Black Hole Binaries Research Articles

Legacy of Boson Clouds on Black Hole Binaries.

Superradiant clouds of ultralight bosons can leave an imprint on the gravitational waveform of black hole binaries through "ionization" and "resonances." We study the sequence of resonances as the binary evolves and show that there are only two possible outcomes, each with a distinct imprint on the waveform. If the cloud and the binary are nearly counterrotating, then the cloud survives in its original state until it enters the sensitivity band of future gravitational wave detectors, such as the Laser Interferometer Space Antenna. In all other cases, resonances destroy the cloud while driving the binary to corotate with it and its eccentricity close to a fixed point. This opens up the possibility of inferring the existence of a new boson from the statistical analysis of a population of black hole binaries.

Resonant history of gravitational atoms in black hole binaries

Resonant history of gravitational atoms in black hole binaries

Signatures of Ultralight Bosons in the Orbital Eccentricity of Binary Black Holes.

We show that the existence of clouds of ultralight particles surrounding black holes during their cosmological history as members of a binary system can leave a measurable imprint on the distribution of masses and orbital eccentricities observable with future gravitational-wave detectors. Notably, we find that for nonprecessing binaries with chirp masses M≲10M_{⊙}, formed exclusively in isolation, larger-than-expected values of the eccentricity, i.e., e≳10^{-2} at gravitational-wave frequencies f_{GW}≃10^{-2} Hz, would provide tantalizing evidence for a new particle of mass between [0.5,2.5]×10^{-12} eV in nature. The predicted evolution of the eccentricity can also drastically affect the in-band phase evolution and peak frequency. These results constitute unique signatures of boson clouds of ultralight particles in the dynamics of binary black holes, which will be readily accessible with the Laser Interferometer Space Antenna, as well as future midband and decihertz detectors.

Prospect of Precision Cosmology and Testing General Relativity using Binary Black Holes- Galaxies Cross-correlation

Abstract Modified theories of gravity predict deviations from General Relativity (GR) in the propagation of gravitational waves (GW) across cosmological distances. A key prediction is that the GW luminosity distance will vary with redshift, differing from the electromagnetic (EM) luminosity distance due to varying effective Planck mass. We introduce a model-independent, data-driven approach to explore these deviations using multi-messenger observations of dark standard sirens (Binary Black Holes, BBH). By combining GW luminosity distance measurements from dark sirens with Baryon Acoustic Oscillation (BAO) measurements, BBH redshifts inferred from cross-correlation with spectroscopic or photometric galaxy surveys, and sound horizon measurements from the Cosmic Microwave Background (CMB), we can make a data-driven test of GR (jointly with the Hubble constant) as a function of redshift. Using the multi-messenger technique with the spectroscopic DESI galaxy survey, we achieve precise measurements of deviations in the effective Planck mass variation with redshift. For the Cosmic Explorer and Einstein Telescope (CEET), the best precision is approximately 3.6%, and for LIGO-Virgo-KAGRA (LVK), it is 7.4% at a redshift of $\rm {z = 0.425}$. Additionally, we can measure the Hubble constant with a precision of about 1.1% from CEET and 7% from LVK over five years of observation with a 75% duty cycle. We also explore the potential of cross-correlation with photometric galaxy surveys from the Rubin Observatory, extending measurements up to a redshift of $\rm {z \sim 2.5}$. This approach can reveal potential deviations from models affecting GW propagation using numerous dark standard sirens in synergy with DESI and the Rubin Observatory.

Forecasting the sensitivity of pulsar timing arrays to gravitational wave backgrounds

Pulsar timing array (PTA) observations hinted towards the existence of a stochastic gravitational wave background (SGWB) in the nHz frequency band. Still, the nature of the SGWB signal cannot be confidently inferred from current data, and the leading explanation invokes mergers of supermassive black holes. If confirmed, such discovery would not only represent a turning point in our understanding of astrophysics, but it may severely limit the capability of searching for additional cosmological sources in the nHz frequency range. In this work, we build a simple framework to forecast the sensitivity of future pulsar timing array configurations and assess the parameter estimation of SGWB, which could consist of several contributions. We release the code , implementing this framework and ready to use. Published by the American Physical Society 2024

Gravitational waves from mergers of Population III binary black holes: roles played by two evolution channels

Gravitational waves from mergers of Population III binary black holes: roles played by two evolution channels

Mergers of hairy black holes: Constraining topological couplings from entropy

Mergers of hairy black holes: Constraining topological couplings from entropy

Differentiable and hardware-accelerated waveforms for gravitational wave data analysis

