Compact Object Forensics: The Question of Origin

Northwestern University, Evanston IL

Investigators

Abstract

Dr. Vassiliki Kalogera of Northwestern University will undertake a comprehensive research project to address fundamental questions concerning the origin of neutron stars and black holes. The research will take advantage of a unique opportunity provided by recent growth in observational constraints for a sizable sample of Galactic and extragalactic X-ray binaries harboring accreting neutron stars or black holes. She will engage in theoretical computations which incorporate many elements necessary for the modeling of X-ray binary evolutionary histories: motion in the Galaxy, mass transfer and its dependence on orbital eccentricity, evolution of detached binary systems due to nuclear burning, stellar tides and angular momentum losses,and the effect of the core-collapse event on binary orbital dynamics. She will also engage in statistical analyses of known systems and binary populations to determine most likely progenitor properties and X-ray binary formation channels. The results will include physical constraints on the immediate progenitors of compact objects and statistical statements about the likelihood of their constrained properties. These will be used as initial conditions for core-collapse hydrodynamic simulations which will test and further our understanding of the core-collapse process. The work will contribute to answering currently open, basic questions about compact object formation. What, for example, is the mass relationship between compact objects and their progenitors? Do some neutron stars acquire natal kicks with magnitudes considerably lower than was thought before? What are the implications for asymmetries in the core-collapse process and the role of electron-capture supernovae? Do most black holes require sizable natal kicks and how is their formation different from that of neutron stars, if at all? What is the true distribution of black hole masses, corrected for observational selection biases? Dr. Kalogera will continue her outreach efforts through public lectures, talks at minority conferences and institutions, participation in school science fairs in the Chicago area and beyond. She is working in collaboration with visualization and graphics experts at Northwestern and the Adler Planetarium and Astronomy Museum in Chicago to develop visualization segments appropriate for the general public telling the story of how compact objects form and evolve in interacting binaries. The products will be presented at Northwestern, the Adler Planetarium, and will be available through web sites for broad dissemination.