The Progenitors of Subluminous Type I[CLC]a[/CLC] Supernovae

Howell, D. A.

doi:10.1086/321702

Cited by 166 publications

(195 citation statements)

References 43 publications

(50 reference statements)

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“…Howell 2001). A long inspiral time of the original WD-WD binary leads to a long delay time between the formation of the progenitor system and the supernova explosion in our model.…”

Section: Comparison With Other Models and Observationsmentioning

confidence: 82%

Violent mergers of nearly equal-mass white dwarf as progenitors of subluminous Type Ia supernovae

Pakmor

Hachinger

Röpke

et al. 2011

A&A

207

265

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Context. The origin of subluminous Type Ia supernovae (SNe Ia) has long eluded any explanation, because all Chandrasekhar-mass models have severe problems reproducing them. Recently, it has been proposed that violent mergers of two white dwarfs of 0.9 M could lead to subluminous SNe Ia events that resemble 1991bg-like SNe Ia. Aims. Here we investigate whether this scenario still works for mergers of two white dwarfs with a mass ratio below one. We aim to determine the range of mass ratios for which a detonation still forms during the merger, as only those events will lead to an SN Ia. This range is an important ingredient for population synthesis and one decisive point for judging the viability of the scenario. In addition, we perform a resolution study of one of the models. Finally we discuss the connection between violent white dwarf mergers with a primary mass of 0.9 M and 1991bg-like SNe Ia. Methods. The latest version of the smoothed particle hydrodynamics code Gadget3 was used to evolve binary systems with different mass ratios until they merge. We analyzed the result and looked for hot spots in which detonations can form. Results. We show that mergers of two white dwarfs with a primary white dwarf mass of ≈0.9 M and a mass ratio more than about 0.8 robustly reach the conditions we require for igniting a detonation and thus produce thermonuclear explosions during the merger itself. We also find that, while our simulations do not yet completely resolve the hot spots, increasing the resolution leads to conditions that are even more likely to ignite detonations. Additionally, we compare the abundance structure of the ejecta of the thermonuclear explosion of two merged white dwarfs with data inferred from observations of a 1991bg-like SN Ia (SN 2005bl). The abundance distributions of intermediate mass and iron group elements in velocity space agree qualitatively, and our model reproduces the lack of material at high velocities inferred from the observations. Conclusions. The violent merger scenario constitutes a robust possibility for two merging white dwarfs to produce a thermonuclear explosion. Mergers with a primary white dwarf mass of ≈0.9 M are very promising candidates for explaining subluminous SNe Ia. This would imply that subluminous SNe Ia form a distinct class of objects, which are not produced in the standard single white dwarf scenario for SNe Ia, but instead arise from a different progenitor channel and explosion mechanism.

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“…Howell 2001). A long inspiral time of the original WD-WD binary leads to a long delay time between the formation of the progenitor system and the supernova explosion in our model.…”

Section: Comparison With Other Models and Observationsmentioning

confidence: 82%

Violent mergers of nearly equal-mass white dwarf as progenitors of subluminous Type Ia supernovae

Pakmor

Hachinger

Röpke

et al. 2011

A&A

207

265

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“…The crucial year was 1991, when the bright, slowly declining SN1991T [74,105], and the faint, intrinsically red and fast declining SN1991bg [50,71,119] were discovered. Other under-and over-luminous objects have been found since then [66].…”

Section: Type Ia Supernovaementioning

confidence: 98%

Classification of Supernovae

Turatto

2003

Supernovae and Gamma-Ray Bursters

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Abstract. The current classification scheme for supernovae is presented. The main observational features of the supernova types are described and the physical implications briefly addressed. Differences between the homogeneous thermonuclear type Ia and similarities among the heterogeneous core collapse type Ib, Ic and II are highlighted. Transforming type IIb, narrow line type IIn, supernovae associated with GRBs and few peculiar objects are also discussed.

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“…SN 1991T is the best characterised exemplar of a sub-class (SNe 91T) of SNe Ia that make up a few percent of all observed SNe Ia (Li et al 2011;Silverman et al 2012;Blondin et al 2012). In contrast to normal SNe Ia, SNe 91T are known to occur preferentially in late-type galaxies (Hamuy et al 2000;Howell 2001), indicating an origin in young stellar populations. SNe 91T further clearly distinguish themselves from normal SNe Ia by their peculiar pre-maximum light spectra.…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional simulations of gravitationally confined detonations compared to observations of SN 1991T

Seitenzahl

Kromer

Ohlmann

et al. 2016

A&A

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The gravitationally confined detonation (GCD) model has been proposed as a possible explosion mechanism for Type Ia supernovae in the single-degenerate evolution channel. It starts with ignition of a deflagration in a single off-centre bubble in a near-Chandrasekharmass white dwarf. Driven by buoyancy, the deflagration flame rises in a narrow cone towards the surface. For the most part, the main component of the flow of the expanding ashes remains radial, but upon reaching the outer, low-pressure layers of the white dwarf, an additional lateral component develops. This causes the deflagration ashes to converge again at the opposite side, where the compression heats fuel and a detonation may be launched. We first performed five three-dimensional hydrodynamic simulations of the deflagration phase in 1.4 M carbon/oxygen white dwarfs at intermediate-resolution (256 3 computational zones). We confirm that the closer the initial deflagration is ignited to the centre, the slower the buoyant rise and the longer the deflagration ashes takes to break out and close in on the opposite pole to collide. To test the GCD explosion model, we then performed a high-resolution (512 3 computational zones) simulation for a model with an ignition spot offset near the upper limit of what is still justifiable, 200 km. This high-resolution simulation met our deliberately optimistic detonation criteria, and we initiated a detonation. The detonation burned through the white dwarf and led to its complete disruption. For this model, we determined detailed nucleosynthetic yields by post-processing 10 6 tracer particles with a 384 nuclide reaction network, and we present multi-band light curves and time-dependent optical spectra. We find that our synthetic observables show a prominent viewing-angle sensitivity in ultraviolet and blue wavelength bands, which contradicts observed SNe Ia. The strong dependence on the viewing angle is caused by the asymmetric distribution of the deflagration ashes in the outer ejecta layers. Finally, we compared our model to SN 1991T. The overall flux level of the model is slightly too low, and the model predicts pre-maximum light spectral features due to Ca, S, and Si that are too strong. Furthermore, the model chemical abundance stratification qualitatively disagrees with recent abundance tomography results in two key areas: our model lacks low-velocity stable Fe and instead has copious amounts of high-velocity 56 Ni and stable Fe. We therefore do not find good agreement of the model with SN 1991T.

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The Progenitors of Subluminous Type I[CLC]a[/CLC] Supernovae

Cited by 166 publications

References 43 publications

Violent mergers of nearly equal-mass white dwarf as progenitors of subluminous Type Ia supernovae

Violent mergers of nearly equal-mass white dwarf as progenitors of subluminous Type Ia supernovae

Classification of Supernovae

Three-dimensional simulations of gravitationally confined detonations compared to observations of SN 1991T

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