scholarly journals From LBV Binary to WR+OB Binary

1991 ◽  
Vol 143 ◽  
pp. 556-556
Author(s):  
D. Vanbeveren
Keyword(s):  
Mass Loss ◽  
Thermal Equilibrium ◽  
General Theorem ◽  
Equipotential Surface ◽  
Roche Lobe ◽  
Close Binary ◽  
Initial Mass ◽  
Close Binaries ◽  
Evolutionary Models ◽  
Massive Close Binary

The LBV phase is generally identified with the hydrogen shell burning phase of a star with initial mass larger than 40-50 M⊙ (see also Humphreys, this volume) and therefore in binaries with ZAMS component masses larger than 40-50 M⊙ and periods larger than 4-7 days the primary may experience a LBV mass loss phase before it reaches its critical equipotential surface (the Roche lobe). I then define the ‘LBV scenario’ of massive close binaries as follows:when a binary component (initial mass larger than 40-50 M⊙) reaches the LBV phase prior to its Roche lobe overflow phase (RLOF), a stellar wind mass loss phase sets in at rates comparable to the rates encounterd during a RLOF process and which are large enough in order to prohibit the occurence of a RLOF.Evolutionary models are computed for close binaries with initial primary masses larger than 50 M⊙ and mass ratios ranging between 0.2 and 1. Special attention is given at the predicted spectral type of the secondary component. In order to determine the mass of the primary at the end of its LBV phase, I have used the following general theorem holding for the most massive stars, i.e.a hydrogen shell burning mass loser with mass larger than 50 M⊙ in a massive close binary restores thermal equilibrium (and becomes a WR star) when helium starts burning in its core and when its atmospherical hydrogen abundance has dropped to Xatm = 0.2-0.3 (by weight).

scholarly journals The Evolution of Massive Close Binary Systems : Estimates of the Parameters Governing Mass and Angular Momentum Loss

1980 ◽  
Vol 88 ◽  
pp. 115-121
Author(s):  
D. Vanbeveren ◽  
C. De Loore
Keyword(s):  
Angular Momentum ◽  
Mass Loss ◽  
Binary Systems ◽  
Mass Loss Rate ◽  
Roche Lobe ◽  
Close Binary ◽  
Close Binaries ◽  
Stellar Winds ◽  
Binary Evolution ◽  
Image Position

It becomes more and more evident that for close binary evolution during Roche lobe overflow as well mass transfer as mass loss occurs. When a mass element ΔM is expelled from the primary during this phase, a fraction β is transferred to the secondary; the remaining part leaves the system. Moreover, angular momentum leaves the system, and also this fraction has to be specified; this fraction is related to a parameter α (Vanbeveren et al., 1979). For the computation of the evolution of massive close binaries also mass loss due to stellar wind of both components, prior to the Roche lobe overflow has to be taken into account. The mass loss rate Ṁ due to radiation driven stellar winds can be expressed as

scholarly journals Empirical Determination of the Gravity-Darkening Exponent for the Secondary Components Filling the Roche Lobe in Semi-Detached Close Binary Systems

1988 ◽  
Vol 108 ◽  
pp. 217-218
Author(s):  
Masatoshi Kitamura ◽  
Yasuhisa Nakamura
Keyword(s):  
Binary Systems ◽  
Main Sequence ◽  
Close Binary System ◽  
Roche Lobe ◽  
Close Binary ◽  
Close Binaries ◽  
Main Sequence Stars ◽  
Local Gravity ◽  
Subsurface Layers

The ordinary semi-detached close binary system consists of a main-sequence primary and subgiant (or giant) secondary component where the latter fills the Roche lobe. From a quantitative analysis of the observed ellipticity effect, Kitamura and Nakamura (1986) have deduced empirical values of the exponent of gravity-darkening for distorted main-sequence stars in detached systems and found that the empirical values of the exponent for these stars with early-type spectra are close to the unity, indicating that the subsurface layers of early-main sequence stars in close binaries are actually in radiative equilibrium. The exponent of gravity-darkening can be defined by H ∝ gα with H as the bolonetric surface brightness and g as the local gravity on the stellar surface.

scholarly journals The influence of stellar wind mass loss on the evolution of massive close binaries.

