High Frequency QPOs due to Black Hole Spin

Science.gov (United States)

Kazanas, Demos; Fukumura, K.

2009-01-01

We present detailed computations of photon orbits emitted by flares at the innermost stable circular orbit (ISCO) of accretion disks around rotating black holes. We show that for sufficiently large spin parameter, i.e. a > 0.94 M, flare a sufficient number of photons arrive at an observer after multiple orbits around the black hole, to produce an "photon echo" of constant lag, i.e. independent of the relative phase between the black hole and the observer, of T approximates 14 M. This constant time delay, then, leads to a power spectrum with a QPO at a frequency nu approximates 1/14M, even for a totally random ensemble of such flares. Observation of such a QPO will provide incontrovertible evidence for the high spin of the black hole and a very accurate, independent, measurement of its mass.

BLACK HOLE-NEUTRON STAR MERGERS WITH A HOT NUCLEAR EQUATION OF STATE: OUTFLOW AND NEUTRINO-COOLED DISK FOR A LOW-MASS, HIGH-SPIN CASE

International Nuclear Information System (INIS)

Deaton, M. Brett; Duez, Matthew D.; Foucart, Francois; O'Connor, Evan; Ott, Christian D.; Scheel, Mark A.; Szilagyi, Bela; Kidder, Lawrence E.; Muhlberger, Curran D.

2013-01-01

Neutrino emission significantly affects the evolution of the accretion tori formed in black hole-neutron star mergers. It removes energy from the disk, alters its composition, and provides a potential power source for a gamma-ray burst. To study these effects, simulations in general relativity with a hot microphysical equation of state (EOS) and neutrino feedback are needed. We present the first such simulation, using a neutrino leakage scheme for cooling to capture the most essential effects and considering a moderate mass (1.4 M ☉ neutron star, 5.6 M ☉ black hole), high-spin (black hole J/M 2 = 0.9) system with the K 0 = 220 MeV Lattimer-Swesty EOS. We find that about 0.08 M ☉ of nuclear matter is ejected from the system, while another 0.3 M ☉ forms a hot, compact accretion disk. The primary effects of the escaping neutrinos are (1) to make the disk much denser and more compact, (2) to cause the average electron fraction Y e of the disk to rise to about 0.2 and then gradually decrease again, and (3) to gradually cool the disk. The disk is initially hot (T ∼ 6 MeV) and luminous in neutrinos (L ν ∼ 10 54 erg s –1 ), but the neutrino luminosity decreases by an order of magnitude over 50 ms of post-merger evolution

BLACK HOLE-NEUTRON STAR MERGERS WITH A HOT NUCLEAR EQUATION OF STATE: OUTFLOW AND NEUTRINO-COOLED DISK FOR A LOW-MASS, HIGH-SPIN CASE

Energy Technology Data Exchange (ETDEWEB)

Deaton, M. Brett; Duez, Matthew D. [Department of Physics and Astronomy, Washington State University, Pullman, WA 99164 (United States); Foucart, Francois; O' Connor, Evan [Canadian Institute for Theoretical Astrophysics, University of Toronto, Toronto, Ontario M5S 3H8 (Canada); Ott, Christian D.; Scheel, Mark A.; Szilagyi, Bela [TAPIR, MC 350-17, California Institute of Technology, Pasadena, CA 91125 (United States); Kidder, Lawrence E.; Muhlberger, Curran D., E-mail: mbdeaton@wsu.edu, E-mail: m.duez@wsu.edu [Center for Radiophysics and Space Research, Cornell University, Ithaca, NY 14853 (United States)

2013-10-10

Neutrino emission significantly affects the evolution of the accretion tori formed in black hole-neutron star mergers. It removes energy from the disk, alters its composition, and provides a potential power source for a gamma-ray burst. To study these effects, simulations in general relativity with a hot microphysical equation of state (EOS) and neutrino feedback are needed. We present the first such simulation, using a neutrino leakage scheme for cooling to capture the most essential effects and considering a moderate mass (1.4 M{sub ☉} neutron star, 5.6 M{sub ☉} black hole), high-spin (black hole J/M {sup 2} = 0.9) system with the K{sub 0} = 220 MeV Lattimer-Swesty EOS. We find that about 0.08 M{sub ☉} of nuclear matter is ejected from the system, while another 0.3 M{sub ☉} forms a hot, compact accretion disk. The primary effects of the escaping neutrinos are (1) to make the disk much denser and more compact, (2) to cause the average electron fraction Y{sub e} of the disk to rise to about 0.2 and then gradually decrease again, and (3) to gradually cool the disk. The disk is initially hot (T ∼ 6 MeV) and luminous in neutrinos (L{sub ν} ∼ 10{sup 54} erg s{sup –1}), but the neutrino luminosity decreases by an order of magnitude over 50 ms of post-merger evolution.

Suzaku Observations of 4U 1957+11: Potentially the Most Rapidly Spinning Black Hole in (the Halo of) the Galaxy

Science.gov (United States)

Nowak, Michael A.; Wilms, Joern; Pottschmidt, Katja; Schulz, Norbert; Maitra, Dipankar; Miller, Jon

2011-01-01

We present three Suzaku observations of the black hole candidate 4U 1957+11 (V 1408 Aql) - a source that exhibits some of. the simplest and cleanest examples of soft, disk-dominated spectra. 4U 1957+ II also presents among the. highest peak temperatures found from disk-dominated spectra. Such temperatures may be associated with rapid black hole spin. The 4U 1957+11 spectra also require a very low normalization, which can be explained by a combination of small inner disk radius and a large distance (> 10 kpc) which places 4U 1957+ 11 well into the Galactic halo. We perform Joint fits to the Suzaku spectra with both relativistic and Comptonized disk models. Assuming a low mass black hole and the nearest distance (3 Stellar Mass, 10 kpc), the dimensionless spin parameter a* = Jc/GM(sup 2)> or approx. 0.9. Higher masses and farther distances yield a* approx. = 1. Similar conclusions are reached with Comptonization models; they imply a combination of small inner disk radii (or, equivalently, rapid spin) and large distance. Low spin cannot be recovered unless 4U 1957+11 is a low mass black hole that is at the unusually large distance of > or approx.40 kpc. We speculate whether the suggested maximal spin is related to how the system came to reside in the halo.

