Collaborative Research: The Weirdest Stars in the Universe: Illuminating the Origins and Evolution of Thorne-Zytkow Objects

Some of the weirdest stars in the universe are called Thorne-Zytkow objects, or TZOs. They represent a completely new model for how the insides of stars can work, a new possible fate for binary star systems, and a new way to produce heavy elements. This research program will carry out an in-depth study of TZOs. The investigators will run computer simulations of the binary star systems that might form TZOs and use some of the planet's largest telescopes to search for TZOs. In addition to learning more about these mysterious stars, this research will transform our understanding of cold and massive stars and explain how they evolve, die, and enrich the chemistry of our universe. The investigators will work closely with high school students on short research projects that can be presented at regional or state science fairs. Thorne-Zytkow objects combine the outward appearance of red supergiants - cold and luminous massive stars - with strange neutron cores supported not by standard stellar fusion, but by extreme quantum physics. The formation and evolution of a TZOs is key for understanding this novel model of supporting a cool luminous exterior with a neutron degenerate interior. Terminal TZO scenarios, which could include mass-loss-driven dissipation of their outer layers, a supernova-like explosion, or direct collapse to a black hole, are crucial for understanding how TZOs contribute to enrichment and add to the population of compact objects. The merger of a red supergiant and neutron star to form a TZO is notably different from the standard scenario assumed for massive binaries, where both stars produce compact objects and eventually merge to generate a gravitational wave transient. Neglecting TZO formation and evolution will lead to incorrect predictions for heavy element enrichment and an over-prediction of gravitational wave transients. Using high-resolution spectroscopy, advanced stellar atmosphere models tailored for cool stars, and archival light curves of these stars, the investigators will determine whether potential TZO candidates have the distinctive surface abundance signatures predicted. As an integral part of this research program, the investigators will work annually with high school students on short research projects suitable for presentation at regional or state science fairs and develop infrastructure for use by other potential project mentors across the field of astronomy. 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.