1979 ◽  
Vol 83 ◽  
pp. 409-414
Author(s):  
D. Vanbeveren ◽  
J.P. De Grève ◽  
C. de Loore ◽  
E.L. van Dessel
Keyword(s):  
Mass Loss ◽  
Stellar Wind ◽  
Binary Systems ◽  
Mass Loss Rate ◽  
Radiation Force ◽  
Roche Lobe ◽  
Close Binaries ◽  
Massive Binary Systems ◽  
Binary Evolution ◽  
X Ray Binaries

It is generally accepted that massive (and thus luminous) stars lose mass by stellar wind, driven by radiation force (Lucy and Solomon, 1970; Castor et al. 1975). For the components of massive binary systems, rotational and gravitational effects may act together with the radiation force so as to increase the mass loss rate. Our intention here is to discuss the influence of a stellar wind mass loss on the evolution of massive close binaries. During the Roche lobe overflow phase, mass and angular momentum can leave the system. Possible reasons for mass loss from the system are for example the expansion of the companion due to accretion of the material lost by the mass losing star (Kippenhahn and Meyer-Hofmeister, 1977) or the fact that due to the influence of the radiation force in luminous stars, mass will be lost over the whole surface of the star and not any longer through a possible Lagrangian point as in the case of classical Roche lobe overflow (Vanbeveren, 1978). We have therefore investigated the influence of both processes on binary evolution. Our results are applied to 5 massive X-ray binaries with a possible implication for the existence of massive Wolf Rayet stars with a very close invisible compact companion. A more extended version of this talk is published in Astronomy and Astrophysics (Vanbeveren et al. 1978; Vanbeveren and De Grève, 1978). Their results will be briefly reviewed.

scholarly journals On the evolutionary time scale of the accreting component in massive close binaries: consequences for the supernova event

1981 ◽  
Vol 59 ◽  
pp. 465-468
Author(s):  
C. Doom ◽  
J.P. De Grève
Keyword(s):  
Mass Loss ◽  
Mass Exchange ◽  
Stellar Wind ◽  
Time Scale ◽  
Roche Lobe ◽  
Close Binaries ◽  
Evolutionary Time ◽  
Hydrogen Burning ◽  
Evolutionary Time Scale ◽  
Evolutionary Scenario

AbstractThe remaining core hydrogen burning lifetime after a case B of mass exchange is computed for the mass gaining component in massive close binaries. Effects of stellar wind mass loss and mass loss during Roche Lobe OverFlow (RLOF) are included. Consequences for the evolutionary scenario are discussed.

Origin and Evolution of Wolf-Rayet Stars

1982 ◽  
Vol 99 ◽  
pp. 377-381
Author(s):  
A. Tutukov ◽  
L. Yungelson
Keyword(s):  
Mass Loss ◽  
Massive Stars ◽  
Close Binary ◽  
Initial Mass ◽  
Convective Stability ◽  
Helium Burning ◽  
Origin And Evolution ◽  
The Core

The larger part of close binary components with initial mass exceeding ∼20 Mo becomes WR stars in the core helium burning stage. Some of the most massive WR stars may be products of evolution of single massive stars with initial masses exceeding ∼50 M0 if the mass loss in the infrared supergiant stage is effective enough. The Ledoux criterion of convective stability seems more promising to explain the observed properties of WR stars.

scholarly journals Close binary models for Luminous Blue Variable stars

1989 ◽  
Vol 113 ◽  
pp. 185-194
Author(s):  
J. S. Gallagher
Keyword(s):  
Mass Loss ◽  
Binary Stars ◽  
Mass Loss Rate ◽  
Variable Stars ◽  
High Mass ◽  
Close Binary ◽  
Close Binaries ◽  
System A ◽  
Close Binary Stars ◽  
High Mass Loss

AbstractThe evolution of massive close binary stars inevitably involves mass exchange between the two stellar components as well as mass loss from the system. A combination of these two processes could produce the stellar wind-modulated behavior seen in LB Vs. The possibility that LBVs are powered by accretion is examined, and does not appear to be a satisfactory general model. Instead, identification of LBVs with close binaries in high mass-loss rate or common envelope evolutionary phases shows promise.

scholarly journals Corrections for Hydrostatic Atmospheric Models: Radii and Effective Temperatures of Wolf Rayet Stars

1982 ◽  
Vol 99 ◽  
pp. 53-56 ◽  
Author(s):  
C. De Loore ◽  
P. Hellings ◽  
H.J.G.L.M. Lamers
Keyword(s):  
Mass Loss ◽  
Optical Depth ◽  
Stellar Wind ◽  
Theoretical Models ◽  
Roche Lobe ◽  
Evolutionary Models ◽  
Atmospheric Models ◽  
Helium Burning ◽  
Effective Temperatures ◽  
Loss Rates

With the assumption of planparallel hydrostatic atmospheres, used generally for the computation of evolutionary models, the radii of WR stars are seriously underestimated. The true atmospheres may be very extended, due to the effect of the stellar wind. Instead of these hydrostatic atmospheres we consider dynamical atmospheres adopting a velocity law. The equation of the optical depth is integrated outwards using the equation of continuity.The “hydrostatic” radii are to be multiplied with a factor 2 to 8, and the effective temperatures with a factor 0.8 to 0.35 when Wolf Rayet characteristics for the wind are considered, and WR mass loss rates are used. With these corrections the effective temperatures of the theoretical models, which are helium burning Roche lobe overflow remnants, range between 30 000 K and 50 000 K. Effective temperatures calculated in the hydrostatic hypothesis can be as high as 150 000 K for helium burning RLOF-remnants with WR mass loss rates.

