High-energy and gravitational-wave astrophysical observations are\r\npotentially capable of finding hypothetical (but well-motivated in\r\nquantum field theory) objects -- axions and cosmic strings. I describe\r\nnew predictions for how light bosons (in particular axions) spin down\r\nblack holes and how cosmic strings form relativistic fireballs. The\r\nemphasis is on the observational signatures of these phenomena.