- ID:
- ivo://CDS.VizieR/J/A+A/453/769
- Title:
- New grids of stellar models. III.
- Short Name:
- J/A+A/453/769
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we present new specific stellar models for the Large Magellanic Cloud. In order to take the observational uncertainties in the chemical composition into account, we have computed two grids: (X, Z) = (0.730, 0.010) and (0.739, 0.007). The covered mass range was 0.80 up to 125M_{sun}. The effects of rotation can be investigated by using the gravity-darkening exponents that are available for each track. The tidal constant E_2_, depth of the convective outer zone, and the radius of gyration are computed and presented in a suitable format for studying the tidal evolution of a given close binary. The isochrones (and also those corresponding to the previous grids) will be presented in a future paper.
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- ID:
- ivo://CDS.VizieR/J/A+A/467/1389
- Title:
- New grids of stellar models. IV.
- Short Name:
- J/A+A/467/1389
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The aim of the present grid of stellar models is to complete our previous calculations and provide a tool for investigating the astrophysical properties of eclipsing binaries, stellar clusters, galactic bulges, and elliptical galaxies with a high metal content. To explore the applicability of high metallic models, we have computed three grids: (X, Z)=(0.64, 0.04), (0.58, 0.06), and (0.46, 0.10). For all these grids, we adopted an enrichment law {Delta}Y/{Delta}Z=2.0, as in our previous papers on this subject. The input physics is almost the same as adopted in our earlier work except for some numerical details, recent measurement of the rate for the reaction ^14^N(p,gamma)^15^O, and the recent mass-loss rate for the Wolf-Rayet stages. Two high-metallicity clusters, NGC 6253 and NGC 6791, were used to test the present calculations with very satisfactory results. On the other hand, as this series of grids was mainly designed to investigate the tidal evolution of close binaries, we analyse the present status of circularization times in both clusters and isolated binaries.
- ID:
- ivo://CDS.VizieR/J/A+A/618/A133
- Title:
- Non standard s-process in massive rotating stars
- Short Name:
- J/A+A/618/A133
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent studies show that rotation significantly affects the s-process in massive stars. We provide tables of yields for non-rotating and rotating massive stars between 10 and 150M_{sun}_ at Z=10^-3^([Fe/H]=-1.8). Tables for different mass cuts are provided. The complete s-process is followed during the whole evolution with a network of 737 isotopes, from Hydrogen to Polonium. A grid of stellar models with initial masses of 10, 15, 20, 25, 40, 60, 85, 120 and 150M_{sun}_ and with an initial rotation rate of both 0 or 40% of the critical velocity was computed. Three extra models were computed in order to investigate the effect of faster rotation (70% of the critical velocity) and of a lower ^17^O({alpha},{gamma}) reaction rate. At the considered metallicity, rotation has a strong impact on the production of s-elements for initial masses between 20 and 60M_{sun}_. In this range, the first s-process peak is boosted by 2-3dex if rotation is included. Above 60M_{sun}_, s-element yields of rotating and non-rotating models are similar. Increasing the initial rotation from 40% to 70% of the critical velocity enhances the production of 40<~Z<~60 elements by ~0.5-1dex. Adopting a reasonably lower ^17^O({alpha},{gamma}) rate in the fast rotating model (70% of the critical velocity) boosts again the yields of s-elements with 55<~Z<~82 by about 1dex. In particular, a modest amount of Pb is produced. Together with s-elements, some light elements (particularly fluorine) are strongly overproduced in rotating models.
