UV and optical quantitative spectroscopy of early B-type supergiants in M 33

We present the analysis of UV and optical spectra of M 33 early B-type supergiants. Stellar parameters, metal abundances (Si, Mg, O and N) and mass loss rates are derived from anlyses of optical spectra by means of non-LTE unblanketed unified model atmospheres (fastwind code, Santolaya-Rey, Puls & Herrero 1997). These analyses use wind terminal velocities previously derived from the analysis of UV P-Cygni profiles. Stellar radial gradients of Si, O and Mg are derived for the M 33 disk. Differential abundances of those elements with respect to Galactic counterparts are also presented, along with nitrogen. Finally, the wind momenta of M 33 stars is derived and compared with the one found for Galactic B-type supergiants.

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ISOCAM and DENIS Survey of 0.5 square degrees in the Bar of the LMC. Detection of the whole TP-AGB Star Population

Symposium - International Astronomical Union ◽

10.1017/s0074180900203550 ◽

1999 ◽

Vol 191 ◽

pp. 561-566

Author(s):

C. Loup ◽

E. Josselin ◽

M.-R. Cioni ◽

H.J. Habing ◽

J.A.D.L. Blommaert ◽

...

Keyword(s):

Mass Loss ◽

High Mass ◽

Evolutionary Models ◽

Agb Stars ◽

Complete Sample ◽

High Mass Loss ◽

Low Mass ◽

The One ◽

Good Agreement ◽

Loss Rates

We surveyed 0.5 square degrees in the Bar of the LMC with ISOCAM at 4.5 and 12 μm, and with DENIS in the I, J, and Ks bands. Our goal was to build a complete sample of Thermally-Pulsing AGB stars. Here we present the first analysis of 0.14 square degrees. In total we find about 300 TP-AGB stars. Among these TP-AGB stars, 9% are obscured AGB stars (high mass-loss rates); 9 of them were detected by IRAS, and only 1 was previously identified. Their luminosities range from 2 500 to 14 000 L⊙, with a distribution very similar to the one of optical TP-AGB stars (i.e. those with low mass-loss rates). Such a luminosity distribution, as well as the percentage of obscured stars among TP-AGB stars, is in very good agreement with the evolutionary models of Vassiliadis & Wood (1993) if most of the TP-AGB stars that we find have initial masses smaller than 1.5 to 2 M⊙.

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Be Components in X-Ray Binaries

Symposium - International Astronomical Union ◽

10.1017/s007418090003802x ◽

1982 ◽

Vol 98 ◽

pp. 347-351 ◽

Cited By ~ 1

Author(s):

C. de Loore ◽

M. Burger ◽

E.L. van Dessel ◽

M. Mouchet

Keyword(s):

Mass Loss ◽

Optical Spectra ◽

X Rays ◽

X Ray ◽

Transient Sources ◽

X Ray Binaries ◽

Periodic Changes ◽

Loss Rates

The Be X-ray binaries show rather weak and variable X-rays. They can be divided into two types, the transient sources and the permanent sources. Two ranges for the X-ray luminosity Lx can be discerned: a) Lx~1034erg s−1 (X Per, λ Cas, 2S0114+65, all permanent sources); b) Lx~1036erg s−1. They have long periods, hence wide orbits, they ar not eclipsing and their mass loss rates are low. The optical spectra are generally very variable and irregular, masking periodic changes. No optical orbits exist and only for 4U0115+63 an X-ray orbit is known (Rappaport et al.1978). An overview of the Be X-ray binaries with some of their characteristics is given in Table 1.

