The accuracy of post-processed nucleosynthesis

ABSTRACT The computational requirements posed by multi-dimensional simulations of type Ia supernovae make it difficult to incorporate complex nuclear networks to follow the release of nuclear energy along with the propagation of the flame. Instead, these codes usually model the flame and use simplified nuclear kinetics, with the goal of determining a sufficiently accurate rate of nuclear energy generation and, afterwards, post-processing the thermodynamic trajectories with a large nuclear network to obtain more reliable nuclear yields. In this work, I study the performance of simplified nuclear networks with respect to reproduction of the nuclear yields obtained with a one-dimensional supernova code equipped with a large nuclear network. I start by defining a strategy to follow the properties of matter in nuclear statistical equilibrium (NSE). I propose to use published tables of NSE properties, together with a careful interpolation routine. Short networks (iso7 and 13α) are able to give an accurate yield of 56Ni, after post-processing, but can fail by order of magnitude in predicting the ejected mass of even mildly abundant species (>10−3 M⊙). A network of 21 species reproduces the nucleosynthesis of the Chandrasekhar and sub-Chandrasekhar explosions studied here with average errors better than 20 per cent for the whole set of stable elements and isotopes followed in the models.

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Understanding nebular spectra of Type Ia supernovae

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa640 ◽

2020 ◽

Vol 494 (2) ◽

pp. 2221-2235 ◽

Cited By ~ 2

Author(s):

Kevin D Wilk ◽

D John Hillier ◽

Luc Dessart

Keyword(s):

Radiative Transfer ◽

Local Thermodynamic Equilibrium ◽

Diagnostic Feature ◽

Type Ia Supernovae ◽

Thermal Heating ◽

One Dimensional ◽

Type Ia ◽

Natural Mechanism ◽

Non Local ◽

Ia Supernovae

ABSTRACT In this study, we present one-dimensional, non-local-thermodynamic-equilibrium, radiative transfer simulations (using cmfgen) in which we introduce micro-clumping at nebular times into two Type Ia supernova ejecta models. We use one sub-Chandrasekhar (sub-MCh) ejecta model with 1.04 M⊙ and one Chandrasekhar (MCh) ejecta model with 1.40 M⊙. We introduce clumping factors f = 0.33, 0.25, and 0.10, which are constant throughout the ejecta, and compare results to the unclumped f = 1.0 case. We find that clumping is a natural mechanism to reduce the ionization of the ejecta, reducing emission from [Fe iii], [Ar iii], and [S iii] by a factor of a few. For decreasing values of the clumping factor f, the [Ca ii] λλ7291,7324 doublet became a dominant cooling line for our MCh model but remained weak in our sub-MCh model. Strong [Ca ii] λλ7291,7324 indicates non-thermal heating in that region and may constrain explosion modelling. Due to the low abundance of stable nickel, our sub-MCh model never showed the [Ni ii] 1.939-μm diagnostic feature for all clumping values.

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One-dimensional delayed-detonation models of Type Ia supernovae: confrontation to observations at bolometric maximum

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/sts484 ◽

2012 ◽

Vol 429 (3) ◽

pp. 2127-2142 ◽

Cited By ~ 82

Author(s):

Stéphane Blondin ◽

Luc Dessart ◽

D. John Hillier ◽

Alexei M. Khokhlov

Keyword(s):

Type Ia Supernovae ◽

One Dimensional ◽

Type Ia ◽

Ia Supernovae

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Light Curve Models for SN 2009dc

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312015268 ◽

2011 ◽

Vol 7 (S281) ◽

pp. 314-315

Author(s):

Yasuomi Kamiya

Keyword(s):

Light Curve ◽

White Dwarfs ◽

Light Curves ◽

Host Galaxy ◽

Type Ia Supernovae ◽

Radiation Hydrodynamics ◽

One Dimensional ◽

Type Ia ◽

Ia Supernovae

AbstractSimplified explosion models of super-Chandrasekhar-mass C-O white dwarfs (WDs) are constructed with parameters such as WD mass and 56Ni mass. Their light curves are obtained by solving one-dimensional equations of radiation hydrodynamics, and compared with the observations of SN 2009dc, one of the overluminous Type Ia supernovae, to estimate its properties. As a result, the progenitor of SN 2009dc is suggested to be a 2.2–2.4-M⊙ C-O WD with 1.2–1.4 M⊙ of 56Ni, if the extinction by its host galaxy is negligible.

