The explosion of sub-Chandrasekhar mass white dwarfs via the double detonation scenario is a potential explanation for type Ia supernovae. In this scenario, a surface detonation in a helium layer initiates a detonation in the underlying carbon/oxygen core leading to an explosion. For a given core mass, a lower bound has been determined on the mass of the helium shell required for dynamical burning during a helium flash, which is a necessary prerequisite for detonation. For a range of core and corresponding minimum helium shell masses, we investigate whether an assumed surface helium detonation is capable of triggering a subsequent detonation in the core even for this limiting case. We carried out hydrodynamic simulations on a co-expanding Eulerian grid in two dimensions assuming rotational symmetry. The detonations are propagated using the level-set approach and a simplified scheme for nuclear reactions that has been calibrated with a large nuclear network. The same network is used to determine detailed nucleosynthetic abundances in a post-processing step. Based on approximate detonation initiation criteria in the literature, we find that secondary core detonations are triggered for all of the simulated models, ranging in core mass from 0.810 up to 1.385 M_solar with corresponding shell masses from 0.126 down to 0.0035 M_solar. This implies that, as soon as a detonation triggers in a helium shell covering a carbon/oxygen white dwarf, a subsequent core detonation is virtually inevitable.
Type Ia supernovae are thought to result from thermonuclear explosions of carbon-oxygen white dwarf stars. This model generally explains the observed properties with certain exceptions, like sub-luminous supernovae. Here we discuss the possibility of sub-Chandrasekhar WDs detonating due to the build up of a layer of helium on the C-O WD by accreting from a helium rich companion star to explain observed deviations such as subluminous type Ia. We also detail some of the energetics involved that will make such scenarios plausible.
The precise nature of Type Ia supernova (SN Ia) progenitors remains a mystery, but the detonation of a sub-Chandrasekhar-mass white dwarf (WD) has become a promising candidate. There is a growing body of work suggesting that the carbon core detonation of a sub-Chandrasekhar-mass WD can be triggered by the detonation of a helium shell accreted from a companion WD, through either inward shock convergence near the center or direct edge-lit detonation. This "double-detonation" SN Ia can be triggered by a small helium shell and is therefore well approximated by the detonation of a bare carbon-oxyge…
Study of the double detonation Type Ia supernova scenario, in which a helium shell detonation triggers a carbon core detonation in a sub-Chandrasekhar-mass white dwarf, has experienced a resurgence in the past decade. New evolutionary scenarios and a better understanding of which nuclear reactions are essential have allowed for successful explosions in white dwarfs with much thinner helium shells than in the original, decades-old incarnation of the double detonation scenario. In this paper, we present the first suite of light curves and spectra from multi-dimensional radiative transfer calcula…
We present theoretical delay times and rates of thermonuclear explosions that are thought to produce Type Ia supernovae, including the double-detonation sub-Chandrasekhar mass model, using the population synthesis binary evolution code StarTrack. If detonations of sub-Chandrasekhar mass carbon-oxygen white dwarfs following a detonation in an accumulated layer of helium on the white dwarf's surface ("double-detonation" models) are able to produce thermonuclear explosions which are characteristically similar to those of SNe Ia, then these sub-Chandrasekhar mass explosions may account for at leas…
The detonation of a sub-Chandrasekhar-mass white dwarf (WD) has emerged as one of the most promising Type Ia supernova (SN Ia) progenitor scenarios. Recent studies have suggested that the rapid transfer of a very small amount of helium from one WD to another is sufficient to ignite a helium shell detonation that subsequently triggers a carbon core detonation, yielding a "dynamically-driven double degenerate double detonation" SN Ia. Because the helium shell that surrounds the core explosion is so minimal, this scenario approaches the limiting case of a bare C/O WD detonation. Motivated by disc…