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Three-component modelling of C-rich AGB star winds – V. Effects of frequency-dependent radiative transfer including drift★

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2714 ◽

2020 ◽

Vol 499 (2) ◽

pp. 1531-1560

Author(s):

Christer Sandin ◽

Lars Mattsson

Keyword(s):

Radiative Transfer ◽

Mass Loss ◽

Density Ratio ◽

Mie Scattering ◽

Speed Ratio ◽

Exponential Dependence ◽

Frequency Dependent ◽

Wind Velocities ◽

Drift Models ◽

Loss Rates

ABSTRACT Stellar winds of cool carbon stars enrich the interstellar medium with significant amounts of carbon and dust. We present a study of the influence of two-fluid flow on winds where we add descriptions of frequency-dependent radiative transfer (RT). Our radiation hydrodynamic models in addition include stellar pulsations, grain growth and ablation, gas-to-dust drift using one mean grain size, dust extinction based on both the small particle limit (SPL) and Mie scattering, and an accurate numerical scheme. We calculate models at high spatial resolution using 1024 gridpoints and solar metallicities at 319 frequencies, and we discern effects of drift by comparing drift models to non-drift models. Our results show differences of up to 1000 per cent in comparison to extant results. Mass-loss rates and wind velocities of drift models are typically, but not always, lower than in non-drift models. Differences are larger when Mie scattering is used instead of the SPL. Amongst other properties, the mass-loss rates of the gas and dust, dust-to-gas density ratio, and wind velocity show an exponential dependence on the dust-to-gas speed ratio. Yields of dust in the least massive winds increase by a factor 4 when drift is used. We find drift velocities in the range $10\!-\!67\, \mbox{km}\, \mbox{s}^{-1}$, which is drastically higher than in our earlier works that use grey RT. It is necessary to include an estimate of drift velocities to reproduce high yields of dust and low wind velocities.

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Asteroseismology of luminous red giants with Kepler. II. Dependence of mass loss on pulsations and radiation

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3970 ◽

2020 ◽

Author(s):

Jie Yu ◽

Saskia Hekker ◽

Timothy R Bedding ◽

Dennis Stello ◽

Daniel Huber ◽

...

Keyword(s):

Mass Loss ◽

Mass Loss Rate ◽

Asymptotic Giant Branch ◽

Red Giants ◽

Asymptotic Giant Branch Stars ◽

Chemical Enrichment ◽

Dust Mass ◽

Red Giant ◽

The Masses ◽

Loss Rates

Abstract Mass loss by red giants is an important process to understand the final stages of stellar evolution and the chemical enrichment of the interstellar medium. Mass-loss rates are thought to be controlled by pulsation-enhanced dust-driven outflows. Here we investigate the relationships between mass loss, pulsations, and radiation, using 3213 luminous Kepler red giants and 135000 ASAS–SN semiregulars and Miras. Mass-loss rates are traced by infrared colours using 2MASS and WISE and by observed-to-model WISE fluxes, and are also estimated using dust mass-loss rates from literature assuming a typical gas-to-dust mass ratio of 400. To specify the pulsations, we extract the period and height of the highest peak in the power spectrum of oscillation. Absolute magnitudes are obtained from the 2MASS Ks band and the Gaia DR2 parallaxes. Our results follow. (i) Substantial mass loss sets in at pulsation periods above ∼60 and ∼100 days, corresponding to Asymptotic-Giant-Branch stars at the base of the period-luminosity sequences C′ and C. (ii) The mass-loss rate starts to rapidly increase in semiregulars for which the luminosity is just above the red-giant-branch tip and gradually plateaus to a level similar to that of Miras. (iii) The mass-loss rates in Miras do not depend on luminosity, consistent with pulsation-enhanced dust-driven winds. (iv) The accumulated mass loss on the Red Giant Branch consistent with asteroseismic predictions reduces the masses of red-clump stars by 6.3%, less than the typical uncertainty on their asteroseismic masses. Thus mass loss is currently not a limitation of stellar age estimates for galactic archaeology studies.

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Helium, [Fe/H] Abundances and the HR (Log TEFF, MBol) Diagram With Hipparcos Data of The Four Nearest Open Clusters: Hyades, Coma Berenices, The Pleiades and Praesepe

Highlights of Astronomy ◽

10.1017/s1539299600022206 ◽

1998 ◽

Vol 11 (1) ◽

pp. 565-565

Author(s):

G. Cayrel de Strobel ◽

R. Cayrel ◽

Y. Lebreton

Keyword(s):

