I am interested in the role of neutrino and nuclear physics in core-collapse supernovae. I have extensive experience in the development and application of general relativistic numerical hydrodynamic supernova models, including detailed neutrino transport.
Simulating turbulence in reduced dimensions (Stir)
Working with Professor Sean Couch, I have aided in the development of a new method for artificially driving core-collapse supernova explosions in 1D simulations. Turbulence is important for understanding the CCSN explosion mechanism, since turbulence may add a >20% correction to the total pressure behind the shock and thus aid in the explosion. We have implemented mixing length theory (MLT) and included a model of the turbulent pressure in the FLASH supernova code for spherically symmetric simulations. Including MLT and corrections for the turbulent pressure may result in successful explosions in spherical symmetry without altering the neutrino luminosities or interactions, as is commonly done to produce explosions in spherical symmetry. This better replicates the physical explosion mechanism and more reliably produces the thermodynamics and composition, which is vital for accurately predicting the nucleosynthesis that occurs in the supernova environment.
Sterile neutrinos are of interest in astrophysics both as dark matter candidates and for their potential impact on core-collapse supernovae. In supernovae, they may serve as an efficient mechanism to transport energy in the protoneutron star and are thus of interest in investigating supernova explosion energies. I have found that the early time explosion energy can be significantly enhanced when oscillations between a sterile neutrino and electron neutrino are included. The enhancement is sufficient to lead to a successful explosion even in a simulation that would not otherwise explode. My papers on this work can be found here, here, and here.
RELIC NEUTRINO BACKGROUND
The collapse of stars more massive than ~20 solar masses results in black holes, rather than a remnant neutron star. These events will not produce significant electromagnetic radiation, but will still generate a large neutrino flux. It may be possible to determine the rate of such failed supernova events through a precision measurement of the diffuse supernova neutrino background (the net neutrino flux produced by all supernovae and failed supernovae). This will also give insight into the initial mass function of stars more massive than about 8 solar masses. I am simulating the neutrino emission from failed supernova events to provide predictions of the diffuse neutrino background for a variety of initial mass functions and nuclear equations of state.
NUCLEAR EQUATION OF STATE
I have contributed to the development of the Notre Dame-Livermore Equation of State (NDL EoS), a nuclear equation of state intended for use in core-collapse supernova and neutron star simulations. A complete understanding of the equation of state of nuclear matter will provide us with a vital link between laboratory measurements and astrophysical phenomena. The NDL EoS meets all modern laboratory and astrophysical constraints and includes 3-body interactions and the possibility of a transition to quark gluon plasma. I have been instrumental in creating this description of nuclear matter and implementing many elements of the model, such as the phase transition to quark gluon plasma. Ultimately, we plan to make this equation of state publicly available for use in core-collapse supernova and neutron star simulations. The paper on this work can be found here.
NEUTRON STAR ACCRETION
Hypercritical accretion onto neutron stars plays a role in a variety of astrophysical events, including supernova fallback, long gamma-ray bursts, and Thorne-Zytkow objects. However, the details of this accretion can be difficult to model, since one must account for the hydrodynamics of the accretion process, the neutrino transport and interactions, and the response of the neutron star. I am investigating hypercritical accretion onto neutron stars with the goal to better understand the neutrino emission in these environments and the conditions for collapse to a black hole. Predictions of the accretion and neutrino cooling rates in this environments will allow us to better understand fallback in core-collapse supernovae and the role that hypercritical accretion may play in long gamma-ray bursts.