Nickel-rich outflows from accretion discs formed by the accretion-induced collapse of white dwarfs

摘要: A white dwarf (WD) approaching the Chandrasekhar mass may in several circumstances undergo accretion-induced collapse (AIC) to a neutron star (NS) before thermonuclear explosion ensues. It has generally been assumed that such an AIC does not produce detectable supernova (SN). If, however, progenitor WD is rapidly rotating (as be expected due its prior accretion), centrifugally supported disc forms around NS upon collapse. We calculate subsequent evolution of this accretion and nuclear composition using time-dependent height-integrated simulations with initial conditions taken from calculations Dessart collaborators. Soon after formation, cooled by neutrinos driven rich (electron fraction Y e ∼ 0.1) electron captures. However, as viscously spreads, it irradiated central proto-NS, which dramatically alters neutron-to-proton ratio. find neutrino captures increase ∼0.5 time weak interactions freeze out. Because becomes radiatively inefficient begins forming α-particles soon out, powerful winds blow away most disc's remaining mass. These 0.5 outflows synthesize up few times 10 ―2 M ⊙ 56 Ni. As result, accompanied radioactively powered SN-like transient peaks on time-scale ∼1 d. Since intermediate elements are likely synthesized, these nickel-rich explosions should spectroscopically distinct other SNe. The time-scale, velocity can modified if wind sweeps ∼0.1 remnant created WD-WD merger; 'enshrouded' account for sub-luminous, sub-Chandrasekhar Type I Optical surveys Panoramic Survey Telescope Rapid Response System Palomar Transient Factory detect transients per year their true rate type Ia rate, Large Synoptic hundred year. High cadence observations (≤1 d) optimal detection followup AIC.