Signatures of bimodality in nebular phase Type Ia supernova spectra

Vallely, P.; Tucker, M. A.; Shappee, B. J.; Brown, J. S.; Stanek, K. Z.; Kochanek, C. S.

doi:10.1093/mnras/staa003

Cited by 22 publications

(14 citation statements)

References 153 publications

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“…Some explosion models can be discarded as they do not reproduce SN 2011fe well near maximum light. 5 Direct (head-on) WD collision models (e.g., Rosswog et al 2009;van Rossum et al 2016;Papish & Perets 2016) predict isotope ratios inconsistent with observations (Papish & Perets 2016) which is supported by the non-detection of bimodal nebularphase emission profiles (e.g., Dong et al 2015;Vallely et al 2020). Similarly, graviationally-confined detonations (grav.…”

Section: Discussionmentioning

confidence: 95%

The Whisper of a Whimper of a Bang: 2400 Days of the Type Ia SN 2011fe Reveals the Decay of $^{55}$Fe

Tucker¹,

Shappee²,

Kochanek³

et al. 2021

Preprint

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We analyze new multi-filter Hubble Space Telescope (HST) photometry of the normal Type Ia supernova (SN Ia) 2011fe out to ≈ 2400 days after maximum light, the latest observations to-date of a SN Ia. We model the pseudo-bolometric light curve with a simple radioactive decay model and find energy input from both 57 Co and 55 Fe are needed to power the late-time luminosity. This is the first detection of 55 Fe in a SN Ia. We consider potential sources of contamination such as a surviving companion star or delaying the deposition timescale for 56 Co positrons but these scenarios are ultimately disfavored. The relative isotopic abundances place direct constraints on the burning conditions experienced by the white dwarf and require a central density of ρ c ∼ 3 × 10 8 g cm −3 . Only 2 classes of explosion models are currently consistent with all observations of SN 2011fe: 1) the delayed detonation of a low-ρ c , near-M Ch (1.2 − 1.3M ) WD, or 2) a sub-M Ch (1.0 − 1.1 M ) WD experiencing a thin-shell double detonation.

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Section: Discussionmentioning

confidence: 95%

The Whisper of a Whimper of a Bang: 2400 Days of the Type Ia SN 2011fe Reveals the Decay of $^{55}$Fe

Tucker¹,

Shappee²,

Kochanek³

et al. 2021

Preprint

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“…Shifts of up to ∼3000 km s −1 (both to the blue and to the red) in iron and nickel forbidden emission lines have been identified in spectra at ∼200 days past maximum, indicating relatively large asymmetries in the inner Fe-rich ejecta, and these seem to be correlated with early-time properties ( Figure 5), perhaps suggesting an orientation effect 99,101 . Approximately 15% of SN Ia show signatures of double-peaked nebular emission lines separated by ∼5000 km s −1 , and the fraction rises for subluminous SN Ia 105,106 ; this may result from two explosion sites in a white dwarf collision model.…”

