- 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.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/497/497
- Title:
- Physical parameters from JHK flux
- Short Name:
- J/A+A/497/497
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The effective temperature scale of FGK stars, especially at the lowest metallicities remains a major problem in the chemical abundance analysis of metal-poor stars. We present a new implementation of the infrared flux method (IRFM) using the 2MASS catalogue.
- ID:
- ivo://CDS.VizieR/J/ApJ/742/L19
- Title:
- Physics of Kepler hot rocky planetary candidates
- Short Name:
- J/ApJ/742/L19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper outlines a simple approach to evaluate the atmospheric composition of hot rocky planets by assuming different types of planetary composition and using corresponding model calculations. To explore hot atmospheres above 1000K, we model the vaporization of silicate magma and estimate the range of atmospheric compositions according to the planet's radius and semi-major axis for the Kepler 2011 February data release. Our results show five atmospheric types for hot, rocky super-Earth atmospheres, strongly dependent on the initial composition and the planet's distance to the star. We provide a simple set of parameters that can be used to evaluate atmospheric compositions for current and future candidates provided by the Kepler mission and other searches.
- ID:
- ivo://CDS.VizieR/J/A+A/533/A109
- Title:
- Pisa pre-main sequence tracks and isochrones
- Short Name:
- J/A+A/533/A109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In recent years new observations of pre-main sequence stars (pre-MS) with Z<Z_{sun}_ have been made available. To take full advantage of the continuously growing amount of data of pre-MS stars in different environments, we need to develop updated pre-MS models for a wide range of metallicity to assign reliable ages and masses to the observed stars. We present updated evolutionary pre-MS models and isochrones for a fine grid of mass, age, metallicity, and helium values. We use a standard and well-tested stellar evolutionary code (i.e. FRANEC), that adopts outer boundary conditions from detailed and realistic atmosphere models. In this code, we incorporate additional improvements to the physical inputs related to the equation of state and the low temperature radiative opacities essential to computing low-mass stellar models. We make available via internet a large database of pre-MS tracks and isochrones for a wide range of chemical compositions (Z=0.0002-0.03), masses (M=0.2-7.0M_{sun}_), and ages (1-100Myr) for a solar-calibrated mixing length parameter alpha (i.e. 1.68). For each chemical composition, additional models were computed with two different mixing length values, namely alpha=1.2 and 1.9. Moreover, for Z>=0.008, we also provided models with two different initial deuterium abundances. The characteristics of the models have been discussed in detail and compared with other work in the literature. The main uncertainties affecting theoretical predictions have been critically discussed. Comparisons with selected data indicate that there is close agreement between theory and observation.
- ID:
- ivo://CDS.VizieR/J/A+A/544/A106
- Title:
- p-mode frequencies of the solar twin 18 Sco
- Short Name:
- J/A+A/544/A106
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Solar twins have been a focus of attention for more than a decade, because their structure is extremely close to that of the Sun. Today, thanks to high-precision spectrometers, it is possible to use asteroseismology to probe their interiors. Our goal is to use time series obtained from the HARPS spectrometer to extract the oscillation frequencies of 18 Sco, the brightest solar twin. We used the tools of spectral analysis to estimate these quantities. We estimate 52 frequencies using a Markov Chain Monte-Carlo (MCMC) algorithm. After examination of their probability densities and comparison with results from direct MAP optimization, we obtain a minimal set of 21 reliable modes. The identification of each pulsation mode is straightforwardly accomplished by comparing to the well-established solar pulsation modes. We also derived some basic seismic indicators using these values. These results offer a good basis to start a detailed seismic analysis of 18 Sco using stellar models.
- ID:
- ivo://CDS.VizieR/J/A+A/496/223
- Title:
- PMS tracks at low Z for 0.1<=M<=1.5
- Short Name:
- J/A+A/496/223
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- While MLT-alpha^2D^ models are not available for lower metallicities, we extend to lower Z the NEMO-FST models, under the hypothesis that in such a way we are simulating the results of MLT-alpha^2D^ models also at smaller Z. We use standard stellar computation techniques in which the atmospheric boundary conditions are derived making use of model atmosphere grids. This allows us to take into account the non greyness of the atmosphere, but adds a new parameter to the stellar structure uncertainty, namely the efficiency of convection in the atmospheric structure, if convection is computed in the atmospheric grid by a model different to the model adopted for the interior integration.
- ID:
- ivo://CDS.VizieR/J/A+A/535/A90
- Title:
- POKER (P. Of k EstimatoR) code
- Short Name:
- J/A+A/535/A90
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe the implementation of an angular power spectrum estimator in the at sky approximation. POKER (P. Of k EstimatoR) is based on the MASTER algorithm developped by Hivon and collaborators in the context of CMB anisotropy. It works entirely in discrete space and can be applied to arbitrary high angular resolution maps. It is therefore particularly suitable for current and future infrared to sub-mm observations of diffuse emission, whether Galactic or cosmological.