Constraints on Black Hole Spin in a Sample of Broad Iron Line AGN

Science.gov (United States)

Brenneman, Laura W.; Reynolds, Christopher S.

2008-01-01

We present a uniform X-ray spectral analysis of nine type-1 active galactic nuclei (AGN) that have been previously found to harbor relativistically broadened iron emission lines. We show that the need for relativistic effects in the spectrum is robust even when one includes continuum "reflection" from the accretion disk. We then proceed to model these relativistic effects in order to constrain the spin of the supermassive black holes in these AGN. Our principal assumption, supported by recent simulations of geometrically-thin accretion disks, is that no iron line emission (or any associated Xray reflection features) can originate from the disk within the innermost stable circular orbit. Under this assumption, which tends to lead to constraints in the form of lower limits on the spin parameter, we obtain non-trivial spin constraints on five AGN. The spin parameters of these sources range from moderate (a approximates 0.6) to high (a > 0.96). Our results allow, for the first time, an observational constraint on the spin distribution function of local supermassive black holes. Parameterizing this as a power-law in dimensionless spin parameter (f(a) varies as absolute value of (a) exp zeta), we present the probability distribution for zeta implied by our results. Our results suggest 90% and 95% confidence limits of zeta > -0.09 and zeta > -0.3 respectively.

EFFECTS OF SPIN ON HIGH-ENERGY RADIATION FROM ACCRETING BLACK HOLES

Energy Technology Data Exchange (ETDEWEB)

O’ Riordan, Michael; Pe’er, Asaf [Physics Department, University College Cork, Cork (Ireland); McKinney, Jonathan C., E-mail: michael_oriordan@umail.ucc.ie [Department of Physics and Joint Space-Science Institute, University of Maryland, College Park, MD 20742 (United States)

2016-11-01

Observations of jets in X-ray binaries show a correlation between radio power and black hole spin. This correlation, if confirmed, points toward the idea that relativistic jets may be powered by the rotational energy of black holes. In order to examine this further, we perform general relativistic radiative transport calculations on magnetically arrested accretion flows, which are known to produce powerful jets via the Blandford–Znajek (BZ) mechanism. We find that the X-ray and γ -ray emission strongly depend on spin and inclination angle. Surprisingly, the high-energy power does not show the same dependence on spin as the BZ jet power, but instead can be understood as a redshift effect. In particular, photons observed perpendicular to the spin axis suffer little net redshift until originating from close to the horizon. Such observers see deeper into the hot, dense, highly magnetized inner disk region. This effect is largest for rapidly rotating black holes due to a combination of frame dragging and decreasing horizon radius. While the X-ray emission is dominated by the near horizon region, the near-infrared (NIR) radiation originates at larger radii. Therefore, the ratio of X-ray to NIR power is an observational signature of black hole spin.

MIGRATION TRAPS IN DISKS AROUND SUPERMASSIVE BLACK HOLES

International Nuclear Information System (INIS)

Bellovary, Jillian M.; Low, Mordecai-Mark Mac; McKernan, Barry; Ford, K. E. Saavik

2016-01-01

Accretion disks around supermassive black holes (SMBHs) in active galactic nuclei (AGNs) contain stars, stellar mass black holes, and other stellar remnants, which perturb the disk gas gravitationally. The resulting density perturbations exert torques on the embedded masses causing them to migrate through the disk in a manner analogous to planets in protoplanetary disks. We determine the strength and direction of these torques using an empirical analytic description dependent on local disk gradients, applied to two different analytic, steady-state disk models of SMBH accretion disks. We find that there are radii in such disks where the gas torque changes sign, trapping migrating objects. Our analysis shows that major migration traps generally occur where the disk surface density gradient changes sign from positive to negative, around 20–300R g , where R g  = 2GM/c 2 is the Schwarzschild radius. At these traps, massive objects in the AGN disk can accumulate, collide, scatter, and accrete. Intermediate mass black hole formation is likely in these disk locations, which may lead to preferential gap and cavity creation at these radii. Our model thus has significant implications for SMBH growth as well as gravitational wave source populations

Accretion Disks Around Binary Black Holes of Unequal Mass: GRMHD Simulations Near Decoupling

Science.gov (United States)

Gold, Roman; Paschalidis, Vasileios; Etienne, Zachariah B.; Shapiro, Stuart L.; Pfeiffer, Harald, P.

