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General Relativity and Quantum Cosmology, gr-qc,
Abstract:
The discovery of gravitational waves (GW) by Advanced LIGO has ushered us
into an era of observational GW astrophysics. Compact binaries remain the
primary target sources for LIGO, of which neutron star-black hole (NSBH)
binaries form an important subset. GWs from NSBH sources carry signatures of
(a) the tidal distortion of the neutron star by its companion black hole during
inspiral, and (b) its potential tidal disruption near merger. In this paper, we
present a Bayesian study of the measurability of neutron star tidal
deformability $\Lambda_\mathrm{NS}\propto (R/M)^{5}$ using observation(s) of
inspiral-merger GW signals from disruptive NSBH coalescences, taking into
account the crucial effect of black hole spins. First, we find that if
non-tidal templates are used to estimate source parameters for an NSBH signal,
the bias introduced in the estimation of non-tidal physical parameters will
only be significant for loud signals with signal-to-noise ratios greater than
$30$. For similarly loud signals, we also find that we can begin to put
interesting constraints on $\Lambda_\mathrm{NS}$ (factor of $1-2$) with
individual observations. Next, we study how a population of realistic NSBH
detections will improve our measurement of neutron star tidal deformability.
For astrophysical populations of {\it disruptive} NSBH coalescences, we find
that $20-35$ events are sufficient to constrain $\Lambda_\mathrm{NS}$ within
$\pm 25-50\%$, depending on the neutron star equation of state. For these
calculations we assume that LIGO will detect black holes with masses within the
astrophysical {\it mass-gap}. In case the mass-gap remains preserved in NSBHs
detected by LIGO, we estimate that approximately $25\%$ additional detections
will furnish comparable $\Lambda_\mathrm{NS}$ measurement accuracy. We
recommend that an effort to measure $\Lambda_\mathrm{NS}$ be planned for
upcoming LIGO-Virgo observing runs.
