Slowly cooling white dwarfs in M13 from stable hydrogen burning

Abstract

White Dwarfs (WDs) are the final evolutionary product of the vast majority of stars in the Universe. They are electron-degenerate structures characterized by no stable thermonuclear activity, and their evolution is generally described as a pure cooling process. Their cooling rate is adopted as cosmic chronometer to constrain the age of several Galactic populations, including the disk, globular and open clusters. By analysing high-resolution photometric data of two twin Galactic globular clusters (M3 and M13), we find a clear-cut and unexpected over-abundance of bright WDs in M13. Theoretical models suggest that, consistently with the horizontal branch morphology, this over-abundance 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. This is the first observational evidence of quiescent thermonuclear activity occurring in cooling WDs and it brings new attention on the use of the WD cooling rate as cosmic chronometer for low metallicity environments.

28 pages, 11 figures, published in Nature Astronomy

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Cited by in corpus (7)

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• White dwarfs as Physics laboratories: lights and shadows
• The HST large programme on NGC 6752 -- IV. The White Dwarf Sequence
• A young white dwarf orbiting PSR J1835-3259B in the bulge globular cluster NGC 6652
• Globular Cluster UVIT legacy Survey (GlobUleS) III. Omega Centauri in Far-Ultraviolet
• Globular Cluster UVIT Legacy Survey (GlobULeS) $-$ II. Evolutionary status of hot stars in M3 and M13