- ID:
- ivo://CDS.VizieR/J/A+AS/105/311
- Title:
- M giants spectra and photometry
- Short Name:
- J/A+AS/105/311
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- From a sample of 97 very bright M-giant stars in the Solar neighbourhood, high-quality `intrinsic' spectra in the spectral range [380-900]nm for all M-spectral subclasses of the Case and MK classification systems are obtained. The results are fitted to photospheric synthetic spectra in the range [99-12500]nm in order to infer the corresponding continua. The synthetic spectra are also compared to the intrinsic spectra. The effective temperatures are derived and mathematical spectral classification criteria are found. The (UB)j(VRI)c(JHKLM)eso photometric data of the sample are also given.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/404/1639
- Title:
- MILES base models & new line index system
- Short Name:
- J/MNRAS/404/1639
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present synthetic spectral energy distributions (SEDs) for single-age, single-metallicity stellar populations (SSPs) covering the full optical spectral range at moderately high resolution [full width at half-maximum (FWHM)=2.3{AA}]. These SEDs constitute our base models, as they combine scaled-solar isochrones with an empirical stellar spectral library [Medium resolution INT Library of Empirical Spectra (MILES)], which follows the chemical evolution pattern of the solar neighbourhood. The models rely as much as possible on empirical ingredients, not just on the stellar spectra, but also on extensive photometric libraries, which are used to determine the transformations from the theoretical parameters of the isochrones to observational quantities. The unprecedented stellar parameter coverage of the MILES stellar library allowed us to safely extend our optical SSP SED predictions from intermediate- to very-old-age regimes and the metallicity coverage of the SSPs from super-solar to [M/H]=-2.3. SSPs with such low metallicities are particularly useful for globular cluster studies. We have computed SSP SEDs for a suite of initial mass function shapes and slopes. We provide a quantitative analysis of the dependence of the synthesized SSP SEDs on the (in)complete coverage of the stellar parameter space in the input library that not only shows that our models are of higher quality than those of other works, but also in which range of SSP parameters our models are reliable.
- ID:
- ivo://CDS.VizieR/J/MNRAS/371/703
- Title:
- MILES library of empirical spectra
- Short Name:
- J/MNRAS/371/703
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A new stellar library developed for stellar population synthesis modelling is presented. The library consists of 985 stars spanning a large range in atmospheric parameters. The spectra were obtained at the 2.5-m Isaac Newton Telescope and cover the range 3525-7500{AA} at 2.3{AA} (full width at half-maximum) spectral resolution. The spectral resolution, spectral-type coverage, flux-calibration accuracy and number of stars represent a substantial improvement over previous libraries used in population-synthesis models.
- ID:
- ivo://CDS.VizieR/J/ApJ/858/28
- Title:
- Mixing-length parameter for a sample of KIC stars
- Short Name:
- J/ApJ/858/28
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stellar models typically use the mixing-length approximation as a way to implement convection in a simplified manner. While conventionally the value of the mixing-length parameter, {alpha}, used is the solar-calibrated value, many studies have shown that other values of {alpha} are needed to properly model stars. This uncertainty in the value of the mixing-length parameter is a major source of error in stellar models and isochrones. Using asteroseismic data, we determine the value of the mixing-length parameter required to properly model a set of about 450 stars ranging in logg, Teff, and [Fe/H]. The relationship between the value of {alpha} required and the properties of the star is then investigated. For Eddington atmosphere, non-diffusion models, we find that the value of {alpha} can be approximated by a linear model, in the form of {alpha}/{alpha}_{sun}_=5.426-0.101, log(g)-1.071, log(Teff)+0.437([Fe/H]). This process is repeated using a variety of model physics, as well as compared with previous studies and results from 3D convective simulations.
- ID:
- ivo://CDS.VizieR/J/ApJS/207/7
- Title:
- Modeling Galactic extinction with dust and PAH
- Short Name:
- J/ApJS/207/7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the remarkable apparent variety of galactic extinction curves by modeling extinction profiles with core-mantle grains and a collection of single polycyclic aromatic hydrocarbons. Our aim is to translate a synthetic description of dust into physically well-grounded building blocks through the analysis of a statistically relevant sample of different extinction curves. All different flavors of observed extinction curves, ranging from the average galactic extinction curve to virtually "bumpless" profiles, can be described by the present model. We prove that a mixture of a relatively small number (54 species in 4 charge states each) of polycyclic aromatic hydrocarbons can reproduce the features of the extinction curve in the ultraviolet, dismissing an old objection to the contribution of polycyclic aromatic hydrocarbons to the interstellar extinction curve. Despite the large number of free parameters (at most the 54x4 column densities of each species in each ionization state included in the molecular ensemble plus the 9 parameters defining the physical properties of classical particles), we can strongly constrain some physically relevant properties such as the total number of C atoms in all species and the mean charge of the mixture. Such properties are found to be largely independent of the adopted dust model whose variation provides effects that are orthogonal to those brought about by the molecular component. Finally, the fitting procedure, together with some physical sense, suggests (but does not require) the presence of an additional component of chemically different very small carbonaceous grains.