- ID:
- ivo://CDS.VizieR/J/ApJ/868/30
- Title:
- OGLE LMC-T2CEP-211 eclipsing binary LCs and RVs
- Short Name:
- J/ApJ/868/30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the analysis of a peculiar W Virginis (pWVir) type II Cepheid, OGLE-LMC-T2CEP-211 (P_puls_=9.393d), in a double-lined binary system (P_orb_=242d), which shed light on virtually unknown evolutionary status and structure of pWVir stars. The dynamical mass of the Cepheid (first ever for a type II Cepheid) is 0.64+/-0.02M_{sun}_, and the radius R=25.1+/-0.3R_{sun}_. The companion is a massive (5.67M_{sun}_) main-sequence star obscured by a disk. Such a configuration suggests a mass transfer in the system history. We found that originally the system (P_orb_^init^=12d) was composed of 3.5 and 2.8M_{sun}_ stars, with the current Cepheid being more massive. The system age is now ~200Myr, and the Cepheid is almost completely stripped of hydrogen, with helium mass of ~92% of the total mass. It finished transferring the mass 2.5Myr ago and is evolving toward lower temperatures passing through the instability strip. Comparison with observations indicates a reasonable 2.7x10^-8^M_{sun}_/yr mass loss from the Cepheid. The companion is most probably a Be main-sequence star with T=22000K and R=2.5R_{sun}_. Our results yield a good agreement with a pulsation theory model for a hydrogen-deficient pulsator, confirming the described evolutionary scenario. We detected a two-ring disk (R_disk_~116R_{sun}_) and a shell (R_shell_~9R_{sun}_) around the companion, which is probably a combination of the matter from the past mass transfer, the mass being lost by the Cepheid owing to wind and pulsations, and a decretion disk around a rapidly rotating secondary. Our study, together with observational properties of pWVir stars, suggests that the majority of them are products of a similar binary evolution interaction.
- ID:
- ivo://CDS.VizieR/J/ApJS/113/121
- Title:
- Optically thick winds from degenerate dwarfs. I.
- Short Name:
- J/ApJS/113/121
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Twenty-six sequences of optically thick wind solutions have been calculated which mimic the time-dependent evolution of classical novae of populations I and II. The peak of the new opacity around log T=5.2 due to iron lines is found to be strong enough to accelerate the winds even in very low iron abundance such as Z=0.001 for massive white dwarfs (>=0.8M_{sun}_). The old population novae show the slow light curve, the long X-ray turn-off time, the small expansion velocity and the small wind mass-loss rate. The X-ray turn-off time is a good indicator of the white dwarf mass because of its strong dependence on the white dwarf mass and weak dependence on the populations. The white dwarf mass is estimated to be ~0.6M_{sun}_ for GQ Mus and ~1.0M_{sun}_ for V1974 Cyg. The systematic difference of the wind velocity is predicted between novae in globular clusters and in galactic disk. Twenty-six tables are presented in the computer readable form of CD-ROM that consists of solutions of the optically thick wind and the static for the decay phase of classical novae with composition of X=0.35, C=0.1 and O=0.2 and heavy elements content Z=0.001, 0.004, 0.02, 0.05 and 0.1 for the white dwarf masses of 0.4, 0.6, 0.7, 0.8, 0.9, 1.0, 1.2 and 1.35M_{sun}_. These tables list the characteristic values of the envelope such as the photospheric temperature, the velocity, the wind mass-loss rate and fluxes of four wavelength bands. The updated OPAL opacity (Iglesias & Rogers, 1996ApJ...464..943I) is used.
- ID:
- ivo://CDS.VizieR/J/A+A/546/A119
- Title:
- Outer boundary conditions for evolving cool WD
- Short Name:
- J/A+A/546/A119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- White dwarf evolution is essentially a gravothermal cooling process, which, for cool white dwarfs, depends on the treatment of the outer boundary conditions. We provide detailed outer boundary conditions that are appropriate to computing the evolution of cool white dwarfs by employing detailed nongray model atmospheres for pure hydrogen composition. We also explore the impact on the white dwarf cooling times of different assumptions for energy transfer in the atmosphere of cool white dwarfs.
- ID:
- ivo://CDS.VizieR/J/AJ/116/1998
- Title:
- Outer planetary systems
- Short Name:
- J/AJ/116/1998
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In order to better understand the range of dynamically long-lived giant planet systems, we present the results of a set of bottom-up numerical simulations designed to generate plausible giant planet systems from a large number of planetary embryos. Our simulations produced systems that are stable for at least a billion years and that exhibit a wide range of characteristics. Some of these systems are reminiscent of the outer solar system. The number of planets ranged from one to seven. Many systems contained only Uranus-mass objects. We constructed systems that were more compact than the outer solar system and systems that were much sparser, with planets on very eccentric orbits. Perhaps most surprisingly, some of the systems that we constructed were stable for at least a billion years despite undergoing macroscopic orbital changes on much shorter timescales.
