Wind accretion in binary stars

Jahanara, B.; Mitsumoto, M.; Oka, Kazutaka; Matsuda, Takuya; Hachisu, Izumi; Boffin, H. M. J.

doi:10.1051/0004-6361:20052828

Cited by 34 publications

(69 citation statements)

References 8 publications

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“…(10)), and a strongly modified wind that carries away twice the average specific angular momentum of the orbit (γ = 2). These assumptions may respresent very wide systems and relatively close systems, respectively, because the specific angular momentum carried away by the wind is likely to decrease with increasing ratio of wind velocity over orbital velocity (Jahanara et al 2005). The dependence of γ on orbital period and mass ratio cannot be quantified further at present, and our simple assumptions can only bracket the real situation.…”

Section: Discussionmentioning

confidence: 99%

“…However, the exact amount of angular momentum lost in a WRLOF situation is not well constrained by the hydrodynamical models of Mohamed (2010). Jahanara et al (2005) have studied angular momentum loss associated with wind mass transfer, also using hydrodynamical simulations but with different assumptions regarding the wind mechanism. In the case of a "radiative wind" -which corresponds best to the case of an AGB wind -with a velocity much lower than the orbital velocity, they find that matter leaving the binary system has an average specific angular momentum of approximately 0.6 × a 2 Ω orb .…”

Section: Angular Momentum Loss In the Wrlof Regimementioning

confidence: 99%

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Wind Roche-lobe overflow: Application to carbon-enhanced metal-poor stars

Abate

Pols

Izzard³

et al. 2013

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Carbon-enhanced metal-poor (CEMP) stars are observed as a substantial fraction of the very metal-poor stars in the Galactic halo. Most CEMP stars are also enriched in s-process elements, and these are often found in binary systems. This suggests that the carbon enrichment is due to mass transfer in the past from an asymptotic giant branch (AGB) star on to a low-mass companion. Models of binary population synthesis are not able to reproduce the observed fraction of CEMP stars without invoking non-standard nucleosynthesis or a substantial change in the initial mass function. This is interpreted as evidence of missing physical ingredients in the models. Recent hydrodynamical simulations show that efficient wind mass transfer is possible in the case of the slow and dense winds typical of AGB stars through a mechanism called wind Roche-lobe overflow (WRLOF), which lies in between the canonical Bondi-Hoyle-Lyttleton (BHL) accretion and Roche-lobe overflow. WRLOF has an effect on the accretion efficiency of mass transfer and on the angular momentum lost by the binary system. The aim of this work is to understand the overall effect of WRLOF on the population of CEMP stars. To simulate populations of low-metallicity binaries we combined a synthetic nucleosynthesis model with a binary population synthesis code. In this code we implemented the WRLOF mechanism. We used the results of hydrodynamical simulations to model the effect of WRLOF on the accretion efficiency, and we took the effect on the angular momentum loss into account by assuming a simple prescription. The combination of these two effects widens the range of systems that become CEMP stars towards longer initial orbital periods and lower mass secondary stars. As a consequence the number of CEMP stars predicted by our model increases by a factor 1.2−1.8 compared to earlier results that consider the BHL prescription. Moreover, higher enrichments of carbon are produced, and the final orbital period distribution is shifted towards shorter periods.

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Section: Discussionmentioning

confidence: 99%

Section: Angular Momentum Loss In the Wrlof Regimementioning

confidence: 99%

Wind Roche-lobe overflow: Application to carbon-enhanced metal-poor stars

Abate

Pols

Izzard³

et al. 2013

A&A

167

263

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“…Asymptotic giant branch stars have slow winds (speed ≈10−15 km s −1 , see e.g. Vassiliadis & Wood 1993) and when they are in relatively close orbits the wind can interact with the orbit and remove specific orbital angular momentum from the binary system (Jahanara et al 2005;Izzard et al 2010).…”

