- ID:
- ivo://CDS.VizieR/J/MNRAS/448/1044
- Title:
- Simulation data for 50 planetary model systems
- Short Name:
- J/MNRAS/448/1044
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe the long-term evolution of compact systems of terrestrial planets, using a set of simulations that match the statistical properties of the observed exoplanet distribution. The evolution is driven by tidal dissipation in the planetary interiors, but the systems evolve as a whole due to secular gravitational interactions. We find that, for Earth-like dissipation levels, planetary orbits can be circularized out to periods ~100 d, an order of magnitude larger than is possible for single planets. The resulting distribution of eccentricities is a qualitative match to that inferred from transit timing variations, with a minority of non-zero eccentricities maintained by particular secular configurations. The coupling of the tidal and secular processes enhance the inward migration of the innermost planets in these systems, and can drive them to short orbital periods. Resonant interactions of both the mean motion and secular variety are observed, although the interactions are not strong enough to drive systemic instability in most cases. However, we demonstrate that these systems can easily be driven unstable if coupled to giant planets on longer period orbits.
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- ID:
- ivo://CDS.VizieR/J/A+A/462/107
- Title:
- Simulations of metal-poor star clusters
- Short Name:
- J/A+A/462/107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The intrinsic uncertainty (due to statistical effects) affecting the integrated colours and mass-to-light ratios as a function of the cluster's integrated visual magnitude (M_V^tot^_) is studied. We investigate the case of metal-poor, single-burst stellar populations with age from a few million years to a likely upper value for the Galactic globular cluster ages. Monte Carlo techniques are used for randomly generating stars distributed according to the cluster's mass function. Integrated colours and mass-to-light ratios in different photometric bands are presented as a function of age for different assumptions on the cluster total V magnitude and they are checked for good agreement with the observational values of low-metallicity Galactic clusters.
- ID:
- ivo://CDS.VizieR/J/ApJ/786/33
- Title:
- Simulations of the late stage of planet formation
- Short Name:
- J/ApJ/786/33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Models of planet formation have shown that giant planets have a large impact on the number, masses, and orbits of terrestrial planets that form. In addition, they play an important role in delivering volatiles from material that formed exterior to the snow line (the region in the disk beyond which water ice can condense) to the inner region of the disk where terrestrial planets can maintain liquid water on their surfaces. We present simulations of the late stages of terrestrial planet formation from a disk of protoplanets around a solar-type star and we include a massive planet (from 1 M_{earth}_ to 1 M_J_) in Jupiter's orbit at ~5.2 AU in all but one set of simulations. Two initial disk models are examined with the same mass distribution and total initial water content, but with different distributions of water content. We compare the accretion rates and final water mass fraction of the planets that form. Remarkably, all of the planets that formed in our simulations without giant planets were water-rich, showing that giant planet companions are not required to deliver volatiles to terrestrial planets in the habitable zone. In contrast, an outer planet at least several times the mass of Earth may be needed to clear distant regions of debris truncating the epoch of frequent large impacts. Observations of exoplanets from radial velocity surveys suggest that outer Jupiter-like planets may be scarce, therefore, the results presented here suggest that there may be more habitable planets residing in our galaxy than previously thought.