Using 2D and 3D simulation, we study the "robustness" of the double detonation scenario for Type Ia supernovae, in which a detonation in the helium shell of a carbon-oxygen white dwarf induces a secondary detonation in the underlying core. We find that a helium detonation cannot easily descend into the core unless it commences (artificially) well above the hottest layer calculated for the helium shell in current presupernova models. Compressional waves induced by the sliding helium detonation, however, robustly generate hot spots which trigger a detonation in the core. Our simulations show tha…
Sub-Chandrasekhar mass carbon-oxygen white dwarfs (CO WDs) with a surface helium (He) shell have been proposed as progenitors of Type Ia supernovae (SNe Ia). If true, the resulting thermonuclear explosions should be able to account for at least some of the range of SNe Ia observables. To study this, we conduct a parameter study based on 3D simulations of double detonations in CO WDs with a He shell, assuming different core and shell masses. An admixture of C to the shell and solar metallicity are included in the models. The hydrodynamic simulations are carried out using the AREPO code. This al…
Multidimensional Nebular-Phase Calculations of Dynamically-Driven Double-Degenerate Double-Detonation Models for Type Ia Supernovae
Queen’s University Belfast（贝尔法斯特女王大学）；Cosmic Dawn Center (DAWN)（宇宙黎明中心）；Niels Bohr Institute, University of Copenhagen（哥本哈根大学尼尔斯·玻尔研究所）；GSI Helmholtzzentrum für Schwerionenforschung（重离子研究中心）；Max-Planck-Institut für Astrophysik（马克斯·普朗克天体物理研究所）；School of Physics, Trinity College Dublin, The University of Dublin（都柏林三一学院物理系）；Heidelberger Institut für Theoretische Studien（海德堡理论研究所）
Several models for type Ia-like supernovae events rely on the production of a self-sustained detonation powered by nuclear reactions. In the absence of hydrogen, the fuel that powers these detonations typically consists of either pure helium (He) or a mixture of carbon and oxygen (C/O). Studies that systematically determine the conditions required to initiate detonations in C/O material exist, but until now no analogous investigation of He matter has been conducted. We perform one-dimensional reactive hydrodynamical simulations at a variety of initial density and temperature combinations and f…
First-Principles Turbulence-Driven Deflagration-to-Detonation Transition Mechanism for Near-Chandrasekhar Mass White Dwarf Progenitors
University of Massachusetts Dartmouth（麻省大学达特茅斯分校）；University of Connecticut, School of Mechanical, Aerospace, and Manufacturing Engineering（康涅狄格大学机械、航空航天与制造工程学院）；Naval Research Laboratory, Laboratories for Computational Physics & Fluid Dynamics（海军研究实验室计算物理与流体动力学实验室）；University of Maryland, Physical Sciences Complex, Stadium Drive（马里兰大学）；Universität Heidelberg, Zentrum für Astronomie, Institut für Theoretische Astrophysik（海德堡大学天文学中心理论天体物理学研究所）
The detonation of a helium shell on a white dwarf has been proposed as a possible explosion triggering mechanism for Type Ia supernovae. Here, we report ZTF 18aaqeasu (SN 2018byg/ATLAS 18pqq), a peculiar Type I supernova, consistent with being a helium-shell double-detonation. With a rise time of $\approx 18$ days from explosion, the transient reached a peak absolute magnitude of $M_R \approx -18.2$ mag, exhibiting a light curve akin to sub-luminous SN 1991bg-like Type Ia supernovae, albeit with an unusually steep increase in brightness within a week from explosion. Spectra taken near peak lig…
Sub-Chandrasekhar mass white dwarfs accreting a helium shell on a carbon-oxygen core are potential progenitors of normal Type Ia supernovae. This work focuses on the details of the onset of the carbon detonation in the double detonation sub-Chandrasekhar model. In order to simulate the influence of core-shell mixing on the carbon ignition mechanism, the helium shell and its detonation are followed with an increased resolution compared to the rest of the star treating the propagation of the detonation wave more accurately. This significantly improves the predictions of the nucleosynthetic yield…
