Asteroseismological constraints on the structure of the ZZ Ceti stars G117-B15A and R548. The formation of DA white dwarfs with thin hydrogen envelopes. A detailed model atmosphere analysis of hot white dwarfs from SDSS DR12. On the spectral evolution of hot white dwarf stars. A large stellar evolution database for population synthesis studies. Salaris, M., Cassisi, S., Pietrinferni, A., Kowalski, P. The remarkable deaths of 9–11 solar mass stars. The presented observational evidence of quiescent thermonuclear activity occurring in cooling WDs brings new attention on the use of the WD cooling rate as cosmic chronometer for low-metallicity environments.Ĭórsico, A. Theoretical models suggest that, consistent with the horizontal branch morphology, this overabundance is due to a slowing down of the cooling process in ~70% of the WDs in M13, caused by stable thermonuclear burning in their residual hydrogen-rich envelope. By analysing high-resolution photometric data of two very similar Galactic globular clusters (M3 and M13), we find a clear-cut and unexpected overabundance of bright WDs in M13. Their cooling rate is adopted as cosmic chronometer to constrain the age of several Galactic populations, including the disk, globular and open clusters. They are electron-degenerate structures characterized by no stable thermonuclear activity, and their evolution is generally described as a pure cooling process. White dwarfs (WDs) are the final evolutionary product of the vast majority of stars in the Universe.
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