- ID:
- ivo://CDS.VizieR/J/A+A/655/A51
- Title:
- Solar evolutionary and structure models
- Short Name:
- J/A+A/655/A51
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- In protoplanetary disks, the growth and inward drift of dust lead to the generation of a temporal "pebble wave" of increased metallicity. This phase must be followed by a phase in which the exhaustion of the pebbles in the disk and the formation of planets lead to the accretion of metal-poor gas. At the same time, disk winds may lead to the selective removal of hydrogen and helium from the disk. Hence, stars grow by accreting gas that has an evolving composition. In this work, we investigated how the formation of the Solar System may have affected the composition and structure of the Sun, and whether it plays any role in solving the so-called solar-abundance problem, that is, the fact that standard models with up-to-date lower-metallicity abundances reproduce helioseismic constraints significantly more poorly than those with old higher-metallicity abundances. We simulated the evolution of the Sun from the protostellar phase to the present age and attempted to reproduce spectroscopic and helioseismic constraints. We performed chi-squared tests to optimize our input parameters, which we extended by adding secondary parameters. These additional parameters accounted for the variations in the composition of the accreted material and an increase in the opacities. We confirmed that, for realistic models, planet formation occurs when the solar convective zone is still massive; thus, the overall changes due to planet formation are too small to significantly improve the chi-square fits. We found that solar models with up-to-date abundances require an opacity increase of 12% to 18% centered at T=10^6.4^K to reproduce the available observational constraints. This is slightly higher than, but is qualitatively in good agreement with, recent measurements of higher Fe opacities. These models result in better fits to the observations than those using old abundances; therefore, they are a promising solution to the solar abundance problem. Using these improved models, we found that planet formation processes leave a small imprint in the solar core, whose metallicity is enhanced by up to 5%. This result can be tested by accurately measuring the solar neutrino flux. In the improved models, the protosolar molecular cloud core is characterized by a primordial metallicity in the range Zproto=0.0127-0.0157 and a helium mass fraction in the range Yproto=0.268-0.274.
- ID:
- ivo://CDS.VizieR/J/ApJ/787/10
- Title:
- Solar s-process contributions with GCE model
- Short Name:
- J/ApJ/787/10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the s-process abundances (A>~90) at the epoch of the solar system formation. Asymptotic giant branch yields are computed with an updated neutron capture network and updated initial solar abundances. We confirm our previous results obtained with a Galactic chemical evolution (GCE) model: (1) as suggested by the s-process spread observed in disk stars and in presolar meteoritic SiC grains, a weighted average of s-process strengths is needed to reproduce the solar s distribution of isotopes with A>130; and (2) an additional contribution (of about 25%) is required in order to represent the solar s-process abundances of isotopes from A=90 to 130. Furthermore, we investigate the effect of different internal structures of the ^13^C pocket, which may affect the efficiency of the ^13^C({alpha},n)^16^O reaction, the major neutron source of the s process. First, keeping the same ^13^C profile adopted so far, we modify by a factor of two the mass involved in the pocket; second, we assume a flat ^13^C profile in the pocket, and we test again the effects of the variation of the mass of the pocket. We find that GCE s predictions at the epoch of the solar system formation marginally depend on the size and shape of the ^13^C pocket once a different weighted range of ^13^C-pocket strengths is assumed. We obtain that, independently of the internal structure of the ^13^C pocket, the missing solar system s-process contribution in the range from A=90 to 130 remains essentially the same.
- ID:
- ivo://CDS.VizieR/J/A+A/642/A71
- Title:
- Spectra of 14 Magellanic Cloud planetary nebulae
- Short Name:
- J/A+A/642/A71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We obtained new spectra of fourteen Magellanic Cloud planetary nebulae with the South African Large Telescope to determine heating rates of their central stars and to verify evolutionary models of post asymptotic giant branch stars. We compared new spectra with observations made in previous years. Five planetary nebulae showed an increase of the excitation with time. Four of their central stars exhibit [WC] features in their spectra, including three new detections. This raises the total number of [WC] central stars of PNe in the Magellanic Clouds to ten. We compared determined heating rates of the four [WC] central stars with the He burning post asymptotic giant branch evolutionary tracks and the remaining star with the H-burning tracks. Determined heating rates are consistent with the evolutionary models for both H and He-burning post asymptotic giant branch stars. The central stars of the PNe which show the fastest increase of excitation are also the most luminous in the sample. This indicates that [WC] central stars in the Magellanic Clouds evolve faster than H-burning central stars and originate from more massive progenitors.
