München 2019 – scientific programme
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EP: Fachverband Extraterrestrische Physik
EP 11: Astrophysics III: Stellar Astrophysics
EP 11.4: Talk
Friday, March 22, 2019, 13:15–13:30, HS 19
A new outburst in the Yellow Hypergiant ρ Cas — •Michaela Kraus1, Indrek Kolka2, Anna Aret1,2, and Dieter Horst Nickeler1 — 1Astronomical Institute AVCR, Ondrejov, Czech Republic — 2Tartu Observatory, University of Tartu, Estonia
Yellow hypergiants are evolved massive stars that were suggested to be in post-red supergiant stage. Post-red supergiants that evolve back to the blue, hot side of the Hertzsprung-Russell diagram can intersect a temperature domain in which their atmospheres become unstable against pulsations (the Yellow Void or Yellow Wall), and the stars can experience outbursts with short, but violent mass eruptions. The yellow hypergiant ρ Cas is famous for its historical and recent outbursts, during which the star develops a cool, optically thick wind with a very brief but high mass-loss rate, causing a sudden drop in the light curve. Here we report on a new outburst of ρ Cas which occurred in 2013, accompanied by a temperature decrease of ∼3000 K and a brightness drop of 0.6 mag. During the outburst TiO bands appear, together with many low excitation metallic atmospheric lines characteristic for a later spectral type. With this new outburst, it appears that the time interval between individual events decreases, which might indicate that ρ Cas is preparing for a major eruption that could help the star to pass through the Yellow Void.