Recognizing black holes in gravitational-wave observations: Challenges in telling apart impostors in mass-gap binaries

Abstract

We study how by careful monitoring of the presence or absence of tidal deformability (TD) and tidal-heating (TH) in the inspiral signal of compact object binaries in ground-based gravitational wave (GW) detectors, one can test if its components are black holes or not. The former property (TD) is finite for neutron stars but vanishes for black holes (in general relativity), whereas the latter is finite for black holes and negligible for neutron stars, and affects the GW phase evolution of binaries in a distinctly different way. We introduce waveform parameters that characterize the strength of tidal-heating, and are zero when there is no horizon. We develop Bayesian methods that use TD and TH for distinguishing the presence or absence of horizons in a binary. This is timely owing to several claims that these stellar-mass objects, especially, with masses heavier than those of neutron stars, may not have a horizon but may be black hole mimickers or exotic compact objects (ECOs). It is also astrophysically important to have the tools to test the presence or absence of horizons in mass-gap binaries and, thereby, help detect the heaviest neutron star or the lightest black hole. A proper accounting of tidal-heating in binary waveform models will also be critical for an unbiased measurement of characteristics of the equation of state of neutron stars in GW observations of binaries containing them -- or even to probe the existence of ECOs. We show that purely based on GW waveforms it will not be possible to discern binary horizons in the mass gap in Advanced LIGO, Virgo and KAGRA detectors unless the binary is within a few tens of Mpc. However, third generation ground-based detectors will be able to do so for binaries a few hundred Mpc away.

References in corpus (20)

• GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral
• GWTC-2: Compact Binary Coalescences Observed by LIGO and Virgo During the First Half of the Third Observing Run
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• Relativistic theory of tidal Love numbers
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• Tidal heating as a discriminator for horizons in extreme mass ratio inspirals
• Distinguishing fuzzballs from black holes through their multipolar structure
• Potential gravitational-wave signatures of quantum gravity
• Horizon-absorption effects in coalescing black-hole binaries: An effective-one-body study of the non-spinning case
• Improved next-to-leading order tidal heating and torquing of a Kerr black hole
• Relativistic theory of surficial Love numbers
• Tidal heating of Quantum Black Holes and their imprints on gravitational waves
• Tidal response and near-horizon boundary conditions for spinning exotic compact objects
• Multipole moments of compact objects with NUT charge: Theoretical and observational implications
• Possible connection between the reflection symmetry and existence of equatorial circular orbit

Cited by in corpus (26)

• Tests of General Relativity with GWTC-3
• The Science of the Einstein Telescope
• Discriminating between Neutron Stars and Black Holes with Imperfect Knowledge of the Maximum Neutron Star Mass
• Modeling horizon absorption in spinning binary black holes using effective worldline theory
• Probing the nuclear equation of state from the existence of a $\sim 2.6M_{\odot }$ neutron star: the GW190814 puzzle
• Dynamical Love for area quantized black holes
• Investigating tidal heating in neutron stars via gravitational Raman scattering
• Tidal heating of black holes and exotic compact objects on the brane
• Towards establishing the presence or absence of horizons in coalescing binaries of compact objects by using their gravitational wave signals
• Imprint of black hole area quantization and Hawking radiation on inspiraling binary
• Population inference of spin-induced quadrupole moments as a probe for non-black hole compact binaries
• Signature of Non-uniform Area Quantization on Black Hole Echoes
• Possible connection between the reflection symmetry and existence of equatorial circular orbit
• Effect of double spin-precession and higher harmonics on spin-induced quadrupole moment measurements
• Modeling and detecting resonant tides of exotic compact objects
• Neutron Stars and Gravitational Waves: the Key Role of Nuclear Equation of State
• Probing Spin-Induced Quadrupole Moments in Precessing Compact Binaries
• Discriminating same-mass Neutron Stars and Black Holes gravitational wave-forms
• Phenomenological gravitational waveform model of binary black holes incorporating horizon fluxes
• Parametrized Tidal Dissipation Numbers of Non-rotating Black Holes
• Probing black hole `charge' from the binary black hole inspiral
• Tidal heating in a Riemann-Cartan spacetime
• Characterizing Compact-object Binaries in the Lower Mass Gap with Gravitational Waves
• Binary black holes in the heat of merger
• Signature of Non-uniform Area Quantization on Gravitational Waves
• Comparing Bayes factors and hierarchical inference for testing general relativity with gravitational waves