On the Possibility of GW190425 Being a Black Hole–Neutron Star Binary Merger

Kyutoku, Koutarou; Fujibayashi, Sho; Hayashi, Kota; Kawaguchi, Kyohei; Kiuchi, Kenta; Shibata, Masaru; Tanaka, Masaomi

doi:10.3847/2041-8213/ab6e70

Cited by 80 publications

(59 citation statements)

References 75 publications

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“…The presence of NSs in a binary can leave behind relativistic ejecta that predominantly contain energetic neutrons, which source r-process heavy elements and kilonovae [19]. Indeed several studies used electromagnetic information to understand whether the low-mass compact binary mergers detected so far are BHNS or BNS systems [20][21][22][23][24]. However, if the primary companion is a massive BH (where the precise mass threshold depends on the BH spin [25][26][27]) then no ejecta might be left behind, as tidal forces will be small.…”

Section: Introductionmentioning

confidence: 99%

Distinguishing double neutron star from neutron star-black hole binary populations with gravitational wave observations

et al. 2020

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Gravitational waves from the merger of two neutron stars cannot be easily distinguished from those produced by a comparable-mass mixed binary in which one of the companions is a black hole. Low-mass black holes are interesting because they could form in the aftermath of the coalescence of two neutron stars, from the collapse of massive stars, from matter overdensities in the primordial Universe, or as the outcome of the interaction between neutron stars and dark matter. Gravitational waves carry the imprint of the internal composition of neutron stars via the so-called tidal deformability parameter, which depends on the neutron star equation of state and is equal to zero for black holes. We present a new data analysis strategy powered by Bayesian inference and machine learning to identify mixed binaries, hence low-mass black holes, using the distribution of the tidal deformability parameter inferred from gravitational-wave observations.

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Section: Introductionmentioning

confidence: 99%

Distinguishing double neutron star from neutron star-black hole binary populations with gravitational wave observations

et al. 2020

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“…Owing to the wideness of the Regge gaps, the range of detectable spin-2 masses is larger than in the scalar case and similar to the vector case. If (spinning) BHs of a few solar masses are detected [93], they can probe m b ∼ 10 −10 eV, whereas BHs as massive as M87 can reach the other hand of the spectrum, m b ∼ 10 −21 eV, where ultralight bosons are also compelling dark-matter candidates [16].…”

mentioning

confidence: 99%

Black Hole Superradiant Instability from Ultralight Spin-2 Fields

2020

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Ultralight bosonic fields are compelling dark-matter candidates and arise in a variety of beyond standard model scenarios. These fields can tap energy and angular momentum from spinning black holes through superradiant instabilities, during which a macroscopic bosonic condensate develops around the black hole. Striking features of this phenomenon include gaps in the spin-mass distribution of astrophysical black holes and a continuous gravitational-wave (GW) signal emitted by the condensate. So far these processes have been studied in great detail for scalar fields and, more recently, for vector fields. Here we take an important step forward in the black hole superradiance program by computing, analytically, the instability timescale, direct GW emission, and stochastic background, in the case of massive tensor (i.e., spin-2) fields. Our analysis is valid for any black hole spin and for small boson masses. The instability of massive spin-2 fields shares some properties with the scalar and vector cases, but its phenomenology is much richer, for example, there exist multiple modes with comparable instability timescales, and the dominant GW signal is hexadecapolar rather than quadrupolar. Electromagnetic and GW observations of spinning black holes in the mass range M ∈ ð1; 10 10 Þ M ⊙ can constrain the mass of a putative spin-2 field in the range 10 −22 ≲ m b c 2 =eV ≲ 10 −10. For 10 −17 ≲ m b c 2 =eV ≲ 10 −15 , the space mission LISA could detect the continuous GW signal for sources at redshift z ¼ 20, or even larger.

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“…As of this writing, in O3, the LIGO and Virgo Collaborations have published seven circulars via the Gamma-ray Coordinates Network (GCN) describing detection candidates for which the probability of the system being a NSBH is larger than 1% and for which the candidate has not been retracted [10][11][12][13][14][15][16]. Furthermore, GW data alone do not exclude the possibility that GW170817 is a NSBH [17][18][19], and it has also been suggested that GW190425 could be a NSBH [20,21]. Therefore it is timely to develop methods that can be used to study NSBHs in GW data.…”

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confidence: 99%

Aligned-spin neutron-star–black-hole waveform model based on the effective-one-body approach and numerical-relativity simulations

Matas

Dietrich²,

Buonanno³

et al. 2020

Phys. Rev. D

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After the discovery of gravitational waves from binary black holes (BBHs) and binary neutron stars (BNSs) with the LIGO and Virgo detectors, neutron-star black holes (NSBHs) are the natural next class of binary systems to be observed. In this work, we develop a waveform model for aligned-spin NSBHs combining a BBH baseline waveform (available in the effective-one-body approach) with a phenomenological description of tidal effects (extracted from numerical-relativity simulations) and correcting the amplitude during the late inspiral, merger and ringdown to account for the NS tidal disruption. In particular, we calibrate the amplitude corrections using NSBH waveforms obtained with the numerical-relativity spectral Einstein code (SpEC) and the SACRA code. The model was calibrated using simulations with NS masses in the range 1.2-1.4 M ⊙ , tidal deformabilities up to 4200 (for a 1.2 M ⊙ NS), and dimensionless BH spin magnitude up to 0.9. Based on the simulations used and on checking that sensible waveforms are produced, we recommend our model to be employed with a NS mass in the range 1-3 M ⊙ , tidal deformability 0-5000, and (dimensionless) BH spin magnitude up to 0.9. We also validate our model against two new, highly accurate NSBH waveforms with BH spin 0.9 and mass ratios 3 and 4, characterized by tidal disruption, produced with SpEC, and find very good agreement. Furthermore, we compute the unfaithfulness between waveforms from NSBH, BBH, and BNS systems, finding that it will be challenging for the Advanced LIGO-Virgo detector network at design sensitivity to distinguish different source classes. We perform a Bayesian parameter-estimation analysis on a synthetic numerical-relativity signal in zero noise to study parameter biases. Finally, we reanalyze GW170817, with the hypothesis that it is a NSBH. We do not find evidence to distinguish the BNS and NSBH hypotheses; however, the posterior for the mass ratio is shifted to less equal masses under the NSBH hypothesis.

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On the Possibility of GW190425 Being a Black Hole–Neutron Star Binary Merger

Cited by 80 publications

References 75 publications

Distinguishing double neutron star from neutron star-black hole binary populations with gravitational wave observations

Distinguishing double neutron star from neutron star-black hole binary populations with gravitational wave observations

Black Hole Superradiant Instability from Ultralight Spin-2 Fields

Aligned-spin neutron-star–black-hole waveform model based on the effective-one-body approach and numerical-relativity simulations

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