Recurrence Time for Dwarf Nova Outbursts: Dependence on Mass Transfer Rate

Ichikawa, S.; Osaki, Yoji

doi:10.1007/978-94-011-0858-4_14

Cited by 44 publications

(41 citation statements)

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“…AsṀ tr increases, the mass accumulation time at the outer radius can become lower than the drift time, triggering an outburst in the outer disc (an outside-in, type A outburst). The accumulation time is (Ichikawa & Osaki 1994; see also Osaki 1995:…”

Section: Quiescencementioning

confidence: 99%

The disc instability model for X-ray transients: Evidence for truncation and irradiation

Dubus

Hameury

Lasota

2001

A&A

347

549

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Abstract.We study the prospect of explaining the outbursts of Soft X-ray Transients (SXTs) by the thermalviscous instability in a thin disc. This instability is linked to hydrogen ionization and is significantly changed when irradiation of the disc by X-rays from the inner regions is included. We present the first numerically reliable, physically consistent calculations of the outburst cycles which include the effects of accretion disc irradiation. The decay from outburst is governed by irradiation, as pointed out by King & Ritter (1998), leading to slow exponential decays. At the end of the outburst, the disc is severely depleted, which lengthens the time needed to rebuild mass to the critical density for an outburst. Despite this, the long recurrence times and quiescent X-ray luminosities of SXTs still require the inner disc to be replaced by another type of flow in quiescence, presumably a hot advection dominated accretion flow (ADAF). We include the effects of such truncation and show that the resulting lightcurves are conclusively similar to those of SXTs like A0620-00. We conclude that the two-α disc instability model provides an adequate description of the outbursts of SXTs when both truncation and irradiation are included. The values for the viscosities in outburst and in quiescence are comparable to those used in CVs. We discuss the model in the context of present observations.

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Section: Quiescencementioning

confidence: 99%

The disc instability model for X-ray transients: Evidence for truncation and irradiation

Dubus

Hameury

Lasota

2001

A&A

347

549

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“…This extra angular momentum leads to the spreading of the disc. The outer disc radius is truncated because of tidal interaction between the disc and the donor star (Lin & Papaloizou 1979;Whitehurst 1988;Ichikawa & Osaki 1994) and, consequently, some angular momentum is returned to the orbit.…”

Section: Dimensionless Equationsmentioning

confidence: 99%

Critically-rotating accretors and non-conservative evolution in Algols

Deschamps

Siess

Davis

et al. 2013

A&A

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Context. During the mass-transfer phase in Algol systems, a large amount of mass and angular momentum are accreted by the gainer star, which can be accelerated up to its critical Keplerian velocity. The fate of the gainer once it reaches this critical value is unclear. Aims. We investigate the orbital and stellar spin evolution in semi-detached binary systems, specifically for systems with rapidly rotating accretors. Our aims are to better distinguish between the different spin-down mechanisms proposed that can consistently explain the slow rotation observed in Algols' final states and to assess the degree of non-conservatism due to the formation of a hotspot. Methods. We use our state-of-the-art binary evolution code, Binstar, which incorporates a detailed treatment of the orbital and stellar spin and includes all torques due to mass transfer, the interactions between a star and its accretion disc, tidal effects, and magnetic braking. We also present a new prescription for mass loss due to the formation of a hotspot based on energy conservation. Results. The coupling between the star and the disc via the boundary layer prevents the gainer from exceeding the critical rotation. Magnetic-field effects, although operating, are not the dominant spin-down mechanism for sensible field strengths. Spin down owing to tides is 2-4 orders of magnitudes too weak to compensate the spinning-up torque due to mass accretion. Moreover, we find that the final separation strongly depends on the spin-down mechanism. The formation of a hotspot leads to a large event of mass loss during the rapid phase of mass transfer. The degree of conservatism strongly depends on the opacity of the impacted material. Conclusions. A statistical study and new observational constraints are needed to find the optimal set of parameters (magnetic-field strength, hotspot geometry, etc.) to reproduce Algol evolutions.

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“…In any case in our code the tidal heating is more important. As far as this effect is concerned Smak's result is based on the calculations of Ichikawa & Osaki (1994) who (Polidan & Holberg 1987). As in Paper I ∆ UV,0 and ∆ EUV,0 denote the delays measured at the onset of the outburst whereas ∆ UV,0.5 and ∆ EUV,0.5 have been determined at half the maximum optical flux.…”

Section: Simulationsmentioning

confidence: 99%

Delays in dwarf novae II: VW Hyi, the tidal instability and enhanced mass transfer models

Schreiber

Hameury

Lasota³

2004

A&A

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Abstract.We discuss the multi-wavelength predictions of the two models proposed for SU UMa stars, i.e. the enhanced mass transfer (EMT) and the tidal thermal instability (TTI) models. We focus on the systematic differences of the suggested scenarios before discussing the model predictions together with the observations of the best-studied SU UMa system, VW Hyi. We find that assuming the standard form of the viscosity parameter α, both models predict only outbursts being triggered at the inner edge of the accretion disc. In the TTI model the superoutbursts are triggered when the outer radius of the disc reaches a certain value, i.e. the 3:1 resonance radius. In contrast, the EMT scenario predicts superoutbursts when the disc mass exceeds a critical value. This causes the EMT model to be much more sensitive to mass transfer variations than the TTI model. In both models we find the predicted UV and EUV delays in agreement with the observations of VW Hyi for α h /α c < ∼ 4. In addition both models can generate precursor outbursts which are more pronounced at short wavelengths, in agreement with observations. Variations found in the observed light curve of single systems (e.g. VW Hyi) as well as the difference between ordinary SU UMa stars and ER UMa systems are a natural outcome of the EMT model while the TTI model fails to explain them.

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Recurrence Time for Dwarf Nova Outbursts: Dependence on Mass Transfer Rate

Cited by 44 publications

References 1 publication

The disc instability model for X-ray transients: Evidence for truncation and irradiation

The disc instability model for X-ray transients: Evidence for truncation and irradiation

Critically-rotating accretors and non-conservative evolution in Algols

Delays in dwarf novae II: VW Hyi, the tidal instability and enhanced mass transfer models

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