School of Astronomy (SoA) - Weekly Seminar

Asteroseismology of the Blue Supergiant Star: Rigel

Rigel (beta Ori, B8 Ia) is a nearby blue supergiant, and a progenitor of a near-future core-collapse supernova (SN-II). We present 7 years of time-resolved high-resolution optical spectroscopy and 28-day space-based dedicated photometry of Rigel. Manifestly, the nature of the observed variabilities lies in non-radial stellar oscillations. The oscillation periods – as deduced by frequency analysis of the radial velocities – broadly range from a day to 75 days! In a search for the underlying pulsation mechanism, we numerically model the structure and evolution of this star. Then, we solve the purturbative non-adiabatic non-radial oscillation equations for the model. We find that that the observed variabilities emerge from the instabilities in the hydrogen burning shell, very close to the helium-rich core. This is the so-called ε-mechanism. We end this journey with predictions and future prospects.

IPM Larak Building, School of Astronomy