188 (42 per cent) binary or multiple star systems. The multiplicity of the sample is examined with regards to the detection of circumstellar discs for stars of spectral types AFGK. In general, discs are less commonly detected around binaries than single stars, though the disc frequency is comparable among A stars regardless of multiplicity. However, this sample reveals the period distribution of disc-bearing binaries is consistent with that of non-disc binaries and with comparison field samples. We find that the properties of discs in binary systems are not statistically different from those around single stars. Although the frequency of disc-bearing FGK binaries may be lower than in single star systems, the processes behind disc formation and the characteristics of these discs are comparable among both populations.
- ID:
- ivo://CDS.VizieR/J/A+A/580/A88
- Title:
- Stellar multiplicity in 3-1000AU
- Short Name:
- J/A+A/580/A88
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Young loose nearby associations are unique samples of close (<150pc), young (~5-100Myr) pre-main sequence (PMS) stars. A significant number of members of these associations have been identified in the SACY collaboration. We can use the proximity and youth of these members to investigate key ingredients in star formation processes, such as multiplicity. We present the statistics of identified multiple systems from 113 confirmed SACY members. We derive multiplicity frequencies, mass-ratio, and physical separation distributions in a consistent parameter space, and compare our results to other PMS populations and the field. We have obtained adaptive-optics assisted near-infrared observations with NACO (ESO/VLT) and IRCAL (Lick Observatory) for at least one epoch of all 113 SACY members. We have identified multiple systems using co-moving proper-motion analysis and using contamination estimates. We have explored ranges in projected separation and mass-ratio of a [3-1000AU], and q [0.1-1], respectively. We have identified 31 multiple systems (28 binaries and 3 triples). We derive a multiplicity frequency (MF) of MF_3-1000AU_=28.4^+4.7^_-3.9_% and a triple frequency (TF) of TF_3-1000AU_=2.8^+2.5^_-0.8_% in the separation range of 3-1000AU. We do not find any evidence for an increase in the MF with primary mass. The estimated mass-ratio of our statistical sample (with power-law index {gamma}=-0.04+/-0.14) is consistent with a flat distribution ({gamma}=0).
- ID:
- ivo://CDS.VizieR/J/AJ/157/216
- Title:
- Stellar multiplicity rate of M dwarfs within 25 pc
- Short Name:
- J/AJ/157/216
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of the largest, most comprehensive study ever done of the stellar multiplicity of the most common stars in the Galaxy, the red dwarfs. We have conducted an all-sky volume-limited survey for stellar companions to 1120 M dwarf primaries known to lie within 25 pc of the Sun via trigonometric parallaxes. In addition to a comprehensive literature search, stars were explored in new surveys for companions at separations of 2"-300". A reconnaissance of wide companions to separations of 300" was done via blinking archival images. I-band images were used to search our sample for companions at separations of 2"-180". Various astrometric and photometric methods were used to probe the inner 2" to reveal close companions. We report the discovery of 20 new companions and identify 56 candidate multiple systems. We find a stellar multiplicity rate of 26.8+/-1.4% and a stellar companion rate of 32.4+/-1.4% for M dwarfs. There is a broad peak in the separation distribution of the companions at 4-20 au, with a weak trend of smaller projected linear separations for lower mass primaries. A hint that M-dwarf multiplicity may be a function of tangential velocity is found, with faster moving, presumably older, stars found to be multiple somewhat less often. We calculate that stellar companions make up at least 17% of mass attributed to M dwarfs in the solar neighborhood, with roughly 11% of M-dwarf mass hidden as unresolved companions. Finally, when considering all M-dwarf primaries and companions, we find that the mass distribution for M dwarfs increases to the end of the stellar main sequence.
- ID:
- ivo://CDS.VizieR/J/AJ/150/133
- Title:
- Stellar noise for 4529 Kepler solar-type dwarfs
- Short Name:
- J/AJ/150/133
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- An earlier study of the Kepler Mission noise properties on timescales of primary relevance to detection of exoplanet transits found that higher than expected noise followed, to a large extent, from the stars rather than instrument or data analysis performance. The earlier study over the first six quarters of Kepler data is extended to the full four years ultimately comprising the mission. Efforts to improve the pipeline data analysis have been successful in reducing noise levels modestly as evidenced by smaller values derived from the current data products. The new analyses of noise properties on transit timescales show significant changes in the component attributed to instrument and data analysis, with essentially no change in the inferred stellar noise. We also extend the analyses to timescales of several days, instead of several hours to better sample stellar noise that follows from magnetic activity. On the longer timescale there is a shift in stellar noise for solar-type stars to smaller values in comparison to solar values.