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Local models of astrophysical discs
(Oxford University PressMonthly Notices of the Royal Astronomical Society, 2017-12-01)
Local models of gaseous accretion discs have been successfully employed for decades to describe an assortment of small-scale phenomena, from instabilities and turbulence, to dust dynamics and planet formation. For the most ...
On the survival of zombie vortices in protoplanetary discs
(Oxford University PressMonthly Notices of the Royal Astronomical Society, 2016-09-06)
Recently it has been proposed that the zombie vortex instability (ZVI) could precipitate hydrodynamical activity and angular momentum transport in unmagnetized regions of protoplanetary discs, also known as ‘dead zones’. ...
Secular evolution of eccentricity in protoplanetary discs with gap-opening planets
(Oxford University PressMonthly Notices of the Royal Astronomical Society, 2017-06)
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 orbit-averaged motion of an ...
Dynamical tides in exoplanetary systems containing hot Jupiters: Confronting theory and observations
(Oxford University PressMonthly Notices of the Royal Astronomical Society, 2017-09-11)
We study the effect of dynamical tides associated with the excitation of gravity waves in an interior radiative region of the central star on orbital evolution in observed systems containing hot Jupiters. We consider ...
Growth of eccentric modes in disc–planet interactions
(Oxford University PressMonthly Notices of the Royal Astronomical Society, 2016-03-07)
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 ...
Nonlinear hydrodynamical evolution of eccentric Keplerian discs in two dimensions: validation of secular theory
(Oxford University PressMonthly Notices of the Royal Astronomical Society, 2016-03-11)
We perform global two-dimensional 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 ...
Nonlinear tides in a homogeneous rotating planet or star: global modes and elliptical instability
(Oxford University PressMonthly Notices of the Royal Astronomical Society, 2016-03-28)
We revisit the global modes and instabilities of homogeneous rotating ellipsoidal fluid masses, which are the simplest global models of rotationally and tidally deformed gaseous planets or stars. The tidal flow in a ...
Nonlinear tides in a homogeneous rotating planet or star: global simulations of the elliptical instability
(Oxford University PressMonthly Notices of the Royal Astronomical Society, 2016)
I present results from the first global hydrodynamical simulations of the elliptical instability in a tidally deformed gaseous planet (or star) with a free surface. The elliptical instability is potentially important for ...
On the orbital evolution of a pair of giant planets in mean motion resonance
(Oxford University PressMonthly Notices of the Royal Astronomical Society, 2016-07-04)
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 time-scale on which ...
On the formation of a quasi-stationary twisted disc after a tidal disruption event
(Oxford University PressMonthly Notices of the Royal Astronomical Society, 2016-08-24)
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 ...