2013-01-01

We report on simulations in general relativity of magnetized disks onto black hole binaries. We vary the binary mass ratio from 1:1 to 1:10 and evolve the systems when they orbit near the binary disk decoupling radius. We compare (surface) density profiles, accretion rates (relative to a single, non-spinning black hole), variability, effective alpha-stress levels and luminosities as functions of the mass ratio. We treat the disks in two limiting regimes: rapid radiative cooling and no radiative cooling. The magnetic field lines clearly reveal jets emerging from both black hole horizons and merging into one common jet at large distances. The magnetic fields give rise to much stronger shock heating than the pure hydrodynamic flows, completely alter the disk structure, and boost accretion rates and luminosities. Accretion streams near the horizons are among the densest structures; in fact, the 1:10 no-cooling evolution results in a refilling of the cavity. The typical effective temperature in the bulk of the disk is approx. 10(exp5) (M / 10(exp 8)M solar mass (exp -1/4(L/L(sub edd) (exp 1/4K) yielding characteristic thermal frequencies approx. 10 (exp 15) (M /10(exp 8)M solar mass) (exp -1/4(L/L (sub edd) (1+z) (exp -1)Hz. These systems are thus promising targets for many extragalactic optical surveys, such as LSST, WFIRST, and PanSTARRS.

MIGRATION TRAPS IN DISKS AROUND SUPERMASSIVE BLACK HOLES

Energy Technology Data Exchange (ETDEWEB)

Bellovary, Jillian M.; Low, Mordecai-Mark Mac; McKernan, Barry; Ford, K. E. Saavik [Department of Astrophysics, American Museum of Natural History, Central Park West at 79th Street, NY 10024 (United States)

2016-03-10

Accretion disks around supermassive black holes (SMBHs) in active galactic nuclei (AGNs) contain stars, stellar mass black holes, and other stellar remnants, which perturb the disk gas gravitationally. The resulting density perturbations exert torques on the embedded masses causing them to migrate through the disk in a manner analogous to planets in protoplanetary disks. We determine the strength and direction of these torques using an empirical analytic description dependent on local disk gradients, applied to two different analytic, steady-state disk models of SMBH accretion disks. We find that there are radii in such disks where the gas torque changes sign, trapping migrating objects. Our analysis shows that major migration traps generally occur where the disk surface density gradient changes sign from positive to negative, around 20–300R{sub g}, where R{sub g} = 2GM/c{sup 2} is the Schwarzschild radius. At these traps, massive objects in the AGN disk can accumulate, collide, scatter, and accrete. Intermediate mass black hole formation is likely in these disk locations, which may lead to preferential gap and cavity creation at these radii. Our model thus has significant implications for SMBH growth as well as gravitational wave source populations.

ACCRETION DISKS AROUND KICKED BLACK HOLES: POST-KICK DYNAMICS

International Nuclear Information System (INIS)

Ponce, Marcelo; Faber, Joshua A.; Lombardi, James C.

2012-01-01

Numerical calculations of merging black hole binaries indicate that asymmetric emission of gravitational radiation can kick the merged black hole at up to thousands of km s –1 , and a number of systems have been observed recently whose properties are consistent with an active galactic nucleus containing a supermassive black hole moving with substantial velocity with respect to its broader accretion disk. We study here the effect of an impulsive kick delivered to a black hole on the dynamical evolution of its accretion disk using a smoothed particle hydrodynamics code, focusing attention on the role played by the kick angle with respect to the orbital angular momentum vector of the pre-kicked disk. We find that for more vertical kicks, for which the angle between the kick and the normal vector to the disk θ ∼ 45°, matter rapidly accretes toward the black hole. There is a systematic trend for higher potential luminosities for more oblique kick angles for a given black hole mass, disk mass, and kick velocity, and we find large amplitude oscillations in time in the case of a kick oriented 60° from the vertical.

NuSTAR observations of the black holes GS 1354-645: Evidence of rapid black hole spin

DEFF Research Database (Denmark)

El-Batal, A. M.; Miller, J. M.; Reynolds, M. T.

2016-01-01

We present the results of a NuSTAR study of the dynamically confirmed stellar-mass black hole GS 1354-645. The source was observed during its 2015 "hard" state outburst; we concentrate on spectra from two relatively bright phases. In the higher-flux observation, the broadband NuSTAR spectra reveal...... a clear, strong disk reflection spectrum, blurred by a degree that requires a black hole spin of a = cf/GM(2) >= 0.98 (1 sigma statistical limits only). The fits also require a high inclination: 0 similar or equal to 75 (2)degrees. Strong "dips" are sometimes observed in the X-ray light curves of sources...... in stellar-mass black holes, and inner accretion flow geometries at moderate accretion rates....

Gravitational lensing by spinning black holes in astrophysics, and in the movie Interstellar

International Nuclear Information System (INIS)

James, Oliver; Tunzelmann, Eugénie von; Franklin, Paul; Thorne, Kip S

2015-01-01

Interstellar is the first Hollywood movie to attempt depicting a black hole as it would actually be seen by somebody nearby. For this, our team at Double Negative Visual Effects, in collaboration with physicist Kip Thorne, developed a code called Double Negative Gravitational Renderer (DNGR) to solve the equations for ray-bundle (light-beam) propagation through the curved spacetime of a spinning (Kerr) black hole, and to render IMAX-quality, rapidly changing images. Our ray-bundle techniques were crucial for achieving IMAX-quality smoothness without flickering; and they differ from physicists’ image-generation techniques (which generally rely on individual light rays rather than ray bundles), and also differ from techniques previously used in the film industry’s CGI community. This paper has four purposes: (i) to describe DNGR for physicists and CGI practitioners, who may find interesting and useful some of our unconventional techniques. (ii) To present the equations we use, when the camera is in arbitrary motion at an arbitrary location near a Kerr black hole, for mapping light sources to camera images via elliptical ray bundles. (iii) To describe new insights, from DNGR, into gravitational lensing when the camera is near the spinning black hole, rather than far away as in almost all prior studies; we focus on the shapes, sizes and influence of caustics and critical curves, the creation and annihilation of stellar images, the pattern of multiple images, and the influence of almost-trapped light rays, and we find similar results to the more familiar case of a camera far from the hole. (iv) To describe how the images of the black hole Gargantua and its accretion disk, in the movie Interstellar, were generated with DNGR—including, especially, the influences of (a) colour changes due to doppler and gravitational frequency shifts, (b) intensity changes due to the frequency shifts, (c) simulated camera lens flare, and (d) decisions that the film makers made about

Gravitational lensing by spinning black holes in astrophysics, and in the movie Interstellar

Science.gov (United States)

James, Oliver; von Tunzelmann, Eugénie; Franklin, Paul; Thorne, Kip S.

