High Spin Values Research Articles

Effect of turbulent pressure on the origin of low-frequency quasi-periodic oscillations in rotating black holes

ABSTRACT Quasi-periodic oscillation (QPO), particularly of low frequency (LF), is a very obvious feature of outbursting black hole candidates. The association of QPOs in a specific spectral state and their transition with states make them a key ingredient in understanding the underlying physical processes that produce them. Observations have revealed that generally, in the hard spectral state of the outburst, the size of the Compton cloud is relatively bigger, which produces low-frequency QPOs (LFQPOs). In progressive days increased cooling shrinks the area of the cloud, the inner edge of the disc comes close to the black holes, and produces higher frequency QPOs. However, rotating black holes with higher spin values are likely to produce LFQPOs even if their inner edge of the disc is closer to the hole. Here, for the first time, we address the issue, solving hydrodynamic flow equations in the presence of qualitative turbulent pressure and cooling in pseudo-Kerr geometry. Increasing turbulence slackens the infalling flow, thus the infall time becomes longer, producing LFQPOs. Our study discovers that the effect of turbulence modifies LFQPOs value significantly, by a factor of a few lower throughout the angular momentum distribution of the flow. We find a strong correlation between the turbulence and the spin parameter of the hole. Finally, we discuss the observed results in light of the present solution.

Black Hole Spin and Accretion Disk Magnetic Field Strength Estimates for More Than 750 Active Galactic Nuclei and Multiple Galactic Black Holes

Abstract Black hole systems, composed of a black hole, accretion disk, and collimated outflow, are studied here. Three active galactic nucleus (AGN) samples including 753 AGNs and 102 measurements of four stellar-mass galactic black holes (GBHs) are studied. Applying the theoretical considerations described by Daly, general expressions for the black hole spin function and accretion disk magnetic field strength are presented and applied to obtain the black hole spin function, spin, and accretion disk magnetic field strength in dimensionless and physical units for each source. Relatively high spin values are obtained; spin functions indicate typical spin values of about 0.6–1 for the sources. The distributions of accretion disk magnetic field strengths for the three AGN samples are quite broad and have mean values of about 104 G, while those for individual GBHs have mean values of about 108 G. Good agreement is found between spin values obtained here and published values obtained with well-established methods; comparisons for one GBH and six AGNs indicate that similar spin values are obtained with independent methods. Black hole spin and disk magnetic field strength demographics are obtained and indicate that black hole spin functions and spins are similar for all of the source types studied, including GBHs and different categories of AGNs. The method applied here does not depend on any specific accretion disk emission model and does not depend on a specific model that relates jet beam power to compact radio luminosity; hence, the results obtained here can be used to constrain and study these models.

Molecular spin frustration in mixed-chelate Fe5 and Fe6 oxo clusters with high ground state spin values

The synthesis, structures, and magnetic properties are reported of three new polynuclear FeIII complexes containing the anions of picolinic acid (picH) and triethanolamine (teaH3) as chelates. The complexes [Fe6O2(OH)2(O2CR)4(pic)4(teaH)2] (R = Me (1), Ph (2)) and [Fe5O2(O2CBut)4(pic)3(teaH)2] (3) were obtained from the reaction of [Fe3O(O2CR)6(H2O)3](NO3) (R = Me, Ph, But) with picH and teaH3 in a 1:2:1 ratio in MeCN. The core of 1 and 2 consists of an [Fe4(µ3-O)2]8+ ‘planar-butterfly’ unit to which is attached an Fe atom on either side by bridging O atoms. The core of 3 consists of an [Fe5(µ3-O)2]11+ unit comprising two near-perpendicular vertex-sharing [Fe3(µ3-O)]7+ triangular units. Variable-temperature (T) and -field (H) solid-state dc and ac magnetization (M) studies in the 5.0–300 K temperature range revealed that 1 and 2 have an S = 5 ground state spin whereas 3 has an S = 5/2 ground state. Jij exchange couplings were calculated by DFT and a magnetostructural correlation (MSC) for polynuclear FeIII/O complexes. This allowed rationalization of the observed ground states from the analysis of the spin frustration effects operative, and provided good input values for fits of the experimental χMT vs T data to obtain the Jij values.

