Nuclear Astrophysics

Explaining anomalies in the spectra of classical novae

Explaining anomalies in the spectra of classical novae: The optical, ultraviolet and infrared spectra of the debris left over after nova explosions – thermonuclear detonations on the surface of accreting white dwarves in stellar binary systems – contain important fingerprints of the chemical elements synthesized and ejected during these cataclysmic events. However, for some elements, namely argon and calcium, much more than expected seems to be present. This flies in the face of theoretical models of nova explosions which say that nucleosynthesis in novae effectively stops at calcium, with around the same amount of calcium being present after the explosion as before the explosion. The volume of elements from Ar-Ca produced in these scenarios depends sensitively on the strengths of nuclear reactions around that region, in particular proton-induced radiative capture reactions. One of these,  p (38K)39Ca has now been experimentally measured for the first time using TRIUMF’s DRAGON facility, previously impossible because if the short lifetime of 38K, but accessible to the inverse kinematics technique of DRAGON using an intense 38K beam made at ISAC. This makes p (38K)39Ca the highest mass reaction ever measured using this technique with radioactive beams.