As neutrinos pass through supernovae, the turbulence they encounter modifies the flavor evolution process. Previous studies of this effect have found that turbulence close to the proto-neutron star during the accretion phase does not change neutrino flavor evolution; only when the turbulence is present in the outer mantle are sizable effects noticeable. These studies however only used three ‘active’ neutrino flavors, but there are experimental hints of a fourth, sterile flavor with a mass splitting such that a neutrino resonance will occur close to the proto-neutron star. In this scenario, turbulence close to the proto-neutron star during the accretion phase would affect neutrino evolution. To study this possibility, we will generate multiple realizations of turbulent profiles, which resemble those from hydrodynamic supernova simulations and investigate the impact upon the neutrinos using a four-flavor neutrino evolution code to calculate the transition probabilities. The ensembles we construct will then be analyzed to determine the conditions under which the neutrinos would be affected and how these changes correlate with the properties of the turbulence.

Previous simulations of core-collapse supernovae have revealed a hydrodynamic instability known as the Spherical Accretion Shock Instability (SASI). Both axisymmetric and non-axisymmetric spiral modes have been studied in 2D and 3D simulations, and rotation of the progenitor star has been shown to influence the growth of the instability. Analytic models predict a dependence of the growth rate on the specific angular momentum of the core. We will use the hydrodynamic code VH1 following the methods of Blondin & Shaw (2007) to induce spiral modes with a specific angular momentum. We will verify the analytic results of SASI growth in cylindrical geometry and extend the simulation to more realistic spherical geometry.

The neutrinos produced during a core-collapse supernova undergo flavor oscillation as they propagate through the mantle of the star. This process has been simulated accounting for standard neutrino interactions with matter but the consequences of non-standard interactions (NSI) are not as well understood, though they could have a significant effect on the process. We will use the 3-flavor neutrino evolution code Sqa to model neutrino propagation through a supernova including NSI in order to determine the effect on the flavor probabilities and the signatures of NSI one might observe from the next Galactic supernova neutrino burst in Earth-based detectors.

Kepler's supernova remnant (SNR) consists of the gaseous remains from the thermonuclear explosion of a white dwarf (Type Ia Supernova) in 1604. But the structure of the SNR is highly complex, which we explain as a combination of the formation of a bow shock from the enormous proper motion of the system and the asymmetric circumstellar medium (CSM) due to asymmetric wind from the hypothesized companion star. While 3-D models are necessary for proper representation, no research has been done to create 3-D models accounting for both of these effects in Kepler. We propose to first create a 3-D hydrodynamic model to describe the dynamics of the bow shock and then make another model with a spherically symmetric explosion in an CSM environment described by the outputs of the bow shock model. Using VH-1 code, we will begin with axisymmetric 2-D models of CSM formation and then advance to 3-D models that include proper motion, exploding the white dwarf in each model to determine what parameters yield in the supernova simulation the result that best resembles Kepler and its current motions. Through our research, we can better predict the angle between the proper motion and orbital plane of the progenitor binary system, which can be evaluated by future observations of the companion star, and can gain a better understanding of CSM formation through comparison of simulations and observations.

Cassiopeia A is a supernova remnant (SNR) in the Milky Way galaxy which exhibits notable asymmetrical structural features. The most prominent of these features are the “jets” of ejecta visible in the northwest, and to a lesser degree southeast, quadrants of the SNR. The current explanation for these jets forces an asymmetrical SN explosion, with bipolar jets from deep within the progenitor driving the SN expansion (Hwang et. al. 2004). This explanation relies on a one-dimensional numerical calculation to discount the possibility that asymmetrical circumstellar medium (CSM) density produced the visible “jets” from a spherically symmetric SN explosion. However, one-dimensional analysis is insufficient to conclude the validity of the “jets” hypothesis. We propose to run three-dimensional hydrodynamic simulations using VH-1 to determine whether asymmetrical CSM could in fact be responsible for the jet-like ejecta seen in Cas A. We predict that varied CSM density would be sufficient to produce features characteristic of those in the Cas A SNR, refuting the primary evidence for a jet-driven explosion, and providing valuable insight into the profile of the shocked ejecta in the system.