Spin evolution and feedback of supermassive black holes in cosmological simulations

ABSTRACT It is well established that the properties of supermassive black holes (BHs) and their host galaxies are correlated through scaling relations. While hydrodynamical cosmological simulations have begun to account for the coevolution of BHs and galaxies, they typically have neglected the BH spin, even though it may play an important role in modulating the growth and feedback of BHs. Here we introduce a new sub-grid model for the BH spin evolution in the moving-mesh code arepo in order to improve the physical faithfulness of the BH modelling in galaxy formation simulations. We account for several different channels of spin evolution, in particular gas accretion through a Shakura–Sunyaev α-disc, chaotic accretion, and BH mergers. For BH feedback, we extend the IllustrisTNG model, which considers two different BH feedback modes, a thermal quasar mode for high accretion states and a kinetic mode for low Eddington ratios, with a self-consistent accounting of spin-dependent radiative efficiencies and thus feedback strength. We find that BHs with a mass $M_{\mbox{{bh}}}\lesssim 10^{8}\, {\rm M}_{\odot }$ reach high spin values as they typically evolve in the coherent gas accretion regime, in which consecutive accretion episodes are aligned. On the other hand, BHs with a mass $M_{\mbox{{bh}}}\gtrsim 10^{8}\, {\rm M}_{\odot }$ have lower spins as BH mergers become more frequent, and their accretion discs fragment due to self-gravity, inducing chaotic accretion. We also explore the hypothesis that the transition between the quasar and kinetic feedback modes is mediated by the accretion mode of the BH disc itself, i.e. the kinetic feedback mode is activated when the disc enters the self-gravity regime instead of by an ad hoc switch tied to the BH mass. We find excellent agreement between the galaxy and BH populations for this approach and the fiducial TNG model with no spin evolution. Furthermore, our new approach alleviates a tension in the galaxy morphology–colour relation of the original TNG model.

High-Spin and Incomplete Spin-Crossover Polymorphs in Doubly Chelated [Ni(L)2Br2] (L = tert-Butyl 5-Phenyl-2-pyridyl Nitroxide).

Complexation of nickel(II) bromide with tert-butyl 5-phenyl-2-pyridyl nitroxide (phpyNO) gave two morphs of doubly chelated [Ni(phpyNO)2Br2] as a 2p-3d-2p heterospin triad. The α phase crystallizes in the orthorhombic space group Pbcn. An asymmetric unit involves a half-molecule. The torsion angle around Ni-O-N-C2py is as small as 6.5(3)° at 100 K and 7.0(6)° at 400 K, guaranteeing an orthogonal arrangement between the magnetic radical π* and metal 3dx2-y2 and 3dz2 orbitals. Magnetic study revealed the high-spin ground state with the exchange coupling constant 2J/kB = +288(5) K, on the basis of a symmetrical spin Hamiltonian. The β phase crystallizes in the monoclinic space group P21/n. The whole molecule is an independent unit. The Ni-O-N-C2py torsion angles are 24.2(6) and 37.2(5)° at 100 K and 10.4(7) and 25.9(6)° at 400 K. A magnetic study revealed a very gradual and nonhysteretic spin transition. An analysis based on the van't Hoff equation gave a successful fit with the spin-crossover temperature of 134(1) K, although the susceptibility did not reach the theoretical high-spin value at 400 K. Density functional theory calculation on the β phase showed ground Stotal = 0 in the low-temperature structure while Stotal = 2 in the high-temperature structure, supporting the synchronized exchange coupling switch on both sides. Consequently, the β phase can be recognized as an "incomplete spin crossover" material, as a result of conflicting thermal depopulation effects in a high-temperature region.