scholarly journals The Occurrence of Different Wolf-Rayet Phases in Massive Close Binaries

1982 ◽  
Vol 99 ◽  
pp. 403-403
Author(s):  
C. Doom ◽  
J.P. De Grève
Keyword(s):  
Binary Systems ◽  
Main Sequence ◽  
Close Binary System ◽  
Close Binary ◽  
Close Binaries ◽  
Mass Ratio ◽  
The Third ◽  
Third Stage ◽  
Definition Of ◽  
Massive Close Binary

In a recent paper (Doom and De Grève, 1981) the remaining main sequence lifetime of the mass gaining component in massive close binary systems was computed. Using results of that paper and the definition of the four important events in the evolution of a massive close binary system (RLOF(M1), RLOF(M2), SN(M1), SN(M2)), four evolutionary stages in the life of the system can be defined: OB+OB, WR+OB, c+OB (or WR+WR) and c+WR. The two possibilities for the third stage depend on the initial mass ratio of the system. The final stage c+c, is not considered here.

scholarly journals A Gentle Process for the Formation of Algols

1989 ◽  
Vol 107 ◽  
pp. 369-369
Author(s):  
C. A. Tout ◽  
P. P. Eggleton
Keyword(s):  
Mass Transfer ◽  
Magnetic Fields ◽  
Mass Loss ◽  
White Dwarf ◽  
Binary Systems ◽  
Roche Lobe ◽  
Close Binary ◽  
Red Giants ◽  
Convective Envelope ◽  
Mass Ratios

AbstractThis work is concerned with binary systems that we call ‘moderately close’. These are systems in which the primary (by which we mean the initially more massive star) fills its Roche lobe when it is on the giant branch with a deep convective envelope but before helium ignition (late case B). We find that if the mass ratio q(= M1/M2) < qCrit = 0.7 when the primary fills its Roche lobe positive feedback will lead to a rapid hydrodynamic phase of mass transfer which will probably lead to common envelope evolution and thence to either coalescence or possibly to a close binary in a planetary nebula. Although most Algols have probably filled their Roche lobes before evolving off the main-sequence we find that some could not have and are therefore ‘moderately close’. Since rapid overflow is unlikely to lead to an Algol-like system there must be some way of avoiding it. The most likely possibility is that the primary can lose sufficient mass to reduce q below qcrit before overflow begins. Ordinary mass loss rates are insufficient but evidence that enhanced mass loss does take place is provided by RS CVn systems that have inverted mass ratios but have not yet begun mass transfer. We postulate that the cause of enhanced mass loss lies in the heating of the corona by by magnetic fields maintained by an α-ω dynamo which is enhanced by tidal effects associated with corotation. In order to model the the effects of enhanced mass loss we ignore the details and adopt an empirical approach calibrating a simple formula with the RS CVn system Z Her. Using further empirical relations (deduced from detailed stellar models) that describe the evolution of red giants we have investigated the effect on a large number of systems of various initial mass ratios and periods. These are notable in that some systems can now enter a much gentler Algol-like overflow phase and others are prevented from transferring mass altogether. We have also investigated the effects of enhanced angular momentum loss induced by corotation of the wind in the strong magnetic fields and consider this in relation to observed period changes. We find that a typical ‘moderately close’ Algol-like system evolves through an RS CVn like system and then possibly a symbiotic state before becoming an Algol and then goes on through a red giant-white dwarf state which may become symbiotic before ending up as a double white dwarf system in either a close or wide orbit depending on how much mass is lost before the secondary fills its Roche lobe.

The influence of mass loss by stellar wind on the evolution of massive helium burning stars

1981 ◽  
Vol 59 ◽  
pp. 275-278 ◽  
Author(s):  
D. Vanbeveren
Keyword(s):  
Mass Transfer ◽  
Mass Loss ◽  
Stellar Wind ◽  
Roche Lobe ◽  
Close Binaries ◽  
Helium Burning ◽  
Red Giant

Helium burning stars with masses between 10 Mo and 40 Mo are evolved up to core helium exhaustion including mass loss by stellar wind at rates between 10-5 Mo/yr and 10-4 Mo/yr appropriate for WR stars. Different M formalisms were used. It should however be noted that the results presented here are only marginally dependent on this formalism. The initial models contain a small hydrogen shell. The atmospherical hydrogen abundance Xatm = 0.2-0.3. These models correspond to primary remnants (with hydrogen ZAMS masses between 30 M0 and 100 M0) after a case B mode of mass transfer in close binaries, or to stars after a red giant phase of huge mass loss comparable to late case B remnants after Roche lobe overflow. Evolutionary details can be found elsewhere (Vanbeveren, D., Ph.D. Thesis, Vrije Universiteit Brussel) and will not be discussed here. I want to focus on two applications

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