Multipolar structure of rotating boson stars

Abstract

The relativistic multipole moments provide a key ingredient to characterize the gravitational field around compact astrophysical objects. They play a crucial role in the description of the orbital evolution of coalescing binary systems and encode valuable information on the nature of the binary's components, which leaves a measurable imprint in their gravitational-wave emission. We present a new study on the multipolar structure of a class of arbitrarily spinning boson stars with quartic self-interactions in the large coupling limit, where these solutions are expected to be stable. Our results strengthen and extend previous numerical analyses, showing that even for the most compact configurations the multipolar structure deviates significantly from that of a Kerr black hole. We provide accurate data for the multipole moments as functions of the object's mass and spin, which can be directly used to construct inspiral waveform approximants, and to perform parameter estimations and searches for boson star binaries.