Star-disc encounters
When a star with a protoplanetary disc passes close to another star, this can produce spiral density waves that lead to an exchange of angular momentum and orbital energy between the disc and the perturbing star. This may change the planet formation process and produce increased accretion onto the host star.
HV and DO Tau: An historic disc-disc encounter!
HV Tau is a triple system in the star forming region Taurus, consisting of a close binary and a third, disc hosting star, HV Tau C, with a separation of ~ 500 au. DO Tau is an apparently unrelated third star, separated from the HV Tau system by approximately 12000 au. However, when viewed at a wavelength of 160 microns, a 'bridge' of dust can be seen between DO and HV Tau. In this work, we modelled the system to show that this dust bridge is probably the result of a disc-disc encounter between HV Tau C and DO Tau, about 100 000 years ago.
Angular momentum transport
In this work, I show theoretically that the angular momentum transport due to a star-disc encounter scales very steeply with the closest approach distance. This means that, for discs, we only need to consider the closest encounter to understand the influence of encounters on disc evolution (however, this is not the case for planets on eccentric orbits!). This theoretical prescription is important for understanding the role of encounters on planet formation and the later evolution of debris discs.