Abstract
ABSTRACT The detonation of a helium shell on top of a carbon–oxygen white dwarf has been argued as a potential explosion mechanism for Type Ia supernovae (SNe Ia). The ash produced during helium shell burning can lead to light curves and spectra that are inconsistent with normal SNe Ia, but may be viable for some objects showing a light-curve bump within the days following explosion. We present a series of radiative transfer models designed to mimic predictions from double-detonation explosion models. We consider a range of core and shell masses, and systematically explore multiple post-explosion compositions for the helium shell. We find that a variety of luminosities and time-scales for early light-curve bumps result from those models with shells containing 56Ni, 52Fe, or 48Cr. Comparing our models to SNe Ia with light-curve bumps, we find that these models can reproduce the shapes of almost all of the bumps observed, but only those objects with red colours around maximum light (B − V ≳ 1) are well matched throughout their evolution. Consistent with previous works, we also show that those models in which the shell does not contain iron-group elements provide good agreement with normal SNe Ia of different luminosities from shortly after explosion up to maximum light. While our models do not amount to positive evidence in favour of the double-detonation scenario, we show that provided the helium shell ash does not contain iron-group elements, it may be viable for a wide range of normal SNe Ia.
Highlights
One of the most debated aspects of research on type Ia supernovae (SNe Ia) is whether multiple progenitor systems are needed to explain the entire population
Assuming a helium shell dominated by intermediate mass elements (IMEs), we find good agreement with the light curves and spectrum close to maximum light, the model spectrum is too blue, which could indicate an alternative explanation for the early light cure bump is possible
We considered a range of white dwarf core masses (0.9 – 1.2 M ) and helium shell masses (0.01 – 0.10 M ), which effectively amounts to a range of 56Ni masses
Summary
One of the most debated aspects of research on type Ia supernovae (SNe Ia) is whether multiple progenitor systems are needed to explain the entire population (see Livio & Mazzali 2018; Wang 2018; Jha et al 2019; Soker 2019 for recent reviews of SNe Ia). This model involves the detonation of a 0.055 M helium shell on a 1.025 M carbonoxygen white dwarf. The helium shell ash following explosion is dominated by IGEs, which includes ∼0.002 M of 56Ni, 0.006 M of 52Fe, and 0.004 M of 48Cr. Figure 1 verifies that with our implementation of the additional decay chains, TURTLS can broadly match the light curves of Noebauer et al (2017). We note that the core mass of model 3 (1.025 M ) is slightly higher than these models (1.0 M ), and we show two shell masses (0.04 and 0.07 M ) to bracket the 0.055 M shell of model 3
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