Main Sequence ◽

Open Clusters ◽

Main Sequence Stars ◽

Spectroscopic Analyses ◽

Solar Metallicity ◽

Metal Abundances ◽

The Mean ◽

The Moment ◽

The One ◽

Best Fit

After having studied in great detail the observational HR diagram (log Teff, Mbol) composed by 40 main sequence stars of the Hyades (Perryman et al.,1997, A&A., in press), we have tried to apply the same method to the observational main sequences of the three next nearest open clusters: Coma Berenices, the Pleiades, and Praesepe. This method consists in comparing the observational main sequence of the clusters with a grid of theoretical ZAMSs. The stars composing the observational main sequences had to have reliable absolute bolometric magnitudes, coming all from individual Hipparcos parallaxes, precise bolometric corrections, effective temperatures and metal abundances from high resolution detailed spectroscopic analyses. If we assume, following the work by Fernandez et al. (1996, A&A,311,127), that the mixing-lenth parameter is solar, the position of a theoretical ZAMS, in the (log Teff, Mbol) plane, computed with given input physics, only depends on two free parameters: the He content Y by mass, and the metallicity Z by mass. If effective temperature and metallicity of the constituting stars of the 4 clusters are previously known by means of detailed analyses, one can deduce their helium abundances by means of an appropriate grid of theoretical ZAMS’s. The comparison between the empirical (log Teff, Mbol) main sequence of the Hyades and the computed ZAMS corresponding to the observed metallicity Z of the Hyades (Z= 0.0240 ± 0.0085) gives a He abundance for the Hyades, Y= 0.26 ± 0.02. Our interpretation, concerning the observational position of the main sequence of the three nearest clusters after the Hyades, is still under way and appears to be greatly more difficult than for the Hyades. For the moment we can say that: ‒ The 15 dwarfs analysed in detailed in Coma have a solar metallicity: [Fe/H] = -0.05 ± 0.06. However, their observational main sequence fit better with the Hyades ZAMS. ‒ The mean metallicity of 13 Pleiades dwarfs analysed in detail is solar. A metal deficient and He normal ZAMS would fit better. But, a warning for absorption in the Pleiades has to be recalled. ‒ The upper main sequence of Praesepe, (the more distant cluster: 180 pc) composed by 11 stars, analysed in detail, is the one which has the best fit with the Hyades ZAMS. The deduced ‘turnoff age’ of the cluster is slightly higher than that of the Hyades: 0.8 Gyr instead of 0.63 Gyr.

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Evolution of O stars and the WR connection

Symposium - International Astronomical Union ◽

10.1017/s0074180900013838 ◽

1979 ◽

Vol 83 ◽

pp. 431-445 ◽

Cited By ~ 3

Author(s):

Peter S. Conti

Keyword(s):

Mass Loss ◽

Stellar Wind ◽

High Luminosity ◽

Loss Mechanism ◽

Evolutionary Scenario ◽

Processed Material ◽

Dominant Process ◽

Highly Evolved ◽

Loss Rates ◽

Enriched Composition

The stellar wind mass loss rates of at least some single Of type stars appear to be sufficient to remove much if not all of the hydrogen-rich envelope such that nuclear processed material is observed at the surface. This highly evolved state can then be naturally associated with classic Population I WR stars that have properties of high luminosity for their mass, helium enriched composition, and nitrogen or carbon enhanced abundances. If stellar wind mass loss is the dominant process involved in this evolutionary scenario, then stars with properties intermediate between Of and WR types should exist. The stellar parameters of luminosity, temperature, mass and composition are briefly reviewed for both types. All late WN stars so far observed are relatively luminous like Of stars, and also contain hydrogen. All early WN stars, and WC stars, are relatively faint and contain little or no hydrogen. The late WN stars seem to have the intermediate properties required if a stellar wind is the dominant mass loss mechanism that transforms an Of star to a WR type.