Black Hole Spin Signature in the Black Hole Shadow of M87 in the Flaring State

Abstract Imaging the immediate vicinity of supermassive black holes (SMBHs) and extracting a BH-spin signature is one of the grand challenges in astrophysics. M87 is known as one of the best targets for imaging the BH shadow and it can be partially thick against synchrotron self-absorption (SSA), particularly in a flaring state with a high mass accretion rate. However, little is known about influences of the SSA-thick region on BH shadow images. Here we investigate BH shadow images of M87 at 230 GHz properly taking into account the SSA-thick region. When the BH has a high spin value, the corresponding BH shadow image shows the positional offset between the center of the photon ring and that of the SSA-thick ring at the innermost stable circular orbit (ISCO) due to the frame-dragging effect in the Kerr spacetime. As a result, we find that a dark-crescent structure is generally produced between the photon ring and the SSA-thick ISCO ring in the BH shadow image. The scale size of the dark crescent increases with BH spin: its width reaches up to ∼2 gravitational radius when the BH spin is 99.8% of its maximum value. The dark crescent is regarded as a new signature of a highly spinning BH. This feature is expected to appear in flaring states with relatively high mass accretion rate rather than the quiescent states. We have simulated the image reconstruction of our theoretical image by assuming the current and future Event Horizon Telescope (EHT) array, and have found that the future EHT including space–very long baseline interferometry in 2020s can detect the dark crescent.

Event horizon silhouette: implications to supermassive black holes in the galaxies M87 and Milky Way

We demonstrate that a dark silhouette of the black hole illuminated by a thin accretion disk and seen by a distant observer is, in fact, a silhouette of the event horizon hemisphere. The boundary of this silhouette is a contour of the event horizon equatorial circle if a thin accretion disk is placed in the black hole equatorial plane. A luminous matter plunging into black hole from different directions provides the observational opportunity for recovering a total silhouette of the invisible event horizon globe. The event horizon silhouette is projected on the celestial sphere within a position of the black hole shadow. A relative position of brightest point in the accretion disk with respect to the position of event horizon silhouette in the image of black hole in the galaxy M87, observed by the Event Horizon Telescope, corresponds to a rather high value of the black hole spin, $a\simeq0.75$.

Black hole mass and spin estimates of the most distant quasars

We investigate the properties of the most distant quasars ULASJ134208.10+092838.61 (z = 7.54), ULASJ112001.48+064124.3 (z = 7.08) and DELSJ003836.10–152723.6 (z = 7.02) studying their Optical-UV emission that shows clear evidence of the presence of an accretion disk. We model such emission applying the relativistic disk models KERRBB and SLIMBH for which we have derived some analytical approximations to describe the observed emission as a function of the black hole mass, accretion rate, spin and the viewing angle. We found that: 1) our black hole mass estimates are compatible with the ones found using the virial argument but with a smaller uncertainty; 2) assuming that the virial argument is a reliable method to have a black hole mass measurement (with no systematic uncertainties involved), we found an upper limit for the black hole spin of the three sources: very high spin values are ruled out; 3) our Eddington ratio estimates are smaller than those found in previous studies by a factor ∼2: all sources are found to be sub-Eddington. Using our results, we explore the parameter space (efficiency, accretion rate) to describe the possible evolution of the black hole assuming a ∼102 − 4 M⊙ seed: if the black hole in these sources formed at redshift z = 10 − 20, we found that the accretion has to proceed at the Eddington rate with a radiative efficiency η ∼ 0.1 in order to reach the observed masses in less than ∼0.7 Gyr.

XRB continuum fitting with sensitive high-energy X-ray detectors

The launch of the Nuclear Spectroscopic Telescope Array (NuSTAR) heralded a new era of sensitive high energy X-ray spectroscopy for X-ray binaries (XRBs). In this paper we show how multiple physical parameters can be measured from the accretion disk spectrum when the high-energy side of the disk spectrum can be measured precisely using NuSTAR. This immediately makes two exciting developments possible. If the mass and distance of the source are known, the continuum fitting method can be used to calculate the spin and inner disk inclination independently of the iron line fitting method. If the mass and distance are unknown, the two methods can be combined to constrain these values to a narrow region of parameter space. In this paper we perform extensive simulations to establish the reliability of these techniques. We find that with high quality spectra, spin and inclination can indeed be simultaneously measured using the disk spectrum. These measurements are much more precise at higher spin values, where the relativistic effects are stronger. The inclusion of a soft X-ray snapshot observation alongside the NuSTAR data significantly improves the reliability, particularly for lower temperature disks, as it gives a greatly improved measurement of the disk peak. High signal to noise data are not necessary for this, as measuring the peak temperature is relatively easy. We discuss the impact of systematic effects on this technique, and the implications of our results such as robust measurements of accretion disk warps and XRB mass surveys.

