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

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.

The final 105 years of stellar AGB evolution in the presence of a pulsating, dust-induced “superwind”

1999 ◽  
Vol 191 ◽  
pp. 389-394
Author(s):  
K.-P. Schröder ◽  
J.M. Winters ◽  
E. Sedlmayr
Keyword(s):  
Radiative Transfer ◽  
Mass Loss ◽  
Stellar Evolution ◽  
Mass Range ◽  
Initial Mass ◽  
Temperature Sensitive ◽  
Dust Formation ◽  
Time Step ◽  
Thermal Pulse ◽  
Loss Rates

We have computed mass-loss histories and tip-AGB stellar evolution models in the presence of a dust-induced, carbon-rich “superwind”, in the initial mass-range of 1.1 to about 2.5 solar masses and for nearly solar composition (X=0.28, Y=0.70, Z=0.02). Consistent, actual mass-loss rates are used in each time-step, based on pulsating and “dust-driven” stellar wind models for carbon-rich stars (Fleischer et al. 1992) which include a detailed treatment of dust-formation, radiative transfer and wind acceleration. Our tip-AGB mass-loss rates reach about 4 · 10−5M⊙yr−1 and become an influencial factor of stellar evolution.Heavy outflows of 0.3 to 0.6 M⊙ within only 2 to 3·104 yrs, exactly as required for PN-formation, occur with tip-AGB models of an initial stellar mass Mi ≳ 1.3M⊙. The mass-loss of our “superwind” varies strongly with effective temperature (Ṁ ∝ T−8eff, see Arndt et al. 1997), reflecting the temperature-sensitive micro-physics and chemistry of dust-formation and radiative transfer on a macroscopic scale. Furthermore, a thermal pulse leads to a very short (100 to 200 yrs) interruption of the “superwind” of these models.For Mi ≲ 1.1M⊙, our evolution models fail to reach the (Eddington-like) critical luminosity Lc required by the radiatively driven wind models, while for the (initial) mass-range in-between, with the tip-AGB luminosity LtAGB near Lc, thermal pulses drive bursts of “superwind”, which could explain the outer shells found with some PN's. In particular, a burst with a duration of only 800 yrs and a mass-loss of about 0.03 M⊙, occurs right after the last AGB thermal pulse of a model with Mi ≈ 1.1M⊙. There is excellent agreement with the thin CO shells found by Olofsson et al. (e.g., 1990, 1998) around some Mira stars.

scholarly journals Progenitors of early-time interacting supernovae

2020 ◽  
Vol 496 (2) ◽  
pp. 1325-1342 ◽  
Author(s):  
Ioana Boian ◽  
Jose H Groh
Keyword(s):  
Mass Loss ◽  
Large Scale ◽  
Massive Stars ◽  
Early Time ◽  
High Mass ◽  
Single Star ◽  
Circumstellar Material ◽  
Wide Range ◽  
Wind Velocities ◽  
Loss Rates

ABSTRACT We compute an extensive set of early-time spectra of supernovae interacting with circumstellar material using the radiative transfer code cmfgen. Our models are applicable to events observed from 1 to a few days after explosion. Using these models, we constrain the progenitor and explosion properties of a sample of 17 observed interacting supernovae at early times. Because massive stars have strong mass-loss, these spectra provide valuable information about supernova progenitors, such as mass-loss rates, wind velocities, and surface abundances. We show that these events span a wide range of explosion and progenitor properties, exhibiting supernova luminosities in the 108 to 1012 L⊙ range, temperatures from 10 000 to 60 000 K, progenitor mass-loss rates from a few 10−4 up to 1 M⊙ yr−1, wind velocities from 100 to 800 km s−1, and surface abundances from solar-like to H-depleted. Our results suggest that many progenitors of supernovae interacting with circumstellar material have significantly increased mass-loss before explosion compared to what massive stars show during the rest of their lifetimes. We also infer a lack of correlation between surface abundances and mass-loss rates. This may point to the pre-explosion mass-loss mechanism being independent of stellar mass. We find that the majority of these events have CNO-processed surface abundances. In the single star scenario this points to a preference towards high-mass RSGs as progenitors of interacting SNe, while binary evolution could impact this conclusion. Our models are publicly available and readily applicable to analyse results from ongoing and future large-scale surveys such as the Zwicky Transient Factory.

