Description
Extreme Mass Ratio Inspirals (EMRIs), binary systems with a secondary stellar mass compact object inspiralling into a massive black hole, are among the main targets for LISA, as they harbour the potential for precise strong gravity tests. Although the description of these systems in modified theories of gravity can be dramatically complex, for a vast class of theories with additional scalar fields great simplifications occur. At leading order in the binary mass ratio, the background spacetime is simply described by the Kerr metric. Moreover, the imprint of the scalar field on the waveform is fully captured by the scalar charge of the secondary - and by the mass of the scalar field. In this talk I will show how, using these simplifications, the secondary’s scalar charge and the scalar field mass affect the EMRI’s orbital evolution, and how such changes get imprinted on the emitted waveforms. By analysing such signals, I will finally present the results on the LISA’s detectability of the scalar field charge and mass, which render EMRIs encouraging probes of gravity and new fundamental fields.