We analyze the nucleosynthesis yields of various Type Ia supernova explosion simulations including pure detonations in sub- Chandrasekhar mass white dwarfs, double detonations and pure helium detonations of sub-Chandrasekhar mass white dwarfs with an accreted helium envelope, a violent merger model of two white dwarfs and deflagrations as well as delayed detonations in Chandrasekhar mass white dwarfs. We focus on the iron peak elements Mn, Zn and Cu. To this end, we also briefly review the different burning regimes and production sites of these elements as well as the results of abundance meas…
White dwarfs (WDs) are believed to detonate via explosive Carbon-fusion in a Type Ia Supernova when their temperature and/or density reach the point where Carbon is ignited in a runaway reaction. Observations of the Type Ia supernova (SN) rate imply all WD binaries that merge through the emission of gravitational radiation within a Hubble time should result in SNe, regardless of total mass. Here we investigate the conditions under which a single WD in a binary system might extract energy from its orbit, depositing enough energy into a resonant mode such that it detonates before merger. We show…
We present 1D non-local thermodynamic equilibrium (non-LTE) time-dependent radiative-transfer simulations of a Chandrasekhar-mass delayed-detonation model which synthesizes 0.51 Msun of 56Ni, and confront our results to the Type Ia supernova (SN Ia) 2002bo over the first 100 days of its evolution. Assuming only homologous expansion, this same model reproduces the bolometric and multi-band light curves, the secondary near-infrared (NIR) maxima, and the optical and NIR spectra. The chemical stratification of our model qualitatively agrees with previous inferences by Stehle et al., but reveals si…
Type Ia supernovae (SNe Ia) are likely the thermonuclear explosions of carbon-oxygen (CO) white-dwarf (WD) stars, but their progenitor systems remain elusive. Recently, Sharon & Kushnir (2022) used The Zwicky Transient Facility Bright Transient Survey to construct a synthesized $^{56}$Ni mass, $M_\text{Ni56}$, distribution of SNe Ia. They found that the rate of low-luminosity ($M_\text{Ni56}\approx0.15\,M_{\odot}$) SNe Ia is lower by a factor of $\sim10$ than the more common $M_\text{Ni56}\approx0.7\,M_{\odot}$ events. We here show that in order for the double-detonation model (DDM, in which a…
Type Ia supernovae are generally thought to be due to the thermonuclear explosions of carbon-oxygen white dwarfs with masses near the Chandrasekhar mass. This scenario, however, has two long-standing problems. First, the explosions do not naturally produce the correct mix of elements, but have to be finely tuned to proceed from sub-sonic deflagration to super-sonic detonation. Second, population models and observations give formation rates of near-Chandrasekhar white dwarfs that are far too small. Here, we suggest that type Ia supernovae instead result from mergers of roughly equal-mass carbon…
While Chandrasekhar-mass ($M_{\rm Ch}$) models with a low $^{56}\rm{Ni}$ yield can match the peak luminosities of fast-declining, 91bg-like Type Ia supernovae (SNe Ia), they systematically fail to reproduce their faster light-curve evolution. Here we illustrate the impact of a low ejecta mass on the radiative display of low-luminosity SNe Ia, by comparing a sub-$M_{\rm Ch}$ model resulting from the pure central detonation of a C-O White Dwarf (WD) to a $M_{\rm Ch}$ delayed-detonation model with the same $^{56}\rm{Ni}$ yield of 0.12 M$_{\odot}$. Our sub-$M_{\rm Ch}$ model from a 0.90 M$_{\odot}…
White dwarfs (WDs) that accrete helium at rates $\sim 10^{-8} \, M_\odot \, \rm yr^{-1}$, such as those in close binaries with sdB stars, can accumulate large ($\gtrsim 0.1 \, M_\odot$) helium envelopes which are likely to detonate. We perform binary stellar evolution calculations of sdB+WD binary systems with MESA, incorporating the important reaction chain $^{14}{\rm N}(e^-, ν) {^{14}{\rm C}} ( α, γ) {^{18}{\rm O}}$ (NCO), including a recent measurement for the ${^{14}{\rm C}} ( α, γ) {^{18}{\rm O}}$ rate. In large accreted helium shells, the NCO reaction chain leads to ignitions at the dens…