Early in galactic evolution, when metal-poor stars formed, elements heaver than iron are postulated to be formed in core-collapse supernova via multiple processes, such as the r-process and neutrino-p process. Core-collapse supernovae produce a neutrino-driven wind, originating from the proto-neutron star, which can be neutron or proton rich. To date, there has been extensive research into heavy element synthesis using the r-process, but very little research on the effects of parameters on the combined weak r-process and neutrino-p process. We will run simulations that hold the nuclear physics inputs and reaction rates constant, while altering initial parameters of the simulation. We will graph the simulated heavy element abundances for the various initial conditions, and compare them to observed elemental abundances in metal-poor stars. We aim to identify whether there is a unique set of conditions or multiple combinations of different initial conditions that match observations of heavy element abundances. These simulations will allow us to determine what initial conditions, prior to the neutrino-p process and weak r-process, will produce the observed heavy element abundances.

The synthesis of elements heavier than iron in the early stages of galactic evolution is commonly attributed to Type II (core collapse) supernova explosions. However, the currently accepted mechanisms of heavy element synthesis through neutron capture processes (r-process and s-process) cannot explain the abundance patterns seen in very old galactic halo stars. A proposed solution to this problem is the neutrino-p-process, which takes place in the strong neutrino winds of core-collapse supernovae. In the neutrino-p-process, antineutrinos absorbed by protons yield neutrons that are quickly captured by the surrounding, proton-rich nuclei through (n,p) reactions. Such interactions allow for the nucleosynthesis of elements with atomic mass numbers A > 64 (this includes Sr, Y, Zr and others possibly up to Sn). This work will study the impact of uncertainties in the nuclear physics inputs (e.g. reaction rates) on the resulting neutrino-p-process abundances.

Vela X-1 is a detached, high-mass x-ray binary star system (HMXB) consisting of a blue supergiant (HD 77581) and a neutron star. By its very nature, it shows a range of variability in its x-ray luminosity, making it difficult to accurately model a self-consistent mass accretion rate. The bright x-ray luminosity of this system is powered by mass accretion onto the companion neutron star, relating the emitted L_x to the mass accretion rate (dm/dt) using the equation L_x = (GM/r)*(dm/dt). Previous studies have not modeled Vela X-1 in three dimensions by accounting for the time-dependent luminosity. I will use observational properties of Vela X-1 to create a time-dependent, three-dimensional model that includes a self-consistent x-ray luminosity given by the equation above, as well as dynamical effects of the variable L_x on the accreting gas. I will use this model to investigate the effects of wind density structure, accretion shock variability, and x-ray heating feedback on the time variability of the x-ray luminosity. Successfully modeling Vela X-1 in three dimensions will provide a self-consistent explanation of L_x and (dm/dt) and explain the time variability of the x-ray luminosity.

Type Ia supernova remnants (SNR), Tycho and SN 1006, are close enough to allow high-resolution observations that make details of fine-scale structures and very minute changes that occur over a few years more defined using the Chandra X-Ray Observatory. The images provided by Chandra show visible changes through time and have allowed observers to measure the proper motion of the shock fronts in x-ray and radio. The proper motion measurements are used to constrain the properties of these remnants. To date, only the sharp outer edges of the SNR have been examined. The motions of the interior material, composed of ejecta from the exploded star, have not been studied but these measurements can provide additional information for how SNR expand. Hydrodynamic simulations in 3-D help analyze the prominent features of ejecta relative to the shock front that will allow more precise measurements of the motions of the interior material and on dynamics of expansion of the SNR. I will generate artificial images using the high-resolution, full 3-D simulations and compare them to actual data of the motion of the gas inside the shock front, which will result in learning more about the internal dynamics of the SNR.