2015-03-01

Interstellar is the first Hollywood movie to attempt depicting a black hole as it would actually be seen by somebody nearby. For this, our team at Double Negative Visual Effects, in collaboration with physicist Kip Thorne, developed a code called Double Negative Gravitational Renderer (DNGR) to solve the equations for ray-bundle (light-beam) propagation through the curved spacetime of a spinning (Kerr) black hole, and to render IMAX-quality, rapidly changing images. Our ray-bundle techniques were crucial for achieving IMAX-quality smoothness without flickering; and they differ from physicists’ image-generation techniques (which generally rely on individual light rays rather than ray bundles), and also differ from techniques previously used in the film industry’s CGI community. This paper has four purposes: (i) to describe DNGR for physicists and CGI practitioners, who may find interesting and useful some of our unconventional techniques. (ii) To present the equations we use, when the camera is in arbitrary motion at an arbitrary location near a Kerr black hole, for mapping light sources to camera images via elliptical ray bundles. (iii) To describe new insights, from DNGR, into gravitational lensing when the camera is near the spinning black hole, rather than far away as in almost all prior studies; we focus on the shapes, sizes and influence of caustics and critical curves, the creation and annihilation of stellar images, the pattern of multiple images, and the influence of almost-trapped light rays, and we find similar results to the more familiar case of a camera far from the hole. (iv) To describe how the images of the black hole Gargantua and its accretion disk, in the movie Interstellar, were generated with DNGR—including, especially, the influences of (a) colour changes due to doppler and gravitational frequency shifts, (b) intensity changes due to the frequency shifts, (c) simulated camera lens flare, and (d) decisions that the film makers made about

A rapidly spinning supermassive black hole at the centre of NGC 1365

DEFF Research Database (Denmark)

Risaliti, G.; Harrison, F. A.; Madsen, K. K.

2013-01-01

and relativistic effects near the black hole, the line shape being sensitive to its spin. Alternative models in which the distortions result from absorption by intervening structures provide an equally good description of the data, and there has been no general agreement on which is correct. Recent claims...... that the black hole (2 × 10(6) solar masses) at the centre of the galaxy NGC 1365 is rotating at close to its maximum possible speed rest on the assumption of relativistic reflection. Here we report X-ray observations of NGC 1365 that reveal the relativistic disk features through broadened Fe-line emission...... and an associated Compton scattering excess of 10-30 kiloelectronvolts. Using temporal and spectral analyses, we disentangle continuum changes due to time-variable absorption from reflection, which we find arises from a region within 2.5 gravitational radii of the rapidly spinning black hole. Absorption...

Supermassive black holes do not correlate with galaxy disks or pseudobulges.

Science.gov (United States)

Kormendy, John; Bender, R; Cornell, M E

2011-01-20

The masses of supermassive black holes are known to correlate with the properties of the bulge components of their host galaxies. In contrast, they seem not to correlate with galaxy disks. Disk-grown 'pseudobulges' are intermediate in properties between bulges and disks; it has been unclear whether they do or do not correlate with black holes in the same way that bulges do. At stake in this issue are conclusions about which parts of galaxies coevolve with black holes, possibly by being regulated by energy feedback from black holes. Here we report pseudobulge classifications for galaxies with dynamically detected black holes and combine them with recent measurements of velocity dispersions in the biggest bulgeless galaxies. These data confirm that black holes do not correlate with disks and show that they correlate little or not at all with pseudobulges. We suggest that there are two different modes of black-hole feeding. Black holes in bulges grow rapidly to high masses when mergers drive gas infall that feeds quasar-like events. In contrast, small black holes in bulgeless galaxies and in galaxies with pseudobulges grow as low-level Seyfert galaxies. Growth of the former is driven by global processes, so the biggest black holes coevolve with bulges, but growth of the latter is driven locally and stochastically, and they do not coevolve with disks and pseudobulges.

Instability of ultra-spinning black holes

International Nuclear Information System (INIS)

Emparan, Roberto; Myers, Robert C.

2003-01-01

It has long been known that, in higher-dimensional general relativity, there are black hole solutions with an arbitrarily large angular momentum for a fixed mass. We examine the geometry of the event horizon of such ultra-spinning black holes and argue that these solutions become unstable at large enough rotation. Hence we find that higher-dimensional general relativity imposes an effective 'Kerr-bound' on spinning black holes through a dynamical decay mechanism. Our results also give indications of the existence of new stationary black holes with 'rippled' horizons of spherical topology. We consider various scenarios for the possible decay of ultra-spinning black holes, and finally discuss the implications of our results for black holes in braneworld scenarios. (author)

Charged spinning black holes as particle accelerators

International Nuclear Information System (INIS)

