Asteroseismic signatures of the helium core flash

MILLER BERTOLAMI, M. M.; BATTICH, T.; CÓRSICO, A. H.; CHRISTENSEN-DALSGAARD, J.; ALTHAUS, L. G.

Nature Astronomy

Nature Publishing Group

Año: 2020

2397-3366

All evolved stars of up to 2 solar masses undergo a heliumcore flash at the end of their first stage as a giant star.Although theoretically predicted more than 50 years ago 1,2 ,this core flash phase has yet to be observationally probed. Weshow here that gravity modes stochastically excited by heliumflash-driven convection are able to reach the stellar surfaceand induce periodic photometric variabilities in hot subdwarfstars with amplitudes of the order of a few thousandths of amagnitude. As such, they can now be detected by space-basedphotometry with the Transiting Exoplanet Survey Satellite inrelatively bright stars (for example, Johnson?Cousins magni-tudes of I C  ≲ 13 mag) 3 . The range of predicted periods spansfrom a few thousand seconds to tens of thousands of seconds,depending on the details of the excitation region. In addition,we find that stochastically excited pulsations reproduce thepulsations observed in a few helium-rich hot subdwarf stars.These stars, particularly the future Transiting ExoplanetSurvey Satellite target Feige 46, are the most promising can-didates to probe the helium core flash for the first time.