A review of Bondi–Hoyle–Lyttleton accretion

Edgar, Richard G.

doi:10.1016/j.newar.2004.06.001

Cited by 337 publications

(307 citation statements)

References 64 publications

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“…However, Bondi & Hoyle (1944) postulated an increase in the IS gas density in the wake behind the star, since many gas particle trajectories cross on the axis. Such behavior is indeed found in multidimensional numerical simulations of Bondi-Hoyle accretion (see Edgar (2004) for a summary). The higher density would facilitate accretion.…”

Section: Contamination Of Stellar Atmospheressupporting

confidence: 56%

Infrared Emission by Dust Around Λ Bootis Stars: Debris Disks or Thermally Emitting Nebulae?

Martínez-Galarza

Kamp

et al. 2009

ApJ

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We present a model that describes stellar infrared excesses due to heating of the interstellar (IS) dust by a hot star passing through a diffuse IS cloud. This model is applied to six λ Bootis stars with infrared excesses. Plausible values for the IS medium (ISM) density and relative velocity between the cloud and the star yield fits to the excess emission. This result is consistent with the diffusion/accretion hypothesis that λ Bootis stars (A-to F-type stars with large underabundances of Fe-peak elements) owe their characteristics to interactions with the ISM. This proposal invokes radiation pressure from the star to repel the IS dust and excavate a paraboloidal dust cavity in the IS cloud, while the metal-poor gas is accreted onto the stellar photosphere. However, the measurements of the infrared excesses can also be fit by planetary debris disk models. A more detailed consideration of the conditions to produce λ Bootis characteristics indicates that the majority of infrared-excess stars within the Local Bubble probably have debris disks. Nevertheless, more distant stars may often have excesses due to heating of IS material such as in our model.

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Section: Contamination Of Stellar Atmospheressupporting

confidence: 56%

Infrared Emission by Dust Around Λ Bootis Stars: Debris Disks or Thermally Emitting Nebulae?

Martínez-Galarza

Kamp

et al. 2009

ApJ

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“…Hydrostatic balance of the envelope structure ensures that typical Mach numbers are consistent, and mildly supersonic. These results are tabulated for = a R 0.5 * in Table 1. directed to Edgar (2004) a recent review, and to Foglizzo et al (2005) for a detailed comparison of published simulations that attempts to synthesize results with respect to flow stability as it depends on Mach number, accretor size, geometry, and equation of state. Rather than restating their work here, we review only a few of the most relevant and recent studies.…”

Section: Previous Numerical Studies Of Hlamentioning

confidence: 99%

“…These studies developed an analytic understanding of the nature of accretion onto a gravitational source moving supersonically through its surrounding medium (see Edgar 2004, for a recent review). Semi-analytical work has used these prescriptions to estimate the inspiral and accretion experienced by an object embedded in an envelope.…”

Section: Introductionmentioning

confidence: 99%

Asymmetric Accretion Flows Within a Common Envelope

MacLeod

Ramírez-Ruiz

2015

ApJ

131

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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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“…The DF in a gaseous background is likely to play an important role in the orbital decay of companions in common-envelope binaries, supermassive black holes (SMBHs) at galaxy centers, massive galaxies in galaxy clusters, etc. For instance, in a binary system, DF causes a lowmass companion engulfed by an extended primary to spiral in toward the core of the primary, which in turn spins up the primary envelope, greatly affecting the subsequent evolution of the system (e.g., Taam & Sandquist 2000;Edgar 2004;Nordhaus & Blackman 2006;Maxted et al 2009, and references therein). Also, numerical simulations show that the DF due to a gaseous medium expedites the growth of SMBHs by mergers in colliding galaxies (e.g., Milosavljević & Merritt 2003;Escala et al 2004Escala et al , 2005Dotti et al 2006;Mayer et al 2007;Colpi & Dotti 2009), potentially explaining the ubiquity of SMBHs at galactic nuclei (e.g., Begelman et al 1980;Menou et al 2001;Ferrarese & Ford 2005).…”

Section: Introductionmentioning

confidence: 99%

Nonlinear Dynamical Friction of a Circular-Orbit Perturber in a Gaseous Medium

Kim¹

2010

ApJ

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We use three-dimensional hydrodynamic simulations to investigate the nonlinear gravitational responses of gas to, and the resulting drag forces on, very massive perturbers moving in circular orbits. This work extends our previous studies that explored the cases of low-mass perturbers in circular orbits and massive perturbers on straight-line trajectories. The background medium is assumed to be non-rotating, adiabatic with index 5/3, and uniform with density ρ 0 and sound speed a 0 . We model the gravitating perturber using a Plummer sphere with mass M p and softening radius r s in a uniform circular motion at speed V p and orbital radius R p , and run various models with differing R ≡ r s /R p , M ≡ V p /a 0 , and B ≡ GM p /(a 2 0 R p ). A quasi-steady density wake of a supersonic model consists of a hydrostatic envelope surrounding the perturber, an upstream bow shock, and a trailing low-density region. The continuous change in the direction of the perturber motion reduces the detached shock distance compared to the linear-trajectory cases, while the orbit-averaged gravity of the perturber gathers the gas toward the center of the orbit, modifying the background preshock density to ρ 1 ≈ (1+0.46B 1.1 )ρ 0 depending weakly on M. For sufficiently massive perturbers, the presence of a hydrostatic envelope makes the drag force smaller than the prediction of the linear perturbation theory, resulting in1; the drag force for low-mass perturbers with η B < 0.1 agrees well with the linear prediction. The nonlinear drag force becomes independent of R as long as R < η B /2, which places an upper limit on the perturber size for accurate evaluation of the drag force in numerical simulations.

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A review of Bondi–Hoyle–Lyttleton accretion

Cited by 337 publications

References 64 publications

Infrared Emission by Dust Around Λ Bootis Stars: Debris Disks or Thermally Emitting Nebulae?

Infrared Emission by Dust Around Λ Bootis Stars: Debris Disks or Thermally Emitting Nebulae?

Asymmetric Accretion Flows Within a Common Envelope

Nonlinear Dynamical Friction of a Circular-Orbit Perturber in a Gaseous Medium

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