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Type Ia supernovae from non-accreting progenitors

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936991 ◽

2020 ◽

Vol 635 ◽

pp. A72 ◽

Cited By ~ 1

Author(s):

J. Antoniadis ◽

S. Chanlaridis ◽

G. Gräfener ◽

N. Langer

Keyword(s):

Nuclear Energy ◽

Mass Range ◽

Type Ia Supernovae ◽

Core Collapse ◽

Star Forming ◽

Helium Stars ◽

Type Ia ◽

Complete Disruption ◽

Ia Supernovae ◽

Thermonuclear Runaway

Type Ia supernovae (SNe Ia) are manifestations of stars that are deficient in hydrogen and helium, and disrupt in a thermonuclear runaway. While explosions of carbon-oxygen white dwarfs are thought to account for the majority of events, part of the observed diversity may be due to varied progenitor channels. We demonstrate that helium stars with masses between ∼1.8 and 2.5 M⊙ may evolve into highly degenerate cores with near-Chandrasekhar mass and helium-free envelopes that subsequently ignite carbon and oxygen explosively at densities of ∼(1.8−5.9) × 109 g cm−3. This occurs either due to core growth from shell burning (when the core has a hybrid CO/NeO composition), or following ignition of residual carbon triggered by exothermic electron captures on 24Mg (for a NeOMg-dominated composition). We argue that the resulting thermonuclear runaway is likely to prevent core collapse, leading to the complete disruption of the star. The available nuclear energy at the onset of explosive oxygen burning suffices to create ejecta with a kinetic energy of ∼1051 erg, as in typical SNe Ia. Conversely, if these runaways result in partial disruptions, the corresponding transients would resemble SN Iax events similar to SN 2002cx. If helium stars in this mass range indeed explode as SNe Ia, then the frequency of events would be comparable to the observed SN Ib/c rates, thereby sufficing to account for the majority of SNe Ia in star-forming galaxies.

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Limits on a population of collisional-triples as progenitors of Type-Ia supernovae

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2535 ◽

2019 ◽

Vol 490 (1) ◽

pp. 657-664 ◽

Cited By ~ 5

Author(s):

Na’ama Hallakoun ◽

Dan Maoz

Keyword(s):

Data Base ◽

Main Sequence ◽

Type Ia Supernovae ◽

Triple Systems ◽

Upper Limit ◽

Type Ia ◽

Order Of Magnitude ◽

Low Mass ◽

Ia Supernovae ◽

Gaia Dr2

ABSTRACT The progenitor systems of Type-Ia supernovae (SNe Ia) are yet unknown. The collisional-triple SN Ia progenitor model posits that SNe Ia result from head-on collisions of binary white dwarfs (WDs), driven by dynamical perturbations by the tertiary stars in mild-hierarchical triple systems. To reproduce the Galactic SN Ia rate, at least ∼30–55 per cent of all WDs would need to be in triple systems of a specific architecture. We test this scenario by searching the Gaia DR2 data base for the postulated progenitor triples. Within a volume out to 120 pc, we search around Gaia-resolved double WDs with projected separations up to 300 au, for physical tertiary companions at projected separations out to 9000 au. At 120 pc, Gaia can detect faint low-mass tertiaries down to the bottom of the main sequence and to the coolest WDs. Around 27 double WDs, we identify zero tertiaries at such separations, setting a 95 per cent confidence upper limit of 11 per cent on the fraction of binary WDs that are part of mild hierarchical triples of the kind required by the model. As only a fraction (likely ∼10 per cent) of all WDs are in <300 au WD binaries, the potential collisional-triple progenitor population appears to be at least an order of magnitude (and likely several) smaller than required by the model.

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An asymmetric explosion mechanism may explain the diversity of Si ii linewidths in Type Ia supernovae

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa974 ◽

2020 ◽

Vol 494 (4) ◽

pp. 5811-5824

Author(s):

Ran Livneh ◽

Boaz Katz

Keyword(s):

Radiative Transfer ◽

Thermodynamic Equilibrium ◽

Local Thermodynamic Equilibrium ◽

Spectral Feature ◽

Type Ia Supernovae ◽

Absorption Region ◽

Type Ia ◽

Order Of Magnitude ◽

Good Tracer ◽

Ia Supernovae

ABSTRACT Near maximum brightness, the spectra of Type Ia supernovae (SNe Ia) present typical absorption features of Silicon II observed at roughly $6100$ and $5750\, \mathring{\rm A}$. The two-dimensional distribution of the pseudo-equivalent widths (pEWs) of these features is a useful tool for classifying SNe Ia spectra (Branch plot). Comparing the observed distribution of SNe on the Branch plot to results of simulated explosion models, we find that one-dimensional models fail to cover most of the distribution. In contrast, we find that tardis radiative transfer simulations of the white dwarf head-on collision models along different lines of sight almost fully cover the distribution. We use several simplified approaches to explain this result. We perform order-of-magnitude analysis and model the opacity of the Si ii lines using local thermodynamic equilibrium and non-local thermodynamic equilibrium approximations. Introducing a simple toy model of spectral feature formation, we show that the pEW is a good tracer for the extent of the absorption region in the ejecta. Using radiative transfer simulations of synthetic SN ejecta, we reproduce the observed Branch plot distribution by varying the luminosity of the SN and the Si density profile of the ejecta. We deduce that the success of the collision model in covering the Branch plot is a result of its asymmetry, which allows for a significant range of Si density profiles along different viewing angles, uncorrelated with a range of 56Ni yields that cover the observed range of SN Ia luminosity. We use our results to explain the shape and boundaries of the Branch plot distribution.

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