- ID:
- ivo://CDS.VizieR/J/A+A/504/259
- Title:
- Polarization models for planets
- Short Name:
- J/A+A/504/259
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Reflected light from giant planets is polarized by scattering, offering the possibility of investigating atmospheric properties with polarimetry. Polarimetric measurements are available for the atmospheres of solar system planets, and instruments are being developed to detect and study the polarimetric properties of extrasolar planets. We investigate the intensity and polarization of reflected light from planets in a systematic way with a grid of model calculations. Comparison of the results with existing and future observations can be used to constrain parameters of planetary atmospheres.
- ID:
- ivo://CDS.VizieR/B/pollux
- Title:
- POLLUX database of synthetic stellar spectra
- Short Name:
- B/pollux
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Synthetic spectra are needed to determine fundamental stellar and wind parameters of all types of stars. They are also used for the construction of theoretical spectral libraries helpful for stellar population synthesis. Therefore, a database of theoretical spectra is required to allow rapid and quantitative comparisons to spectroscopic data. We provide such a database offering an unprecedented coverage of the entire Hertzsprung-Russell diagram. We present the POLLUX database of synthetic stellar spectra. For objects with Teff<=6000K, MARCS atmosphere models are computed and the program TURBOSPECTRUM provides the synthetic spectra. ATLAS12 models are computed for stars with 7000K<=Teff<=15000K. SYNSPEC gives the corresponding spectra. Finally, the code CMFGEN provides atmosphere models for the hottest stars (Teff>25000K). Their spectra are computed with CMF_FLUX_. STAGGER 3D RHD models are computed for stars with 3900K<=Teff<=7000K. OPTIM3D gives the corresponding spectra. MARCS (from the AMBRE project, https://doi.org/10.1051/0004-6361/201219330) and ATLAS12 data consist of high resolution (R>150000) optical spectra in the range 3000 to 12000{AA} for a large variety of metallicities and chemical compositions. The CMFGEN data are high resolution (R > 150000) spectra in the optical, the UV and the IR domains and spectral energy distributions extending from the UV to near-IR ranges at solar metallicity and at the subsolar metallicities of Z=1/5Zsun and Z=1/30Zsun (https://arxiv.org/pdf/2010.13430.pdf). The OPTIM3D-STAGGER data are medium resolution (R=20000) spectra in the optical, the UV and the IR domains from 2000 to 200000{AA}. The OPTIM3D-Gaia data are very high resolution spectra (R=300000) in the Gaia-RVS spectral domain (from 8395{AA} to 8905{AA} ) (https://doi.org/10.1051/0004-6361/201732147). All the spectra cover the HR diagram at various metallicities. We propose a wide variety of synthetic spectra for various types of stars in a format that is compliant with th Virtual Observatory standards. A user-friendly web interface allows an easy selection of spectra and data retrieval. Upcoming developments will include an extension to a large range of metallicities and to the near-IR high resolution spectra, as well as a better coverage of the HR diagram, with the inclusion of models for Wolf-Rayet stars and large datasets for cool stars. The POLLUX database is accessible at http://pollux.oreme.org/ and through the Virtual Observatory.
- ID:
- ivo://CDS.VizieR/J/MNRAS/398/451
- Title:
- PopStar I: Evolutionary synthesis models
- Short Name:
- J/MNRAS/398/451
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new evolutionary synthesis models for Simple Stellar Populations for a wide range of ages and metallicities. The models are based on the Padova isochrones. The core of the spectral library is provided by the medium resolution Lejeune et al. atmosphere models. These spectra are complemented by NLTE atmosphere models for hot stars that have an important impact in the stellar cluster's ionizing spectra: O, B and WR stellar spectra at the early ages, and spectra of post-AGB stars and planetary nebulae, at intermediate and old ages. At young ages, our models compare well with other existing models but we find that, the inclusion of the nebular continuum, not considered in several other models, reddens significantly the integrated colours of very young stellar populations. This is consistent with the results of spectral synthesis codes particularly devised for the study of starburst galaxies. At intermediate and old ages, the agreement with literature model is good and, in particular, we reproduce well the observed colours of star clusters in LMC. Given the ability to produce good integrated spectra from the far-UV to the infrared at any age, we consider that our models are particularly suited for the study of high redshift galaxies. These models are available on the web site http://www.fractal-es.com/SEDmod.htm and also through the Virtual Observatory Tools on the PopStar server.
