The evolution of rotation in cool stars on the main sequence is fairly well-studied — and has been the focus of splinter sessions in several preceding iterations of Cool Stars. By contrast, their internal rotational and magnetic evolution, and the phenomenology of both in sub- and red-giant stars, have been less prominently featured in preceding Cool Stars meetings. The relatively short-lived nature of the sub- and red-giant phases of evolution render them difficult and expensive to approach using traditional modelling techniques. However, these evolved stars dominate our observational sample (being far more luminous), and play an outsize role in influencing their environments, and possible planetary or (main-sequence) stellar companions. Moreover, over the past decade, evolved stars have proven uniquely amenable to observational inspection: they are now the only stars for which rotation and magnetism are measurable in the deepest interior layers, through new applications of asteroseismology.

This splinter session covers new developments in understanding how rotation and magnetism operate, evolve, and determine other physical properties of post-main-sequence stars in particular. These developments include new characterisations of magnetic features on stellar surfaces, new ensemble measurements of internal magnetic fields in red giants, new insights into how engulfments and tidal interactions with companions may modify these features, and new theoretical descriptions of how these processes drive, and in turn can be used to understand, the physics behind mass loss and angular momentum transport.

Splinter Organisers