Browsing Department of Materials Science and Metallurgy by Subject "accretion, accretion discs"
Now showing items 111 of 11

Growth of eccentric modes in disc–planet interactions
(Oxford University PressMonthly Notices of the Royal Astronomical Society, 20160307)We formulate a set of linear equations that describe the behaviour of small eccentricities in a protoplanetary system consisting of a gaseous disc and a planet. Eccentricity propagates through the disc by means of pressure ...

MRI turbulence and thermal instability in accretion discs
(Oxford University PressMonthly Notices of the Royal Astronomical Society, 201706)A longstanding puzzle in the study of black hole accretion concerns the presence or not of thermal instability. Classical theory predicts that the encircling accretion disc is unstable, as do some selfconsistent ...

Nonaxisymmetric instabilities in discs with imposed zonal flows
(Oxford University PressMonthly Notices of the Royal Astronomical Society, 20160906)We conduct a linear stability calculation of an ideal Keplerian flow on which a sinusoidal zonal flow is imposed. The analysis uses the shearing sheet model and is carried out both in isothermal and adiabatic conditions, ...

Nonlinear hydrodynamical evolution of eccentric Keplerian discs in two dimensions: validation of secular theory
(Oxford University PressMonthly Notices of the Royal Astronomical Society, 20160311)We perform global twodimensional hydrodynamical simulations of Keplerian discs with free eccentricity over thousands of orbital periods. Our aim is to determine the validity of secular theory in describing the evolution ...

On the energy dissipation rate at the inner edge of circumbinary discs
(Oxford University PressMonthly Notices of the Royal Astronomical Society, 20161003)We study, by means of numerical simulations and analysis, the details of the accretion process from a disc on to a binary system. We show that energy is dissipated at the edge of a circumbinary disc and this is associated ...

On the formation of a quasistationary twisted disc after a tidal disruption event
(Oxford University PressMonthly Notices of the Royal Astronomical Society, 20160824)We investigate misaligned accretion discs formed after tidal disruption events that occur when a star encounters a supermassive black hole. We employ the linear theory of warped accretion discs to find the shape of a disc ...

On the orbital evolution of a pair of giant planets in mean motion resonance
(Oxford University PressMonthly Notices of the Royal Astronomical Society, 20160704)Pairs of extrasolar giant planets in a mean motion commensurability are common with 2:1 resonance occurring most frequently. Disc–planet interaction provides a mechanism for their origin. However, the timescale on which ...

Quasiperiodic oscillations and the global modes of relativistic, MHD accretion discs
The highfrequency quasiperiodic oscillations (HFQPOs) that punctuate the light curves of Xray binary systems present a window onto the intrinsic properties of stellarmass black holes and hence a testbed for general ...

Secular evolution of eccentricity in protoplanetary discs with gapopening planets
(Oxford University PressMonthly Notices of the Royal Astronomical Society, 201706)We explore the evolution of the eccentricity of an accretion disc perturbed by an embedded planet whose mass is sufficient to open a large gap in the disc. Various methods for representing the orbitaveraged motion of an ...

The stress–pressure relationship in simulations of MRIinduced turbulence
(Oxford University PressMonthly Notices of the Royal Astronomical Society, 20160101)We determine how MRI (magnetorotational instability)turbulent stresses depend on gas pressure via a suite of unstratified shearing box simulations. Earlier numerical work reported only a very weak dependence at best, ...

Zonal flow evolution and overstability in accretion discs
(Oxford University PressMonthly Notices of the Royal Astronomical Society, 20170401)This work presents a linear analytical calculation on the stability and evolution of a compressible, viscous selfgravitating (SG) Keplerian disc with both horizontal thermal diffusion and a constant cooling timescale ...