We present nebular spectra of the Type Ia supernova (SN Ia) SN 2019yvq, which had a bright flash of blue and ultraviolet light after exploding, followed by a rise similar to other SNe Ia. Although SN 2019yvq displayed several other rare characteristics such as persistent high ejecta velocity near peak brightness, it was not especially peculiar and if the early "excess" emission were not observed, it would likely be included in cosmological samples. The excess flux can be explained by several different physical models linked to the details of the progenitor system and explosion mechanism. Each …
The dynamics of helium shell convection driven by nuclear burning establish the conditions for runaway in the sub-Chandrasekhar mass, double detonation model for Type Ia supernovae, as well as for a variety of other explosive phenomena. We explore these convection dynamics for a range of white dwarf core and helium shell masses in three dimensions using the low Mach number hydrodynamics code Maestro. We present calculations of the bulk properties of this evolution, including time-series evolution of global diagnostics, lateral averages of the 3D state, and the global 3D state. We find a variet…
Accreted helium layers on white dwarfs have been highlighted for many decades as a possible site for a detonation triggered by a thermonuclear runaway. In this paper, we find the minimum helium layer thickness that will sustain a steady laterally propagating detonation and show that it depends on the density and composition of the helium layer, specifically C12 and O16. Detonations in these thin helium layers have speeds slower than the Chapman-Jouget (CJ) speed from complete helium burning, v_cj=1.5e9 cm/s. Though gravitationally unbound, the ashes still have unburned helium (~ 80% in the thi…
Observational evidences point to a common explosion mechanism of Type Ia supernovae based on a delayed detonation of a white dwarf. Although several scenarios have been proposed and explored by means of one, two, and three-dimensional simulations, the key point still is the understanding of the conditions under which a stable detonation can form in a destabilized white dwarf. One of the possibilities that have been invoked is that an inefficient deflagration leads to the pulsation of a Chandrasekhar-mass white dwarf, followed by formation of an accretion shock around a carbon-oxygen rich core.…
A promising model for normal Type Ia supernova (SN Ia) explosions are delayed detonations of Chandrasekhar-mass white dwarfs, in which the burning starts out as a subsonic deflagration and turns at a later phase of the explosion into a supersonic detonation. The mechanism of the underlying deflagration-to-detonation transition (DDT) is unknown in detail, but necessary conditions have been determined recently. The region of detonation initiation cannot be spatially resolved in multi-dimensional full-star simulations of the explosion. We develop a subgrid-scale (SGS) model for DDTs in thermonucl…
Calculations of synthetic spectropolarimetry are one means to test multi-dimensional explosion models for Type Ia supernovae. In a recent paper, we demonstrated that the violent merger of a 1.1 and 0.9 M$_{\odot}$ white dwarf binary system is too asymmetric to explain the low polarization levels commonly observed in normal Type Ia supernovae. Here, we present polarization simulations for two alternative scenarios: the sub-Chandrasekhar mass double-detonation and the Chandrasekhar mass delayed-detonation model. Specifically, we study a two-dimensional double-detonation model and a three-dimensi…
Some explosion models for Type Ia supernovae (SN Ia), such as the gravitationally confined detonation (GCD) or the double detonation sub-Chandrasekhar (DDSC) models, rely on the spontaneous initiation of a detonation in the degenerate C/O material of a white dwarf. The length scales pertinent to the initiation of the detonation are notoriously unresolved in multi-dimensional stellar simulations, prompting the use of results of 1D simulations at higher resolution, such as the ones performed for this work, as guidelines for deciding whether or not conditions reached in the higher dimensional ful…
Observational evidences point to a common explosion mechanism of Type Ia supernovae based on a delayed detonation of a white dwarf. However, all attempts to find a convincing ignition mechanism based on a delayed detonation in a destabilized, expanding, white dwarf have been elusive so far. One of the possibilities that has been invoked is that an inefficient deflagration leads to pulsation of a Chandrasekhar-mass white dwarf, followed by formation of an accretion shock that confines a carbon-oxygen rich core, while transforming the kinetic energy of the collapsing halo into thermal energy of …
