Related papers: Accretion disc viscosity: a limit on the anisotrop…
X-ray binary accretion disk winds can carry away a significant fraction of the matter transferred from the companion and hence strongly affect the accretion flow and the long-term evolution of the binary. However, accurate mass outflow rate…
We present an analytic model in which an inefficiently radiating accretion disk drives upward wind from its surfaces. The accretion process is controlled simultaneously by a global magnetic field penetrating the disk and by a viscosity of…
We consider the shape of an accretion disc whose outer regions are misaligned with the spin axis of a central black hole and calculate the steady state form of the warped disc in the case where the viscosity and surface densities are power…
Dwarf Novae and low-mass X-ray binaries are eruptive binary systems comprised of a Roche-lobe overflowing solar-type star and an accreting compact object. Their recurrence time can be explained by a low-accreting phase, the quiescence,…
We conjecture that observed protoplanetary disc accretion rates may be explained with low viscosities which could be the result of hydrodynamic turbulence. We show that viscosities parameterized in the usual way with $\alpha \gtrsim…
We use well-established observational evidence to draw conclusions about the fundamental nature of the viscosity in accretion discs. To do this, we first summarise the observational evidence for the value of the dimensionless accretion disc…
Accretion discs are generally warped. If a warp in a disc is too large, the disc can `break' apart into two or more distinct planes, with only tenuous connections between them. Further if an initially planar disc is subject to a strong…
We show that the distribution of observed accretion rates is a powerful diagnostic of protoplanetary disc physics. Accretion due to turbulent ("viscous") transport of angular momentum results in a fundamentally different distribution of…
We simulate the viscous evolution of an accretion disc around a spinning black hole. In general any such disc is misaligned, and warped by the Lense-Thirring effect. Unlike previous studies we use effective viscosities constrained to be…
The self-sustained turbulence which develops in magnetized accretion disks is suppressed in the weakly-ionized, quiescent disks of close binary stars. Because accretion still proceeds during quiescence, another viscosity mechanism operates…
We explore the properties of cold gravitoturbulent accretion disks - non-fragmenting disks hovering on the verge of gravitational instability - using a realistic prescription for the effective viscosity caused by gravitational torques. This…
Purely hydrodynamic numerical experiments into the evolution of astrophysical discs typically include some sort of viscosity in order to cause accretion. In this paper, we demonstrate an alternative method of implementing viscous forces,…
Simulations and analytic arguments suggest that the turbulence driven by magnetorotational instability (MRI) in accretion discs can amplify the toroidal (azimuthal) component of the magnetic field to a point at which magnetic pressure…
The traditional paradigm of viscosity-dominated evolution of protoplanetary discs has been recently challenged by magnetized disc winds. However, distinguishing wind-driven and turbulence-driven accretion through observations has been…
Observational evidence accumulated over the past decade indicates that accretion discs in X-ray binaries are viscously stable unless they accrete very close to the Eddington limit. This is at odds with the most basic standard accretion disc…
We present evidence for an identical behavior of the precession of the accretion disk and that of the neutron star (NS) in Her X-1, based on investigating the well established 35 day modulation in Her X-1 in two different ways: 1) following…
We investigate angular momentum transport and accretion properties in a sample of protoplanetary discs with dynamical measurements of stellar masses, disc masses, and scale radii. From these data we infer effective $\alpha$-viscosities,…
We review results on the dynamics of warped gaseous discs. We consider tidal perturbation of a Keplerian disc by a companion star orbiting in a plane inclined to the disc. The perturbation induces the precession of the disc, and thus of any…
Sillanp\"a\"a, {\it et al.} (1996) have demonstrated that the AGN OJ287 has intensity peaks which recur with a period of about 12 years. I suggest that this is the result of the sweeping of a precessing relativistic beam across our line of…
We study protoplanetary disc evolution assuming that angular momentum transport is driven by gravitational instability at large radii, and magnetohydrodynamic (MHD) turbulence in the hot inner regions. At radii of the order of 1 AU such…