| Astrophysics (Index) | About |
Thermal pulse (TP) literally refers to an episode in which something is hotter for a limited time, which is something that stars can undergo at various stages of their evolution. The term is commonly used for asymptotic giant branch (AGB) episodes of helium fusion which exhaust the helium supply sufficiently to cease after a short timespan, i.e., the TP-AGB stage. Such pulses can recur after additional helium is produced by a surrounding shell of H burning. Under various circumstances, the fusion may last mere seconds (helium flash), or may last longer, to hundreds of years.
Helium runaway (which fits the definition of thermal pulse) is helium fusion that increases its fusion rate through the heat it creates, quickly depleting the supply.
The term thermal pulse cycle (TPC) is used for the sequence of thermal pulses in an AGB star. The terms late thermal pulse (LTP) and very late thermal pulse (VLTP) are generally used for thermal pulses subsequent to the AGB phase (i.e., in post-AGB stars).