Section: Stellar Windmentioning

confidence: 99%

Theoretical uncertainties of the Type Ia supernova rate

Claeys

Pols

Izzard

et al. 2014

A&A

270

326

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It is thought that Type Ia supernovae (SNe Ia) are explosions of carbon-oxygen white dwarfs (CO WDs). Two main evolutionary channels are proposed for the WD to reach the critical density required for a thermonuclear explosion: the single degenerate (SD) scenario, in which a CO WD accretes from a non-degenerate companion, and the double degenerate (DD) scenario, in which two CO WDs merge. However, it remains difficult to reproduce the observed SN Ia rate with these two scenarios. With a binary population synthesis code we study the main evolutionary channels that lead to SNe Ia and we calculate the SN Ia rates and the associated delay-time distributions. We find that the DD channel is the dominant formation channel for the longest delay times. The SD channel with helium-rich donors is the dominant channel at the shortest delay times. Our standard model rate is a factor of five lower than the observed rate in galaxy clusters. We investigate the influence of ill-constrained aspects of single-and binary-star evolution and uncertain initial binary distributions on the rate of Type Ia SNe. These distributions, as well as uncertainties in both helium star evolution and common envelope evolution, have the greatest influence on our calculated rates. Inefficient common envelope evolution increases the relative number of SD explosions such that for α ce = 0.2 they dominate the SN Ia rate. Our highest rate is a factor of three less than the galaxy-cluster SN Ia rate, but compatible with the rate determined in a field-galaxy dominated sample. If we assume unlimited accretion onto WDs, to maximize the number of SD explosions, our rate is compatible with the observed galaxy-cluster rate.

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“…Since X-rays may be generated by several physical processes in a binary system, their detection in an M giant is a strong argument in favour of its binary nature. First, X-rays may be produced at the shocks resulting from the collision of streams in the complex flow pattern associated with wind accretion in a detached binary system involving an AGB star (Theuns & Jorissen 1993;Theuns et al 1996;Mastrodemos & Morris 1998;Jahanara et al 2005). Second, X-rays are generated when the gravitational energy of the M giant wind falling in the potential well of the companion star is converted into radiative energy when hitting the stellar surface.…”

Section: X-ray Emission As Binarity Diagnosticmentioning

confidence: 99%

Spectroscopic binaries among Hipparcos M giants

Famaey¹,

Pourbaix²,

Frankowski³

et al. 2009

A&A

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Context. This paper is a follow-up on the vast effort to collect radial velocity data for stars belonging to the Hipparcos survey. Aims. We aim at extending the orbital data available for binaries with M giant primaries. The data presented in this paper will be used in the companion papers of this series to (i) derive the binary frequency among M giants and compare it to that of K giants (Paper II); and (ii) analyse the eccentricity -period diagram and the mass-function distribution (Paper III). Methods. Keplerian solutions are fitted to radial-velocity data. However, for several stars, no satisfactory solution could be found, even though the radial-velocity standard deviation is greater than the instrumental error, because M giants suffer from intrinsic radialvelocity variations due to pulsations. We show that these intrinsic radial-velocity variations can be linked with both the average spectral-line width and the photometric variability. Results. We present an extensive collection of spectroscopic orbits for M giants with 12 new orbits, plus 17 from the literature. On top of these, 1 preliminary orbit yielded an approximate value for the eccentricity and the orbital period. Moreover, to illustrate how the large radial-velocity jitter present in Mira and semi-regular variables may easily be confused with orbital variations, we also present examples of pseudo-orbital variations (in S UMa, X Cnc, and possibly in HD 115 521, a former IAU radial-velocity standard). Because of this difficulty, M giants involving Mira variables were excluded from our monitored sample. We finally show that the majority of M giants detected as X-ray sources are actually binaries. Conclusions. The data presented in this paper considerably increase the orbital data set for M giants, and will allow us to conduct a detailed analysis of the eccentricity -period diagram in a companion paper (Paper III).

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Wind accretion in binary stars

Cited by 34 publications

References 8 publications

Wind Roche-lobe overflow: Application to carbon-enhanced metal-poor stars

Wind Roche-lobe overflow: Application to carbon-enhanced metal-poor stars

Theoretical uncertainties of the Type Ia supernova rate

Spectroscopic binaries among Hipparcos M giants

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