Wei Shaowen; Liu Yuxiao; Guo Heng; Fu Chune

2010-01-01

It has recently been pointed out that the spinning Kerr black hole with maximal spin could act as a particle collider with arbitrarily high center-of-mass energy. In this paper, we will extend the result to the charged spinning black hole, the Kerr-Newman black hole. The center-of-mass energy of collision for two uncharged particles falling freely from rest at infinity depends not only on the spin a but also on the charge Q of the black hole. We find that an unlimited center-of-mass energy can be approached with the conditions: (1) the collision takes place at the horizon of an extremal black hole; (2) one of the colliding particles has critical angular momentum; (3) the spin a of the extremal black hole satisfies (1/√(3))≤(a/M)≤1, where M is the mass of the Kerr-Newman black hole. The third condition implies that to obtain an arbitrarily high energy, the extremal Kerr-Newman black hole must have a large value of spin, which is a significant difference between the Kerr and Kerr-Newman black holes. Furthermore, we also show that, for a near-extremal black hole, there always exists a finite upper bound for center-of-mass energy, which decreases with the increase of the charge Q.

Computations of Photon Orbits Emitted by Flares at the ISCO of Accretion Disks Around Rotating Black Holes

Science.gov (United States)

Kazanas, Demosthenes; Fukumura, K.

2009-01-01

We present detailed computations of photon orbits emitted by flares at the ISCO of accretion disks around rotating black holes. We show that for sufficiently large spin parameter, i.e. $a > 0.94 M$, following a flare at ISCO, a sufficient number of photons arrive at an observer after multiple orbits around the black hole, to produce an "photon echo" of constant lag, i.e. independent of the relative phase between the black hole and the observer, of $\\Delta T \\simeq 14 M$. This constant time delay, then, leads to the presence of a QPO in the source power spectrum at a frequency $\

"Iron-Clad" Evidence For Spinning Black Hole

Science.gov (United States)

2003-09-01

Telltale X-rays from iron may reveal if black holes are spinning or not, according to astronomers using NASA's Chandra X-ray Observatory and the European Space Agency's XMM-Newton Observatory. The gas flows and bizarre gravitational effects observed near stellar black holes are similar to those seen around supermassive black holes. Stellar black holes, in effect, are convenient `scale models' of their much larger cousins. Black holes come in at least two different sizes. Stellar black holes are between five and 20 times the mass of the Sun. At the other end of the size scale, supermassive black holes contain millions or billions times the mass of our Sun. The Milky Way contains both a supermassive black hole at its center, as well as a number of stellar black holes sprinkled throughout the Galaxy. At a press conference at the "Four Years of Chandra" symposium in Huntsville, Ala., Jon Miller of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. discussed recent results on the X-ray spectra, or distribution of X-rays with energy, from the iron atoms in gas around three stellar black holes in the Milky Way. "Discovering the high degree of correspondence between stellar and supermassive black holes is a real breakthrough," said Miller. "Because stellar black holes are smaller, everything happens about a million times faster, so they can be used as a test-bed for theories of how spinning black holes affect the space and matter around them." X-rays from a stellar black hole are produced when gas from a nearby companion star is heated to tens of millions of degrees as it swirls toward the black hole. Iron atoms in this gas produce distinctive X-ray signals that can be used to study the orbits of particles around the black hole. For example, the gravity of a black hole can shift the X-rays to lower energies. "The latest work provides the most precise measurements yet of the X-ray spectra for stellar black holes," said Miller. "These data help rule out

On the Calculation of the Fe K-alpha Line Emissivity of Black Hole Accretion Disks

Energy Technology Data Exchange (ETDEWEB)

Krawczynski, H.; Beheshtipour, B., E-mail: krawcz@wustl.edu [Physics Department and McDonnell Center for the Space Sciences, Washington University in St. Louis, 1 Brookings Drive, CB 1105, St. Louis, MO 63130 (United States)

2017-11-01

Observations of the fluorescent Fe K α emission line from the inner accretion flows of stellar mass black holes in X-ray binaries and supermassive black holes in active galactic nuclei have become an important tool to study the magnitude and inclination of the black hole spin, and the structure of the accretion flow close to the event horizon of the black hole. Modeling spectral, timing, and soon also X-ray polarimetric observations of the Fe K α emission requires the calculation of the specific intensity in the rest frame of the emitting plasma. We revisit the derivation of the equation used for calculating the illumination of the accretion disk by the corona. We present an alternative derivation leading to a simpler equation, and discuss the relation to previously published results.

Binary black holes: Spin dynamics and gravitational recoil

International Nuclear Information System (INIS)

Herrmann, Frank; Hinder, Ian; Shoemaker, Deirdre M.; Laguna, Pablo; Matzner, Richard A.

2007-01-01

We present a study of spinning black hole binaries focusing on the spin dynamics of the individual black holes as well as on the gravitational recoil acquired by the black hole produced by the merger. We consider two series of initial spin orientations away from the binary orbital plane. In one of the series, the spins are antialigned; for the second series, one of the spins points away from the binary along the line separating the black holes. We find a remarkable agreement between the spin dynamics predicted at 2nd post-Newtonian order and those from numerical relativity. For each configuration, we compute the kick of the final black hole. We use the kick estimates from the series with antialigned spins to fit the parameters in the Kidder kick formula, and verify that the recoil in the direction of the orbital angular momentum is ∝sinθ and on the orbital plane ∝cosθ, with θ the angle between the spin directions and the orbital angular momentum. We also find that the black hole spins can be well estimated by evaluating the isolated horizon spin on spheres of constant coordinate radius

CONSTRAINTS ON COMPTON-THICK WINDS FROM BLACK HOLE ACCRETION DISKS: CAN WE SEE THE INNER DISK?

International Nuclear Information System (INIS)

Reynolds, Christopher S.