Section: Type Ia Supernovaementioning

confidence: 99%

Observational properties of thermonuclear supernovae

2019

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The explosive death of a star as a supernova is one of the most dramatic events in the Universe. Supernovae have an outsized impact on many areas of astrophysics: they are major contributors to the chemical enrichment of the cosmos and significantly influence the formation of subsequent generations of stars and the evolution of galaxies. Here we review the observational properties of thermonuclear supernovae, exploding white dwarf stars resulting from the stellar evolution of low-mass stars in close binary systems. The best known objects in this class are type Ia supernovae (SN Ia), astrophysically important in their application as standardisable candles to measure cosmological distances and the primary source of iron group elements in the Universe. Surprisingly, given their prominent role, SN Ia progenitor systems and explosion mechanisms are not fully understood; the observations we describe here provide constraints on models, not always in consistent ways. Recent advances in supernova discovery and follow-up have shown that the class of thermonuclear supernovae includes more than just SN Ia, and we characterise that diversity in this review.The modern classification scheme for supernovae traces back to Minkowski 1 who in 1941 split "Type I" from "Type II" supernovae based on optical spectra. Further subdivision of these basic classes has continued on an empirical basis 2, 3 , and in our review we describe the observational properties of what are now called SN Ia, along with other similar objects. The observational classification effort arises from a desire for physical understanding of these objects, explaining our use of the term thermonuclear supernovae in the title. That categorisation is based on the explosion mechanism: objects where the energy released in the explosion is primarily the result of thermonuclear fusion. Given our current state of knowledge, we could equally well call this a review of the observational properties of white dwarf supernovae, a categorisation based on the kind of object that explodes. This is contrasted with core-collapse or massive star supernovae, respectively, in the explosion mechanism or exploding object categorisations. Unlike those objects, where clear observational evidence exists for massive star progenitors and corecollapse (from both neutrino emission and remnant pulsars), the direct evidence for thermonuclear supernova explosions of white dwarfs is limited 4, 5 and not necessarily simply interpretable 6, 7 . Nevertheless, the indirect evidence is strong, though many open questions about the progenitor systems and explosion mechanisms remain.SN Ia are important both to the evolution of the Universe and to our understanding of it. As standardisable candles whose distance can be observationally inferred 8 , SN Ia have a starring role in the discovery of the accelerating expansion of the Universe 9, 10 and in measurement of its current expansion rate 11 . SN Ia are also major contributors to the chemical enrichment of the Universe, producing most of its iron 12 and elem...

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“…They showed that various uncertainties related to the physical processes and to the initial profiles of the WD are unlikely to resolve the tension with observations, although they can deteriorate the agreement with observations of low-luminosity SNe Ia. While there are some reasonable initial compositions and reaction rate values for which DDM successfully explains the lowluminosity part of the t0 − MNi56 relation, this model may be in conflict with the observed 56 Ni mass-weighted line-of-sight velocity distribution for a large fraction of these events, as measured from nebular spectra (Dong et al 2015(Dong et al , 2018Vallely, et al 2020). Specifically, the 56 Ni velocity distribution is either double-peaked or highly shifted, which so far has not been predicted by the DDM.…”

Section: Summary and Discussionmentioning

confidence: 83%

Confronting double-detonation sub-Chandrasekhar models with the low-luminosity suppression of Type Ia supernovae

Ghosh¹,

Kushnir²

2021

Preprint

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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 (2021) used The Zwicky Transient Facility Bright Transient Survey to construct a synthesized 56 Ni mass, M Ni56 , distribution of SNe Ia. They found that the rate of lowluminosity (M Ni56 ≈ 0.15 M ⊙ ) SNe Ia is lower by a factor of ∼10 than the more common M Ni56 ≈ 0.7 M ⊙ events. We here show that in order for the double-detonation model (DDM, in which a propagating thermonuclear detonation wave, TNDW, within a thin helium shell surrounding a sub-Chandrasekhar mass CO core triggers a TNDW within the core) to explain this low-luminosity suppression, the probability of a low-mass (≈ 0.85 M ⊙ ) WD explosion should be ∼100-fold lower than that of a high-mass (≈ 1.05 M ⊙ ) WD. One possible explanation is that the ignition of low-mass CO cores is somehow suppressed. We use one-dimensional numerical simulations to show that if a TNDW is able to propagate within the helium shell, then the ignition within the CO core is guaranteed, even for very low-mass, 0.7 M ⊙ , WDs. Our accurate and efficient numerical scheme allows us, for the first time, to numerically resolve the core ignition in a full-star simulation. Since we do not expect multi-dimensional perturbations to significantly change our results, we conclude that the DDM provides no natural explanation for the low-luminosity suppression of SNe Ia. The low-luminosity suppression poses a challenge for any model.

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Signatures of bimodality in nebular phase Type Ia supernova spectra

Cited by 22 publications

References 153 publications

The Whisper of a Whimper of a Bang: 2400 Days of the Type Ia SN 2011fe Reveals the Decay of $^{55}$Fe

The Whisper of a Whimper of a Bang: 2400 Days of the Type Ia SN 2011fe Reveals the Decay of $^{55}$Fe

Observational properties of thermonuclear supernovae

Confronting double-detonation sub-Chandrasekhar models with the low-luminosity suppression of Type Ia supernovae

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