HELIUM-IGNITED VIOLENT MERGERS AS A UNIFIED MODEL FOR NORMAL AND RAPIDLY DECLINING TYPE Ia SUPERNOVAE

By Rüdiger Pakmor, M. Kromer, Stefan Taubenberger, Volker Springel. 2013

162 citations recorded by the source corpus.

The progenitors of Type Ia supernovae (SNe Ia) are still unknown, despite significant progress during the past several years in theory and observations. Violent mergers of two carbon–oxygen (CO) white dwarfs (WDs) are a candidate scenario suggested to be responsible for at least a significant fraction of normal SNe Ia. Here, we simulate the merger of two CO WDs using a moving-mesh code that allows for the inclusion of thin helium (He) shells (0.01 M☉) on top of the WDs at an unprecedented numerical resolution. The accretion of He onto the primary WD leads to the formation of a detonation in its He shell. This detonation propagates around the CO WD and sends a converging shock wave into its core, known to robustly trigger a second detonation, as in the well-known double-detonation scenario for He-accreting CO WDs. However, in contrast to that scenario where a massive He shell is required to form a detonation through thermal instability, here the He detonation is ignited dynamically. Accordingly the required He-shell mass is significantly smaller, and hence its burning products are unlikely to affect the optical display of the explosion. We show that this scenario, which works for CO primary WDs with CO- as well as He-WD companions, has the potential to explain the different brightness distributions, delay times, and relative rates of normal and fast declining SNe Ia. Finally, we discuss extensions to our unified merger model needed to obtain a comprehensive picture of the full observed diversity of SNe Ia.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/b97fb54f3306a0d4f5972c180bfe35825bb07e4d

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In Astronomy and Astrophysics

1. Rüdiger Pakmor
2. D. Kasen
3. F. Mannucci
4. D. Maoz
5. M. Kromer
6. G. Nelemans
7. W. Hillebrandt
8. Friedrich K. Röpke

Citations in the corpus

• Improving the convergence properties of the moving-mesh code AREPO (2015, background): “G A ] 2014; Genel et al. 2014), as well as in first star formation (e.g. Greif et al. 2011, 2012; Smith et al. 2014), and to a smaller extent in stellar astrophysics (Pakmor et al. 2013) and in problems related to planet formation (Duffell & MacFadyen 2012; Muñoz et al. 2014, 2015).”
• Three Hypervelocity White Dwarfs in Gaia DR2: Evidence for Dynamically Driven Double-degenerate Double-detonation Type Ia Supernovae (2018, background): “…are accounted for (Shen & Moore 2014), helium shell detonations, and subsequent carbon core detonations, may even occur during the relatively quiescent initial phases of dynamical mass transfer, before the complete tidal disruption of the companion WD (Pakmor et al. 2013; Shen & Schwab 2017).”
• Sub-Chandrasekhar-mass White Dwarf Detonations Revisited (2017, background): “In parallel work, studies of unstable double WD mergers uncovered the possibility that helium could detonate as it was transferred during the dynamical phase of the merger (Guillochon et al. 2010; Raskin et al. 2012; Pakmor et al. 2013; Moll et al. 2014; Tanikawa et al. 2015).”
• Three-dimensional pure deflagration models with nucleosynthesis and synthetic observables for type ia supernovae (2013, background): “Both violent WD–WD mergers (Pakmor et al. 2013; Ruiter et al. 2013) and sub-Chandrasekhar double detonations (Fink et al. 2010; Kromer et al. 2010; Woosley & Kasen 2011; Moll & Woosley 2013) may account for normal and subluminous types of SNe Ia.”
• Observational Clues to the Progenitors of Type Ia Supernovae (2013, background): “Recently, Guillochon et al. (2010), Pakmor et al. (2013), and Shen & Bildsten (2013) have found that also in “violent mergers” (see Section 2.2, above) there may first be a surface He detonation, triggering the C detonation, if the merger is between a He and a C/O WD, or in mergers between two C/O…”
• Theoretical uncertainties of the Type Ia supernova rate (2014, background): “Only recently, some studies indicate that the merger can lead to a SN Ia explosion under certain circumstances (Pakmor et al. 2010, 2011, 2013; Shen et al. 2013; Dan et al. 2013).”