Type Iax supernovae as a few-parameter family

Abstract

We present direct spectroscopic modeling of five Type Iax supernovae (SNe) with the one dimensional Monte Carlo radiative transfer code TARDIS. The abundance tomography technique is used to map the chemical structure and physical properties of the SN atmosphere. Through via fitting of multiple spectral epochs with self-consistent ejecta models, we can then constrain the location of some elements within the ejecta. The synthetic spectra of the best-fit models are able to reproduce the flux continuum and the main absorption features in the whole sample. We find that the mass fractions of IGEs and IMEs show a decreasing trend toward the outer regions of the atmospheres using density profiles similar to those of deflagration models in the literature. Oxygen is the only element, which could be dominant at higher velocities. The stratified abundance structure contradicts the well-mixed chemical profiles predicted by pure deflagration models. Based on the derived densities and abundances, a template model atmosphere is created for the SN Iax class and compared to the observed spectra. Free parameters are the scaling of the density profile, the velocity shift of the abundance template, and the peak luminosity. The results of this test support the idea that all SNe Iax can be described by a similar internal structure, which argues for a common origin of this class of explosions.

The Lowest of the Low: Discovery of SN 2019gsc and the Nature of Faint Iax Supernovae

“…structure (Magee et al 2016(Magee et al , 2017Barna et al 2017Barna et al , 2018 and presence of helium in the ejecta (Magee et al 2019). tardis takes a model for the ejecta with arbitrary density and abundance profiles as input, along with a luminosity and time since explosion.…”

SN 2019muj – a well-observed Type Iax supernova that bridges the luminosity gap of the class

“…The thin outer region allows insight to the deeper, thus, hotter layers, which changes as the photosphere starts forming in the more dense regions. Such density structure may resemble more with that of the more luminous objects in the outer region with a cut-off at the highest velocities (see the N5def and N20def deflagration models and the abundance tomographies of SNe Iax, Fink et al 2014;Barna et al 2018), and the profile quickly increase towards the innermost regions (see the N1def and the hybrid N5def deflagration models, Fink et al 2014;Kromer et al 2015). It cannot be stated whether this behaviour is regular among the moderately luminous SNe Iax, or not, without studying more objects with approximately the same luminosity.…”

“…In order to test the physical structure of the ejecta, we fit the spectral time series with synthetic spectra calculated via the 1D Monte Carlo radiative transfer code TARDIS (Kerzendorf & Sim 2014;Kerzendorf et al 2018;Vogl et al 2016) in multiple ways. First, we use the abundance template proposed by Barna et al (2018) for the sample of more luminous SNe Iax. The template (see Fig.…”

“…In the case of 2019muj, we use this velocity shift of the abundance template as a free parameter for fitting the spectra. The assumed density function is the same as those used by Barna et al (2018, note that the related equation 1 in the cited paper is incorrect) for reproducing the density structure of various deflagration models of Fink et al (2014). The density function contains an exponential inner part, which continues with a shallow cut-off past the velocity v cut :…”

“…At the same time, the pure deflagration producing a bound remnant picture might contradict the bright SN Iax 2012Z (Stritzinger et al 2015), in which the velocity distribution of intermediate mass elements (IMEs) do not indicate significant mixing in the outer ejecta. Barna et al (2018) performed abundance tomography for a small sample of SNe Iax and found a stratified structure as a feasible solution for the outer regions of SNe Iax, however, the impact of the outermost layers are strongly affected by the choice of the density profile.…”