Black Hole Research Articles

We performed N-body simulations of both individual cluster evolution and subcluster coalescence, demonstrating that cluster evolution and its outcomes strongly depend on the cluster formation process through comparisons of different gas expulsion modes and formation channels. The evolution of star clusters is significantly shaped by the gas expulsion mode, with faster expulsion producing greater mass loss. A broader degeneracy exists among initial cluster mass, gas expulsion timescale, and formation channel (monolithic vs. coalescence), which manifests in both evolutionary pathways and black-hole production. In individual cluster simulations, slower gas expulsion enables progressively lower mass clusters to retain central black holes within the tidal radius. As the gas expulsion mode transitions from fast to moderate to slow, the fraction of high-velocity stars decreases. Variations in gas expulsion mode and formation channel ultimately influence the stellar velocity distribution (within the tidal radius) and, thus, the expansion speed, which governs both cluster mass loss and black-hole retention. Slowly expanding clusters are more likely to retain black holes and multiple systems, making them prime candidates for black-hole searches with Gaia . Our results highlight the crucial influence of early gas expulsion and cluster formation mechanisms on the dynamical evolution of star clusters and black-hole production. These factors should be carefully incorporated into the initial conditions of N-body simulations, which necessarily rely on input from the star formation community.

Abstract The Kerr–Bertotti–Robinson (Kerr–BR) black hole, a theoretical model of a rotating black hole immersed in a uniform magnetic field, has been proposed recently by Podolsky and Ovcharenko. This study investigates the optical characteristics of the Kerr–BR black hole based on the exact solution. We analyze the black hole shadow and the optical image under two illumination models: a celestial light source and a geometrically thin accretion disk. We reveal distinct roles for the fundamental parameters in the model. Specifically, it is found that under both illumination models, the influence of the rotation parameter on the optical image of the Kerr–BR black hole is significant different from that of the magnetic field. As the magnetic field increases, the radii of both the shadow and the Einstein ring enlarge. We also attempt to use the data from M87* and Sgr A* to constrain the BR-like magnetic fields surrounding them. These results enhance our understanding of the optical characteristics of the Kerr–BR black hole and establish a theoretical foundation for interpreting future observations on the optical image of the black hole immersed in a uniform magnetic field. Finally, we point out that with advances in the resolution of the black hole image, it is possible to detect the BR-like magnetic fields surrounding black holes.

Abstract A regular black hole, unconstrained by the weak cosmic censorship conjecture, can exceed its critical spin limit and transition into a superspinar. In this paper, we investigate the observational appearance of a rotating regular black hole, specifically the Ghosh black hole and its superspinar counterpart, when surrounded by a thin accretion disk. The resulting images reveal distinct features: the black hole closely resembles its Kerr counterpart with slight deviations, while the superspinar configuration exhibits an inner photon ring structure. Furthermore, we investigate the image transition of the Ghosh black hole that has recently been destroyed by a collapsing null shell carrying a specific angular momentum. The results indicate that, apart from a possible sudden burst of light, the inner photon ring undergoes gradual transitions over time, with the transition times depending on the additional angular momentum gained by the black hole. Our findings also suggest that the transition timescale becomes significant for supermassive black holes, with masses at least less than about twice that of M87*.

Abstract In this paper, we investigate quasinormal modes (QNMs) and greybody factors within the framework of Symmergent gravity, an emergent gravity model with an $$R + R^2$$ R + R 2 curvature sector. Building on our previous work on static spherically-symmetric solutions [Puliçe et al. in Class Quantum Gravity 40(19):195003, 2023], we explore the effects of the key parameters, including the quadratic curvature coupling parameter $$c_\textrm{O}$$ c O and the vacuum energy parameter $$\alpha $$ α . For all the three perturbations considered here viz., scalar, electromagnetic and gravitational perturbations, an increase in $$\alpha $$ α leads to a nearly linear rise in both oscillation frequencies and damping rates. The other parameter $$c_\textrm{O}$$ c O affects the QNMs spectrum nonlinearly. Additionally, the charge Q of the black hole introduces nonlinear behavior, where higher charges amplify the black hole’s electromagnetic field, resulting in increased oscillation frequencies and faster stabilization. These findings enhance our understanding of charged black hole stability and gravitational wave astrophysics. Further, the analysis of greybody factors reveals that increasing $$\alpha $$ α , $$c_\textrm{O}$$ c O , and Q reduces the absorption of radiation, with gravitational perturbations reaching maximum absorption at slightly lower frequencies compared to electromagnetic and scalar perturbations.

