Courtney Crawford

The Kepler Secondary Clump Stars– the amplitude-activity relation, potential binary indicators, and a high-velocity star

The Kepler sample of oscillating red giants has advanced our understanding of low to intermediate-mass stars, though most studies have focused on low-mass stars. This talk presents research on high-mass red giants, specifically secondary clump stars. Many of these stars show suppressed dipole modes, potentially indicating strong internal magnetic fields. However, spectroscopy reveals no correlation between surface chromospheric activity (S-index) and dipole mode suppression. Instead, a stronger S-index is linked to weaker radial modes, which are localised to the star’s surface. This is the first direct evidence that chromospheric activity can suppress overall oscillation strength, and also may suggest that internal and surface magnetic fields in red giants are not necessarily correlated. We also explore the possibility of binary interactions but find no strong candidates. Additionally, we identify a secondary clump star kinematically consistent with the Galactic Halo despite its young age and high metallicity, possibly ejected from a triple system early in its life. Future work will use these stars to test scaling relations at the high-mass end of red giants through individual frequency modelling of their oscillations.