2023NatAs...7.1218M

Massive astrophysical compact halo object (MACHO) 80.7443.1718 is a high mass, eccentric binary system exhibiting the largest-known-amplitude tidally excited oscillations. The system's ±20% photometric amplitude, along with the high mass of the primary star, ∼35 M_⊙, make this the most extreme of the class of periodically perturbed 'heartbeat stars.' Here, we use a hydrodynamic simulation to demonstrate that with each periapse passage, an unseen companion star raises tidal waves so large that they break, shock-heating and dissipating energy and angular momentum on the surface of the star. The shock-heated material forms a rapidly rotating circumstellar atmosphere, which is stripped and reassembled with each periapse passage. The dissipation of nonlinear tides through surface wave breaking explains the super-synchronous rotation of the primary star, the evolution of spectral emission features and the observed decay of the binary orbital period. Connecting these features demonstrates that MACHO 80.7443.1718 is a natural product of massive binary star evolution, and that it provides an ideal laboratory for the direct study of nonlinear tidal dissipation.