Abstract This paper defends an epistemology for terrestrial black hole simulations based on Hesse’s theory of material analogy in science. We outline the main verdicts and recommendations of this approach, arguing that they not only fit the experimental practice but are also more credible than those supported by competing proposals. Our analysis questions the role of so-called ‘universality results’ in establishing an evidential function for current experiments, while also escaping the conclusion that we learn nothing about black holes from simulating them.

Abstract Supermassive black holes (SMBHs) are observed in diverse galaxy populations across cosmic time, yet a clear understanding of how they coevolve with their hosts has not been reached. Physical models of SMBH accretion and feedback vary widely between galaxy formation simulations due to the difficulty of modeling the range of scales important for galactic and SMBH processes. Here we use observational data to build an empirical model for SMBH growth. We apply observed specific accretion rate probability distributions as a function of star formation rate between z = 0 and 2 to the UniverseMachine galaxy formation model to determine SMBH accretion rates based on galaxy properties. We use observed z = 0 SMBH–stellar mass relations for the quiescent and star-forming populations to provide the local boundary conditions for SMBH growth histories. We then track the coevolutionary histories of SMBH and galaxy stellar mass backward in time to z = 2. We find that the most massive SMBHs at z = 0 have grown very little of their mass between z = 0 and 2, indicating early SMBH mass assembly for these systems. Conversely, lower-mass SMBHs at z = 0 assembled gradually across z = 0–2. This results in substantial evolution of the SMBH–stellar mass relation, shifting to higher normalization and shallower slope with increasing redshift. We find that the substantial scatter observed in the z = 0 SMBH–stellar mass relation results in the diversity of growth pathways found in our model, with some galaxies assembling their stellar mass before their SMBHs and others doing the opposite.

Abstract We perform two-dimensional, multigroup radiation hydrodynamic simulations to explore the observational properties of a solar-like star colliding with an accretion disk around a supermassive black hole at a separation of ∼100 gravitational radii. We find that the star-disk collision produces ejecta on both sides of the disk. As the ejecta expand and cool, transient flares arise, reaching peak bolometric luminosity of up to L ≳ 10 43 erg s −1 . We estimate that the typical light curve rises and decays on an hour timescale. The spectral energy distribution (SED) peaks in 20–50 eV. The optical depth in soft X-rays is lower than the frequency-integrated optical depth, yielding 100 eV–1 keV luminosity νL ν ≳ 10 42 erg s −1 . The ejecta aligned with the star’s incident direction shows breakout emission, leading to asymmetric SED evolution of the two ejecta. The SED evolution is roughly consistent with those seen in short-period quasiperiodic eruptions, which have eruption durations ranging from subhour to hours, but the ejecta cooling emission alone may not be sufficient to explain the longer duration flares. Increasing incident velocity generally produces a brighter and harder flare. A larger disk scale height prolongs the breakout emission but leads to a somewhat softer SED. A higher disk surface density can lead to higher ejecta temperature, reducing bound–free opacity and increasing luminosity. When lowering the disk surface density, we find that the ejecta becomes optically thin when the scattering optical depth across the disk is at the order of τ disk ∼ 200, and the ejecta disappear when τ disk ∼ 10.

Thermodynamic insights into ModMax-AdS black holes: A bridge between electrodynamic corrections and black hole physics

Diet-dependent acid-base load is not associated with rate of relapse, annualised disability change, FLAIR, and black hole lesion volume on MRI in a prospective cohort study of those with multiple sclerosis.

Multifractal chaos in gravitational waves from binary black hole mergers

Exploring black hole phenomena in Kaluza-Klein gravity with massive vector fields discussing the particle dynamics and gravitational deflection of light

Barrow entropy effects on thermodynamics and QPOs of a quintessence surrounded Frolov black hole model

4D Einstein-Gauss-Bonnet Black Holes Surrounded by Quintessence in Noncommutative Spacetime

Coiled sonic black hole based contactless sensor for physical signal processing and its application in mechanical fault diagnosis

Probing the weak gravity conjecture: Novel Aschenbach signatures in superextremal non-linear charged AdS black holes

The “Octopus Concept” Unifying Adenomyosis and Endometriosis and Understanding the Nerve Entrapment - “the Black Hole Effect”

Longitudinal-flexural composite axe-shaped sandwich piezoelectric ultrasonic transducer designed based on the principle of acoustic black hole

Shadows, Quasinormal Modes, and Optical Appearances of Black Holes in Horndeski Theory

Acoustic scattering from underwater multiple cylindrical shells with acoustic black holes

Superradiant bound states of charged scalars around Melvin-Kerr black holes