2012-01-01

Strong evidence is emerging that winds can be driven from the central regions of accretion disks in both active galactic nuclei and Galactic black hole binaries. Direct evidence for highly ionized, Compton-thin inner-disk winds comes from observations of blueshifted (v ∼ 0.05-0.1c) iron-K X-ray absorption lines. However, it has been suggested that the inner regions of black hole accretion disks can also drive Compton-thick winds—such winds would enshroud the inner disk, preventing us from seeing direct signatures of the accretion disk (i.e., the photospheric thermal emission, or the Doppler/gravitationally broadened iron Kα line). Here, we show that, provided the source is sub-Eddington, the well-established wind-driving mechanisms fail to launch a Compton-thick wind from the inner disk. For the accelerated region of the wind to be Compton-thick, the momentum carried in the wind must exceed the available photon momentum by a factor of at least 2/λ, where λ is the Eddington ratio of the source, ruling out radiative acceleration unless the source is very close to the Eddington limit. Compton-thick winds also carry large mass fluxes, and a consideration of the connections between the wind and the disk shows this to be incompatible with magneto-centrifugal driving. Finally, thermal driving of the wind is ruled out on the basis of the large Compton radii that typify black hole systems. In the absence of some new acceleration mechanisms, we conclude that the inner regions of sub-Eddington accretion disks around black holes are indeed naked.

Self-gravitating axially symmetric disks in general-relativistic rotation

Science.gov (United States)

Karkowski, Janusz; Kulczycki, Wojciech; Mach, Patryk; Malec, Edward; Odrzywołek, Andrzej; Piróg, Michał

2018-05-01

We integrate numerically axially symmetric stationary Einstein equations describing self-gravitating disks around spinless black holes. The numerical scheme is based on a method developed by Shibata, but contains important new ingredients. We derive a new general-relativistic Keplerian rotation law for self-gravitating disks around spinning black holes. Former results concerning rotation around spinless black holes emerge in the limit of a vanishing spin parameter. These rotation curves might be used for the description of rotating stars, after appropriate modification around the symmetry axis. They can be applied to the description of compact torus-black hole configurations, including active galactic nuclei or products of coalescences of two neutron stars.

POWERFUL RADIO EMISSION FROM LOW-MASS SUPERMASSIVE BLACK HOLES FAVORS DISK-LIKE BULGES

Energy Technology Data Exchange (ETDEWEB)

Wang, J.; Xu, Y.; Xu, D. W.; Wei, J. Y., E-mail: wj@bao.ac.cn [CAS Key Laboratory of Space Astronomy and Technology, National Astronomical Observatories, Chinese Academy of Sciences, Beijing (China)

2016-12-10

The origin of spin of low-mass supermassive black holes (SMBHs) is still a puzzle at present. We report here a study on the host galaxies of a sample of radio-selected nearby ( z < 0.05) Seyfert 2 galaxies with a BH mass of 10{sup 6–7} M{sub ⊙}. By modeling the SDSS r -band images of these galaxies through a two-dimensional bulge+disk decomposition, we identify a new dependence of SMBH's radio power on host bulge surface brightness profiles, in which more powerful radio emission comes from an SMBH associated with a more disk-like bulge. This result means low-mass and high-mass SMBHs are spun up by two entirely different modes that correspond to two different evolutionary paths. A low-mass SMBH is spun up by a gas accretion with significant disk-like rotational dynamics of the host galaxy in the secular evolution, while a high-mass one by a BH–BH merger in the merger evolution.

ACCRETION DISKS WITH A LARGE SCALE MAGNETIC FIELD AROUND BLACK HOLES

Directory of Open Access Journals (Sweden)

Gennady Bisnovatyi-Kogan

2013-12-01

Full Text Available We consider accretion disks around black holes at high luminosity, and the problem of the formation of a large-scale magnetic field in such disks, taking into account the non-uniform vertical structure of the disk. The structure of advective accretion disks is investigated, and conditions for the formation of optically thin regions in central parts of the accretion disk are found. The high electrical conductivity of the outer layers of the disk prevents outward diffusion of the magnetic field. This implies a stationary state with a strong magnetic field in the inner parts of the accretion disk close to the black hole, and zero radial velocity at the surface of the disk. The problem of jet collimation by magneto-torsion oscillations is investigated.

Extraordinary light transmission through opaque thin metal film with subwavelength holes blocked by metal disks.

Science.gov (United States)

Li, Wen-Di; Hu, Jonathan; Chou, Stephen Y

2011-10-10

We observed that when subwavelength-sized holes in an optically opaque metal film are completely covered by opaque metal disks larger than the holes, the light transmission through the holes is not reduced, but rather enhanced. Particularly we report (i) the observation of light transmission through the holes blocked by the metal disks up to 70% larger than the unblocked holes; (ii) the observation of tuning the light transmission by varying the coupling strength between the blocking disks and the hole array, or by changing the size of the disks and holes; (iii) the observation and simulation that the metal disk blocker can improve light coupling from free space to a subwavelength hole; and (iv) the simulation that shows the light transmission through subwavelength holes can be enhanced, even though the gap between the disk and the metal film is partially connected with a metal. We believe these finding should have broad and significant impacts and applications to optical systems in many fields.

