Speaker
Description
Potassium (K; Z = 19) is an essential element for life and for the formation of rocky planets. Along with other odd-Z elements such as scandium (Sc) and vanadium (V), potassium is generally thought to be synthesized during the evolution of massive stars or at the moment of core-collapse supernova explosions. However, quantitative predictions of potasium yields in massive stars, as well as the relative contributions from hydrostatic and explosive nucleosyntehsis, remain uncertain.
We used the High-Dispersion Spectrograph (HDS) on the Subaru Telescope to determine potassium abundances in 18 extremely metal-poor stars ([Fe/H]=log(N_Fe/N_H) − log (N_Fe/N_H)_Sun<-3), whose surface chemical compositions likely reflect the yields of individual massive-star supernovae.
We detected weak potasium resonance lines at 766/769 nm in seven stars.For these stars, we find that the potassium-to-calcium ratios ([K/Ca]) are nearly constant, with a mean value of +0.11 dex and a very small scatter, below the level of observational uncertainties. In contrast, large star-to-star variations are observed in Na/Mg ratios. In this talk, I will discuss the implications of these chemical abundance trends for the origin and chemical evolution of potassium.
| Category | Observation |
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