Low compressibility accretion disc formation in close binaries: the role of physical viscosity

Lanzafame, G.; Belvedère, G.; Molteni, D.

doi:10.1051/0004-6361:20054225

Cited by 11 publications

(39 citation statements)

References 47 publications

(63 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Physical viscosity supports accretion disc development inside the primary gravitational potential well in close binaries (CBs), even for low compressibility modelling, (Lanzafame et al 2006). In Molteni et al (1991) and Lanzafame et al (1992), physically inviscid conditions do not produce a high enough particle concentration to get a significant particle resolution and statistics.…”

Section: Introductionmentioning

confidence: 99%

Effects of local thermodynamics and of stellar mass ratio on accretion disc stability in close binaries

Lanzafame¹

2009

Astron Nachr

Self Cite

View full text Add to dashboard Cite

Inflow kinematics at the inner Lagrangian point L1, gas compressibility, and physical turbulent viscosity play a fundamental role on accretion disc dynamics and structure in a close binary (CB). Physical viscosity supports the accretion disc development inside the primary gravitational potential well, developing the gas radial transport, converting mechanical energy into heat. The Stellar-Mass-Ratio (SMR) between the compact primary and the secondary star (M1/M2) is also effective, not only in the location of the inner Lagrangian point, but also in the angular kinematics of the mass transfer and in the geometry of the gravitational potential wells. In this work we pay attention in particular to the role of the SMR, evaluating boundaries, separating theoretical domains in compressibility-viscosity graphs where physical conditions allow a well-bound disc development, as a function of mass transfer kinematic conditions. In such domains, the lower is the gas compressibility (the higher the polytropic index γ), the higher is the physical viscosity (α) requested. In this work, we show how the boundaries of such domains vary as a function of M1/M2. Conclusions as far as dwarf novae outbursts are concerned, induced by mass transfer rate variations, are also reported. The smaller M1/M2, the shorter the duration of the active-to-quiet and vice-versa transitional phases. Time-scales are of the order of outburst duration of SU Uma, OY Car, Z Cha and SS Cyg-like objects. Moreover, conclusions as far as active-quiet-active phenomena in a CB, according to viscous-thermal instabilities, in accordance to such domains, are also reported.

show abstract

Section: Introductionmentioning

confidence: 99%

Effects of local thermodynamics and of stellar mass ratio on accretion disc stability in close binaries

Lanzafame¹

2009

Astron Nachr

Self Cite

View full text Add to dashboard Cite

show abstract

“…To our knowledge, there are no models of accretion disc formation during the peak of the irradiation of a nova. General simulations, as those by Lanzafame, Belvedere & Molteni (2006) (see their figure 2), still allow a great range of values for f , which varies from effectively 0 for high viscosity material to about 10 −1 for very low viscosity values.…”

Section: The Modelmentioning

confidence: 91%

The slow decline of the Galactic recurrent novae T Pyxidis, IM Normae, and CI Aquilae

Caleo

Shore

2015

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

A distinguishing trait of the three known Galactic recurrent novae with the shortest orbital periods, T Pyx, IM Nor, and CI Aql, is that their optical decline time-scales are significantly longer than those of the other recurrent systems. On the other hand, some estimates of the mass of the ejecta, the velocity of the ejecta, and the duration of the soft X-rays emission of these systems are of the order of those of the other recurrent systems and the fast classical novae. We put forth a tentative explanation of this phenomenon. We propose that in these systems part of the material transferred from the companion during the first few days of the eruption remains within the Roche lobe of the white dwarf, preventing the radiation from ionizing the ejecta of the system and increasing the optical decline time-scale. We explain why this phenomenon is more likely in systems with a high mass transfer rate and a short orbital period. Finally, we present a schematic model that shows that the material transferred from the companion is sufficient to absorb the radiation from the white dwarf in these systems, ultimately supporting this scenario as quantitatively realistic.

show abstract

“…In [9] it is shown that physical viscosity supports the accretion disc development inside the primary gravitational potential well, despite the low compressibility conditions adopted. Inviscid simulations in low compressibility conditions (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…This means that physical viscosity plays a relevant role mainly in the radial transport, while it has little influence on the tangential dynamics. It converts mechanical energy into thermal energy (heating the disc), supporting the development of well-bound accretion discs inside the primary potential well, even in spite of a hypothetical low compressibility gas ( [9]). It reduces the disc thickness and increases the accretion rate onto the accreting star, but, and this is the most important thing, it hampers the repulsive pressure forces among contiguous fluid elements supporting the accretion disc in developing a well-bound consistency.…”

Section: Introductionmentioning

confidence: 99%

Hydrodynamic simulations of outburst events in accretion discs in close binaries

Lanzafame

2009

Proceedings of VII Microquasar Workshop: Microquasars and Beyond — PoS(MQW7)

View full text Add to dashboard Cite

In this work, the role of both inflow kinematic at the inner Lagrangian point L1 as initial boundary condition, and gas compressibility, and physical turbulent viscosity, on accretion disc's dynamics and structure in a Close Binary (CB), are investigated via simulations of 3D SPH stationary accretion disc models. Physical viscosity hampers the gas dynamics (rarefaction or compression), supporting the accretion disc development inside the primary gravitational potential well in a CB system, even for low compressibility modelling. Currently, the turbulent Shakura-Sunyaev parameter α ≃ 0.1 is widely adopted for these structures. Such investigation is here carried out in both high and low compressibility regimes, with the aim of evaluating, in a compressibility-viscosity graph, the most suitable domains where physical conditions allow a well-bound disc development as a function of mass transfer kinematic conditions. A selection of the adopted α physical turbulent viscosity parameter (α ≤ 1 according to the well-known Shakura-Sunjaev formulation) has been considered, whilst the adopted polytropic index γ is chosen in the range between 1 ÷ 5/3. Results show that domains exist where physical turbulent viscosity supports the accretion disc formation. In such domains, the lower the gas compressibility, the higher the physical viscosity requested. A role played by the injection kinematics at the inner Lagrangian point L1 is also found. Conclusions as far as dwarf novae outbursts are concerned, induced by mass transfer rate variations, are also reported. Considerations as far as periodicities in an accretion disc are also reported.

show abstract

Low compressibility accretion disc formation in close binaries: the role of physical viscosity

Cited by 11 publications

References 47 publications

Effects of local thermodynamics and of stellar mass ratio on accretion disc stability in close binaries

Effects of local thermodynamics and of stellar mass ratio on accretion disc stability in close binaries

The slow decline of the Galactic recurrent novae T Pyxidis, IM Normae, and CI Aquilae

Hydrodynamic simulations of outburst events in accretion discs in close binaries

Contact Info

Product

Resources

About