Roche potentials including radiation effects

Schuerman, D. W.

doi:10.1007/bf00645718

Cited by 74 publications

(31 citation statements)

References 7 publications

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“…One possibility is that our assumption of conservative evolution does not hold for systems with primaries of initially ∼ 25 M . This can be motivated by the increasing role of radiation pressure in higher mass systems (cf., Schuerman 1972;Vanbeveren 1978). On the other hand, strong non-conservative effects in massive systems may result in an uncomfortably large upper critical ZAMS mass for neutron star formation of ∼ 40 M , as imposed by the massive X-ray binary Wray 977 (Kaper et al 1995, Ergma & van den Heuvel 1998, Vanbeveren 1998b).…”

Section: Comparison With Observationsmentioning

confidence: 99%

Formation of contact in massive close binaries

Wellstein

Langer

Braun

2001

A&A

402

666

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Abstract. We present evolutionary calculations for 74 close binaries systems with initial primary masses in the range 12...25 M , and initial secondary masses between 6 and 24 M . The initial periods were chosen such that mass overflow starts during the core hydrogen burning phase of the primary (Case A), or shortly thereafter (Case B). We use a newly developed binary code with up-to-date physics input. Of particular relevance is the use of OPAL opacities, and the time-dependent treatment of semiconvective and thermohaline mixing. We assume conservative evolution for contact-free systems, i.e., no mass or angular momentum loss from those system except due to stellar winds. We investigate the borderline between contact-free evolution and contact, as a function of the initial system parameters. The fraction of the parameter space where binaries may evolve while avoiding contact -which we found already small for the least massive systems considered -becomes even smaller for larger initial primary masses. At the upper end of the considered mass range, no contact-free Case B systems exist. While for primary masses of 16 M and higher the Case A systems dominate the contact-free range, at primary masses of 12 M contact-free systems are more frequent for Case B. We identify the drop of the exponent x in the main sequence mass-luminosity relation of the form L ∝ M x as the main cause for this behaviour. For systems which evolve into contact, we find that this can occur for distinctively different reasons. While Case A systems are prone to contact due to reverse mass transfer during or after the primary's main sequence phase, all systems obtain contact for initial mass ratios below ∼ 0.65, with a merger as the likely outcome. We also investigate the effect of the treatment of convection, and found it relevant for contact and supernova order in Case A systems, particularly for the highest considered masses. For Case B systems we find contact for initial periods above ∼ 10 d. However, in that case (and for not too large periods) contact occurs only after the mass ratio has been reversed, due to the increased fraction of the donor's convective envelope. As most of the mass transfer occurs conservatively before contact is established, this delayed contact is estimated to yield to the ejection of only a fraction of the donor star's envelope. Our models yield the value of β, i.e., the fraction of the primaries envelope which is accreted by the secondary. We derive the observable properties of our systems after the major mass transfer event, where the mass gainer is a main sequence or supergiant O or early B type star, and the mass loser is a helium star. We point out that the assumption of conservative evolution for contact-free systems could be tested by finding helium star companions to O stars. Those are also predicted by non-conservative models, but with different periods and mass ratios. We describe strategies for increasing the probability to find helium star companions in observational search programs.

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Section: Comparison With Observationsmentioning

confidence: 99%

Formation of contact in massive close binaries

Wellstein

Langer

Braun

2001

A&A

402

666

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“…Calculations from Schuerman (1972) show that, when one takes into account the radiation pressure of the AGB-star in a close binary system, the critical Roche potential degenerates into a surface containing the inner Lagrangian point L 1 and the outer Lagrangian point L 2 for a critical ratio of the radiation pressure force to the gravitational attraction. For this critical ratio, material lost by the AGB star flows through the L 1 point and can settle itself through the L 2 point into a circumbinary disc (see also .…”

Section: Binary Evolutionmentioning

confidence: 99%

Post-AGB stars with hot circumstellar dust: binarity of the low-amplitude pulsators

