- ID:
- ivo://CDS.VizieR/J/A+AS/106/275
- Title:
- Theoretical isochrones
- Short Name:
- J/A+AS/106/275
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we present large grids of theoretical isochrones for the initial chemical compositions [Z=0.0004, Y=0.23], [Z=0.004, Y=0.24], [Z=0.008, Y=0.25], [Z=0.02, Y=0.28], and [Z= 0.05, Y=0.352] and ages in the range 4Myr to 16Gyr. These isochrones are derived from stellar models computed with the most recent radiative opacities by Iglesias et al. (1992). In addition to this we present another set with chemical composition [Z=0.001, Y=0.23] based on models calculated with the radiative opacities by Huebner et al. (1977). All the stellar models are followed from the zero age main sequence (ZAMS) to the central carbon ignition for massive stars or to the beginning of the thermally pulsing regime of the asymptotic giant branch phase (TP-AGB) for low and intermediate mass stars. For each isochrone, we give the current mass, effective temperatures, bolometric and visual magnitudes, (U-B), (B-V), (V-R), (V-I), (V-J), (V-H), and (V-K) colors, and the luminosity function for the case of the Salpeter law. In addition to this, integrated magnitudes and colors at several characteristic points are also presented together with the mass of the remnant star when appropriate. The main characteristic that makes this set of isochrones very valuable is based on their extension in mass and chemical composition, besides the calculation of late stages of evolution, beyond the red giant tip till the white dwarf stage after the planetary nebula phase.
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- ID:
- ivo://CDS.VizieR/J/ApJ/692/L9
- Title:
- Tidal evolution of transiting extrasolar planets
- Short Name:
- J/ApJ/692/L9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We revisit the tidal stability of extrasolar systems harboring a transiting planet and demonstrate that, independently of any tidal model, none, but one (HAT-P-2b) of these planets has a tidal equilibrium state, which implies ultimately a collision of these objects with their host star. Consequently, conventional circularization and synchronization timescales cannot be defined because the corresponding states do not represent the endpoint of the tidal evolution. Using numerical simulations of the coupled tidal equations for the spin and orbital parameters of each transiting planetary system, we confirm these predictions and show that the orbital eccentricity and the stellar obliquity do not follow the usually assumed exponential relaxation but instead decrease significantly, eventually reaching a zero value only during the final runaway merging of the planet with the star. The only characteristic evolution timescale of all rotational and orbital parameters is the lifetime of the system, which crucially depends on the magnitude of tidal dissipation within the star. These results imply that the nearly circular orbits of transiting planets and the alignment between the stellar spin axis and the planetary orbit are unlikely to be due to tidal dissipation. Other dissipative mechanisms, for instance interactions with the protoplanetary disk, must be invoked to explain these properties.
- ID:
- ivo://CDS.VizieR/J/MNRAS/403/1213
- Title:
- Tracers of stellar mass-loss. I.
- Short Name:
- J/MNRAS/403/1213
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present optical and IR integrated colours and SBF magnitudes, computed from stellar population synthesis models that include emission from the dusty envelopes surrounding TP-AGB stars undergoing mass-loss. We explore the effects of varying the mass-loss rate by one order of magnitude around the fiducial value, modifying accordingly both the stellar parameters and the output spectra of the TP-AGB stars plus their dusty envelopes. The models are single burst, and range in age from a few Myr to 14Gyr, and in metallicity between Z=0.0001 and Z=0.07; they combine new calculations for the evolution of stars in the TP-AGB phase, with star plus envelope SEDs produced with the radiative transfer code DUSTY. We compare these models to optical and near-IR data of single AGB stars and Magellanic star clusters. This comparison validates the current understanding of the role of mass-loss in determining stellar parameters and spectra in the TP-AGB. However, neither broad-band colours nor SBF measurements in the optical or the near-IR can discern global changes in the mass-loss rate of a stellar population. We predict that mid-IR SBF measurements can pick out such changes, and actually resolve whether a relation between metallicity and mass-loss exists.
- ID:
- ivo://CDS.VizieR/J/ApJ/856/170
- Title:
- Tracers of stellar mass-loss. II.