Most of the leading explosion scenarios for Type Ia supernovae involve the nuclear incineration of a white dwarf star through a detonation wave. Several scenarios have been proposed as to how this detonation may actually occur, but the exact mechanism and environment in which it takes place remain unknown. We explore the effects of an off-center initiated detonation on the spatial distribution of the nucleosynthetic yield products in a toy model -- a pre-expanded near Chandrasekhar-mass white dwarf. We find that a single-point near edge-lit detonation results in asymmetries in the density and …
The origins of type Ia supernovae (SNe Ia) are still debated. Some of the leading scenarios involve a double detonation in double white dwarf (WD) systems. In these scenarios, helium shell detonation occurs on top of a carbon-oxygen (CO) WD, which then drives the detonation of the CO-core, producing a SN Ia. Extensive studies have been done on the possibility of a double helium detonation, following a dynamical helium mass-transfer phase onto a CO-WD. However, 3D self-consistent modeling of the double-WD system, the mass transfer, and the helium shell detonation have been little studied. Here …
The progenitor problem of Type Ia supernovae (SNe Ia) is still unsolved. Most of these events are thought to be explosions of carbon-oxygen (CO) white dwarfs (WDs), but for many of the explosion scenarios, particularly those involving the externally triggered detonation of a sub-Chandrasekhar mass WD (sub-M Ch WD), there is also a possibility of having an oxygen-neon (ONe) WD as progenitor. We simulate detonations of ONe WDs and calculate synthetic observables from these models. The results are compared with detonations in CO WDs of similar mass and observational data of SNe Ia. We perform hyd…
We present a large parameter study where we investigate the structure of white dwarf (WD) merger remnants after the dynamical phase. A wide range of WD masses and compositions are explored and we also probe the effect of different initial conditions. We investigated the degree of mixing between the WDs, the conditions for detonations as well as the amount of gas ejected. We find that systems with lower mass ratios have more total angular momentum and as a result more mass is flung out in a tidal tail. Nuclear burning can affect the amount of mass ejected. Many WD binaries that contain a helium…
In a companion paper, Seitenzahl et al. (2013) presented a set of three-dimensional delayed detonation models for thermonuclear explosions of near-Chandrasekhar mass white dwarfs (WDs). Here, we present multi-dimensional radiative transfer simulations that provide synthetic light curves and spectra for those models. The model sequence explores both changes in the strength of the deflagration phase (controlled by the ignition configuration) and the WD central density. In agreement with previous studies, we find that the strength of the deflagration significantly affects the explosion and the ob…
We use non-local thermal equilibrium radiative transport modeling to examine observational signatures of sub-Chandrasekhar mass double detonation explosions in the nebular phase. Results range from spectra that look like typical and subluminous Type Ia supernovae (SNe) for higher mass progenitors to spectra that look like Ca-rich transients for lower mass progenitors. This ignition mechanism produces an inherent relationship between emission features and the progenitor mass as the ratio of the nebular [Ca II]/[Fe III] emission lines increases with decreasing white dwarf mass. Examining the [Ca…
We conduct numerical simulations of the interacting ejecta from an exploding CO white dwarf (WD) with a He WD donor in the double-detonation scenario for Type Ia supernovae (SNe Ia), and study the possibility of exploding the companion WD. We also study the long time imprint of the collision on the supernova remnant. When the donor He WD has a low mass, M_WD = 0.2Msun, it is at a distance of ~ 0.08Rsun from the explosion, and helium is not ignited. The low mass He WD casts an 'ejecta shadow' behind it. By evolving the ejecta for longer times, we find that the outer parts of the shadowed side a…
