Explosion Models

Abstract

In this chapter discusses explosion models for Type Ia supernovae (SN Ia). The explosions are thermonuclear disruptions of carbon-oxygen white dwarfs in which nuclear burning fronts propagate as subsonic deflagrations or supersonic detonations (chapter “Degenerate Carbon Burning”). In the canonical single-degenerate (SD) model (chapter “Progenitors”) the white dwarf accretes matter from a companion star to approach the Chandrasekhar mass, 1.4 solar masses. In this case, neither a detonation-only nor a deflagration-only model leads to acceptable agreement with observations of SN Ia. In the delayed-detonation model, which can account for many of the properties of SN Ia, nuclear burning begins near the center of the white dwarf as a deflagration that subsequently makes an (unproven) unconfined transition to a detonation. Alternative models, such as the pulsating delayed-detonation and gravitationally-confined detonation models, arrange for a deflagration to be followed by a confined detonation. In SD models for substantially super-Chandrasekhar SN Ia, rapid rotation is usually invoked, and SD models for sub-Chandrasekhar SN Ia usually involve initial nuclear ignition in a surface shell of helium. In the canonical double-degenerate (DD) model (chapter “Progenitors”) the explosion usually is of a mildly super-Chandrasekhar white dwarf, with consequences perhaps not strongly differing from those of the canonical SD model. Alternative DD models, which may involve super- or sub-Chandrasekhar combined mass, invoke prompt explosions during violent mergers of binary white dwarfs and direct white-dwarf collisions.