Title: Putting compact objects where they don’t belong: Hawking stars, dark matter stars, Thorne–Żytkow objects, and quasi-stars
Abstract: Compact objects are typically the remnants of stellar evolution, yet under certain conditions they may be found deep within living stars. In this talk, I will present recent advances in modeling such exotic hybrid systems using the Modules for Experiments in Stellar Astrophysics (MESA) software instrument. By modifying the inner boundary condition to incorporate sub-grid physics for an embedded compact object, we can follow the evolution of stars that harbor black holes or other dense cores. We have applied this approach to a diverse set of astrophysical phenomena: Hawking stars containing primordial black holes, solar models with dark matter cores, neutron-star-enveloped Thorne–Żytkow objects, and direct-collapse black holes (quasi-stars) that may seed supermassive black holes. These models offer new explanations and predictions for observed anomalies such as red stragglers and the recently discovered “Little Red Dots” seen by JWST. Embedding compact objects “where they don’t belong” may help illuminate both the nature of dark matter and the origin of supermassive black holes in the early universe.