CDSA

Gravitational waves (GWs) are ripples in space-time caused by massive, accelerating objects, such as binary neutron stars and black hole inspiral systems. Because they weakly interact with matter, GWs, and the information they carry, travel through space undisturbed and can be detected on Earth. In addition to previously detected GWs from compact binary inspiral systems, core-collapse supernovae (CCSNe) are predicted to produce GWs detectable by LIGO/Virgo. This work aims to examine the correlations between GW frequencies and the characteristic observables of CCSNe, such as the amount of nickel produced. Within this study, data from each simulations’ initial conditions and GW frequency will be fed to a neural network model aiming to emulate and characterize CCSNe. We will provide code containing different isotopes and the thermodynamic history of the star during core collapse within each simulation. We will track these characteristics using a nucleosynthesis simulation. Machine learning capable of detecting the patterns of and emulating CCSNe was out of scope for previous studies, so the primary goal of this work is to contribute important nucleosynthetic data to further the development of a physics-informed machine learning model, which will be able to accurately emulate CCSNe through observed parameters.

A supernova releases on the scale of 10⁵² neutrinos and antineutrinos. The neutrino burst from a supernova may travel through the Earth before reaching a detector. This passage leaves a distinctive pattern of modulations upon the neutrino signal which a sufficiently sensitive detector will register. This phenomenon is known as the Earth-Matter Effect. We will explore the visibility of the Earth-Matter Effect in a supernova neutrino signal and determine the circumstances in which the Earth-Matter Effect is significant. Past endeavors were held back by limited data sets and the difficulty of modeling the neutrino signal from supernova simulations. We will use the SNEWPY code to undertake our study because it has the ability to access data from hundreds of supernova simulations, and directly model the neutrino signal. SNEWPY has been recently modified to use the EMEWS code which we will use to determine the Earth-Matter Effect. From a comprehensive scan of multiple supernova simulations, sky and detector locations we will develop a better understanding of the Earth-Matter Effect and its visibility. An improved interpretation of the supernova neutrino signals will aid us in better understanding supernovae, better characterizing and locating a singular supernova, and uncovering the mysteries of the neutrino.

The missing baryonic problem leads scientists to analyze the circumgalactic medium of galaxies to determine the unknown locations of matter. Utilizing NIRCam’s Wide Field Slitless Spectroscopy(WFSS) on the James Webb Space Telescope, observers can collect spectra data of objects between Earth and high redshift (z) quasars. This specific project will focus on interpreting data that illustrates the flux and wavelength in the spectroscopy of hundreds of high-z quasars and analyze the absorption signatures in order to recognize chemical elements of intervening gas. A chemical element that is emphasized in this process is Magnesium II. This heavy element indicates recent supernovae activity and that stars formed and died in that location. The redshift values provide insight on the formation of heavy elements in the circumgalactic medium and the formation process of galaxies. By analyzing recycled matter from galaxies and star formation, astronomers will develop a greater chance of locating the missing baryons and have a better understanding of the early universe.

The first discovered extrasolar X-ray source, Scorpius (SCO) X-1, is a low-mass X-ray binary system where its companion star provides material for accretion to the neutron star. When the Roche-Lobe of a star overflows, material falls into the binary companion, creating and feeding an accretion disk. Using the hydrodynamics code VH-1, we investigate the behavior and structure of the accretion disk formed around the neutron star in SCO X-1. The system provides an opportunity to study how the tidal stream merges with the accretion disk. Our code is constructed to model the system in its entirety, allowing us to observe various parameters of the binary system that were previously unattainable. This simulation expands upon the field as it will serve as a baseline for all other X-ray binary systems with low-mass stars.

Hercules X-1 (Her X-1) is a widely observed X-ray binary system of a $1.6M_\odot$ neutron star and a $2.4M_\odot$ primary star. It possesses a unique 35-day cycle of X-ray flux caused by the tilt and precession of the accretion disk around the neutron star. No Her X-1 hydrodynamic model exists detailing the primary's tidal stream and disk together, which presents issues to understanding the effect of the tidal stream on the tilt and precession of the disk. This project aims to produce a high-resolution model of the Her X-1 system using the VH-1 hydrodynamics code. It will generate a program that tilts the disk of Her X-1, which data will be used in VH-1. The resulting model will serve as a basis for further research on the hydrodynamics of Her X-1 and the code will provide a method for modeling other precessing disks in binary systems.

As a supernova explodes it sends out a powerful shockwave, expanding outward and capturing material from the interstellar medium. Once enough material is captured the Supernova remnant enters the snowplow phase, where the shocked gas radiates heat, collapsing into a thin shell of high density. During this phase, expansion is driven by a high-pressure interior region. Previous research has indicated dynamical instability during the transition of the remnant into the snowplow phase. These distortions in the shock wave were analyzed using 1D and 2D hydrodynamical simulations but have not been explored in 3D. The proposed project will model the supernova remnant in 3D, producing a more complete understanding of unstable behavior at the shock front as well as realistic images of a supernova remnant during this transition. Better understanding supernova remnant morphology gives insights into nucleosynthesis, galaxy formation, and cosmic ray acceleration.

Red supergiants (RSGs) are the progenitors of core-collapse supernovae, the most likely source of coincident neutrino bursts in terrestrial neutrino detectors. The neutrino burst from a supernova depends on the exploding star’s mass, so determining accurate RSG masses will allow for an easier determination of the burst’s origin. RSG masses can rarely be measured directly, and surface properties (luminosity, temperature) are needed to infer the RSG’s mass. These inference methods have allowed for the construction of a grid of RSG models, but surface properties depend on factors such as the treatment of mass loss, which is not well understood. The uncertainty present in mass loss therefore extends to estimations of the mass of an RSG. We aim to use the stellar evolution tool MESA to explore this topic by evolving RSGs with varying mass loss to observe how mass loss affects the surface properties of RSGs and the inferred masses. The results will allow for more accurate mass estimates, which will facilitate locating the origin of neutrino signals.

The oldest and most metal-poor stars in our Milky Way reveal the elements that were present in the star-forming gas in the early Galaxy. We present a detailed abundance analysis of carbon and nitrogen in a sample of 311 metal-poor stars. A recent study derived improved stellar parameters (temperature, surface gravity, metallicity, and microturbulent velocity) for this sample, and we will apply the improved parameters to rederive abundances by spectrum synthesis. By using stellar spectroscopy, we rederive the chemical composition of these 311 stars by generating synthetic spectra to match against high-resolution optical spectra. We perform this analysis using the MOOG spectral line analysis code, implemented in the Spectroscopy Made HardeR (SMHR) software. The new abundances will be compared with previous results, and they will be useful to constrain stellar nucleosynthesis, stellar evolution, and Galactic chemical evolution models of the early Galaxy.