We propose the use of automatic differentiation through the programming framework for accelerating a variety of analysis tasks throughout gravitational wave (GW) science. Firstly, we demonstrate that complete waveforms which cover the inspiral, merger, and ringdown of binary black holes (i.e., IMRPhenomD) can be written in and demonstrate that the serial evaluation speed of the waveform (and its derivative) is similar to the implementation in . Moreover, allows for graphics processing unit–accelerated waveform calls which can be over an order of magnitude faster than serial evaluation on a CPU. We then focus on three applications where efficient and differentiable waveforms are essential. Firstly, we demonstrate how gradient descent can be used to optimize the ∼200 coefficients that are used to calibrate the waveform model. In particular, we demonstrate that the typical with numerical relativity waveforms can be improved by more than 50%. Secondly, we show that Fisher forecasting calculations can be sped up by ∼3–5× (on a CPU) with no loss in accuracy. This increased speed makes Fisher forecasting for a population of events substantially simpler. Finally, we show that gradient-based samplers like Hamiltonian Monte Carlo lead to significantly reduced autocorrelation values when compared to traditional Monte Carlo methods. Since differentiable waveforms have substantial advantages for a variety of tasks throughout GW science, we propose that waveform developers use to build new waveforms moving forward. Our waveform code, , can be found on GitHub website and will continue to be updated with new waveforms as they are implemented. Published by the American Physical Society 2024

Iterative extraction of overtones from black hole ringdown

Abstract Extraction of multiple quasinormal modes (QNMs) from ringdown gravitational waves emitted from a binary black hole coalescence is a touchstone to test whether a remnant black hole is described by the Kerr spacetime in general relativity. However, it is not straightforward to check the consistency between the ringdown signal and the QNM frequencies predicted by the linear perturbation theory. While the longest-lived mode can be extracted in a stable manner, the higher overtones damp more quickly and hence the fitting of overtones tends to end up with the overfit. To improve the extraction of overtones, we propose an iterative procedure consisting of fitting and subtraction of the longest-lived mode of the ringdown waveform in the time domain. Through the analyses of the mock waveform and numerical relativity waveform, we clarify that the iterative procedure allows us to extract the overtones in a more stable manner.

Residual eccentricity as a systematic uncertainty on the formation channels of binary black holes

Residual eccentricity as a systematic uncertainty on the formation channels of binary black holes

JADES. The diverse population of infant black holes at 4<z<11: Merging, tiny, poor, but mighty

Spectroscopy with the James Webb Space Telescope has opened the possibility of identifying moderate-luminosity active galactic nuclei (AGNs) in the early Universe, at and beyond the epoch of re-ionisation, complementing previous surveys of much more luminous (and much rarer) quasars. We present 12 new AGNs at 4$<$z$<$7 in the JADES survey (in addition to the previously identified AGN in GN-z11 at z=10.6) revealed through the detection of a broad-line region (BLR) seen in the Balmer emission lines. The depth of JADES, together with the use of three different spectral resolutions, enables us to probe a lower-mass regime relative to previous studies. In a few cases, we find evidence for two broad components of Halpha , which suggests that these could be candidate merging black holes (BHs), although a complex BLR geometry cannot be excluded. The inferred BH masses range from $ 10^7 M_ down to $ 10^5 M_ interestingly probing the regime expected for direct collapse BHs. The inferred AGN bolometric luminosities ($ $ erg/s) imply accretion rates that are $< 0.5$ times the Eddington rate in most cases. However, small BHs, with $ BH 10^6 M_ tend to accrete at Eddington or super-Eddington rates. These BHs at zsim 4-11 are over-massive relative to their host galaxies' stellar masses when compared to the local $ BH -M_ star $ relation, even approaching $ BH star $, as was expected from heavy BH seeds and/or super-Eddington accretion scenarios. However, we find that these early BHs tend to be more consistent with the local relation between $ BH $ and velocity dispersion, as well as between $ BH $ and dynamical mass, suggesting that these are more fundamental and universal relations. On the classical, optical narrow-line excitation-diagnostic diagrams, these AGNs are located in the region that is that is locally occupied by star-forming galaxies, implying that they would be missed by the standard classification techniques if they did not display broad lines. Their location on the diagram is consistent with what is expected for AGNs hosted in metal-poor galaxies ($ Z 0.1-0.2 Z_ The fraction of broad-line AGNs with $ AGN erg/s$ among galaxies in the redshift range of $4<z<6$ is about 10<!PCT!>, suggesting that the contribution of AGNs and their hosts to the re-ionisation of the Universe is $>$10<!PCT!>.