- ID:
- ivo://CDS.VizieR/J/A+A/524/A45
- Title:
- Overproduction factors of s-nuclei in massive stars
- Short Name:
- J/A+A/524/A45
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the "post-processing" technique, we explore the role of the convective overshooting on the production of s-nuclei in stellar models of different initial mass and metallicity (M_ZAMS_ in the range 15-25M_{sun}_ Z in the range 10^-4^-0.02), considering a range of values for the parameter f, which determines the overall efficiency of convective overshooting. We find enhancements in the production of s-nuclei until a factor ~6 (measured as the average overproduction factor of the 6 s-only nuclear species with 60<A<90) in all our models of different initial mass and metallicity having f in the range 0.01-0.035 (i.e. models with overshooting), compared to the production obtained with "no-overshooting" models (i.e. models having the same initial mass and metallicity but f=10^-5^). Moreover the results indicate that the link between the overshooting parameter f and the s-process efficiency is essentially monotonic in all our models of different initial mass and metallicity. Also evident is the higher s-process efficiency when, for a given f value, we progressively increase both the mass of the models from 15 to 25M_{sun}_ and the Z value from 10^-4^ to 0.02.
- ID:
- ivo://CDS.VizieR/J/A+A/574/A17
- Title:
- Period spacings in gamma Dor stars
- Short Name:
- J/A+A/574/A17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The analysis of stellar oscillations is one of the most reliable ways to probe stellar interiors. Recent space missions such as Kepler have provided us with an opportunity to study these oscillations with unprecedented detail. For many multi-periodic pulsators such as gamma Doradus stars, this led to the detection of dozens to hundreds of oscillation frequencies that could not be found from ground-based observations. We aim to detect non-uniform period spacings in the Fourier spectra of a sample of gamma Doradus stars observed by Kepler. Such detection is complicated by both the large number of significant frequencies in the space photometry and by overlapping non-equidistant rotationally split multiplets. Guided by theoretical properties of gravity-mode oscillation of gamma Doradus stars, we developed a period-spacing detection method and applied it to Kepler observations of a few stars, after having tested the performance from simulations. The application of the technique resulted in the clear detection of non-uniform period spacing series for three out of the five treated Kepler targets. Disadvantages of the technique are also discussed, and include the disability to distinguish between different values of the spherical degree and azimuthal order of the oscillation modes, without additional theoretical modelling. Despite the shortcomings, the method is shown to enable solid detections of period spacings for gamma Doradus stars, which will allow future asteroseismic analyses of these stars.
- ID:
- ivo://CDS.VizieR/J/A+A/490/151
- Title:
- Photometric evolution of star clusters models
- Short Name:
- J/A+A/490/151
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To obtain an accurate description of broad-band photometric star cluster evolution, certain effects should be accounted for. Energy equipartition leads to mass segregation and the preferential loss of low-mass stars, while stellar remnants severely influence cluster mass-to-light ratios. Moreover, the stellar initial mass function and cluster metallicity affect photometry as well. Due to the continuous production of stellar remnants, their impact on cluster photometry is strongest for old systems like globular clusters. This, in combination with their low metallicities, evidence for mass segregation, and a possibly deviating stellar initial mass function, makes globular clusters interesting test cases for cluster models. In this paper we describe cluster models that include the effects of the preferential loss of low-mass stars, stellar remnants, choice of initial mass function and metallicity. The photometric evolution of clusters is predicted, and the results are applied to Galactic globular clusters. The cluster models presented in this paper represent an analytical description of the evolution of the underlying stellar mass function due to stellar evolution and dynamical cluster dissolution. Stellar remnants are included by using initial-remnant mass relations, while cluster photometry is computed from the Padova 1999 isochrones.
