Following V509 Cas into the void with FIES

V509 Cas is one of the rare evolved massive stars known as yellow hypergiants. These stars are in
an unstable phase of evolution, during which their atmospheres undergo recurring outbursts. Over
the 20th century, V509 Cas went through multiple eruptive mass-loss episodes, during which its
temperature, luminosity and other physical parameters changed rapidly. At the beginning of the 21st
century, the behaviour of V509 Cas suddenly changed and the star started to show signs of reaching a
more stable phase of evolution. Using the FIbre-fed Echelle Spectrograph (FIES) at the Nordic Optical
Telescope, we have explored the surface movements of the star to get a glimpse of its circumstellar
environment and we have found confirmation to the hypothesis of a disc surrounding the star.