- Short Name:
- J/ApJ/856/170
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- I present integrated colors and surface brightness fluctuation magnitudes in the mid-infrared (IR), derived from stellar population synthesis models that include the effects of the dusty envelopes around thermally pulsing asymptotic giant branch (TP-AGB) stars. The models are based on the Bruzual & Charlot CB* isochrones; they are single-burst, range in age from a few Myr to 14Gyr, and comprise metallicities between Z=0.0001 and Z=0.04. I compare these models to mid-IR data of AGB stars and star clusters in the Magellanic Clouds, and study the effects of varying self-consistently the mass-loss rate, the stellar parameters, and the output spectra of the stars plus their dusty envelopes. I find that models with a higher than fiducial mass-loss rate are needed to fit the mid-IR colors of "extreme" single AGB stars in the Large Magellanic Cloud. Surface brightness fluctuation magnitudes are quite sensitive to metallicity for 4.5{mu}m and longer wavelengths at all stellar population ages, and powerful diagnostics of mass-loss rate in the TP-AGB for intermediate-age populations, between 100Myr and 2-3Gyr.
- ID:
- ivo://CDS.VizieR/J/A+A/625/A87
- Title:
- Ultra-massive white dwarfs evolution models
- Short Name:
- J/A+A/625/A87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Ultra-massive white dwarfs are powerful tools to study various physical processes in the Asymptotic Giant Branch (AGB), type Ia supernova explosions and the theory of crystallization through white dwarf asteroseismology. Despite the interest in these white dwarfs, there are few evolutionary studies in the literature devoted to them. Here, we present new ultra-massive white dwarf evolutionary sequences that constitute an improvement over previous ones. In these new sequences, we take into account for the first time the process of phase separation expected during the crystallization stage of these white dwarfs, by relying on the most up-to-date phase diagram of dense oxygen/neon mixtures. Realistic chemical profiles resulting from the full computation of progenitor evolution during the semidegenerate carbon burning along the super-AGB phase are also considered in our sequences. Outer boundary conditions for our evolving models are provided by detailed non-gray white dwarf model atmospheres for hydrogen and helium composition. We assessed the impact of all these improvements on the evolutionary properties of ultra-massive white dwarfs, providing up-dated evolutionary sequences for these stars. We conclude that crystallization is expected to affect the majority of the massive white dwarfs observed with effective temperatures below 40000K. Moreover, the calculation of the phase separation process induced by crystallization is necessary to accurately determine the cooling age and the mass-radius relation of massive white dwarfs. We also provide colors in the GAIA photometric bands for our H-rich white dwarf evolutionary sequences on the basis of new models atmospheres. Finally, these new white dwarf sequences provide a new theoretical frame to perform asteroseismological studies on the recently detected ultra-massive pulsating white dwarfs.
- ID:
- ivo://CDS.VizieR/J/A+A/523/A64
- Title:
- UV properties of starbursts
- Short Name:
- J/A+A/523/A64
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have computed evolutionary synthesis models covering metallicities from PopIII to solar, a wide range of IMFs, and two star-formation histories (bursts and constant star-formation). The detailed predictions these models, including their time dependence, are given here. The predicted quantities include ionising fluxes, UV continuum properties, recombination line strengths (for Ly{alpha}, HeII and other lines), as well as several other quantities of interest. The models provided here cover a wider range of parameter space than our earlier calculations (Schaerer, 2003A&A...397..527S, Cat. VI/109).
- ID:
- ivo://CDS.VizieR/J/MNRAS/380/1098
- Title:
- UV-upturn of elliptical galaxies model
- Short Name:
- J/MNRAS/380/1098
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A long-standing problem in the study of elliptical galaxies is the far-ultraviolet (FUV) excess in their spectra (also known as UV-upturn, UV rising-branch, UV rising flux, or UVX). While it is now clear that this UV excess is caused by an old population of hot helium-burning stars without large hydrogen-rich envelopes. We have developed an evolutionary population synthesis (EPS) model for the FUV excess of elliptical galaxies based on the binary model of Han et al. (2002MNRAS.336..449H and 2003MNRAS.341..669H) for the formation of hot subdwarfs in our Galaxy. We give the colour evolution of a simple stellar population (SSP) (including binaries) of 10^10^M_{sun}_ for our standard simulation set. We have also compiled a file for the SED evolution, in which the SEDs without binary interactions are also supplied.
