Planet formation around intermediate-mass stars. I: different disc evolutionary pathways as a function of stellar mass

Abstract

Context. The study of protoplanetary disc evolution and theories of planet formation has predominantly concentrated on solar- (andlow-) mass stars since they host the majority of confirmed exoplanets. Nevertheless, the confirmation of numerous planets orbitingstars more massive than the Sun (up to ∼3 M⊙) has sparked considerable interest in understanding the mechanisms involved in theirformation, and thus in the evolution of their hosting protoplanetary discs.Aims. We aim to improve our knowledge of the evolution of the gaseous component of protoplanetary discs around intermediate-massstars and to set the stage for future studies of planet formation around them.Methods. We study the long-term evolution of protoplanetary discs affected by viscous accretion and photoevaporation by X-ray andfar-ultraviolet (FUV) photons from the central star around stars in the range of 1–3 M⊙, considering the effects of stellar evolution andsolving the vertical structure equations of the disc. We explore the effect of different values of the viscosity parameter and the initialmass of the disc.Results. We find that the evolutionary pathway of protoplanetary disc dispersal due to photoevaporation depends on the stellar mass.Our simulations reveal four distinct evolutionary pathways for the gas component not reported before that are a consequence of stellarevolution and that likely have a substantial impact on the dust evolution, and thus on planet formation. As the stellar mass increasesfrom one solar mass to ∼1.5–2 M⊙, the evolution of the disc changes from the conventional inside-out clearing, in which X-ray photoevaporation generates inner holes, to a homogeneous disc evolution scenario where both inner and outer discs formed after a gap isopened by photoevaporation vanish over a similar timescale. As the stellar mass continues to increase, reaching ∼2–3 M⊙, we identifya distinct pathway that we refer to as revenant disc evolution. In this scenario, the inner and outer discs reconnect after the gap opened.For the largest masses, we observe outside-in disc dispersal, in which the outer disc dissipates first due to a stronger FUV photoevaporation rate. Revenant disc evolution stands out as it is capable of extending the disc lifespan. Otherwise, the disc dispersal timescaledecreases with increasing stellar mass except for low-viscosity discs