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X-ray observations of active galactic nuclei (AGNs) reveal relativistic reflections from the innermost regions of accretion disks, which contain general-relativistic footprints caused by spinning supermassive black holes (SMBH). We anticipate the spin of a SMBH to be stable over the human timeframe, so brightness changes in the high-energy corona above the SMBH should slightly alter relativistic reflection. In this brief review, we discuss the latest developments in modeling relativistic reflection, as well as the rapid small variation in relativistic emission disclosed by the principal component analysis (PCA) of X-ray variability in AGN. PCA studies of X-ray spectra from AGNs have shown that relativistically blurred reflection has negligible fluctuations over the course of observations, which could originate from rapid (intrahour) intrinsic variations in near-horizon accretion flows and photon rings. The PCA technique is an effective way to disclose relativistic reflection from X-ray observations of AGNs, simplifying the complexity of largely variable X-ray data for automated spectral analysis with machine learning algorithms. [ABSTRACT FROM AUTHOR]

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.

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 R I S C O parameter, assumed to be the inner radius of the accretion disk, which determines its optical depth τ d i s k . In our results, the differential photon fluxes after the absorption effect are depicted as a function of the photon energy in the range 1 GeV ≤ E ≤ 10 3 GeV. It is worth noting that when the black holes' spin ( α * ) increases, the differential photon flux becomes significantly lower. [ABSTRACT FROM AUTHOR]

Constraining the primary growth channel of supermassive black holes (SMBHs) remains one the most actively debated questions in the context of cosmological structure formation. Owing to the expected connection between SMBH spin parameter evolution and the accretion and merger history of individual black holes, population spin measurements offer a rare observational window into the cosmic growth of SMBHs. As of today, the most common method for estimating SMBH spin relies on modeling the relativistically broaden atomic profiles in the reflection spectrum observed in X-rays. In this paper, we study the observational requirements needed to confidently distinguish between the primary SMBH growth channels based on their distinct spin-mass distributions predicted by the Horizon-AGN cosmological simulation. Indoing so, we characterize outstanding limitations associated with the existing measurements and discuss the landscape of future observational campaigns which could be planned and executed with future X-ray observatories. We focus our attention on the High-Energy X-ray Probe (HEX-P), a proposed probe-class mission designed to serve the high- energy community in the 2030s. [ABSTRACT FROM AUTHOR]

Previous studies have identified the Fundamental Plane (FP) of Active Galactic Nuclei (AGNs) in recent years. However, these findings relied on total black hole mass, also known as dynamical mass, (Mdyn). Instead the fundamental plane may be governed by BH spin. In this study, we take the black hole spin-mass energy ( M spin ) as a new variable, which is closely related to the supermassive black hole (SMBH). We collected a sample of 62 flat-spectrum radio quasars (FSRQs) with gamma-ray luminosity ( L γ ), X-ray luminosity ( L X ) and spin-mass energy ( M spin ) to construct a new fundamental plane of blazars. Our analysis demonstrates that the fundamental plane (log L γ = 0.662 + 0.193 − 0.193 log L X + 0.495 + 0.154 − 0.154 log M spin + 14.579 + 7.140 − 7.140 with R-Square = 0.783) has a stronger correlation with spin-mass energy ( M spin ) compared to the black hole mass. Therefore, M spin should be considered as an essential variable for the fundamental plane of blazars. Our findings may improve the understanding of the Blandford-Znajek process in FSRQs. [ABSTRACT FROM AUTHOR]

This work investigates the spectra of coloured particles radiated from Schwarzschild black holes and Kerr black holes as their mass decrease from ~1013 g to Planck mass. The emission rate formulas in terms of black hole mass, temperature, entropy, and spin are derived. The variation of spectra with time, and black hole parameters such as mass, temperature, entropy, and spin are obtained and discussed. During the last stages of black hole evaporation, black hole loses its mass at a drastic rate. When the orders of magnitude of particles were disregarded, the spectrum of quarks and gluons emitted from the 1013 g black hole over 3171 millennia was emitted from the 108 g black hole within 2.5 × 10-4 s. It only took 3.5 × 10-25 s for a Schwarzschild black hole to reduce its mass from 10.00 g to 2.55 × 10-5 g. As the black hole reaches the end of its lifetime, the emission rates of the high energetic particles gradually recede and reach the limit of zero as Planck mass is reached. By the time the black hole begins to emit coloured particles its temperature is ~1012 K, but when it reaches the Planck mass its temperature has reached closer to the Planck temperature. As Planck mass is reached, the entropy of the black hole gradually decreases and gets very close to zero. [ABSTRACT FROM AUTHOR]

Abstract Correlations between jet power and active time for z

In this work, we present and discuss recent results of analytical investigations of black hole (BH) shadow. First of all, we discuss definition of shadow in details. Then, we describe fully analytical approach for extraction of spin of BH from the deformation of its shadow. Finally, we present analytical investigation of plasma influence on the shadow size. This paper is based on talk given at the conference ‘High-Energy Phenomena in Relativistic Outflows VI', September 11–15, 2017, Moscow, Russia. [ABSTRACT FROM AUTHOR]