RUI: Neutron Star Oscillations as Probes of Dense Matter Properties and Phases

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Neutron stars are astrophysical objects that weigh as much as the Sun but are only about as large as a city. Little is known about the state of matter inside neutron stars, yet, the properties of matter in such extremely dense conditions is crucial to understanding the complexities of the strong nuclear force, which determines the sub-structure of neutrons and protons out of which all atoms are made. The recent discovery of gravitational waves from merging neutron stars opens a unique avenue for the study of this dense matter inside neutron stars. This project will quantify the properties of such matter by studying how it impacts the amplitude and frequency of observed gravitational waves. This will be accomplished by using Einstein's general theory of relativity and a judicious selection of models describing the strong nuclear force. The main outcome of this research will be discovering the best lines of scientific evidence for new states of matter from the analysis of gravitational wave data. In addition, the PI will train students on advanced computational methods in the course of this research and share cutting-edge scientific knowledge with high school students via teacher-training workshops.The project addresses the converging domain of nuclear theory, neutron stars and gravitational waves. In this project, the PI will calculate the spectrum of non-radial neutron star oscillations, with particular attention to modes that are most likely to manifest in gravitational wave signals from continuously emitting sources and which can constrain key properties of dense matter such as the symmetry energy. The emphasis is on applying accurate and efficient numerical methods known from quantum scattering theory to the computation of the spectrum of fluid oscillations in full General Relativity, while employing select equations of state (cold or hot conditions) for neutron star matter that satisfy current experimental and astrophysical constraints, including the recent tidal polarizability data. The research will also address relatively unexplored features of dense matter that impact neutron star oscillations, such as superfluidity and phase transitions, by sifting through a database of equation of states for select models that include these aspects. The project will involve several graduate students culminating in their Masters thesis, and the PI will work with experts in science education to communicate current knowledge of topics in astrophysics to local high school teachers involved with implementing next generation science standards (NGSS).This project advances the objectives of "Windows on the Universe: the Era of Multi-Messenger Astrophysics", one of the 10 Big Ideas for Future NSF Investments.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.