Radiative losses from unbound orbits at quadratic order in spin from MPM formalism

Abstract

We study the spinning two-body system in the aligned spin case for hyperboliclike motions computing all radiative losses (at the 2PN absolute accuracy and including spin-squared corrections) using the MPM formalism and generalizing previous results valid at linear order in spin [Phys. Rev. D \textbf{108}, no.6, 064049 (2023)]. Leading PM order results are checked against existing literature, whereas higher-order PM results (within the 2PN accuracy) are new with this work. As a by-product of our general results we analyze the spinning situation which supports radial fall (at 2PN and including spin-squared accuracy level contributions), showing that as soon as the PN accuracy increases deviations from radial fall appear necessarily.