Observational Predictions for Sub-Chandrasekhar Mass Explosions: Further Evidence for Multiple Progenitor Systems for Type Ia Supernovae. (arXiv:1811.07127v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Polin_A/0/1/0/all/0/1">Abigail Polin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nugent_P/0/1/0/all/0/1">Peter Nugent</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kasen_D/0/1/0/all/0/1">Daniel Kasen</a>
We present a numerical parameter survey of 1-D sub-Chandrasekhar mass white
dwarf explosions. Carbon-oxygen white dwarfs accreting a helium shell have the
potential to explode in the sub-Chandrasekhar mass regime. Previous studies
have shown how the ignition of a helium shell can either directly ignite the
white dwarf at the core-shell interface or propagate a shock wave into the
center of the core causing a shock driven central ignition. We examine the
explosions of white dwarfs from 0.6 – 1.2 $M_{odot}$ with Helium shells of
0.01 $M_{odot}$, 0.05 $M_{odot}$ and 0.08$M_{odot}$. Distinct observational
signatures of sub-Chandrasekhar mass white dwarf explosions are predicted for
two categories of shell size. Thicker-shell models show an excess of flux
combined with red colors for the first few days after explosion. The flux
excess is caused by the presence of radioactive material in the ashes of the
helium shell, and the red colors are due to these ashes creating significant
line blanketing in the UV through the blue portion of the spectrum. Models with
thin helium shells reproduce several typical Type Ia supernova signatures. We
identify a relationship between Si II velocity and luminosity which, for the
first time, identifies a sub-class of observed supernovae that are consistent
with these models. This sub-class is further delineated by the absence of
carbon in their atmospheres. Finally, we suggest that the proposed difference
in the ratio of selective to total extinction between the high velocity and
normal velocity Type Ia supernovae is not due to differences in the properties
of the dust around these events, but is rather an artifact of applying a single
extinction correction to two populations of supernovae which likely have
different intrinsic colors.
We present a numerical parameter survey of 1-D sub-Chandrasekhar mass white
dwarf explosions. Carbon-oxygen white dwarfs accreting a helium shell have the
potential to explode in the sub-Chandrasekhar mass regime. Previous studies
have shown how the ignition of a helium shell can either directly ignite the
white dwarf at the core-shell interface or propagate a shock wave into the
center of the core causing a shock driven central ignition. We examine the
explosions of white dwarfs from 0.6 – 1.2 $M_{odot}$ with Helium shells of
0.01 $M_{odot}$, 0.05 $M_{odot}$ and 0.08$M_{odot}$. Distinct observational
signatures of sub-Chandrasekhar mass white dwarf explosions are predicted for
two categories of shell size. Thicker-shell models show an excess of flux
combined with red colors for the first few days after explosion. The flux
excess is caused by the presence of radioactive material in the ashes of the
helium shell, and the red colors are due to these ashes creating significant
line blanketing in the UV through the blue portion of the spectrum. Models with
thin helium shells reproduce several typical Type Ia supernova signatures. We
identify a relationship between Si II velocity and luminosity which, for the
first time, identifies a sub-class of observed supernovae that are consistent
with these models. This sub-class is further delineated by the absence of
carbon in their atmospheres. Finally, we suggest that the proposed difference
in the ratio of selective to total extinction between the high velocity and
normal velocity Type Ia supernovae is not due to differences in the properties
of the dust around these events, but is rather an artifact of applying a single
extinction correction to two populations of supernovae which likely have
different intrinsic colors.
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