My current research focuses on nucleosynthesis in the post-bounce supernova environment. After collapse and bounce in a type II supernova, a proto-neutron star may be left behind. After an initial relaxation to near hydrostatic equilibrium, this proto-neutron star goes through Kelvin-Helmholtz contraction mediated by neutrinos and anti-neutrinos of all flavors. This gravitational contraction releases on the order of ~10^52 ergs in neutrinos over ~20 seconds. These neutrinos will deposit energy in the dense envelope of material present near the surface of the proto-neutron star and drive a thermal wind. The neutrino interactions drive the material in the wind to entropies and electron fractions favorable for an r-process. The r-process is a nuclear burning process which involves a series of neutron captures on heavy seed nuclei and subsequent beta decays. This process increases the mass of the seed nuclei significantly. Therefore, it seems the r-process is responsible for producing many of the elements heavier than iron.

Although this is an appealing site, previous calculations of the neutrino driven wind have not been able to reproduce the conditions required for the r-process. These calculations have not followed the nuclear evolution of the material. Rather, they have relied on separate, parameterized studies of the r-process to determine if sufficient conditions were achieved.

Recently, I have started running spherically symmetric calculations of the neutrino driven wind with accurate microphysics, including a full nuclear reaction network that can follow the entire r-process.

Type I X-ray bursts (XRBs) are thought to be thermonuclear explosions occurring under degenerate conditions on the surface of accreting neutron stars in Low Mass X-ray Binaries. These are some of the more energetic events in the universe. Because XRBs are driven by nuclear reaction sequences, specifically the rp-process and the alpha,p-process, uncertainties in input nuclear physics translate to uncertainties in XRB model predictions, such as light curves and final nuclear abundances.

We have studied the effects of nuclear uncertainties on the rp-process in XRBs in a robust fashion. This is done with Monte Carlo (MC) simulations using a post-processing element burning code that calculates XRB nucleosynthesis. We have also done a similar study of nuclear sensitivities in classical novae.

During black hole (BH) -neutron star (NS) mergers, a portion of the NS material is ejected in the form of tidal tails. Initially, the temperatures and densities of the tails are sufficient for nuclear statistical equilibrium (NSE) to obtain. As these tails move outward, they expand quasi-adiabatically. These are requisite conditions for r-process nuclear burning to occur. Once the density and temperature in the tails reach a point at which neutron captures cease, a distribution of radioactive nuclides with half-lives ranging between milliseconds and days is left over. If the decay timescales of a significant fraction of nuclei are on the order of the timescale for the tails to become optically thin, a short sub-energetic supernova like event may occur.

To address this question, we are running calculations of nuclear burning in the tails and then mapping these into a radiation transport code to determine the character of possible transients.