scholarly journals Massive Stars: Evolution with Mass Loss. III. Low Metal Stars, and WR's in SMC

1980 ◽  
Vol 85 ◽  
pp. 107-107 ◽  
Author(s):  
C. Chiosi ◽  
G. Bertelli ◽  
E. Nasi
Keyword(s):  
Chemical Composition ◽  
Mass Loss ◽  
Metal Content ◽  
Main Sequence ◽  
Constant Mass ◽  
Initial Chemical Composition ◽  
The Galaxy ◽  
Metal Abundance ◽  
Effective Temperatures ◽  
Stars Evolution

In this paper we investigate the effect of mass loss by stellar wind on the evolution from the main sequence to the He exhaustion stage of stars in the range of mass 20 to 100 M⊙ with low metal abundance. To this purpose we compute the set of evolutionary sequences with initial mass 20, 30, 40, 60, 80, and 100 M⊙ and chemical composition parameters X=0.700, Z=0.001. The models are first computed at constant mass to provide the fundamental network to which we compare the mass losing models. This choice of the initial chemical composition is aimed to represent the case of luminous supergiants in the Small Magellanic Cloud. The rate of mass loss follows the formulation of Castor, Abbot and Klein (1975), but it incorporates the effect of different metal content in the regions of high effective temperatures in the HR diagram. The rate of mass loss for models at low effective temperature is given by the acoustic flux mechanism according to the formulation of Chiosi, Nasi and Sreenivasan (1978). The results are compared with those of Chiosi, Nasi and Sreenivasan (1978), and those of Chiosi, Nasi and Bertelli (1979) for normal metal abundance supergiant stars of the Galaxy. On the basis of the present results we suggest an interpretative scenario for the existence of single WR stars in galaxies of different chemical composition. These results allow us to interpret also the different percentages of WR's among subclasses that are observed in the Galaxy, LMC, and SMC (Conti and Vanbeveren, 1979).

scholarly journals The Ratio of the Numbers of Carbon Stars to M Stars in Galaxies

1989 ◽  
Vol 106 ◽  
pp. 51-51
Author(s):  
Yu. L. Frantsman
Keyword(s):  
Chemical Composition ◽  
Mass Loss ◽  
Agb Stars ◽  
Carbon Stars ◽  
Initial Chemical Composition ◽  
The Galaxy ◽  
M Stars

Simulated populations of the AGB stars were calculated with different assumptions about mass loss, initial chemical composition and dredge-up efficiency. The early-AGB (E-AGB) phase was taken into account. The numbers of carbon and oxygen stars per 106 generated stars and the ratio (NC/NM) of these numbers were obtained. It is possible to match theoretically obtained NC/NM with the observations only if the luminosity of observed stars Mbol < -3.5; otherwise it is necessary to take into account the E-AGB phase. The data in the Table are for all AGB stars in the Galaxy and for stars with Mbol < -1.80 in the LMC.

scholarly journals Spectroscopy of hot subdwarf binaries

2018 ◽  
Vol 27 (1) ◽  
pp. 95-97
Author(s):  
Simon Kreuzer ◽  
Andreas Irrgang ◽  
Ulrich Heber
Keyword(s):  
Spectral Analysis ◽  
Chemical Composition ◽  
Main Sequence ◽  
Spectroscopic Analysis ◽  
Status Report ◽  
Significant Excess ◽  
Composite Spectrum ◽  
Infra Red ◽  
Metal Abundance ◽  
Individual Star

Abstract We present a status report of our spectroscopic analysis of subdwarf binaries consisting of a subdwarf and a F/G/K-type main-sequence companion. These systems selected from SDSS photometry show significant excess in the (infra-)red which can not be explained by interstellar reddening. Inspection of SDSS spectra revealed that most of them are composite spectrum sdB binaries. Once their spectra are disentangled, a detailed spectral analysis can be carried out. It reveals Teff, log g and the metal abundance of each individual star. The cool companion is of particular interest, because its spectrum reveals the original chemical composition of the binary.

scholarly journals Short Period Variables in the Magellanic Cloud Cluster NGC 1466

1973 ◽  
Vol 21 ◽  
pp. 113-119 ◽  
Author(s):  
M. V. Norris
Keyword(s):  
Globular Cluster ◽  
Metal Content ◽  
Globular Clusters ◽  
Magellanic Clouds ◽  
Horizontal Branch ◽  
A Value ◽  
Short Period ◽  
Magnitude Diagram ◽  
The Galaxy ◽  
Metal Abundance

NGC 1466 (α1950 = 3h44.m6, δ1950= -71°45’) is a globular cluster which appears to be situated between the two Magellanic Clouds. Previous estimates (Gascoigne, 1966) put it at roughly the same distance from us as the LMC, so it is regarded as a member of the Cloud system. It is globular in appearance, and its colour-magnitude diagram confirms this classification. It has a fairly well-developed horizontal branch, and was found by Wesselink (1970) to be quite rich in variables. The metallicity index, Q, (van den Bergh, 1967) has a value of -0.36 for NGC 1466 (Andrews and Lloyd Evans, 1971). This would rank it with M5 and NGC 6171 as a cluster of intermediate metal content. This comparison is consistent with the value of Δ V for the cluster, which, at 2.m6, is representative of the Δ V values of globular clusters of intermediate metal abundance in the Galaxy.