Winckel¹,

Evans

Briquet³

et al. 2009

A&A

139

141

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Context. The influence of binarity on the late stages of stellar evolution remains an open issue. Aims. While the first binary post-AGB stars were serendipitously discovered, the distinct characteristics of their spectral energy distribution (SED) allowed us to launch a more systematic search for binaries. We selected post-AGB objects, which exhibit a broad dust excess starting either at H or K, pointing to the presence of a gravitationally bound dusty disc in the system. We initiated an extensive multiwavelength study of those systems and here report on our radial velocity and photometric monitoring results for six stars of early F type, which are pulsators of small amplitude. Methods. To determine the radial velocity of low signal-to-noise ratio time-series data, we constructed dedicated autocorrelation masks based on high signal-to-noise ratio spectra, used in our published chemical studies. The radial velocity variations were analysed in detail to differentiate between pulsational variability and variability caused by orbital motion. When available, the photometric monitoring data were used to complement the time series of radial velocity data and to establish the nature of the pulsation. Finally, orbital minimalisation was performed to constrain the orbital elements. Results. All of the six objects are binaries with orbital periods ranging from 120 to 1800 days. Five systems have non-circular orbits. The mass functions range from 0.004 to 0.57 M and the companions are probably unevolved objects of (very) low initial mass. We argue that these binaries must have evolved through a phase of strong binary interaction when the primary was a cool supergiant. Although the origin of the circumstellar disc is not well understood, the disc is generally believed to have formed during this strong interaction phase. The eccentric orbits of these highly evolved objects remain poorly understood. In one object, the line-of-sight grazes the edge of the puffed-up inner rim of the disc. Conclusions. These results corroborate our earlier statement that evolved objects in binary stars create a Keplerian dusty circumbinary disc. With the measured orbits and mass functions, we conclude that the circumbinary discs seem to have a major impact on the evolution of a significant fraction of binary systems. Tables 4-6 are only available in electronic form at

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“…Two mechanisms might occur that leave this possibility open however, but they can be discarded with quantitative arguments. First, radiation pressure reduces the gravitational acceleration influence, so that the Roche potential surface shrinks (Schuerman 1972). Dermine et al (2009) estimated the ratio of the radiation to the gravitational force to be f ∼ 10 −2 to 10 −1 for the M giant of SS Lep.…”

Section: μ αmentioning

confidence: 99%

An incisive look at the symbiotic star SS Leporis

Blind

Boffin

Berger

et al. 2011

A&A

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Context. Determining the mass transfer in a close binary system is of prime importance for understanding its evolution. SS Leporis, a symbiotic star showing the Algol paradox and presenting clear evidence of ongoing mass transfer, in which the donor has been thought to fill its Roche lobe, is a target particularly suited to this kind of study. Aims. Since previous spectroscopic and interferometric observations have not been able to fully constrain the system morphology and characteristics, we go one step further to determine its orbital parameters, for which we need new interferometric observations directly probing the inner parts of the system with a much higher number of spatial frequencies. Methods. We use data obtained at eight different epochs with the VLTI instruments AMBER and PIONIER in the H and K bands. We performed aperture synthesis imaging to obtain the first model-independent view of this system. We then modelled it as a binary (whose giant is spatially resolved) that is surrounded by a circumbinary disc. Results. Combining these interferometric measurements with previous radial velocities, we fully constrain the orbit of the system. We then determine the mass of each star and significantly revise the mass ratio. The M giant also appears to be almost twice smaller than previously thought. Additionally, the low spectral resolution of the data allows the flux of both stars and of the dusty disc to be determined along the H and K bands, and thereby extracting their temperatures. Conclusions. We find that the M giant actually does not stricto sensus fill its Roche lobe. The mass transfer is more likely to occur through the accretion of an important part of the giant wind. We finally rise the possibility for an enhanced mass loss from the giant, and we show that an accretion disc should have formed around the A star.

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Roche potentials including radiation effects

Cited by 74 publications

References 7 publications

Formation of contact in massive close binaries

Formation of contact in massive close binaries

Post-AGB stars with hot circumstellar dust: binarity of the low-amplitude pulsators

An incisive look at the symbiotic star SS Leporis

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