- ID:
- ivo://CDS.VizieR/J/ApJ/732/65
- Title:
- Modeling the local velocity field with SNIa
- Short Name:
- J/ApJ/732/65
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We apply statistically rigorous methods of nonparametric risk estimation to the problem of inferring the local peculiar velocity field from nearby Type Ia supernovae (SNIa). We use two nonparametric methods -weighted least squares (WLS) and coefficient unbiased (CU)- both of which employ spherical harmonics to model the field and use the estimated risk to determine at which multipole to truncate the series. We show that if the data are not drawn from a uniform distribution or if there is power beyond the maximum multipole in the regression, a bias is introduced on the coefficients using WLS. CU estimates the coefficients without this bias by including the sampling density making the coefficients more accurate but not necessarily modeling the velocity field more accurately. After applying nonparametric risk estimation to SNIa data, we find that there are not enough data at this time to measure power beyond the dipole. The WLS Local Group bulk flow is moving at 538+/-86km/s toward (l,b)=(258+/-10{deg},36+/-11{deg}) and the CU bulk flow is moving at 446+/-101km/s toward (l,b)=(273+/-11{deg},46+/-8{deg}). We find that the magnitude and direction of these measurements are in agreement with each other and previous results in the literature.
- ID:
- ivo://CDS.VizieR/J/ApJ/857/46
- Title:
- Modelled vs observed abundances of EMP stars
- Short Name:
- J/ApJ/857/46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We compare the elemental abundance patterns of ~200 extremely metal-poor (EMP; [Fe/H]{<}-3) stars to the supernova yields of metal-free stars, in order to obtain insights into the characteristic masses of the first (Population III or Pop III) stars in the universe. The supernova yields are prepared with nucleosynthesis calculations of metal-free stars with various initial masses (M=13, 15, 25, 40 and 100M_{sun}_) and explosion energies (E_51_=E/10^51^[erg]=0.5-60), to include low-energy, normal-energy, and high-energy explosions. We adopt the mixing-fallback model, to take into account possible asymmetry in the supernova explosions, and the yields that best fit the observed abundance patterns of the EMP stars are searched by varying the model parameters. We find that the abundance patterns of the EMP stars are predominantly best- fitted by the supernova yields with initial masses M<40M_{sun}_, and that more than than half of the stars are best-fitted by the M=25M_{sun}_ hypernova (E_51_=10) models. The results also indicate that the majority of the primordial supernovae have ejected 10^-2^-10^-1^M_{sun}_ of ^56^Ni, leaving behind a compact remnant (either a neutron star or a black hole), with a mass in the range of ~1.5-5M_{sun}_. These results suggest that the masses of the first stars responsible for the first metal enrichment are predominantly <40M_{sun}_. This implies that the higher-mass first stars were either less abundant, directly collapsed into a black hole without ejecting heavy elements, or a supernova explosion of a higher-mass first star inhibits the formation of the next generation of low-mass stars at [Fe/H]{<}-3.
- ID:
- ivo://CDS.VizieR/J/A+A/453/635
- Title:
- Modelling the Galactic Interstellar Extinction
- Short Name:
- J/A+A/453/635
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Two Micron All Sky Survey (Cat. <II/246>), along with the Stellar Population Synthesis Model of the Galaxy, developed in Besancon, is used to calculate the extinction distribution along different lines of sight. The Galaxy model is used to provide the intrinsic colour of stars and their probable distances, so that the near infrared colour excess, and hence the extinction, may be calculated and its distance evaluated.
- ID:
- ivo://CDS.VizieR/J/AZh/79/259
- Title:
- Models for Intermediate-Mass Eclipsing Binaries
- Short Name:
- J/AZh/79/259
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use estimates of ages and abundances made for a set of eclipsing binaries (Kovaleva, 2001, Cat. <J/AZh/78/1104), to re-calculate observational values of radii, effective temperatures and luminosities of these stars for solar abundance ZAMS. Geneva group evolutionary grids of models were used for this recalculation. We also present empirical and semi-empirical (for ZAMS evolutionary stage and solar metallicity) relations between mass and luminosity, temperature and radius.
- ID:
- ivo://CDS.VizieR/J/A+A/463/455
- Title:
- Nearby early-type gal. with ionized gas. III.
- Short Name:
- J/A+A/463/455
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The paper is devoted to the study of the underlying stellar population of a sample of 62 nearby early-type galaxies, predominantly located in low density environments, a large fraction of which showing emission lines. Ages, metallicities and [{alpha}/Fe] ratios have been derived through the comparison of Lick indices measured at different galacto-centric distances (7 apertures and 4 gradients) with new Simple Stellar Population (SSP) models which account for the presence of alpha/Fe-enhancement. The SSPs cover a wide range of ages (10^8^-16x10^9^yr), metallicities (0.0004<=Z<=0.05) and [{alpha}/Fe] ratios (0-0.8). To derive the stellar population parameters we use an algorithm that provides, together with the most likely solution in the (age, Z, [{alpha}/Fe]) space, also the probability density function along the age-metallicity degeneracy. We derive a large spread in age, with SSP-equivalent ages ranging from a few to 15Gyrs. Age does not show any significant trend with central velocity dispersion sigma_c_ but E galaxies appear on average older than lenticulars.
