Accretion from an inhomogeneous medium – III. General case and observational consequences

Livio, Mario; Soker, Noam; Kool, M. de; Savonije, G. J.

doi:10.1093/mnras/222.2.235

Cited by 70 publications

(53 citation statements)

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“…Many numerical simulations have been performed to study wind accretion and test the validity of the predictions of the canonical BHL model of wind mass transfer (e.g., Hunt 1971;Anzer et al 1987;Livio et al 1986;Bowen & Willson 1991;Matsuda et al 1992;Sawada & Matsuda 1992;Ruffert 1994;Bate et al 1995).…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional Hydrodynamical Simulations of Mass Transfer in Binary Systems by a Free Wind

Liu

Stancliffe

Abate

et al. 2017

ApJ

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A large fraction of stars in binary systems are expected to undergo mass and angular momentum exchange at some point in their evolution, which can drastically alter the chemical and dynamical properties and fates of the systems. Interaction by stellar wind is an important process in wide binaries. However, the details of wind mass transfer are still not well understood. We perform threedimensional hydrodynamical simulations of wind mass transfer in binary systems to explore mass accretion efficiencies and geometries of mass outflows, for a range of mass ratios from 0.05 to 1.0. In particular, we focus on the case of a free wind, in which some physical mechanism accelerates the expelled wind material balancing the gravity of the mass-losing star with the wind velocity comparable to the orbital velocity of the system. We find that the mass accretion efficiency and accreted specific angular momentum increase with the mass ratio of the system. For an adiabatic wind, we obtain that the accretion efficiency onto the secondary star varies from about 0.1% to 8% for mass ratios between 0.05 and 1.0.

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Section: Introductionmentioning

confidence: 99%

Three-dimensional Hydrodynamical Simulations of Mass Transfer in Binary Systems by a Free Wind

Liu

Stancliffe

Abate

et al. 2017

ApJ

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“…This work builds on analytic considerations (Dodd & McCrea 1952;Illarionov & Sunyaev 1975;Shapiro & Lightman 1976;Davies & Pringle 1980) and simulations of nonaxisymmetric flow conditions in HLA (Soker & Livio 1984;Soker et al 1986;Livio et al 1986a;Fryxell & Taam 1988;Ruffert 1999). However, since much of this work was motivated by inhomogeneities in wind-capture binaries, typical density gradients tend to be much milder than those experienced by an embedded object within a CE.…”

Section: Introductionmentioning

confidence: 99%

Asymmetric Accretion Flows Within a Common Envelope

MacLeod

Ramírez-Ruiz

2015

ApJ

128

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This paper examines flows in the immediate vicinity of stars and compact objects dynamically inspiralling within a common envelope (CE). Flow in the vicinity of the embedded object is gravitationally focused, leading to drag and potentially to gas accretion. This process has been studied numerically and analytically in the context of HoyleLyttleton accretion (HLA). Yet, within a CE, accretion structures may span a large fraction of the envelope radius, and in so doing sweep across a substantial radial gradient of density. We quantify these gradients using detailed stellar evolution models for a range of CE encounters. We provide estimates of typical scales in CE encounters that involve main sequence stars, white dwarfs, neutron stars, and black holes with giant-branch companions of a wide range of masses. We apply these typical scales to hydrodynamic simulations of three-dimensional HLA with an upstream density gradient. This density gradient breaks the symmetry that defines HLA flow, and imposes an angular momentum barrier to accretion. Material that is focused into the vicinity of the embedded object thus may not be able to accrete. As a result, accretion rates drop dramatically, by one to two orders of magnitude, while drag rates are only mildly affected. We provide fitting formulae to the numerically derived rates of drag and accretion as a function of the density gradient. The reduced ratio of accretion to drag suggests that objects that can efficiently gain mass during CE evolution, such as black holes and neutron stars, may grow less than implied by the HLA formalism.

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“…Livio et al (1986;see also Ruffert 1999) find that the actual accreted specific angular momentum for high Mach number flows is j a ¼ j BH , where $ 0:1 and $ 0:3 for isothermal and adiabatic flows, respectively. The relative velocity is…”

Section: Accretion By the Companion Starmentioning

confidence: 95%

X‐Ray Emission from Central Binary Systems of Planetary Nebulae

Soker

Kastner

2002

ApJ

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We study the conditions under which a main-sequence binary companion to the central ionizing star of a planetary nebula (PN) might become magnetically active and thereby display strong X-ray luminosity, L X e5 Â 10 29 ergs s À1 . Since most PNs are older than few billion years, any main-sequence companion will rotate too slowly to have magnetic activity and hence bright X-ray emission unless it is spun up. We demonstrate that if the orbital separation during the asymptotic giant branch (AGB) phase of the PN progenitor is ad30 60 AU, main-sequence companions in the spectral type range F7-M4 (mass range 0:3 M dM 2 d1:3 M ) will accrete enough angular momentum from the AGB wind to rotate rapidly, become magnetically active, and exhibit X-ray luminosities L X e5 Â 10 29 ergs s À1 . Lower mass M stars and brown dwarfs can also become magnetically active, but they should have small orbital separations and hence are less likely to survive the AGB phase of the progenitor. For orbital separation of ad0:3 AU, i.e., for a binary systems that went through a common envelope phase, the fast wind from the central white dwarf (WD) star will interact with (and potentially disrupt) the companion's corona on the side facing the central star, while for ad6 R , i.e., an orbital period of P orb d30 hr, the WD's fast wind will compress a dense small region near the surface of the companion. This region may thermally emit X-rays with nonnegligible luminosity. We estimate that 20%-30% of elliptical PNs and 30%-50% of bipolar PNs are likely to have magnetically active companions that will reveal themselves in X-ray observations. Reanalysis of Chandra spectroscopy of the compact central source of NGC 7293 indicates that the emitting region of this object possesses abundance anomalies similar to those of coronally active main-sequence stars. High-resolution X-ray spectroscopy of this and other compact sources in PNs are necessary to confirm a coronal origin for the X-ray emission.

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Accretion from an inhomogeneous medium – III. General case and observational consequences

Cited by 70 publications

References 0 publications

Three-dimensional Hydrodynamical Simulations of Mass Transfer in Binary Systems by a Free Wind

Three-dimensional Hydrodynamical Simulations of Mass Transfer in Binary Systems by a Free Wind

Asymmetric Accretion Flows Within a Common Envelope

X‐Ray Emission from Central Binary Systems of Planetary Nebulae

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