The progenitor system(s) and the explosion mechanism(s) of Type Ia supernovae (SNe Ia) are still under debate. Non-electromagnetic observables, in particular gravitational waves and neutrino emission, of thermonuclear supernovae are a complementary window to light curves and spectra for studying these enigmatic objects. A leading model for SNe Ia is the thermonuclear incineration of a near-Chandrasekhar mass carbon-oxygen white dwarf star in a "delayed-detonation". We calculate a three-dimensional hydrodynamic explosion for the N100 delayed-detonation model extensively discussed in the literat…
It has been proposed that Type Ia supernovae (SNe Ia) that are normal in their spectra and brightness can be explained by a double detonation that ignites first in a helium shell on the surface of the white dwarf (WD). This proposition is supported by the satisfactory match between simulated explosions of sub-Chandrasekhar-mass WDs with no surface He layer and observations of normal SNe Ia. However, previous calculations of He-ignited double detonations have required either artificial removal of the He shell ashes or extreme enrichment of the surface He layer in order to obtain normal SNe Ia. …
Delayed detonations of Chandrasekhar-mass white dwarfs (WDs) have been very successful in explaining the spectra, light curves, and the width-luminosity relation of spectroscopically normal Type Ia supernovae (SNe Ia). The ignition of the thermonuclear deflagration flame at the end of the convective carbon "simmering" phase in the core of the WD is still not well understood and much about the ignition kernel distribution remains unknown. Furthermore, the central density at the time of ignition depends on the still uncertain screened carbon fusion reaction rates, the accretion history and cooli…
Off-centre ignition of sub-Chandrasekhar white dwarfs does not resolve the tension with the observed $t_0$-$M_{\rm{Ni}56}$ relation of type Ia supernovae
It has recently been proposed that one sub-class of type Ia supernovae (SNe Ia) is sufficiently both distinct and common to be classified separately from the bulk of SNe Ia, with a suggested class name of "type Iax supernovae" (SNe Iax), after SN 2002cx. We show that the population properties of this class can be understood if the events originate from helium double-detonation sub-Chandrasekhar mass explosions, in which a carbon--oxygen white dwarf (CO WD) accumulates a helium layer from a non-degenerate helium star. We have incorporated detailed binary evolution calculations for the progenito…
Type Ia supernovae (SNe Ia) have been an important tool for astronomy for quite some time; however, the nature of their progenitors remains somewhat mysterious. Recent theoretical studies indicated the possibility of producing thermonuclear detonations of carbon-oxygen white dwarfs (CO WDs) at masses less than the Chandrasekhar mass through accretion of helium-rich matter, which would, depending on mass accretion rate, mass, and initial temperature of the WD, spectrally resemble either a normal SN Ia or a peculiar one. This study aims to further resolve the state of binary systems comprised of…
Recently, it has been found that off-centre carbon burning in a subset of intermediate-mass stars does not propagate all the way to the center, resulting in a class of hybrid CONe cores. Here, we consider the possibility that stars hosting these hybrid CONe cores might belong to a close binary system and, eventually, become white dwarfs accreting from a non-degenerate companion at rates leading to a supernova explosion. We have computed the hydrodynamical phase of the explosion of Chandrasekhar-mass white dwarfs harboring hybrid cores, assuming that the explosion starts at the center, either a…
The double-detonation explosion scenario of Type Ia supernovae has gained increased support from the SN Ia community as a viable progenitor model, making it a promising candidate alongside the well-known single degenerate and double degenerate scenarios. We present delay times of double-detonation SNe, in which a sub-Chandrasekhar mass carbon-oxygen white dwarf accretes non-dynamically from a helium-rich companion. One of the main uncertainties in quantifying SN rates from double-detonations is the (assumed) retention efficiency of He-rich matter. Therefore, we implement a new prescription for…
