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General Relativity and Quantum Cosmology, gr-qc
Abstract:
Binary systems containing boson stars---self-gravitating configurations of a
complex scalar field--- can potentially mimic black holes or neutron stars as
gravitational-wave sources. We investigate the extent to which tidal effects in
the gravitational-wave signal can be used to discriminate between these
standard sources and boson stars. We consider spherically symmetric boson stars
within two classes of scalar self-interactions: an
effective-field-theoretically motivated quartic potential and a solitonic
potential constructed to produce very compact stars. We compute the tidal
deformability parameter characterizing the dominant tidal imprint in the
gravitational-wave signals for a large span of the parameter space of each
boson star model. We find that the tidal deformability for boson stars with a
quartic self-interaction is bounded below by $\Lambda_{\rm min}\approx 280$ and
for those with a solitonic interaction by $\Lambda_{\rm min}\approx 1.3$.
Employing a Fisher matrix analysis, we estimate the precision with which
Advanced LIGO and third-generation detectors can measure these tidal parameters
using the inspiral portion of the signal. We discuss a new strategy to improve
the distinguishability between black holes/neutrons stars and boson stars by
combining deformability measurements of each compact object in a binary system,
thereby eliminating the scaling ambiguities in each boson star model. Our
analysis shows that current-generation detectors can potentially distinguish
boson stars with quartic potentials from black holes, as well as from
neutron-star binaries if they have either a large total mass or a large mass
ratio. Discriminating solitonic boson stars from black holes using only tidal
effects during the inspiral will be difficult with Advanced LIGO, but
third-generation detectors should be able to distinguish between binary black
holes and these binary boson stars.
