Type Iax supernovae from deflagrations in Chandrasekhar mass white dwarfs

Abstract

Context. Due to the ever increasing number of observations during the past decades Type Ia supernovae are nowadays regarded as a heterogeneous class of optical transients consisting of several sub-types. One of the largest of these subclasses is the class of Type Iax supernovae. They have been suggested to originate from pure deflagrations in carbon-oxygen Chandrasekhar-mass white dwarfs because the outcome of this explosion scenario is in general agreement with their sub-luminous nature. Aims. Although a few deflagration studies have already been carried out, the full diversity of the class is not captured yet. This, in particular, holds for the faint end of the subclass. We therefore present a parameter study of single-spot ignited deflagrations in Chandrasekhar-mass white dwarfs varying the location of the ignition spark, the central density, the metallicity and the composition of the white dwarf. We also explore a rigidly rotating progenitor to investigate whether the effect of rotation can spawn additional trends. Methods. We carry out three dimensional hydrodynamic simulations employing the leafs code. Subsequently, detailed nucleosynthesis results are obtained with the nuclear network code yann. In order to compare our results to observations we calculate synthetic spectra and light curves with the artis code. Results. The new set of models extends the range in brightness covered by previous studies to the lower end. Our single-spot ignited explosions produce 56 Ni masses from 5.8 × 10 −3 to 9.2 × 10 −2 M . In spite of the wide exploration of the parameter space the main characteristics of the models are primarily driven by the mass of 56 Ni and form a one-dimensional sequence. Secondary parameters seem to have too little impact to explain the observed trend in the faint part of the Type Iax supernova class. We report kick velocities of the gravitationally bound explosion remnants from 6.9 to 369.8 km s −1 . The magnitude as well as the direction of the natal kick is found to depend on the strength of the deflagration. Conclusions. This work corroborates the results of previous studies of deflagrations in Chandrasekhar-mass white dwarfs. The wide exploration of the parameter space in initial conditions and viewing-angle effects in the radiative transfer lead to a significant spread in the synthetic observables. The trends in observational properties towards the faint end of the class are, however, not reproduced. This motivates a quantification of the systematic uncertainties in the modelling procedure and the influence of the 56 Ni -rich bound remnant to get to the bottom of these discrepancies. Moreover, while the pure deflagration scenario remains a favorable explanation for bright and intermediate luminosity Type Iax supernovae, the possibility that this subclass does not consist of only one explosion scenario needs to be taken into account.

Models of pulsationally assisted gravitationally confined detonations with different ignition conditions

“…4). This is in agreement with the commonly accepted fact that M Ch explosions are responsible for a substantial amount of Mn in the Universe (Seitenzahl et al 2013a;Lach et al 2020). For decreasing deflagration strength the contribution of the detonation becomes larger and [Mn/Fe] falls below the solar value.…”

“…Second, we observe high values of [Cr/Fe] in some explosions which is a direct imprint of low-mass ( 0.8 M ) CO detonation models (compare also Fig. 3 in Lach et al 2020) but special for M Ch models. Third, the usual overproduction of stable Ni in M Ch deflagrations is suppressed by the detonation yields.…”

“…4 also shows signs of the strong odd-even effect in the detonation IME yields smoothed out by the deflagration products (compare again Fig. 3 in Lach et al 2020). The α-elements Si, S, Ar and Ca are even synthesized in supersolar amounts in the core detonation of Model r10_d2.6.…”

“…Here, we focus solely on explosions of M Ch WDs. Specifically, we extend the models of asymmetric deflagrations in M Ch WDs of Lach et al (2021), hereafter L21, and trigger detonations in late stages of the explosion. The models presented in that study were ignited asymmetrically in a single spot, and, hence, lead to weak deflagrations ejecting only little mass.…”

Properties and applications of a predicted population of runaway He-sdO/B stars ejected from single degenerate He-donor SNe

“…The possibility of a near-Chandrasekhar mass double detonation is usually predicated on inclusion of microphysics, such as magnetic torques, as proposed by Spruit (2002) and modelled by Neunteufel et al (2017Neunteufel et al ( , 2019. However, Chandrasekhar mass explosions originating from He-accretion have also been connected to SNe of Type Iax and have been predicted to leave a partially burnt remnant (Gamezo et al 2005;Branch et al 2004;Phillips et al 2007;Foley et al 2009;Kromer et al 2013;Fink et al 2014;Kromer et al 2015;Magee et al 2016;Lach et al 2021).…”