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Matsuda, Takuya; Makita, M.; Fujiwara, Hajime; Nagae, T.; Haraguchi, Kei; Hayashi, Eiji; Boffin, H. M. J.

doi:10.1023/a:1026524728950

Cited by 11 publications

(5 citation statements)

References 42 publications

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“…3.6, is not 1 but 0.34. Spiral shocks, typical of RLOF flows Matsuda et al 2000;Fujiwara et al 2001) are not seen in this case.…”

Section: Roche Lobe Overflowmentioning

confidence: 69%

Wind accretion in binary stars

Nagae¹,

Oka²,

Matsuda³

et al. 2004

A&A

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Abstract. Three-dimensional hydrodynamic calculations are performed in order to investigate mass transfer in a close binary system, in which one component undergoes mass loss through a wind. The mass ratio is assumed to be unity. The radius of the mass-losing star is taken to be about a quarter of the separation between the two stars. Calculations are performed for gases with a ratio of specific heats γ = 1.01 and 5/3. Mass loss is assumed to be thermally driven so that the other parameter is the sound speed of the gas on the mass-losing star. Here, we focus our attention on two features: flow patterns and mass accretion ratio, which we define as the ratio of the mass accretion rate onto the companion,Ṁ acc , to the mass loss rate from the mass-losing primary star,Ṁ loss . We characterize the flow by the mean normal velocity of the wind on the critical Roche surface of the mass-losing star, V R . When V R < 0.4 AΩ, where A and Ω are the separation between the two stars and the angular orbital frequency of the binary, respectively, we obtain Roche-lobe over-flow (RLOF), while for V R > 0.7 AΩ we observe wind accretion. We find very complex flow patterns in between these two extreme cases. We derive an empirical formula of the mass accretion ratio as 0.18 × 10 −0.75V R /AΩ in the low velocity regime and 0.05 (V R /AΩ) −4 in the high velocity regime.

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“…3.6, is not 1 but 0.34. Spiral shocks, typical of RLOF flows Matsuda et al 2000;Fujiwara et al 2001) are not seen in this case.…”

Section: Roche Lobe Overflowmentioning

confidence: 69%

Wind accretion in binary stars

Nagae¹,

Oka²,

Matsuda³

et al. 2004

A&A

View full text Add to dashboard Cite

show abstract

“…In the present study, we use the same scheme as in Makita et al (2000), Matsuda et al (2000) and Fujiwara et al (2001): the simplified flux splitting (SFS) finite-volume method proposed by Jyounouchi et al (1993) and Shima & Jyounouchi (1994). We refer to Makita et al (2000) for the numerical and the SFS schemes.…”

Section: Methodsmentioning

confidence: 99%

“…Our main target in the present paper is to investigate the surface layer, the L1 region and the L1 stream numerically. The region around the accreting compact star has been investigated separately by our group Matsuda et al 2000;Fujiwara et al 2001). Lubow and Shu (1975) stated that "the horizontal component of the fluid velocity is parallel to isobars in the astrostrophic approximation.…”

Section: Introductionmentioning

confidence: 99%

Numerical simulation of the surface flow of a companion star in a close binary system

Oka¹,

Nagae²,

Matsuda³

et al. 2002

A&A

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Abstract. We simulate numerically the surface flow of a gas-supplying companion star in a semi-detached binary system. Calculations are carried out for a region including only the mass-losing star, thus not the mass accreting star. The equation of state is that of an ideal gas characterized by a specific heat ratio γ, and the case with γ = 5/3 is mainly studied. A system of eddies appears on the surface of the companion star: an eddy in the low pressure region near the L1 point, one around the high pressure at the north pole, and one or two eddies around the low pressure at the opposite side of the L1 point. Gas elements starting near the pole region rotate clockwise around the north pole (here the binary system rotates counter-clockwise as seen from the north pole). Because of viscosity, the gas drifts to the equatorial region, switches to the counter-clockwise eddy near the L1 point and flows through the L1 point to finally form the L1 stream. The flow field in the L1 region and the structure of the L1 stream are also considered.

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“…Numerical simulations show that the circumstellar disks in a forming binary system settle into a quasi-steady state in which angular momentum is continually transferred from the disks to the binary orbit (Bate and Bonnell 1997;Bate 2000), although the internal transport of angular momentum within the disks is not accurately modeled in these simulations and may result partly from an artificial viscosity. Tidal transport mechanisms may be of quite general importance in astrophysics, and may drive accretion flows in many types of binary systems containing disks (Matsuda et al 2000;Menou 2000;Blondin 2000;Boffin 2001).…”

Section: The Role Of Tidal Interactionsmentioning

confidence: 99%

The physics of star formation

2003

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Our current understanding of the physical processes of star formation is reviewed, with emphasis on processes occurring in molecular clouds like those observed nearby. The dense cores of these clouds are predicted to undergo gravitational collapse characterized by the runaway growth of a central density peak that evolves toward a singularity. As long as collapse can occur, rotation and magnetic fields do not change this qualitative behavior. The result is that a very small embryonic star or protostar forms and grows by accretion at a rate that is initially high but declines with time as the surrounding envelope is depleted. Rotation causes some of the remaining matter to form a disk around the protostar, but accretion from protostellar disks is not well understood and may be variable. Most, and possibly all, stars form in binary or multiple systems in which gravitational interactions can play a role in redistributing angular momentum and driving episodes of disk accretion. Variable accretion may account for some peculiarities of young stars such as flareups and jet production, and protostellar interactions in forming systems of stars will also have important implications for planet formation. The most massive stars form in the densest environments by processes that are not yet well understood but may include violent interactions and mergers. The formation of the most massive stars may have similarities to the formation and growth of massive black holes in very dense environments. ‡ In his first letter to Bentley, as quoted by Jeans (1929), Newton said "It seems to me, that if the matter of our sun and planets, and all the matter of the universe, were evenly scattered throughout all the heavens, and every particle had an innate gravity towards all the rest, and the whole space throughout which this matter was scattered, was finite, the matter on the outside of this space would by its gravity tend towards all the matter on the inside, and by consequence fall down into the middle of the whole space, and there compose one great spherical mass. But if the matter were evenly disposed throughout an infinite space, it could never convene into one mass; but some of it would convene into one mass and some into another, so as to make an infinite number of great masses, scattered great distances from one to another throughout all that infinite space. And thus might the sun and fixed stars be formed, supposing the matter were of a lucid nature."

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Untitled

Cited by 11 publications

References 42 publications

Wind accretion in binary stars

Wind accretion in binary stars

Numerical simulation of the surface flow of a companion star in a close binary system

The physics of star formation

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