- ID:
- ivo://CDS.VizieR/J/ApJS/188/242
- Title:
- Variations on debris disks. II.
- Short Name:
- J/ApJS/188/242
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe comprehensive calculations of the formation of icy planets and debris disks at 30-150AU around 1-3M_{sun}_ stars. Disks composed of large, strong planetesimals produce more massive planets than disks composed of small, weak planetesimals. The maximum radius of icy planets ranges from ~1500km to 11500km. The formation rate of 1000km objects-"Plutos"-is a useful proxy for the efficiency of icy planet formation. Plutos form more efficiently in massive disks, in disks with small planetesimals, and in disks with a range of planetesimal sizes. Although Plutos form throughout massive disks, Pluto production is usually concentrated in the inner disk. Despite the large number of Plutos produced in many calculations, icy planet formation is inefficient. At the end of the main sequence lifetime of the central star, Plutos contain less than 10% of the initial mass in solid material. This conclusion is independent of the initial mass in the disk or the properties of the planetesimals. Debris disk formation coincides with the formation of planetary systems containing Plutos. As Plutos form, they stir leftover planetesimals to large velocities. A cascade of collisions then grinds the leftovers to dust, forming an observable debris disk. In disks with small (<~1-10km) planetesimals, collisional cascades produce luminous debris disks with maximum luminosity ~10-2 times the stellar luminosity. Disks with larger planetesimals produce debris disks with maximum luminosity ~5x10^-4^ (10km) to 5x10^-5^ (100km) times the stellar luminosity. Following peak luminosity, the evolution of the debris disk emission is roughly a power law, f{propto}t^-n^ with n~0.6-0.8. Observations of debris disks around A-type and G-type stars strongly favor models with small planetesimals. In these models, our predictions for the time evolution and detection frequency of debris disks agree with published observations. We suggest several critical observations that can test key features of our calculations.
- ID:
- ivo://CDS.VizieR/J/A+A/543/A67
- Title:
- WDA and WDB apsidal-motion constants
- Short Name:
- J/A+A/543/A67
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The internal structure constants k_j_ and the radius of gyration are useful tools for investigating the apsidal motion and tidal evolution of close binaries and planetary systems. These parameters are available for various evolutionary phases but they are scarce for the late stages of stellar evolution. To cover this gap, we present here the calculations of the apsidal-motion constants, the fractional radius of gyration, and the gravitational potential energy for two grids of cooling evolutionary sequences of white dwarfs and for neutron star models. The cooling sequences of white dwarfs were computed with LPCODE. An additional alternative to the white dwarf models was also adopted with the MESA code which allows non-stop calculations from the pre main-sequence (PMS) to the white dwarf cooling sequences. Neutron star models were acquired from the NSCool/TOV subroutines. The apsidal-motion constants, the moment of inertia and the gravitational potential energy were computed with a fourth-order Runge-Kutta method. The parameters are made available for four cooling sequences of white dwarfs (DA and DB types): 0.52, 0.57, 0.837 and 1.0M_{sun}_ and for neutron star models covering a mass range from 1.0 up to 2.183M_{sun}_, in 0.1 mass step. We show that, contrary to previously established opinion, the product of the form-factors {beta} and {alpha}, which are related to the moment of inertia, and gravitational potential energy, is not constant during some evolutionary phases. Regardless of the final products of stellar evolution (white dwarfs, neutron stars and perhaps black holes), we found that they recover the initial value of product {alpha}{beta} at the pre main-sequence phase (~0.4). These results may have important consequences for the investigation of the Jacobi virial equation.
- ID:
- ivo://CDS.VizieR/J/A+A/549/A102
- Title:
- White dwarf cooling sequences
- Short Name:
- J/A+A/549/A102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new diagnostics of white dwarf (WD) cooling sequences and luminosity functions (LFs) in the near-infrared (NIR) bands that will exploit the sensitivity and resolution of future extremely large telescopes. The collision-induced absorption (CIA) of molecular hydrogen causes a clearly defined blue turn-off along the WD (WDBTO) cooling sequences and a bright secondary maximum in the WD LFs. These features are independent of age over a broad age range and are minimally affected by metal abundance. This means that the NIR magnitudes of the WDBTO are very promising distance indicators.