Eccentric signatures of stellar-mass binary black holes with circumbinary disks in LISA

Abstract Stellar-mass binary black holes may have circumbinary disks if formed through common-envelope evolution or within gaseous environments. Disks can drive binaries into wider and more eccentric orbits, while gravitational waves harden and circularise them. We combine cutting-edge evolution prescriptions for disk-driven binaries with well-known equations for gravitational-wave-driven evolution, and study the evolution of stellar-mass binary black holes. We find that binaries are driven by their disk to an equilibrium eccentricity, 0.2 ≲ eeq ≲ 0.5, that dominates their evolution. Once they transition to the GW-dominated regime their eccentricity decreases rapidly; we find that stellar-mass binary black holes with long-lived disks will likely be observed in LISA with detectable eccentricities ∼10−2 at 0.01 Hz, with the precise value closely correlating with the binary’s initial mass ratio. This may lead stellar-mass binary black holes with CBDs observed in LISA to be confused with dynamically-formed binary black holes.

Galactic Stellar Black Hole Binaries: Spin Effects on Jet Emissions of High-Energy Gamma-Rays

In the last few decades, galactic stellar black hole X-ray binary systems (BHXRBs) have aroused intense observational and theoretical research efforts specifically focusing on their multi-messenger emissions (radio waves, X-rays, γ-rays, neutrinos, etc.). In this work, we investigate jet emissions of high-energy neutrinos and gamma-rays created through several hadronic and leptonic processes taking place within the jets. We pay special attention to the effect of the black hole’s spin (Kerr black holes) on the differential fluxes of photons originating from synchrotron emission and inverse Compton scattering and specifically on their absorption due to the accretion disk’s black-body radiation. The black hole’s spin (dimensionless spin parameter a*) enters into the calculations through the radius of the innermost circular orbit around the black hole, the RISCO parameter, assumed to be the inner radius of the accretion disk, which determines its optical depth τdisk. In our results, the differential photon fluxes after the absorption effect are depicted as a function of the photon energy in the range 1GeV ≤E≤103GeV. It is worth noting that when the black holes’ spin (α*) increases, the differential photon flux becomes significantly lower.

Exploring dark forces with multimessenger studies of extreme mass ratio inspirals

The exploration of dark sector interactions via gravitational waves (GWs) from binary inspirals has been a subject of recent interest. We study dark forces using extreme mass ratio inspirals (EMRIs), pointing out two issues of interest. Firstly, the innermost stable circular orbit (ISCO) of the EMRI, which sets the characteristic length scale of the system and hence the dark force range to which it exhibits enhanced sensitivity, probes force mediator masses that complement those studied with supermassive black hole (SMBH) or neutron star binaries. The LISA mission (the proposed μAres detector) will probe mediators with masses m V ∼ 10-16 eV (m V ∼ 10-18 eV), corresponding to ISCOs of 106 M ⊙ (108 M ⊙) central SMBHs. Secondly, while the sensitivity to dark couplings is typically limited by the uncertainty in the binary component masses, independent mass measurements of the central SMBH through reverberation mapping campaigns or the motion of dynamical tracers enable one to break this degeneracy. Our results therefore highlight the necessity for coordinated studies, loosely referred to as “multimessenger”, between future μHz- mHz GW observatories and ongoing and forthcoming SMBH mass measurement campaigns, including OzDES-RM, SDSS-RM, and SDSS-V Black Hole Mapper.

An effective model for the tidal disruption of satellites undergoing minor mergers with axisymmetric primaries

According to the hierarchical formation paradigm, galaxies form through mergers of smaller entities and massive black holes (MBHs), if present at their centers, migrate to the nucleus of the newly formed galaxy, where they form binary systems. The formation and evolution of MBH binaries, and in particular their coalescence timescale, is highly relevant for current and future facilities aimed at detecting the gravitational wave signal produced by the MBHs close to coalescence. While most of the studies targeting this process are based on hydrodynamic simulations, the high computational cost makes a complete parameter space exploration prohibitive. Semianalytic approaches represent a valid alternative, but they require ad hoc prescriptions for the mass loss of the merging galaxies in minor mergers due to tidal stripping, which is not commonly considered or is at best modelled assuming very idealised geometries. In this work we propose a novel, effective model for the tidal stripping in axisymmetric potentials, to be implemented in semi-analytic models. We validated our semi-analytic approach against N-body simulations considering different galaxy sizes, inclinations, and eccentricities, finding only a moderate dependence on the orbit eccentricity. In particular, we find that, for almost circular orbits, our model mildly overestimates the mass loss, and this is due to the adjustment of the stellar distribution after the mass is removed. Nonetheless, the model exhibits a very good agreement with simulations in all the considered conditions, and thus represents an extremely powerful addition to semi-analytic calculations.

