Constraining black hole mimickers with gravitational wave observations

LIGOand Virgo have recently observed a number of gravitational wave (GW) signals that are fully consistent with being emitted by binary black holesdescribed by general relativity. However, there are theoretical proposals of exotic objects that can be massive and compact enough to be easily confused with black holes. Nevertheless, these objects differ from black holesin having nonzero tidal deformabilities, which can allow one to distinguish binaries containing such objects from binary black holesusing GW observations. Using full Bayesian parameter estimation, we investigate the possibility of constraining the parameter space of such " black holemimickers" with upcoming GW observations. Employing perfect fluidstars with a polytropic equationof stateas a simple model that can encompass a variety of possible black holemimickers, we show how the observed masses and tidal deformabilities of a binary constrain the equationof state. We also show how such constraints can be used to rule out some simple models of boson stars.