Innermost stable circular orbit of spinning particle in charged spinning black hole background

Science.gov (United States)

Zhang, Yu-Peng; Wei, Shao-Wen; Guo, Wen-Di; Sui, Tao-Tao; Liu, Yu-Xiao

2018-04-01

In this paper we investigate the innermost stable circular orbit (ISCO) (spin-aligned or anti-aligned orbit) for a classical spinning test particle with the pole-dipole approximation in the background of Kerr-Newman black hole in the equatorial plane. It is shown that the orbit of the spinning particle is related to the spin of the test particle. The motion of the spinning test particle will be superluminal if its spin is too large. We give an additional condition by considering the superluminal constraint for the ISCO in the black hole backgrounds. We obtain numerically the relations between the ISCO and the properties of the black holes and the test particle. It is found that the radius of the ISCO for a spinning test particle is smaller than that of a nonspinning test particle in the black hole backgrounds.

Eternal higher spin black holes: a thermofield Interpretation

International Nuclear Information System (INIS)

Castro, Alejandra; Iqbal, Nabil; Llabrés, Eva

2016-01-01

We study Lorentzian eternal black holes in the Chern-Simons sector of AdS 3 higher spin gravity. We probe such black holes using bulk Wilson lines and motivate new regularity conditions that must be obeyed by the bulk connections in order for the geometry to be consistent with an interpretation as a thermofield state in the dual CFT 2 . We demonstrate that any higher spin black hole may be placed in a gauge that satisfies these conditions: this is the Chern-Simons analogue of the construction of Kruskal coordinates that permit passage through the black hole horizon. We also argue that the Wilson line provides a higher-spin notion of causality in higher spin gravity that can be used to associate a Penrose diagram with the black hole. We present some applications of the formalism, including a study of the time-dependent entanglement entropy arising from the higher spin black hole interior and evidence for an emergent AdS 2 region in the extremal limit.

Thin accretion disk around regular black hole

Directory of Open Access Journals (Sweden)

QIU Tianqi

2014-08-01

Full Text Available The Penrose′s cosmic censorship conjecture says that naked singularities do not exist in nature.So,it seems reasonable to further conjecture that not even a singularity exists in nature.In this paper,a regular black hole without singularity is studied in detail,especially on its thin accretion disk,energy flux,radiation temperature and accretion efficiency.It is found that the interaction of regular black hole is stronger than that of the Schwarzschild black hole. Furthermore,the thin accretion will be more efficiency to lost energy while the mass of black hole decreased. These particular properties may be used to distinguish between black holes.

Gravitomagnetic acceleration from black hole accretion disks

International Nuclear Information System (INIS)

Poirier, J; Mathews, G J

2016-01-01

We demonstrate how the motion of the neutral masses in an accretion disk orbiting a black hole creates a general-relativistic magnetic-like (gravitomagnetic) field that vertically accelerates neutral particles near an accretion disk upward and then inward toward the axis of the accretion disk. Even though this gravitomagnetic field is not the only mechanism contributing to the production of jets, it presents a novel means to identify one general relativistic effect from a much more complicated problem. In addition, as the accelerated material above or below the accretion disk nears the axis with a nearly vertical direction, a frame-dragging effect twists the trajectories around the axis thus contributing to the collimation of the jet. (note)

Gravitomagnetic acceleration from black hole accretion disks

Science.gov (United States)

Poirier, J.; Mathews, G. J.

2016-05-01

We demonstrate how the motion of the neutral masses in an accretion disk orbiting a black hole creates a general-relativistic magnetic-like (gravitomagnetic) field that vertically accelerates neutral particles near an accretion disk upward and then inward toward the axis of the accretion disk. Even though this gravitomagnetic field is not the only mechanism contributing to the production of jets, it presents a novel means to identify one general relativistic effect from a much more complicated problem. In addition, as the accelerated material above or below the accretion disk nears the axis with a nearly vertical direction, a frame-dragging effect twists the trajectories around the axis thus contributing to the collimation of the jet.

Measuring Quasar Spin via X-ray Continuum Fitting

Science.gov (United States)

Jenkins, Matthew; Pooley, David; Rappaport, Saul; Steiner, Jack

2018-01-01

We have identified several quasars whose X-ray spectra appear very soft. When fit with power-law models, the best-fit indices are greater than 3. This is very suggestive of thermal disk emission, indicating that the X-ray spectrum is dominated by the disk component. Galactic black hole binaries in such states have been successfully fit with disk-blackbody models to constrain the inner radius, which also constrains the spin of the black hole. We have fit those models to XMM-Newton spectra of several of our identified soft X-ray quasars to place constraints on the spins of the supermassive black holes.

Simulating merging binary black holes with nearly extremal spins

International Nuclear Information System (INIS)

Lovelace, Geoffrey; Scheel, Mark A.; Szilagyi, Bela

2011-01-01

Astrophysically realistic black holes may have spins that are nearly extremal (i.e., close to 1 in dimensionless units). Numerical simulations of binary black holes are important tools both for calibrating analytical templates for gravitational-wave detection and for exploring the nonlinear dynamics of curved spacetime. However, all previous simulations of binary-black-hole inspiral, merger, and ringdown have been limited by an apparently insurmountable barrier: the merging holes' spins could not exceed 0.93, which is still a long way from the maximum possible value in terms of the physical effects of the spin. In this paper, we surpass this limit for the first time, opening the way to explore numerically the behavior of merging, nearly extremal black holes. Specifically, using an improved initial-data method suitable for binary black holes with nearly extremal spins, we simulate the inspiral (through 12.5 orbits), merger and ringdown of two equal-mass black holes with equal spins of magnitude 0.95 antialigned with the orbital angular momentum.

