Ricerc@Sapienza

The direct detection of gravitational waves (GWs) by LIGO and Virgo has opened a new observational window on the strong-field regime of gravity, almost unexplored so far. This regime forges the arena in which binaries composed by black holes (BHs) and neutron stars (NSs) evolve, acting as physics laboratories to test the rich phenomenology exhibited by fundamental fields and particles. Indeed, GWs emitted by coalescing systems carry specific signatures which can be used to trace back the structure of the binary components, and to distinguish among different compact sources. This is particularly relevant as it has been recently proposed that BHs may not represent the (only) endpoint of stellar evolution, and that other Exotic Compact Objects (ECOs) may populate the Universe and be potentially detectable by ground and space borne detectors, as the LISA satellite to be launched in 2034. Among the variety of astrophysical sources targeted by LISA, Extreme Mass Ratio Inspirals (EMRIs), i.e. binary systems in which a stellar-mass compact object orbits around a supermassive body, represent unique binaries to test fundamental physics. During the inspiral, the small source follows thousands of cycles before the plunge and the emitted GWs, which are continuously observable, allow to build a detailed map of the binary's spacetime. Most of the studies so far assumes that the EMRI central object is a Kerr BH. In this project we propose to make a step further and to study the GW emission by systems in which the massive object is a Boson Star (BS), a model of ECO which has received considerable attention in literature. The main goal of our proposal is to provide a consistent description of EMRI beyond the standard BH scenario, modelling their orbital evolution and GW-emission. We aim to provide ready-to-use waveforms that can be used, together with the large amount of data expected for LISA, to test the nature of compact objects and potentially unveil the existence of new physics.