Characterising thermal sweeping: a rapid disc dispersal mechanism

Abstract

(Abridged) We consider the properties of protoplanetary discs that are undergoing inside-out clearing by photoevaporation. In particular, we aim to characterise the conditions under which a protoplanetary disc may undergo `thermal sweeping', a rapid (< 1e4 years) disc destruction mechanism proposed to occur when a clearing disc reaches sufficiently low surface density at its inner edge and where the disc is unstable to runaway penetration by the X-rays. We use a large suite of 1D radiation-hydrodynamic simulations to probe the observable parameter space, which is unfeasible in higher dimensions. These models allow us to determine the surface density at which thermal sweeping will take over the disc's evolution and to evaluate this critical surface density as a function of X-ray luminosity, stellar mass and inner hole radius. We find that this critical surface density scales linearly with X-ray luminosity, increases with inner hole radius and decreases with stellar mass and we develop an analytic model that reproduces these results. This surface density criterion is then used to determine the evolutionary state of protoplanetary discs at the point that they become unstable to destruction by thermal sweeping. We find that transition discs created by photoevaporation will undergo thermal sweeping when their inner holes reach 20-40 AU, implying that transition discs with large holes and no accretion (which were previously a predicted outcome of the later stages of all flavours of photoevaporation model) will not form. We emphasise that the surface density criteria that we have developed apply to all situations where the disc develops an inner hole that is optically thin to X-rays. It thus applies not only to the case of holes originally created by photoevaporation but also to holes formed, for example, by the tidal influence of planets.

10 Pages, MNRAS accp

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Cited by in corpus (22)

• The dispersal of protoplanetary discs I: A new generation of X-ray photoevaporation models
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• Observations of Solids in Protoplanetary Disks
• The origin and evolution of transition discs: successes, problems and open questions
• X-ray Super-Flares From Pre-Main Sequence Stars: Flare Energetics And Frequency
• Probing the Final Stages of Protoplanetary Disk Evolution with ALMA
• Radiation pressure clear-out of dusty photoevaporating discs
• Large gaps and high accretion rates in photoevaporative transition disks with a dead zone
• On dust entrainment in photoevaporative winds
• Photoevaporation of Grain-Depleted Protoplanetary Disks around Intermediate-Mass Stars: Investigating Possibility of Gas-Rich Debris Disks as Protoplanetary Remnants
• Making Planet Nine: Pebble Accretion at 250--750 AU in a Gravitationally Unstable Ring
• Photoevaporation of protoplanetary discs with PLUTO+PRIZMO I. Lower X-ray-driven mass-loss rates due to enhanced cooling
• The long-term evolution of photoevaporating transition discs with giant planets
• Global axisymmetric simulations of photoevaporation and magnetically driven protoplanetary disk winds
• Evolution of X-ray Activity in <25 Myr Old Pre-Main Sequence Stars
• Strong Biases in Estimating the Time Dependence of Mass Accretion Rates in Young Stars
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• Changing disc compositions via internal photoevaporation I: Solar-mass stars
• Irradiation Instability at the Inner Edges of Accretion Disks
• Millimeter emission in photoevaporating disks is determined by early substructures
• Emerging population of gap-opening planets around type-A stars -- Long-term evolution of the forming planets around HD 163296
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