scholarly journals Interacting stellar winds in a binary system

1981 ◽  
Vol 59 ◽  
pp. 499-502
Author(s):  
Sun Kwok
Keyword(s):  
Binary System ◽  
Mass Loss ◽  
Stellar Winds ◽  
Long Time ◽  
Wind Velocities ◽  
M Stars ◽  
Hr Diagram ◽  
Loss Rates

It is now known that strong stellar winds develop in stars mostly at the red and blue sides of the HR diagram. However, although the mass loss rates observed in O and M stars are comparable, the corresponding wind velocities are vastly different. It would thus be of great interest to find a binary system, containing both a cool and a hot star each with its own wind, and observe the resultant interaction. For a long time, α Sco (M1.5 Iab + B2.5 V) was the only known example (Kudritzki and Reimers 1978, van der Hucht et al. 1980). The situation in this case is best illustrated by a VLA map made by Gibson (1979) who finds that a shock develops at the surface of interaction of the two winds. In this paper I shall describe another binary system in which two stellar winds are interacting with dramatic effects.

scholarly journals Radiatively driven winds of OB stars

1994 ◽  
Vol 162 ◽  
pp. 487-489 ◽  
Author(s):  
Michihiro R. Shimada ◽  
Masaki Ito ◽  
Ryuko Hirata ◽  
Toshihiro Horaguchi
Keyword(s):  
Mass Loss ◽  
Radiative Force ◽  
Ob Stars ◽  
Temperature Range ◽  
Wind Velocities ◽  
Atomic Lines ◽  
Loss Rates

We newly calculated the line radiative force with 520,000 atomic lines, which is twice as many as those of Abbott (1982), for OB supergiants. Our results are as follows. (1) The mass loss rates for O stars with Teff = 50,000K are seven times as large as Abbott's (1982) because of contribution from Fe iv lines. (2) Contribution from many weak lines increases the mass loss rates and decreases the wind velocities of OB stars within a temperature range of 10,000K ≤ Teff ≤ 30,000K. This result is qualitatively in accordance with the results from the recent observations of O stars. (3) The mass loss rates of OB stars depend on metallicity with Ṁ ∼ Z.

scholarly journals Predictions for mass-loss rates and terminal wind velocities of massive O-type stars

2012 ◽  
Vol 537 ◽  
pp. A37 ◽  
Author(s):  
L. E. Muijres ◽  
Jorick S. Vink ◽  
A. de Koter ◽  
P. E. Müller ◽  
N. Langer
Keyword(s):  
Mass Loss ◽  
Wind Velocities ◽  
Loss Rates

scholarly journals What do binaries teach us about mass-loss from late-type stars?

1987 ◽  
Vol 122 ◽  
pp. 307-318
Author(s):  
Dieter Reimers
Keyword(s):  
Mass Loss ◽  
Light Source ◽  
Stellar Evolution ◽  
Binary Systems ◽  
Late Type ◽  
Stellar Radius ◽  
Hydrogen Ionization ◽  
Wind Velocities ◽  
Red Giant ◽  
Loss Rates

It is shown that the binary technique - a B star companion is used as a light source which probes the wind of the red giant primary - has yielded accurate mass-loss rates and wind velocities for 8 G to M (super) giants and (in some cases) estimates of wind temperature.Eclipsing binary systems have in addition revealed that G and K supergiants possess extended chromospheres which could be detected outwards to ∼ 1 R* stellar radius) above the photospheres. Electron temperatures Te and hydrogen ionization ne/nH seem to increase with height up to at least 0.5 R* (ne/nH= 10−2, Te = 104 K at 0.5 R*), and the winds start to be accelerated at heights above ∼ 0.5 R*.Mass-loss rates appear to increase steeper than linearly with L/g · R. It is shown that the observed mass-loss rates are consistent with stellar evolution constraints for both Pop. II and Pop I stars.

