Numerical Modeling of Type Ia Supernovae Explosions (original) (raw)

Pulsating reverse detonation models of Type Ia supernovae. II: Explosion

Observational evidences point to a common explosion mechanism of Type Ia supernovae based on a delayed detonation of a white dwarf. However, all attempts to find a convincing ignition mechanism based on a delayed detonation in a destabilized, expanding, white dwarf have been elusive so far. One of the possibilities that has been invoked is that an inefficient deflagration leads to pulsation of a Chandrasekhar-mass white dwarf, followed by formation of an accretion shock that confines a carbon-oxygen rich core, while transforming the kinetic energy of the collapsing halo into thermal energy of the core, until an inward moving detonation is formed. This chain of events has been termed Pulsating Reverse Detonation (PRD). In this work we present three dimensional numerical simulations of PRD models from the time of detonation initiation up to homologous expansion. Different models characterized by the amount of mass burned during the deflagration phase, M_defl, give explosions spanning a range of kinetic energies, K ~ (1.0-1.2) foes, and 56Ni masses, M(56Ni) ~ 0.6-0.8 M_sun, which are compatible with what is expected for typical Type Ia supernovae. Spectra and light curves of angle-averaged spherically symmetric versions of the PRD models are discussed. Type Ia supernova spectra pose the most stringent requirements on PRD models.

PULSATING REVERSE DETONATION MODELS OF TYPE Ia SUPERNOVAE. I. DETONATION IGNITION

The Astrophysical Journal, 2009

Observational evidences point to a common explosion mechanism of Type Ia supernovae based on a delayed detonation of a white dwarf. However, all attempts to find a convincing ignition mechanism based on a delayed detonation in a destabilized, expanding, white dwarf have been elusive so far. One of the possibilities that has been invoked is that an inefficient deflagration leads to pulsation of a Chandrasekhar-mass white dwarf, followed by formation of an accretion shock that confines a carbon-oxygen rich core, while transforming the kinetic energy of the collapsing halo into thermal energy of the core, until an inward moving detonation is formed. This chain of events has been termed Pulsating Reverse Detonation (PRD). In this work we present three dimensional numerical simulations of PRD models from the time of detonation initiation up to homologous expansion. Different models characterized by the amount of mass burned during the deflagration phase, M defl , give explosions spanning a range of kinetic energies, K ∼ (1.0 − 1.2) × 10 51 erg, and 56 Ni masses, M ( 56 Ni) ∼ 0.6 − 0.8 M ⊙ , which are compatible with what is expected for typical Type Ia supernovae. Spectra and light curves of angle-averaged spherically symmetric versions of the PRD models are discussed. Type Ia supernova spectra pose the most stringent requirements on PRD models.

Modeling the Diversity of Type Ia Supernova Explosions

2010

Type Ia supernovae (SNe Ia) are a prime tool in observational cosmology. A relation between their peak luminosities and the shapes of their light curves allows to infer their intrinsic luminosities and to use them as distance indicators. This relation has been established empirically. However, a theoretical understanding is necessary in order to get a handle on the systematics in SN Ia cosmology. Here, a model reproducing the observed diversity of normal SNe Ia is presented. The challenge in the numerical implementation arises from the vast range of scales involved in the physical mechanism. Simulating the supernova on scales of the exploding white dwarf requires specific models of the microphysics involved in the thermonuclear combustion process. Such techniques are discussed and results of simulations are presented.

On Simulating Type Ia Supernovae

Journal of Physics: Conference Series, 2012

Type Ia supernovae are bright stellar explosions distinguished by standardizable light curves that allow for their use as distance indicators for cosmological studies. Despite their highly successful use in this capacity, the progenitors of these events are incompletely understood. We describe simulating type Ia supernovae in the paradigm of a thermonuclear runaway occurring in a massive white dwarf star. We describe the multi-scale physical processes that realistic models must incorporate and the numerical models for these that we employ. In particular, we describe a flame-capturing scheme that addresses the problem of turbulent thermonuclear combustion on unresolved scales. We present the results of our study of the systematics of type Ia supernovae including trends in brightness following from properties of the host galaxy that agree with observations. We also present performance results from simulations on leadership-class architectures.

Type Ia supernovae: Advances in large scale simulation

Journal of Physics: Conference Series, 2009

Using the newly developed petascale codes, MAESTRO and CASTRO, the Computational Astrophysics Consortium is simulating the explosion of white dwarf stars as Type Ia supernovae. Since the outcome is sensitive to where the nuclear runaway ignites, three sorts of calculations are being carried out. In the first, the presupernova convection of rotating and non-rotating white dwarfs is followed for several hours (star time), using MAESTRO, in order to determine just where the first sparks ignite. The turbulent nuclear combustion of the explosion is then followed using the compressible hydro code CASTRO in two other studies that assume either central or off-center ignition. Current calculations are running on 4000 -12000 CPU, but larger studies, on a greater number of CPU, will be required to increase the Reynolds number of the ignition study and the fidelity of the turbulence in the explosion studies.

Thermonuclear supernova models, and observations of Type Ia supernovae

Arxiv preprint astro-ph/0412155, 2004

In this paper, we review the present state of theoretical models of thermonuclear supernovae, and compare their predicitions with the constraints derived from observations of Type Ia supernovae. The diversity of explosion mechanisms usually found in one-dimensional simulations is a direct consequence of the impossibility to resolve the flame structure under the assumption of spherical symmetry. Spherically symmetric models have been successful in explaining many of the observational features of Type Ia supernovae, but they rely on two kinds of empirical models: one that describes the behaviour of the flame on the scales unresolved by the code, and another that takes account of the evolution of the flame shape. In contrast, three-dimensional simulations are able to compute the flame shape in a self-consistent way, but they still need a model for the propagation of the flame in the scales unresolved by the code. Furthermore, in three dimensions the number of degrees of freedom of the initial configuration of the white dwarf at runaway is much larger than in one dimension. Recent simulations have shown that the sensitivity of the explosion output to the initial conditions can be extremely large. New paradigms of thermonuclear supernovae have emerged from this situacion, as the Pulsating Reverse Detonation. The resolution of all these issues must rely on the predictions of observational properties of the models, and their comparison with current Type Ia supernova data, including X-ray spectra of Type Ia supernova remnants.

Type Ia Supernova models arising from different distributions of igniting points

Astronomy & Astrophysics, 2005

In this paper we address the theory of Type Ia supernovae from the moment of carbon runaway up to several hours after the explosion. We have concentrated on the boiling-pot model: a deflagration characterized by the (nearly-) simultaneous ignition of a number of bubbles that pervade the core of the white dwarf. Thermal fluctuations larger than >1% of the background temperature (7x10^8 K) on lengthscales of < 1m could be the seeds of the bubbles. Variations of the homogeneity of the temperature perturbations can lead to two alternative configurations at carbon runaway: if the thermal gradient is small, all the bubbles grow to a common characteristic size related to the value of the thermal gradient, but if the thermal gradient is large enough, the size spectrum of the bubbles extends over several orders of magnitude. The explosion phase has been studied with the aid of a smoothed particle hydrodynamics code suited to simulate thermonuclear supernovae. In spite of important procedural differences and different physical assumptions, our results converge with the most recent calculations of 3D deflagrations in white dwarfs carried out in supernova studies by different groups. For large initial numbers of bubbles (>3-4 per octant), the explosion produces about 0.45 solar masses of 56Ni, and the kinetic energy of the ejecta is 0.45x10^{51} ergs. However, all three-dimensional deflagration models share three main drawbacks: 1) the scarce synthesis of intermediate-mass elements, 2) the loss of chemical stratification of the ejecta due to mixing by Rayleigh-Taylor instabilities during the first second of the explosion, and 3) the presence of big clumps of 56Ni at the photosphere at the time of maximum brightness.

Beyond the Bubble Catastrophe of Type Ia Supernovae: Pulsating Reverse Detonation Models

The Astrophysical Journal, 2006

We describe a mechanism by which a failed deflagration of a Chandrasekharmass carbon-oxygen white dwarf can turn into a successful thermonuclear supernova explosion, without invoking an ad hoc high-density deflagration-detonation transition. Following a pulsating phase, an accretion shock develops above a core of ∼ 1 M ⊙ composed of carbon and oxygen, inducing a converging detonation. A three-dimensional simulation of the explosion produced a kinetic energy of 1.05 × 10 51 ergs and 0.70 M ⊙ of 56 Ni, ejecting scarcely 0.01 M ⊙ of C-O moving at low velocities. The mechanism works under quite general conditions and is flexible enough to account for the diversity of normal Type Ia supernovae. In given conditions the detonation might not occur, which would reflect in peculiar signatures in the gamma and UV-wavelengths.

Inferring Explosion Properties from Type II-Plateau Supernova Light Curves

The Astrophysical Journal, 2019

We present advances in modeling Type IIP supernovae using MESA for evolution to shock breakout coupled with STELLA for generating light and radial velocity curves. Explosion models and synthetic light curves can be used to translate observable properties of supernovae (such as the luminosity at day 50 and the duration of the plateau, as well as the observable quantity ET , defined as the time-weighted integrated luminosity that would have been generated if there was no 56 Ni in the ejecta) into families of explosions which produce the same light curve and velocities on the plateau. These predicted families of explosions provide a useful guide towards modeling observed SNe, and can constrain explosion properties when coupled with other observational or theoretical constraints. For an observed supernova with a measured 56 Ni mass, breaking the degeneracies within these families of explosions (ejecta mass, explosion energy, and progenitor radius) requires independent knowledge of one parameter. We expect the most common case to be a progenitor radius measurement for a nearby supernova. We show that ejecta velocities inferred from the Fe II 5169Å line measured during the majority of the plateau phase provide little additional information about explosion characteristics. Only during the initial shock cooling phase can photospheric velocity measurements potentially aid in unraveling light curve degeneracies.