Magnetic, electronic, and transport properties of the high-pressure-synthesized chiral magnets Mn1−xRhxGe

We report on structural, magnetic and transport properties of a new set of the high-pressuresynthesized compounds Mn$_{1-x}$Rh$x$Ge ($0 \leq x \leq 1$) with the chiral magnetic ordering. The magnetic and transport properties depend substantially on the concentration of rhodium (x) and the pressure. The saturation magnetic moment corresponds to a known high-spin value for pristine MnGe (x = 0) and decreases almost linearly with increasing concentration $x$. In addition, XMCD spectra taken at 10 K and 2 T indicate magnetic polarization of the Rh 4d electron states and Ge $4p$ states, which decreases with $x$, too. In rhodium rich compounds ($x \geq 0.5$) the temperature of the magnetic ordering increases significantly with pressure, whereas in manganese rich compounds ($x < 0.5$) the temperature decreases. Three different tendencies are also found for several structural and transport properties. In the intermediate range ($0.3 \leq x \leq 0.7$) samples are semiconducting in the paramagnetic phase, but become metallic in the magnetically ordered state. We carried out ab initio density-functional calculations of Mn$_{1-x}$Rh$_x$Ge at various concentrations $x$ and traced the evolution of electronic and magnetic properties. The calculation results are in good agreement with the measured magnetic moments and qualitatively explain the observed trends in transport properties.

Relating Kerr SMBHs in active galactic nuclei to RADs configurations

There is strong observational evidence that many active galactic nuclei (AGNs) harbour super-massive black holes (SMBHs), demonstrating multi-accretion episodes during their life-time. In such AGNs, corotating and counterrotating tori, or strongly misaligned disks, as related to the central Kerr SMBH spin, can report traces of the AGNs evolution. Here we concentrate on aggregates of accretion disks structures, ringed accretion disks (RADs) orbiting a central Kerr SMBH, assuming that each torus of the RADs is centered in the equatorial plane of the attractor, tori are coplanar and axi-symmetric. Many of the RAD aspects are governed mostly by the spin of the Kerr geometry. We classify Kerr black holes (BHs) due to their dimensionless spin, according to possible combinations of corotating and counterrotating equilibrium or unstable (accreting) tori composing the RADs. The number of accreting tori in RADs cannot exceed n = 2. We present list of 14 characteristic values of the Kerr BH dimensionless spin a governing the classification in whole the black hole range , uniquely constrained by the RAD properties. The spin values are remarkably close providing an accurate characterization of the Kerr attractors based on the RAD properties. RAD dynamics is richer in the spacetimes of high spin values. One of the critical predictions states that a RAD tori couple formed by an outer accreting corotating and an inner accreting counterrotating torus is expected to be observed only around slowly spinning (a < 0.46M) BHs. The analysis strongly binds the fluid and BH characteristics providing indications on the situations where to search for RADs observational evidences. Obscuring and screening tori, possibly evident as traces in x-ray spectrum emission, are strongly constrained, eventually ruling out many assumptions used in the current investigations of the screening effects. We expect relevance of our classification of Kerr spacetimes in relation to astrophysical phenomena arising in different stages of AGNs life that could be observed by the planned x-ray satellite observatory ATHENA (Advanced Telescope for High ENergy Astrophysics).

The black hole spin in coalescing binary black holes and high-mass X-ray binaries

AbstractThe six LIGO detections of merging black holes (BHs) allowed to infer slow spin values for the two pre-merging BHs. The three cases where the spins of the BHs can be determined in high-mass X-ray binaries (HMXBs) show that those BHs have high spin values. We discuss here scenarios explaining these differences in spin properties in these two classes of object.

