Progenitors of SNE Iax
Thermonuclear supernovae come in all shapes and sizes. One peculiar sub-class of objects are Type Iax (SN Iax) supernovae: explosions that are have low kinetic energies, low ejecta velocities and lower peak luminosities than typical Type Ia supernovae (SNe Ia). Here I summarize a recent paper on the modeling of all known SNe Iax and the resulting constraints made on their unknown progenitors. (Press)
Figure 1
While their progenitors of these SNe are currently ambiguous, observational evidence indicates that they may be the result of a white dwarf (WD) accreting mass from a helium star companion. On the left is such a scenario wherein the WD grows in size as it gains mass from its companion Helium star. Once it reaches the Chandrasekhar limit (~1.4 Msun) the WD will explode and, under the right explosion physics, produce a SN Iax.
Figure 2
The explosion scenario described above is motivated by the detection of a blue, likely helium-rich, progenitor star in pre-explosion images of SN Iax, 2012Z (to the right). Furthermore, there have also been two other SNe Iax that show prominent helium emission in their spectra: SN 2004cs and SN 2007J.
Example of SYNAPPS spectral modeling of SNe Iax, 2014dt.
Top: Data in black, model in green.
Middle: Subtracting model from the data yields residuals. We then cross-correlate residuals with helium emission lines (red) to search for a detection.
Bottom: Results from cross-correlation show no evidence for positive detection of He I in SN 2014dt. Using this method, the combination of helium detections and non-detections allows us to understand statistically how many SNe Iax progenitor systems contain helium.
Figure 3
Motivated by the potential helium composition of the companion star, this paper focused on determining the presence of elemental helium in the spectra of SNe Iax and the relative amount needed for detection. To accomplish this, we modeled spectra of all known SNe Iax using spectral synthesis codes SYN++ and SYNAPPS (left). These spectral models fit a given spectra to determine the relative strengths of all ions present during the explosion. These models were run on the NERSC supercomputing facility at Lawrence Berkeley Labs (Press). This work places limits on the amount of helium in these systems and constrains the explosive mechanisms responsible for SNe Iax.