scholarly journals Observations of Wolf-Rayet Mass Loss

1991 ◽  
Vol 143 ◽  
pp. 265-280 ◽  
Author(s):  
Allan J Willis
Keyword(s):  
Mass Loss ◽  
Current Knowledge ◽  
Mass Loss Rate ◽  
Intrinsic Variability ◽  
Order Of Magnitude ◽  
Wind Velocities ◽  
Optical Line ◽  
Thermal Sources ◽  
Line P ◽  
Loss Rates

Current knowledge of the stellar winds and mass loss rates for WR stars is reviewed. Recent IR spectroscopy and reassessments of UV resonance line P Cygni profiles have led to revisions of terminal velocities, with v∞ ≃ 0.75 × previous estimates. Radio and IR (10μm) free-free emission for well-established thermal sources, coupled with recent considerations of the wind ionisation balance and chemistry, leads to WR mass loss rates lying in the range 10-5 − 10-4 M⊙ yr–1. This scale is confirmed by independent analyses of optical polarisation modulation in WR+O binaries. No significant differences are apparent between the mean mass loss rates of: (a) single and binary WR stars; (b) WN and WC stars, and (c) the WN and WC subclasses. The overall mean WR mass loss rate is ~ 5 × 10-5 M⊙ yr–1. Although WR radiative luminosities are uncertain, there may be a rough scaling of MWR with L∗, with a spread of up to an order of magnitude at a given L∗. WR winds have the highest momenta of the hot luminous stars, with values of M v∞ c/L∗ in the range 1-30 (WN7,8 and WC9 stars may lie near the lower bound). An additional mechanism to radiation pressure may be required to initiate the high WR mass loss, although thereafter the winds may be radiatively accelerated. Intrinsic variability in optical light, polarisation and emission lines, and in UV P Cygni profiles, indicate significant instability in the WR winds. For extragalactic WR stars in the Local Group, optical line strengths and widths do not suggest substantial differences in wind velocities and mass loss rates of subtypes compared to galactic counterparts.

scholarly journals Determining mass-accretion and jet mass-loss rates in post-asymptotic giant branch binary systems

2020 ◽  
Vol 641 ◽  
pp. A175
Author(s):  
D. Bollen ◽  
D. Kamath ◽  
O. De Marco ◽  
H. Van Winckel ◽  
M. Wardle
Keyword(s):  
Mass Transfer ◽  
Radiative Transfer ◽  
Mass Loss ◽  
Mass Transfer Rate ◽  
Accretion Disc ◽  
Asymptotic Giant Branch ◽  
Transfer Model ◽  
Density Structure ◽  
Accretion Rates ◽  
Loss Rates

Aims. In this study we determine the morphology and mass-loss rate of jets emanating from the companion in post-asymptotic giant branch (post-AGB) binary stars with a circumbinary disc. In doing so we also determine the mass-accretion rates onto the companion, and investigate the source feeding the circum-companion accretion disc. Methods. We perform a spatio-kinematic modelling of the jet of two well-sampled post-AGB binaries, BD+46°442 and IRAS 19135+3937, by fitting the orbital phased time series of Hα spectra. Once the jet geometry, velocity, and scaled density structure are computed, we carry out radiative transfer modelling of the jet for the first four Balmer lines to determine the jet densities, thus allowing us to compute the jet mass-loss rates and mass-accretion rates. We distinguish the origin of the accretion by comparing the computed mass-accretion rates with theoretically estimated mass-loss rates, both from the post-AGB star and from the circumbinary disc. Results. The spatio-kinematic model of the jet reproduces the observed absorption feature in the Hα lines. The jets have an inner region with extremely low density in both objects. The jet model for BD+46°442 is tilted by 15° with respect to the orbital axis of the binary system. IRAS 19135+3937 has a smaller tilt of 6°. Using our radiative transfer model, we find the full 3D density structure of both jets. By combining these results, we can compute the mass-loss rates of the jets, which are of the order of 10−7 − 10−5 M⊙ yr−1. From this we estimate mass-accretion rates onto the companion of 10−6 − 10−4 M⊙ yr−1. Conclusions. Based on the mass-accretion rates found for these two objects, we conclude that the circumbinary disc is most likely the source feeding the circum-companion accretion disc. This is in agreement with the observed depletion patterns in post-AGB binaries, which is caused by re-accretion of gas from the circumbinary disc that is under-abundant in refractory elements. The high accretion rates from the circumbinary disc imply that the lifetime of the disc will be short. Mass transfer from the post-AGB star cannot be excluded in these systems, but it is unlikely to provide a sufficient mass-transfer rate to sustain the observed jet mass-loss rates.