Room temperature ferromagnetism in Fe-doped semiconductor ZrS2 single crystals

Two dimensional (2D) layered magnetic materials have obtained much attention due to their intriguing properties with a potential application in the field of spintronics. Herein, room-temperature ferromagnetism with 0.2 emu g−1 magnetic moment is realized in Fe-doped ZrS2 single crystals of millimeter size, in comparison with diamagnetic behaviour in ZrS2. The electron paramagnetic resonance spectroscopy reveals that 5.2wt% Fe-doping ZrS2 crystal exhibit high spin value of g-factor about 3.57 at room temperature also confirmed this evidence, due to the unpaired electrons created by doped Fe atoms. First principle static electronic and magnetic calculations further confirm the increased stability of long range ferromagnetic ordering and enhanced magnetic moment in Fe-doped ZrS2, originating from the Fe spin polarized electron near the Fermi level.

How to constrain mass and spin of supermassive black holes through their disk emission

We investigate the global properties of the radiation emitted by the accretion disk around Kerr black holes. Using the Kerr blackbody numerical model, we build an analytic approximation of the disk emission features focusing on the pattern of the produced radiation as a function of the black hole spin, mass, accretion rate and viewing angle. The assumption of having a geometrically thin disk limits our analysis to systems emitting below ~0.3 of the Eddington luminosity. We apply this analytical model to four blazars (whose jets are pointing at us) at high redshift that show clear signatures of disk emission. For them, we derive the black hole masses as a function of spin. If these jetted sources are powered by the black hole rotation, they must have high spin values, further constraining their masses.

Constraints on spin of a supermassive black hole in quasars with big blue bump

We determined the spin value of supermassive black hole (SMBH) in active galactic nuclei (AGN) with investigated ultraviolet-to-optical spectral energy distribution, presented in the sample of Shang et al. (2005). The estimates of the spin values have been produced at the base of the standard geometrically thin accretion disk model and with using the results of the polarimetric observations. The polarimetric observations are very important for determining the inclination angle of AGN disk. We presented the results of our determinations of the radiation efficiency of the accretion flow and values of the spins of SMBHs, that derives the coefficient of radiation efficiency. The majority of SMBHs of AGNs from Shang et al. (2005) sample are to be the Kerr black holes with the high spin value.

Pseudoclathrochelate n-hexadecylboron-capped metal(II) tris-pyrazoloximates: synthesis, X-ray structure, spectral and magnetic characteristics

Abstract Self-assembly of monohexadecylboron-capped zinc, cobalt, iron and manganese(II) tris-pyrazoloximate pseudoclathrochelates was performed using one-pot template condensation of 2-acetylpyrazole oxime with n-hexadecylboronic acid as a capping Lewis-acidic agent on the corresponding metal ion as a matrix. Hydrogen atoms of three terminal pyrazolyl NH groups of three pyrazoloxime synthons form a pseudomacrobicyclic ligand through their hydrogen bonding with a chloride counterion Cl− … (HN)3, thus allowing an encapsulation of the corresponding metal ion. The complexes obtained were characterized using elemental analysis, MALDI-TOF mass spectrometry, IR, UV-Vis-NIR, 57Fe Mossbauer (for the iron complex), 1H and 13C NMR spectroscopy, as well as by SQUID magnetometry. The structure of the complexes synthesized was also confirmed by single crystal X-ray diffraction analysis of the zinc(II) pseudoclathrochelate. Its pseudocaged zinc(II) ion is located almost in the center of ZnN6-coordination polyhedron, which adopts a trigonal prismatic geometry with a very low distortion angle. As follows from variable-temperature magnetometry data, the χT values for manganese and iron(II) pseudoclathrochelates in the temperature range 50–300 К are close to theoretical pure high-spin values without of orbital contribution. 1H and 13C NMR chemical shifts of their pyrazoloximate nuclei reach to some hundreds of ppm, while those chemical shifts of the normal hexadecyl chain's nuclei, on the distance of more than five chemical bonds from the pseudoencapsulated paramagnetic metal ion, are close to those for the diamagnetic zinc(II) pseudoclathrochelate. This is indicative of the contact nature of thus induced paramagnetic shifts, as well as a weak pseudocontact contribution.

