Crime in Australia

Hazlehurst, Kayleen M.

doi:10.1007/978-1-349-15184-4_12

Cited by 4 publications

(3 citation statements)

References 24 publications

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“…An increase of the turbulent envelope in the secondary is in conflict with Roche geometry. An increase in the primary is compatible with Roche geometry, but the resulting model (Kähler 1989, Kähler & Fehlberg 1991 is in conflict with the second law of thermodynamics (Hazlehurst 1993) since (in a large region) internal mass motions transfer energy from cooler to hotter layers.…”

Section: Introductionmentioning

confidence: 91%

On the structure of contact binaries

Kahler

2002

A&A

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Abstract. In a preceding paper a simple model for contact binaries has been proposed, based on the usual assumption that the energy sources/sinks caused by the interaction of the components occur only in the secondary's/primary's outer layers. Here the model is applied to a typical late-type system. First we imposed the restriction that the fractional extent in mass of the sources/sinks in the layers above the critical surface is the same in both components, and found solutions evolving in thermal cycles. If the energy transfer is assumed to be sufficiently effective, loss of contact is avoided. Otherwise the cycle consists of a long quiet phase in good contact and a short violent phase with rapid changes between contact, semidetached, and detached configurations. In both cases there are cycles in which the temperatures of the components are similar in the largest part of the time. Other observational tests are also passed. Next we removed the restriction. In the resulting model with three free parameters we found (besides cycles) a large range of solutions in stable thermal equilibrium which are compatible with the observations. From a theoretical viewpoint however all these solutions are unsatisfactory since suffering from several inconsistencies. This result shows that the usual assumption on the energy sources and sinks is too restrictive. We are led to look for modifications of the model which remove the inconsistencies. This will be done in a forthcoming paper.

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Section: Introductionmentioning

confidence: 91%

On the structure of contact binaries

Kahler

2002

A&A

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“…All these attempts failed. In particular, the contact discontinuity hypothesis (Shu et al 1976) violates the second law of thermodynamics (Hazlehurst & Refsdal 1978;Papaloizou & Pringle 1979), the assumption of an extended turbulent envelope in the primary (Kähler 1989;Kähler & Fehlberg 1991) is also in conflict with the second law (Hazlehurst 1993), and the assumption of sufficiently rapid internal mass motions in the primary's envelope (Kähler 1995) is in conflict with the observations (Kähler 1997a). For additional arguments against the possibility of thermal equlibrium see Hazlehurst (1993).…”

Section: Introductionmentioning

confidence: 99%

The structure equations of contact binaries

Kahler

2002

A&A

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Abstract. The structure equations of contact binaries are discussed. An equation for the transfer of mass between the components is derived. Serious uncertainties concern only the transfer of energy. They are expressed as unknown functions. An evolution code for contact binaries is presented. The restrictions imposed by a spherically averaged treatment of the components are discussed. Apart from these restrictions the code can be adapted to any choice of the functions describing the energy transfer. A simple tentative choice for these functions is proposed.

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“…An increase of the turbulent envelope in the secondary is in conflict with Roche geometry. An increase in the primary is compatible with Roche geometry, but the resulting model (Kähler 1989;Kähler & Fehlberg 1991) is in conflict with the second law of thermodynamics (Hazlehurst 1993) since (in a large region) internal mass motions transfer energy from cooler to hotter layers.…”

Section: Introductionmentioning

confidence: 99%

The structure of contact binaries

Kaehler

2004

A&A

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Abstract. In radiative layers of rotating stars the luminosity carried by circulation currents through a surface of constant entropy (circulation luminosity) is shown to be positive. The corresponding decrease in the temperature gradient is important in the secondary of contact binaries. This result removes the deadlock in the theory of contact binaries. The resulting treatment of contact binaries is investigated, assuming thermal equilibrium. The sources of the circulation luminosity in the secondary can be written as the product of a circulation function (a normalized non-negative function of the fractional mass) and an amplitude. If the amplitude is adjusted to give a prescribed temperature difference ∆T e = T e1 − T e2 , the choice of the circulation function is (in a broad range) unimportant. This invariance extends in a close approximation to all observable properties as well as to the internal structure. The temperature difference is bound to be positive. The fractional extent of radiative regions is larger in the secondary than in the primary. In the course of evolution the period increases and the mass ratio decreases. Comparing thermodynamic quantites on level surfaces, pressure and density are larger in the secondary than in the primary. The specific entropy is larger in the primary than in the secondary. The temperature difference is remarkably small and almost vanishing when averaged over the level surfaces occupied in both components. The only free parameter (apart from ∆T e ) is the efficiency f E of the energy transfer from the primary to the secondary. Using standard values for the parameters, a survey of unevolved and evolved contact configurations is presented. Observational tests are passed. In stable systems the degree of contact is small. Stable systems in the period-colour diagram, unevolved and evolved, cover the strip (and only the strip) of observed systems in this diagram. Lower limits for period and effective temperature, compatible with the observed limits, are caused by the requirement of thermal stability. Stable systems with mass ratios very close to unity are possible, in accordance with recent observations. Since stability considerations are essential in these observational tests the results support the assumption of thermal equilibrium as well as the treatment of the stability problem. Models for individual observed systems with reliable data are well-determined (apart from some freedom in ∆T e ) and can be used to calibrate the efficiency and to determine metallicity and age. All models obtained so far are stable. This again supports the assumption of thermal stability. The results show that evolutionary effects are important and that the efficiency is very small ( f E = 10 −3 . . . 10 −5 ). Arguments are presented that the velocity field in the common envelope has a reversing layer, with motions from the secondary to the primary in the layers just above the critical surface and from the primary to the secondary in the surface layers.

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Crime in Australia

Cited by 4 publications

References 24 publications

On the structure of contact binaries

On the structure of contact binaries

The structure equations of contact binaries

The structure of contact binaries

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