Degenerate thermal pulses in AGB stars

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We report on the discovery of a new kind of thermal pulse in intermediate mass AGB stars. Deep dredge-up during normal thermal pulses on the AGB leads to the formation of a long, unburnt tail to the helium profile. Eventually the tail ignites under partially degenerate conditions producing a strong shell flash with very deep subsequent dredge-up. The carbon content of the intershell convective region (XC 0.6) is substantially higher than in a normal thermal pulse (XC 0.25) and about 4 times more carbon is dredged-up than in a normal pulse.