The SAMI Galaxy Survey: the intrinsic shape of kinematically selected galaxies

Using the stellar kinematic maps and ancillary imaging data from the Sydney AAO Multi Integral field (SAMI) Galaxy Survey, the intrinsic shape of kinematically-selected samples of galaxies is inferred. We implement an efficient and optimised algorithm to fit the intrinsic shape of galaxies using an established method to simultaneously invert the distributions of apparent ellipticities and kinematic misalignments. The algorithm output compares favourably with previous studies of the intrinsic shape of galaxies based on imaging alone and our re-analysis of the ATLAS3D data. Our results indicate that most galaxies are oblate axisymmetric. We show empirically that the intrinsic shape of galaxies varies as a function of their rotational support as measured by the "spin" parameter proxy Lambda_Re. In particular, low spin systems have a higher occurrence of triaxiality, while high spin systems are more intrinsically flattened and axisymmetric. The intrinsic shape of galaxies is linked to their formation and merger histories. Galaxies with high spin values have intrinsic shapes consistent with dissipational minor mergers, while the intrinsic shape of low-spin systems is consistent with dissipationless multi-merger assembly histories. This range in assembly histories inferred from intrinsic shapes is broadly consistent with expectations from cosmological simulations.

Separation of arbitrary spin wave equations in a class of $\Lambda$ Λ LTB cosmologies

The arbitrary spin field equations that are not separable, contrarily to what happens in the Robertson-Walker and Schwarzschild metrics, are studied in a general comoving spherically symmetric metric. They result to be separable by variable separation in a class of metrics governing the Lemâitre Tolman Bondi cosmological models whose physical radius has a special factorized parametric representation. The result is proved by induction by explicitly considering the spin 1, 3/2, 2 case and then the higher spin values. The procedure is based on the Newman-Penrose formalism, which takes into account the strong analogy with the Robertson-Walker metric case. The existence of a nontrivial Weyl spinor requires a symmetrization of one of the spinor wave equations for spin values greater than 1.

On the black hole mass of the γ-ray emitting narrow-line Seyfert 1 galaxy 1H 0323+342

Narrow-line Seyfert 1 galaxies have been identified by the Fermi Gamma-Ray Space Telescope as a rare class of gamma-ray emitting active galactic nuclei (AGN). The lowest-redshift candidate among them is the source 1H 0323+342. Here we present quasi-simultaneous Gemini near-infrared and Keck optical spectroscopy for it, from which we derive a black hole mass based on both the broad Balmer and Paschen emission lines. We supplement these observations with a NuSTAR X-ray spectrum taken about two years earlier, from which we constrain the black hole mass based on the short timescale spectral variability. Our multiwavelength observations suggest a black hole mass of ~2x10^7 solar masses, which agrees well with previous estimates. We build the spectral energy distribution and show that it is dominated by the thermal and reprocessed emission from the accretion disc rather than the non-thermal jet component. A detailed spectral fitting with the energy-conserving accretion disc model of Done et al. constrains the Eddington ratio to L/L_Edd ~ 0.5 for a (non-rotating) Schwarzschild black hole and to L/L_Edd ~ 1 for a Kerr black hole with dimensionless spin of a*=0.8. Higher spin values and so higher Eddington ratios are excluded, since they would strongly overpredict the observed soft X-ray flux.

Erratum to: Electron Magnetic Resonance in Magnetic Nanoparticles: Dependence on the Particle Size and Applicability of the Modified Giant Spin Model

Electron magnetic resonance is experimentally studied in dilute solid suspensions of iron oxide nanoparticles as the function of the particle size, and discussed in the frames of the modified giant spin approach. Gradual evolution of features specific for small nanoparticles including a narrow component at the main resonance field and a weak half-field line is observed with the increase in the particle size, manifesting the transition from quantum to fully classical behavior. The shape, width, position of the resonance spectra, and the specific features are described quantitatively with a single set of fitting parameters for nanoparticles of 5–20 nm size. Limitations of the quantum model at high spin values are discussed.