scholarly journals A Comparison Between the Relative Heavy Metal Abundance of the Extreme Halo Field Stars and Giant Stars of Globular Clusters

1978 ◽  
Vol 80 ◽  
pp. 169-172
Author(s):  
M. Spite ◽  
F. Spite
Keyword(s):  
Heavy Metal ◽  
Chemical Composition ◽  
Globular Clusters ◽  
Giant Stars ◽  
The Galaxy ◽  
Metal Abundance

Until very recently, estimates of the chemical composition at early epochs of the Galaxy were made through the analysis of halo field stars. Recently, however some medium dispersion studies of stars in globular clusters have appeared. It would be expected that both approaches would lead to identical results. However, a quick glance at the literature gives the opposite impression.

scholarly journals Metallicity Mapping with gri Photometry: The Virgo Overdensity and the Halos of the Galaxy

2009 ◽  
Vol 5 (S262) ◽  
pp. 127-130
Author(s):  
Timothy C. Beers ◽  
Deokkeun An ◽  
Jennifer A. Johnson ◽  
Marc H. Pinsonneault ◽  
Donald M. Terndrup ◽  
...  
Keyword(s):  
Main Sequence ◽  
Main Sequence Stars ◽  
Abundance Estimates ◽  
The Galaxy ◽  
Metal Abundance ◽  
Nearby Stars ◽  
Metal Abundances ◽  
Photometric Measurements ◽  
Halo Population ◽  
Recent Interpretation

AbstractWe describe the methodology required for estimation of photometric estimates of metallicity based on the SDSS gri passbands, which can be used to probe the properties of main-sequence stars beyond ~10 kpc, complementing studies of nearby stars from more metallicity-sensitive color indices that involve the u passband. As a first application of this approach, we determine photometric metal abundance estimates for individual main-sequence stars in the Virgo Overdensity, which covers almost 1000 deg2 on the sky, based on a calibration of the metallicity sensitivity of stellar isochrones in the gri filter passbands using field stars with well-determined spectroscopic metal abundances. Despite the low precision of the method for individual stars, internal errors of σ[Fe/H]~0.1 dex can be achieved for bulk stellar populations. The global metal abundance of the Virgo Overdensity determined in this way is 〈[Fe/H]〉 = −2.0±0.1 (internal) ±0.5 (systematic), from photometric measurements of 0.7 million stars with heliocentric distances from ~10 kpc to ~20 kpc. A preliminary metallicity map, based on results for 2.9 million stars in the northern SDSS DR-7 footprint, exhibits a shift to lower metallicities as one proceeds from the inner- to the outer-halo population, consistent with recent interpretation of the kinematics of local samples of stars with spectroscopically available metallicity estimates and full space motions.

scholarly journals Behavior and Significance of Circumstellar Clouds

1980 ◽  
Vol 87 ◽  
pp. 479-486
Author(s):  
B. Zuckerman
Keyword(s):  
Chemical Composition ◽  
Physical Properties ◽  
Mass Loss ◽  
Main Sequence ◽  
Main Sequence Stars

We will discuss molecular envelopes around post main sequence stars. Topics that will be covered include chemical composition, physical properties, mass loss and evolution. In view of the following papers by Drs. Snyder and Goldreich we will have little to say about circumstellar masers here.

scholarly journals Calibration of the Pre-Main Sequence Binary System RS Cha: Impact of the Initial Chemical Mixture

2006 ◽  
Vol 2 (S240) ◽  
pp. 652-657
Author(s):  
E. Alecian ◽  
Y. Lebreton ◽  
M.-J. Goupil ◽  
M.-A. Dupret ◽  
C. Catala
Keyword(s):  
Binary System ◽  
Main Sequence ◽  
Reaction Rates ◽  
Helium Abundance ◽  
Chemical Mixture ◽  
Spectroscopic Binary ◽  
Initial Chemical Composition ◽  
Effective Temperatures ◽  
Stellar Models ◽  
The Impact

AbstractAccurate observational data are available for the eclipsing double-lined spectroscopic binary system RS Cha, composed of two stars in the pre-main sequence stage of evolution: masses, radii, luminosities and effective temperatures of each component and metallicity of the system. This allows to build pre-main sequence stellar models representing the components of RS Cha and to constrain them in terms of physical ingredients, initial chemical composition and age.We present stellar models we have calculated using the CESAM stellar evolution code for different sets of physical inputs (opacities, nuclear reaction rates, etc.) and different initial parameters (global metallicity, helium abundance, individual abundances of heavy elements). We discuss their ability to reproduce the observational constraints simultaneously for the two components. We focus on the impact on the models of the chemical mixture adopted and we propose a calibration for the RS Cha system providing an estimate of its age and initial helium abundance.

