Twinkle, twinkle, undersampled star

During the late subgiant/early giant stage, stars undergo fast evolutionary changes such as the readjustment of their internal rotation. It is of paramount importance to study this phase, in particular to understand the transport of angular momentum from the cores of stars to their envelopes. Bridging this knowledge gap is crucial to obtain more precise stellar age determinations. Asteroseismology is a potent tool to analyse the internal structure and dynamics of stars. However, the sample of seismically characterised late subgiant/early RGBs is very small with Kepler data, mainly because of instrumentation limitations: the modes of these stars happen to be located beyond the Nyquist frequency. We investigate the ways to detect undersampled stars in the Kepler data set and measure their seismic modes and global parameters with an extension to the new Python Py-A2Z pipeline. Our methodology relies on the asymptotic repeating structure of the oscillation spectra of solar-like stars to detect and characterise oscillations. We also extensively use seismic scaling relations to discriminate between undersampled and correctly sampled light curves. In this poster, I will showcase the efficiency of the methodology. This enabled the measurement of global seismic parameters of over 350 stars whose modes were close or beyond the Nyquist frequency, expanding the known sample of super-Nyquist oscillators by a factor of 4. Finally, I will also briefly discuss the prospects these results open up for the advancements of stellar modelling.