Presentation #621.12 in the session Protoplanetary Disks - Observations.
The young star β Pictoris is seen orbited by a warped edge-on debris disc of gas and dust, as well as a massive planet. β Pictoris shows variable, velocity-shifted absorptions in the Ca II H & K lines, which are attributed to infalling, evaporating, comet-like bodies (exocomets). In order to gain insights into the mechanisms of planetary system formation it is useful to study the properties, behaviour and interaction of exocomets within this young planetary system. We have analyzed Ca II H & K absorptions in β Pictoris obtained with the 1.0-metre telescope at the University of Canterbury Mt John Observatory, New Zealand. Our data support the division of the comets into two families, as identified by Kiefer et al. (2014). One family is characterized by shallow, broader absorptions with a larger mean velocity and velocity range, which the authors attribute to old comets which have been perturbed into stargrazing orbits by mean motion resonances with a massive planet. The other family is characterized by deeper, narrower absorptions and a smaller mean velocity and velocity range, which perhaps are related to recent fragmentation of one or a few parent bodies. The deep absorptions occur in streams that last for weeks, far exceeding the crossing time of individual comets.