Asteroseismic signatures of the helium core flash

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

Nature Astronmy

Springer Nature

Lugar: Londres; Año: 2019

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 ago1,2,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 IC ≲ 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.