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Progenitors and Hydrodynamics of Type II and lb Supernovae

International Astronomical Union Colloquium ◽

10.1017/s0252921100008009 ◽

1996 ◽

Vol 145 ◽

pp. 137-147

Author(s):

S. E. Woosley ◽

T. A. Weaver ◽

R. G. Eastman

Keyword(s):

Black Holes ◽

Light Curve ◽

Mass Loss ◽

Massive Stars ◽

The Other ◽

Shock Interaction ◽

Type Ii ◽

Residual Hydrogen ◽

Ordinary Type ◽

The One

We review critical physics affecting the observational characteristics of those supernovae that occur in massive stars. Particular emphasis is given to 1) how mass loss, either to a binary companion or by a radiatively driven wind, affects the type and light curve of the supernova, and 2) the interaction of the outgoing supernova shock with regions of increasing pr3 in the stellar mantle. One conclusion is that Type II-L supernovae may occur in mass exchanging binaries very similar to the one that produced SN 1993J, but with slightly larger initial separations and residual hydrogen envelopes (∼1 Mʘ and radius ∼ several AU). The shock interaction, on the other hand, has important implications for the formation of black holes in explosions that are, near peak light, observationally indistinguishable from ordinary Type II-p and lb supernovae.

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Carbon star wind models at solar and sub-solar metallicities: a comparative study

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834778 ◽

2019 ◽

Vol 623 ◽

pp. A119 ◽

Cited By ~ 11

Author(s):

S. Bladh ◽

K. Eriksson ◽

P. Marigo ◽

S. Liljegren ◽

B. Aringer

Keyword(s):

Mass Loss ◽

Agb Stars ◽

Carbon Stars ◽

Dust Production ◽

Grain Sizes ◽

Solar Metallicity ◽

Effective Temperatures ◽

Carbon Excess ◽

Thermal Pulses ◽

Loss Rates

Context. The heavy mass loss observed in evolved stars on the asymptotic giant branch (AGB) is usually attributed to dust-driven winds, but it is still an open question how much AGB stars contribute to the dust production in the interstellar medium, especially at lower metallicities. In the case of C-type AGB stars, where the wind is thought to be driven by radiation pressure on amorphous carbon grains, there should be significant dust production even in metal-poor environments. Carbon stars can manufacture the building blocks needed to form the wind-driving dust species themselves, irrespective of the chemical composition they have, by dredging up carbon from the stellar interior during thermal pulses. Aims. We investigate how the mass loss in carbon stars is affected by a low-metallicity environment, similar to the Large and Small Magellanic Clouds (LMC and SMC). Methods. The atmospheres and winds of C-type AGB stars are modeled with the 1D spherically symmetric radiation-hydrodynamical code Dynamic Atmosphere and Radiation-driven Wind models based on Implicit Numerics (DARWIN). The models include a time-dependent description for nucleation, growth, and evaporation of amorphous carbon grains directly out of the gas phase. To explore the metallicity-dependence of mass loss we calculate model grids at three different chemical abundances (solar, LMC, and SMC). Since carbon may be dredged up during the thermal pulses as AGB stars evolve, we keep the carbon abundance as a free parameter. The models in these three different grids all have a current mass of one solar mass; effective temperatures of 2600, 2800, 3000, or 3200 K; and stellar luminosities equal to logL*∕L⊙ = 3.70, 3.85, or 4.00. Results. The DARWIN models show that mass loss in carbon stars is facilitated by high luminosities, low effective temperatures, and a high carbon excess (C–O) at both solar and subsolar metallicities. Similar combinations of effective temperature, luminosity, and carbon excess produce outflows at both solar and subsolar metallicities. There are no large systematic differences in the mass-loss rates and wind velocities produced by these wind models with respect to metallicity, nor any systematic difference concerning the distribution of grain sizes or how much carbon is condensed into dust. DARWIN models at subsolar metallicity have approximately 15% lower mass-loss rates compared to DARWIN models at solar metallicity with the same stellar parameters and carbon excess. For both solar and subsolar environments typical grain sizes range between 0.1 and 0.5 μm, the degree of condensed carbon varies between 5 and 40%, and the gas-to-dust ratios between 500 and 10 000. Conclusions. C-type AGB stars can contribute to the dust production at subsolar metallicities (down to at least [Fe∕H] = −1) as long as they dredge up sufficient amounts of carbon from the stellar interior. Furthermore, stellar evolution models can use the mass-loss rates calculated from DARWIN models at solar metallicity when modeling the AGB phase at subsolar metallicities if carbon excess is used as the critical abundance parameter instead of the C/O ratio.

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