scholarly journals New predictions for radiation-driven, steady-state mass-loss and wind-momentum from hot, massive stars

2019 ◽  
Vol 632 ◽  
pp. A126 ◽  
Author(s):  
J. O. Sundqvist ◽  
R. Björklund ◽  
J. Puls ◽  
F. Najarro
Keyword(s):  
Steady State ◽  
Radiative Transfer ◽  
Mass Loss ◽  
Stellar Evolution ◽  
Massive Stars ◽  
Life Cycles ◽  
Distribution Functions ◽  
Moving Frame ◽  
Large Radius ◽  
Loss Rates

Context. Radiation-driven mass loss plays a key role in the life cycles of massive stars. However, basic predictions of such mass loss still suffer from significant quantitative uncertainties. Aims. We develop new radiation-driven, steady-state wind models for massive stars with hot surfaces, suitable for quantitative predictions of global parameters like mass-loss and wind-momentum rates. Methods. The simulations presented here are based on a self-consistent, iterative grid solution to the spherically symmetric, steady-state equation of motion, using full non-local thermodynamic equilibrium radiative transfer solutions in the co-moving frame to derive the radiative acceleration. We do not rely on any distribution functions or parametrization for computation of the line force responsible for the wind driving. The models start deep in the subsonic and optically thick atmosphere and extend up to a large radius at which the terminal wind speed has been reached. Results. In this first paper, we present models representing two prototypical O-stars in the Galaxy, one with a higher stellar mass M*∕M⊙ = 59 and luminosity log10L*∕L⊙ = 5.87 (spectroscopically an early O supergiant) and one with a lower M*∕M⊙ = 27 and log10L*∕L⊙ = 5.1 (a late O dwarf). For these simulations, basic predictions for global mass-loss rates, velocity laws, and wind momentum are given, and the influence from additional parameters like wind clumping and microturbulent speeds is discussed. A key result is that although our mass-loss rates agree rather well with alternative models using co-moving frame radiative transfer, they are significantly lower than those predicted by the mass-loss recipes normally included in models of massive-star evolution. Conclusions. Our results support previous suggestions that Galactic O-star mass-loss rates may be overestimated in present-day stellar evolution models, and that new rates might therefore be needed. Indeed, future papers in this series will incorporate our new models into such simulations of stellar evolution, extending the very first simulations presented here toward larger grids covering a range of metallicities, B supergiants across the bistability jump, and possibly also Wolf-Rayet stars.

scholarly journals Line driven winds, ionizing fluxes and UV-spectra of hot stars at extremely low metalIicity

2003 ◽  
Vol 212 ◽  
pp. 325-333
Author(s):  
Rolf-Peter Kudritzki
Keyword(s):  
Mass Loss ◽  
Galaxy Formation ◽  
Scaling Laws ◽  
Massive Stars ◽  
Uv Spectra ◽  
Spectral Lines ◽  
Metal Abundance ◽  
Wind Velocities ◽  
New Treatment ◽  
Loss Rates

Wind models of very massive stars with metallicities in a range from 10–4-1.0 Z⊙ are presented using a new treatment of radiation driven winds with depth dependent radiative force multipliers and a comprehensive list of more than two million of spectral lines in non-LTE. The models yield mass-loss rates, wind velocities, wind momenta and wind energies as a function of metallicity and can be used to discuss the influence of stellar winds on the evolution of very massive stars in the early universe and on the interstellar medium in the early phases of galaxy formation. It is shown that the normal scaling laws, which predict stellar mass-loss rates and wind momenta to decrease as a power law with metal abundance break down at a certain threshold. The new wind models are applied to calculate ionizing fluxes and observable UV-spectra of very massive stars as a function of metallicity using the wm-basic code developed by Pauldrach et al. (2001), and the efffects of metallicity are discussed.

Sign in / Sign up

Export Citation Format

Share Document