HD 226766: a hierarchical SB3 system with two twin Am stars

2019 ◽  
Vol 487 (1) ◽  
pp. 919-927 ◽  
Author(s):  
G Catanzaro ◽  
M Gangi ◽  
M Giarrusso ◽  
M Munari ◽  
F Leone
Keyword(s):  
Chemical Composition ◽  
Main Sequence ◽  
Point Of View ◽  
Eccentric Orbit ◽  
Orbital Inclination ◽  
Orbital Parameters ◽  
Component C ◽  
Effective Temperatures ◽  
Chemical Anomalies ◽  
The Masses

ABSTRACT In this paper, we present a detailed revision of the orbital parameters and the first quantitative abundance analysis of the spectroscopic triple system HD 226766. By means of a simultaneous fit of the radial velocities of all the three components, we derived precise orbital parameters for the system, in particular inner pair has P(d)  =  31.9187 ± 0.0001, e  =  0.28 ± 0.01, and MA/MB  = 1.03 ± 0.03, while the C component orbits around the inner pair with a period of P(d)  =  1615 ± 59 in a very eccentric orbit (e  =  0.54 ± 0.11). From the fit of the Hβ and Hα profiles, we determined the effective temperatures and surface gravities of each component of the inner pair: Teff  =  8600 ± 500 K and log g  =  3.8 ± 0.2 for HD 226766 A and Teff  =  8500 ± 400 K and log g  =  4.0 ± 0.2 for HD 226766 B. In the hypothesis that component C is a main sequence star (log g  =  4.0) we derived Teff  =  8000 ± 500 K. Rotational velocities have been estimated by modeling the profiles of metallic lines: v sin i  =  13 ± 1 km s−1 for inner pair and v sin i  =  150 ± 20 km s−1 for the C component. We find that the inner pair is heterogeneous from the point of view of the chemical composition: both stars are very similar and show chemical anomalies typical of Am stars. With some hypothesis about the masses of the components, we estimated the orbital inclination angle for the inner binary, i = (47 ± 1)○, and for the outer orbit, i = (54 ± 19)○.

scholarly journals The Metallicity Dependence of the Mass Loss of Early-Type Massive Stars

2007 ◽  
Vol 3 (S250) ◽  
pp. 39-46
Author(s):  
Alex de Koter
Keyword(s):  
Mass Loss ◽  
Metal Content ◽  
Massive Stars ◽  
Magellanic Clouds ◽  
Stellar Winds ◽  
Early Type ◽  
The Galaxy ◽  
Early Type Stars ◽  
Good Agreement ◽  
Comprehensive Study

AbstractWe report on a comprehensive study of the wind properties of 115 O- and early B-type stars in the Galaxy and the Large Magellanic Clouds. This work is part of the VLT/FLAMES Survey of Massive Stars. The data is used to construct the empirical dependence of the mass-loss in stellar winds on the metal content of their atmospheres. The metal content of early-type stars in the Magellanic Clouds is discussed. Assuming a power-law dependence of mass loss on metal content, Ṁ ∝ Zm, we find m = 0.83 ± 0.16 from an analysis of the wind momentum luminosity relation (Mokiem et al. 2007b). This result is in good agreement with the prediction m = 0.69 ± 0.10 by Vink et al. (2001). Though the scaling agrees, the absolute empirical value of mass loss is found to be a factor of two higher than predictions. This may be explained by a modest amount of clumping in the outflows of the objects studied.

scholarly journals Colours and Teff of Main Sequence Stars Covering the Galactic Metallicity Range

1995 ◽  
Vol 164 ◽  
pp. 368-368
Author(s):  
A. Alonso ◽  
S. Arribas ◽  
C. Martínez-Roger
Keyword(s):  
Temperature Scale ◽  
Main Sequence ◽  
Main Sequence Stars ◽  
Flux Method ◽  
Absolute Flux ◽  
The Galaxy ◽  
Effective Temperatures ◽  
Bolometric Correction ◽  
Flux Calibration ◽  
Hr Diagram

We present the results of a general programme aimed to study the effects of metallicity on the temperature scale of late main sequence stars (F0-K5). A sample of approximately 400 stars with published UBV(RI) and ubvy – β photometry has been collected from the literature. A three years campaign of observations (Alonso et al. 1994b) was carried out to obtain JHK photometry in order to apply the InfraRed Flux Method (IRFM) to derive effective temperatures. The effect of metallicity on Colour-Colour IR diagrams is discussed. The absolute flux calibration in the IR was revised in Alonso et al. (1994a). The effect of metallicity on the bolometric correction has been studied in Alonso et al. (1995) in order to derive bolometric fluxes. The temperatures have been derived by applying the IRFM using new Kurucz models. Teff = f(Colours, [Fe/H], log(g)) relations are obtained for dwarfs covering the ranges 4000K ≤ Teff ≤ 8000K, 3.5 ≤ logg ≤ 5.00, +0.5 ≤ [Fe/H] ≤ −3.00 which expands considerably the database of previous works. These relations are used to check atmosphere models through the analysis of UBV RIJH Kubvy – β synthetic photometry in combination with the IRFM. The transformation from the theoretical HR diagram into an observational one is analyzed with the new relations. The influence of these points on the study of the evolution of the Galaxy is briefly discussed.

Sign in / Sign up

Export Citation Format

Share Document