| Abstrakt: |
Type Ia supernovae (SNe Ia) are likely the thermonuclear explosions of carbon–oxygen (CO) white-dwarf (WD) stars, but their progenitor systems remain elusive. Recent studies have suggested that a propagating detonation within a thin helium shell surrounding a sub-Chandrasekhar mass CO core can subsequently trigger a detonation within the core (the double-detonation model, DDM). The outcome of this explosion is similar to a central ignition of a sub-Chandrasekhar mass CO WD (SCD). While SCD is consistent with some observational properties of SNe Ia, several computational challenges prohibit a robust comparison to the observations. We focus on the observed t 0− M Ni56 relation, where t 0 (the γ-rays' escape time from the ejecta) is positively correlated with M Ni56 (the synthesized 56Ni mass). We apply our recently developed numerical scheme to calculate SCD and show that the calculated t 0− M Ni56 relation, which does not require radiation transfer calculations, converges to an accuracy of a few per cent. We find a clear tension between our calculations and the observed t 0− M Ni56 relation. SCD predicts an anticorrelation between t 0 and M Ni56, with |$t_0\approx 30\, \textrm{d}$| for luminous (|$M_\text{Ni56}\gtrsim 0.5\, \mathrm{ M}_{\odot }$|) SNe Ia, while the observed t 0 is in the range of |$35\!-\!45\, \textrm{d}$|. We show that this tension is larger than the uncertainty of the results, and that it exists in all previous studies of the problem. Our results hint that more complicated models are required, but we argue that DDM is unlikely to resolve the tension with the observations. [ABSTRACT FROM AUTHOR] |
