Inward Propagation of Nuclear‐burning Shells in Merging C‐O and He White Dwarfs

Saio, Hideyuki; Nomoto, K.

doi:10.1086/305696

Cited by 156 publications

(130 citation statements)

References 31 publications

(59 reference statements)

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“…Tutukov & Yungelson 1979;Mochkovitch & Livio 1990) leads to its collapse to a neutron star (e.g. Nomoto & Kondo 1991;Dessart et al 2006;Yoon et al 2007) following its transformation to an O-Ne-Mg core (Saio & Nomoto 1985;Timmes 1994;Saio & Nomoto 1998), Piersanti et al (2003a,b) and Saio & Nomoto (2004) argue that for rapidly rotating primaries, central carbon ignition may be possible. The latter case would result in a near-M Ch SN Ia event, with the same potential explosion mechanisms listed above.…”

Section: Introductionmentioning

confidence: 99%

Solar abundance of manganese: a case for near Chandrasekhar-mass Type Ia supernova progenitors

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Röpke

et al. 2013

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Context. Manganese is predominantly synthesised in Type Ia supernova (SN Ia) explosions. Owing to the entropy dependence of the Mn yield in explosive thermonuclear burning, SNe Ia involving near Chandrasekhar-mass (M Ch ) white dwarfs (WDs) are predicted to produce Mn-to-Fe ratios that significantly exceed those of SN Ia explosions involving sub-Chandrasekhar mass primary WDs. Of all current supernova explosion models, only SN Ia models involving near-M Ch WDs produce [Mn/Fe] 0.0. Aims. Using the specific yields for competing SN Ia scenarios, we aim to constrain the relative fractions of exploding near-M Ch to sub-M Ch primary WDs in the Galaxy. Methods. We extract the Mn yields from three-dimensional thermonuclear supernova simulations that refer to different initial setups and progenitor channels. We then compute the chemical evolution of Mn in the solar neighborhood, assuming SNe Ia are made up of different relative fractions of the considered explosion models. Results. We find that due to the entropy dependence of freeze-out yields from nuclear statistical equilibrium, [Mn/Fe]

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Section: Introductionmentioning

confidence: 99%

Solar abundance of manganese: a case for near Chandrasekhar-mass Type Ia supernova progenitors

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et al. 2013

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“…It has also been shown (e.g. Nomoto & Iben 1985;Saio & Nomoto 1998) that the most likely result of such a merger is an inward propagating deflagration flame that converts the white dwarf into an O-Ne Article published by EDP Sciences A117, page 1 of 9 white dwarf. This white dwarf then undergoes accretion-induced collapse rather than thermonuclear explosion (Nomoto & Kondo 1991).…”

Section: Introductionmentioning

confidence: 99%

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

Pakmor

Hachinger

Röpke

et al. 2011

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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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“…Unlike CO WDs, WDs made of ONe that belong to a binary system collapse, rather than explode, when they accrete matter up to the Chandrasekhar mass; this is why they are usually excluded from the set of putative progenitors of SNIa (Miyaji et al 1980;Nomoto 1984;Nomoto 1987;Gutiérrez et al 1996;Gutiérrez et al 2005). Furthermore, merging of two WDs made of CO in a DD scenario may lead to nonexplosive C-burning and mutation of the composition into ONe, with the same result as in single Chandrasekhar-mass WDs made of ONe of collapsing to a neutron star rather than exploding (Saio & Nomoto 1998). Current multidimensional simulations of the merging of WDs nurture the hope of avoiding this collapse (e.g., Pakmor et al 2010;Moll et al 2014; Raskin et al 2014).…”

Section: Introductionmentioning

confidence: 99%

Explosion of white dwarfs harboring hybrid CONe cores

Bravo

Gil‐Pons

Gutiérrez

et al. 2016

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Recently, it has been found that off-center 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. The implications of a significant presence of carbon in the resulting massive degenerate cores have not been thoroughly explored so far. 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 nondegenerate companion at rates leading to a supernova explosion. We computed the hydrodynamical phase of the explosion of Chandrasekhar-mass white dwarfs harboring hybrid cores, assuming that the explosion starts at the center; this explosion occurs either as a detonation, as may be expected in some degenerate merging scenarios, or as a deflagration that afterward transitions into a delayed detonation. We assume these hybrid cores are made of a central CO volume, of mass M CO , surrounded by an ONe shell. We show that, in the case of a pure detonation, a medium-sized carbon-rich region, M CO (<0.4 M ), results in the ejection of a small fraction of the mantle while leaving a massive bound remnant. Part of this remnant is made of the products of the detonation, that is, Fe-group nuclei, but they are buried in its inner regions unless convection is activated during the ensuing cooling and shrinking phase of the remnant. In contrast, and somehow paradoxically, delayed detonations do not leave remnants other than for the minimum M CO we explored of M CO = 0.2 M , and even in this case the remnant is as small as 0.13 M . The ejecta produced by these delayed detonations are characterized by slightly smaller masses of 56 Ni and substantially smaller kinetic energies than the ejecta obtained for a delayed detonation of a "normal" CO white dwarf. The optical emission expected from these explosions most likely do not match the observational properties of typical Type Ia supernovae, although they make interesting candidates for the subluminous class of SN2002cx-like or SNIax.

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Inward Propagation of Nuclear‐burning Shells in Merging C‐O and He White Dwarfs

Abstract: heating during inter-pulse phases, in contrast to the case of carbon-burning flame where the conduction drives the inward propagation of the flame. We infer that such a low mass double white dwarf system could be a progenitor of the AM CVn stars.

Cited by 156 publications

References 31 publications

Solar abundance of manganese: a case for near Chandrasekhar-mass Type Ia supernova progenitors

Solar abundance of manganese: a case for near Chandrasekhar-mass Type Ia supernova progenitors

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

Explosion of white dwarfs harboring hybrid CONe cores

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