Close Encounters of Wide Binaries Induced by the Galactic Tide: Implications for Stellar Mergers and Gravitational-wave Sources

A substantial fraction of stars can be found in wide binaries with projected separations between ∼102 and 105 au. In the standard lore of binary physics, these would evolve as effectively single stars that remotely orbit one another on stationary Keplerian ellipses. However, embedded in their Galactic environment, the low binding energy of wide binaries makes them exceptionally prone to perturbations from the gravitational potential of the Milky Way and encounters with passing stars. Employing a fully relativistic N-body integration scheme, we study the impact of these perturbations on the orbital evolution of wide binaries along their trajectory through the Milky Way. Our analysis reveals that the torques exerted by the Galaxy can cause large-amplitude oscillations of the binary eccentricity to 1 − e ≲ 10−8. As a consequence, the wide binary members pass close to each other at periapsis, which, depending on the type of binary, potentially leads to a mass transfer or collision of stars or to an inspiral and subsequent merger of compact remnants due to gravitational-wave radiation. Based on a simulation of 105 wide binaries across the Galactic field, we find that this mechanism could significantly contribute to the rate of stellar collisions and binary black hole mergers as inferred from observations of luminous red novae and gravitational-wave events by LIGO/Virgo/Kagra. We conclude that the dynamics of wide binaries, despite their large mean separation, can give rise to extreme interactions between stars and compact remnants.

Repeated Partial Disruptions in a White Dwarf–Neutron Star or White Dwarf–Black Hole Merger Modulate the Prompt Emission of Long-duration Merger-type GRBs

The progenitors of gamma-ray bursts (GRBs) have long been an unresolved issue. GRB 230307A stands out as an exceptionally bright event, belonging to the long-duration GRBs but also exhibiting a late-emission component reminiscent of a kilonova. Together with the similar events GRBs 060614 and 211211A, they make up a new subgroup of GRBs with intriguing progenitors. If such long-duration merger-type GRBs originated from the coalescence of a white dwarf (WD) with a neutron star (NS) or a black hole (BH), as proposed in the recent literature, then the larger tidal disruption radius of the WD, together with a nonnegligible residual orbital eccentricity, would make repeated partial tidal disruptions inevitable. This may modulate the mass accretion and jet launching process at the NS or BH, resulting in a quasiperiodic modulation (QPM) in the light curve of the GRB, with a period equal to the orbital period. The detection of potential QPMs during the early episode of prompt emission of these three GRBs supports this scenario, and the relatively slow QPM (> 1 s) suggests that the lighter object cannot be an NS. We propose that the progenitor system of GRBs 230307A, 060614, and 211211A consist of a WD of mass 1.3 M ⊙, 0.9 M ⊙, and 1.4 M ⊙, respectively, and an NS (or BH). After several cycles of modulations, the WD is completely destroyed, and the accretion of the remaining debris dominates the extended emission episode.

Constraining the Earth-mass Primordial Black Hole Mergers Model of the Non-repeating FRBs Using the First CHIME/FRB Catalog

In this paper, we upgrade the constraints for the Earth-mass primordial black hole mergers model based on the first Canadian Hydrogen Intensity Mapping Experiment (CHIME)/fast radio burst (FRB) catalog. Assuming the null hypothesis that the observed non-repeating FRBs originate from Earth-mass primordial black hole mergers, we find that how the charges were distributed in the primordial black hole population is well described by a double power-law function with typical charge value of qc/10−5=1.60−0.28+0.28 , where the power-law index α1=2.33−0.18+0.15 for q < q c and α2=4.56−0.26+0.30 for q ≥ q c. Here, q represents the charge of the black hole in units of GM , where M is the mass of the black hole. Furthermore, we infer the local event rate of the bursts is 8.8−2.1+5.7×104Gpc−3yr−1 , which indicates that an abundance of the primordial black hole population f ≳ 10−4 is needed to account for the observed FRBs by CHIME. The results of this paper lay the basis for further research on the electromagnetic radiation background generated by the merger of primordial black hole mergers.

Unequal-mass highly spinning binary black hole mergers in the stable mass transfer formation channel

Unequal-mass highly spinning binary black hole mergers in the stable mass transfer formation channel

Analytical and Numerical Analysis of Circumbinary Disk Dynamics. I. Coplanar Systems

We present an analytical and numerical study of a system composed of a stellar binary pair and a massless, locally isothermal viscous accretion disk that is coplanar to the binary orbital plane. Analytically, we study the effect of the binary’s gravitational potential over short timescales through the stability of epicyclic orbits, and over long timescales by revisiting the concept of resonant torques. Numerically, we perform two-dimensional Newtonian simulations of the disk-binary system over a range of binary mass ratios. We find that the results of our simulations are consistent with those of previous numerical studies. We additionally show, by comparison of the analytical and numerical results, that the circumbinary gap is maintained on the orbital timescale through the driving of epicyclic instabilities, and does not depend on resonant torquing, contrary to the standard lore. While our results are applicable to any disk-binary system, we highlight the importance of this result in the search for electromagnetic and gravitational-wave signatures from supermassive black hole binaries.