A SCALING RELATION BETWEEN MEGAMASER DISK RADIUS AND BLACK HOLE MASS IN ACTIVE GALACTIC NUCLEI

International Nuclear Information System (INIS)

Wardle, Mark; Yusef-Zadeh, Farhad

2012-01-01

Several thin, Keplerian, sub-parsec megamaser disks have been discovered in the nuclei of active galaxies and used to precisely determine the mass of their host black holes. We show that there is an empirical linear correlation between the disk radius and the black hole mass. We demonstrate that such disks are naturally formed by the partial capture of molecular clouds passing through the galactic nucleus and temporarily engulfing the central supermassive black hole. Imperfect cancellation of the angular momenta of the cloud material colliding after passing on opposite sides of the hole leads to the formation of a compact disk. The radial extent of the disk is determined by the efficiency of this process and the Bondi-Hoyle capture radius of the black hole, and naturally produces the empirical linear correlation of the radial extent of the maser distribution with black hole mass. The disk has sufficient column density to allow X-ray irradiation from the central source to generate physical and chemical conditions conducive to the formation of 22 GHz H 2 O masers. For initial cloud column densities ∼ 23.5 cm –2 the disk is non-self-gravitating, consistent with the ordered kinematics of the edge-on megamaser disks; for higher cloud columns the disk would fragment and produce a compact stellar disk similar to that observed around Sgr A* at the galactic center.

THE DISK-WIND-JET CONNECTION IN THE BLACK HOLE H 1743-322

Energy Technology Data Exchange (ETDEWEB)

Miller, J. M.; King, A. L. [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109-1042 (United States); Raymond, J. [Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States); Fabian, A. C. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 OHA (United Kingdom); Reynolds, C. S. [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Kallman, T. R. [Laboratory for High Energy Astrophysics, NASA Goddard Space Flight Center, Code 662, Greenbelt, MD 20771 (United States); Cackett, E. M. [Department of Physics and Astronomy, Wayne State University, 666 West Hancock Street, Detroit, MI 48201 (United States); Van der Klis, M. [Astronomical Institute ' Anton Pannekoek' , University of Amsterdam, Science Park 904, 1098-XH, Amsterdam (Netherlands); Steeghs, D. T. H., E-mail: jonmm@umich.edu [Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom)

2012-11-01

X-ray disk winds are detected in spectrally soft, disk-dominated phases of stellar-mass black hole outbursts. In contrast, compact, steady, relativistic jets are detected in spectrally hard states that are dominated by non-thermal X-ray emission. Although these distinctive outflows appear to be almost mutually exclusive, it is possible that a disk wind persists in hard states but cannot be detected via X-ray absorption lines owing to very high ionization. Here, we present an analysis of a deep, 60 ks Chandra/HETGS observation of the black hole candidate H 1743-322 in the low/hard state. The spectrum shows no evidence of a disk wind, with tight limits, and within the range of ionizing flux levels that were measured in prior Chandra observations wherein a wind was clearly detected. In H 1743-322, at least, disk winds are actually diminished in the low/hard state, and disk winds and jets are likely state dependent and anti-correlated. These results suggest that although the launching radii of winds and jets may differ by orders of magnitude, they may both be tied to a fundamental property of the inner accretion flow, such as the mass accretion rate and/or the magnetic field topology of the disk. We discuss these results in the context of disk winds and jets in other stellar-mass black holes, and possible launching mechanisms for black hole outflows.

Properties of a thin accretion disk around a rotating non-Kerr black hole

International Nuclear Information System (INIS)

Chen Songbai; Jing Jiliang

2012-01-01

We study the accretion process in the thin disk around a rotating non-Kerr black hole with a deformed parameter and an unbound rotation parameter. Our results show that the presence of the deformed parameter ε modifies the standard properties of the disk. For the case in which the black hole is more oblate than a Kerr black hole, the larger deviation leads to the smaller energy flux, the lower radiation temperature and the fainter spectra luminosity in the disk. For the black hole with positive deformed parameter, we find that the effect of the deformed parameter on the disk becomes more complicated. It depends not only on the rotation direction of the black hole and the orbit particles, but also on the sign of the difference between the deformed parameter ε and a certain critical value ε c . These significant features in the mass accretion process may provide a possibility to test the no-hair theorem in the strong-field regime in future astronomical observations.

EVOLUTION OF WARPED ACCRETION DISKS IN ACTIVE GALACTIC NUCLEI. I. ROLES OF FEEDING AT THE OUTER BOUNDARIES

International Nuclear Information System (INIS)

Li, Yan-Rong; Wang, Jian-Min; Cheng, Cheng; Qiu, Jie

2013-01-01

We investigate the alignment processes of spinning black holes and their surrounding warped accretion disks in a frame of two different types of feeding at the outer boundaries. We consider (1) fixed flows in which gas is continually fed with a preferred angular momentum, and (2) free flows in which there is no gas supply and the disks diffuse freely at their outer edges. As expected, we find that for the cases of fixed flows the black hole disk systems always align on timescales of several 10 6 yr, irrespective of the initial inclinations. If the initial inclination angles are larger than π/2, the black hole accretion transits from retrograde to prograde fashion, and the accreted mass onto the black holes during these two phases is comparable. On the other hand, for the cases of free flows, both alignments and anti-alignments can occur, depending on the initial inclinations and the ratios of the angular momentum of the disks to that of the black holes. In such cases, the disks will be consumed within timescales of 10 6 yr by black holes accreting at the Eddington limit. We propose that there is a close connection between the black hole spin and the lifetime for which the feeding persists, which determines the observable episodic lifetimes of active galactic nuclei. We conclude that careful inclusion of the disk feeding at the outer boundaries is crucial for modeling the evolution of the black hole spin.

Precessional Instability in Binary Black Holes with Aligned Spins.

Science.gov (United States)

Gerosa, Davide; Kesden, