Nucleosynthesis of Iron-Peak Elements in Type-Ia Supernovae

Abstract

The observed features of typical Type Ia supernovae are well-modeled as the explosions of carbonoxygen white dwarfs both near Chandrasekhar mass and sub-Chandrasekhar mass. However, observations in the last decade have shown that Type Ia supernovae exhibit a wide diversity, which implies models for wider range of parameters are necessary. Based on the hydrodynamics code we developed, we carry out a parameter study of Chandrasekhar mass models for Type Ia supernovae. We conduct a series of two-dimensional hydrodynamics simulations of the explosion phase using the turbulent flame model with the deflagration-detonation-transition (DDT). To reconstruct the nucleosynthesis history, we use the particle tracer scheme. We examine the role of model parameters by examining their influences on the final product of nucleosynthesis. The parameters include the initial density, metallicity, initial flame structure, detonation criteria and so on. We show that the observed chemical evolution of galaxies can help constrain these model parameters. KEYWORDS:Type Ia supernovae, hydrodynamics, nucleosynthesis MethodWe carry out two-dimensional hydrodynamics simulations [1] by solving the Euler equations in cylindrical coordinates. The spatial and temporal discretization are calculated by the fifth-order weighted essentially non-oscillatory (WENO) scheme [2] and the five-step third-order non-strong stability preserving Runge-Kutta scheme [3]. We use the Helmholtz equation of states, which contains contributions from ideal electron gas of arbitrarily relativistic and degenerate levels, blackbody photon gas, ions with Coulomb interactions and positron-electron annihilation pairs [4]. To describe the nuclear reactions, we use a 7-isotope network coupled with the simulations, including 4 He, 12 C, 16 O, 20 Ne, 24 Mg, 28 Si and 56 Ni [5]. We use the turbulent deflagration model [6] with delayed detonation transition [7]. The flame and detonation are described by the level-set scheme [8]. The laminar flame and detonation speed are taken from [9] and calculated using the scheme in [10]. The energy production by the explosion follows the three-step scheme as in [11], which includes carbon burning, nuclear quasi-statistical equilibrium (NQSE) burning and NSE burning. In NSE burning, electron capture is included.To calculate the detailed nucleosynthesis, we use the torch nuclear reaction subroutine which consists of 495 isotopes from 1 H to 91 Tc [12]. The nuclear reaction rates are taken from [13] and [14]. Weak interaction rates of iron-peaked elements are obtained from [15], whereas other isotopes are obtained from [16]. We perform a parameter survey to study the influences of model parameters based on a benchmark model, which satisfies three criteria: 1. Healthy 56 Ni production about 0.6 solar mass; 2. Consistency of the 55 Mn to the galactic chemical evolution; 3. Agreement of 58 Ni with the solar abundance.

Hydrodynamic Simulations of Pre-supernova Outbursts in Red Supergiants: Asphericity and Mass Loss

“…We use a two-dimensional hydrodynamics code that we previously used extensively for SN simulations. The code is designed for multiple purposes and has been used in simulations of Type Ia SNe (Leung et al 2015;Leung & Nomoto 2018, electron capture SNe (Leung & Nomoto 2017Zha et al 2019b; and accretion-induced collapse (Leung et al 2019b;Zha et al 2019a). The code utilizes the fifth-order shock-capturing weighted essentially non-oscillatory (WENO) scheme (Barth & Deconinck 1999) and the five-step third-order non-strongstability-preserving Runge-Kutta scheme for time discretization (Wang & Spiteri 2007) of the Euler equations.…”