Deciphering the explosion mechanism of Type Ia SNe using their remnants II: a deep dive into double detonations with SNR 0509-67.5
University of Virginia（弗吉尼亚大学）；Virginia Institute for Theoretical Astronomy, University of Virginia（弗吉尼亚大学理论天体物理研究所）；Towson University（陶森大学）；The University of New South Wales（新南威尔士大学）；Australian National University（澳大利亚国立大学）；South African Astronomical Observatory（南非天文台）；University of Cape Town（开普敦大学）；National Institute for Theoretical and Computational Sciences（国家理论与计算科学研究所）
Type Ia supernovae (SNe Ia) originate from the thermonuclear explosion of carbon-oxygen white dwarfs (CO WDs), giving rise to luminous optical transients. A relatively common variety of subluminous SNe Ia events, referred to as SNe Iax, are believed to arise from the failed detonation of a CO WD. In this paper, we explore failed detonation SNe Ia in the context of the double-degenerate channel of merging white dwarfs. In particular, we have carried out the first fully three-dimensional simulation of the merger of a ONe WD with a CO WD. While the hot, tidally-disrupted carbon-rich disk material…
We study the violent phase of the merger of massive binary white dwarf systems. Our aim is to characterize the conditions for explosive burning to occur, and identify a possible explosion mechanism of Type Ia supernovae. The primary components of our model systems are carbon-oxygen (C/O) white dwarfs, while the secondaries are made either of C/O or of pure helium. We account for tidal effects in the initial conditions in a self-consistent way, and consider initially well-separated systems with slow inspiral rates. We study the merger evolution using an adaptive mesh refinement, reactive, Euler…
Recent observational and theoretical progress has favored merging and helium-accreting sub-Chandrasekhar mass white dwarfs in the double-degenerate and the double-detonation channels, respectively, as the most promising progenitors of normal Type Ia supernovae (SNe Ia). Thus the fate of rapidly-accreting Chandrasekhar mass white dwarfs in the single-degenerate channel remains more mysterious then ever. In this paper, we clarify the nature of ignition in Chandrasekhar-mass single-degenerate SNe Ia by analytically deriving the existence of a characteristic length scale which establishes a transi…
We present UV through NIR broad-band photometry, and optical and NIR spectroscopy of Type Iax supernova 2012Z. The data set consists of both early and late-time observations, including the first late phase NIR spectrum obtained for a spectroscopically classified SN Iax. Simple model calculations of its bolometric light curve suggest SN 2012Z produced ~0.3 M_sun of (56)Ni, ejected about a Chandrasekhar mass of material, and had an explosion energy of ~10^51 erg, making it one of the brightest and most energetic SN Iax yet observed. The late phase NIR spectrum of SN 2012Z is found to broadly res…
The faster light-curve evolution of low-luminosity Type Ia supernovae (SNe Ia) suggests that they could result from the explosion of white dwarf (WD) progenitors below the Chandrasekhar mass ($M_{\rm Ch}$). Here we present 1D non-LTE time-dependent radiative transfer simulations of pure central detonations of carbon-oxygen WDs with a mass ($M_\rm{tot}$) between 0.88 M$_{\odot}$ and 1.15 M$_{\odot}$, and a $^{56}\rm{Ni}$ yield between 0.08 M$_{\odot}$ and 0.84 M$_{\odot}$. Their lower ejecta density compared to $M_{\rm Ch}$ models results in a more rapid increase of the luminosity at early time…
Over the past decades, many explosion scenarios for Type Ia supernovae have been proposed and investigated including various combinations of deflagrations and detonations in white dwarfs of different masses up to the Chandrasekhar mass. One of these is the gravitationally confined detonation model. In this case a weak deflagration burns to the surface, wraps around the bound core, and collides at the antipode. A subsequent detonation is then initiated in the collision area. Since the parameter space for this scenario, that is, varying central densities and ignition geometries, has not been stu…