- ID:
- ivo://CDS.VizieR/J/A+A/392/1
- Title:
- Spectrophotometry of simulated Stellar Populations
- Short Name:
- J/A+A/392/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A new set of evolutionary synthesis spectra are presented for Simple Stellar Populations (SSPs) covering ranges in metallicity from 0.02<=Z/Z_{sun}_<=2.5 and ages from 4*10^6^yr<=t<=16Gyr. They are based on the most recent isochrones from the Padova group that extend earlier models by the inclusion of the thermal pulsing AGB phase for stars in the mass range 2M_{sun}_<=m<=7M_{sun}_ in accordance with the fuel consumption theorem. We show that with respect to earlier models, inclusion of the TP-AGB phase leads to significant changes in the (V-I) and (V-K) colors of SSPs in the age range from 10^8^ to >~10^9^yr. Using model atmosphere spectra from Lejeune et al. (1997, Cat. <J/A+AS/125/229>, 1998, Cat. <J/A+AS/130/65>), we calculate the spectral evolution of single burst populations of various metallicities covering the wavelength range from 90{AA} through 160{mu}m. Isochrone spectra are convolved with filter response functions to describe the time evolution of luminosities and colors in Johnson, Thuan & Gunn, Koo, HST, Washington and Stroemgren filters. The models and their results are not only intended for use in the interpretation of star clusters but also for combination with any kind of dynamical galaxy formation and/or evolution model that contains a star formation criterion. Moreover, the evolution of these single burst single metallicity stellar populations is readily folded with any kind of star formation -- and eventually chemical enrichment -- history to describe the evolutionary spectral synthesis of composite stellar populations like galaxies of any type with continuous or discontinuous star formation. For these latter purposes we also present the time evolution of ejection rates for gas and metals for two different Initial Mass Functions (IMFs) as well as cosmological and evolutionary corrections for all the filters as a function of redshift for 0<=z<=5 and two different cosmologies.
- ID:
- ivo://CDS.VizieR/J/A+A/582/A97
- Title:
- SSP in NIR. II. Synthesis models
- Short Name:
- J/A+A/582/A97
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present unresolved single stellar population synthesis models in the near-infrared (NIR) range. The extension to the NIR is important for the study of early-type galaxies, since these galaxies are predominantly old and therefore emit most of their light in this wavelength range. The models are based on a library of empirical stellar spectra, the NASA infrared telescope facility (IRTF) spectral library. Integrating these spectra along theoretical isochrones, while assuming an initial mass function (IMF), we have produced model spectra of single age-metallicity stellar populations at a resolution R~2000. These models can be used to fit observed spectral of globular clusters and galaxies, to derive their age distribution, chemical abundances and IMF. The models have been tested by comparing them to observed colours of elliptical galaxies and clusters in the Magellanic Clouds. Predicted absorption line indices have been compared to published indices of other elliptical galaxies. The comparisons show that our models are well suited for studying stellar populations in unresolved galaxies. They are particularly useful for studying the old and intermediate-age stellar populations in galaxies, relatively free from contamination of young stars and extinction by dust. These models will be indispensable for the study of the upcoming data from JWST and extremely large telescopes, such as the E-ELT.
- ID:
- ivo://CDS.VizieR/J/A+A/502/817
- Title:
- SSP models for star clusters in tidal fields
- Short Name:
- J/A+A/502/817
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Evolutionary synthesis models are the primary means of constructing spectrophotometric models of stellar populations, and deriving physical parameters from observations compared with these models. One of the basic assumptions of evolutionary synthesis models has been the time-independence of the stellar mass function, apart from the successive removal of high-mass stars by stellar evolution. However, dynamical simulations of star clusters in tidal fields have demonstrated that the mass function can be changed by the preferential removal of low-mass stars from clusters. We combine the results of dynamical simulations of star clusters in tidal fields with our evolutionary synthesis code GALEV. We extend the models to consider the total cluster disruption time as additional parameter.
- ID:
- ivo://CDS.VizieR/J/A+A/321/29
- Title:
- Star cluster evolution
- Short Name:
- J/A+A/321/29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A model of spectral evolution of star forming galaxies of various metallicity has been used to study the relation between the optical emission line ratio R_23_=([OII]{lambda}3727+[OIII]{lambda}{lambda}4959,5007)/H{beta} and the nebular oxygen abundance. It is shown that the scatter in an empirical comparison sample could be due to various upper stellar mass limits or different slopes of the stellar initial mass function in these objects.
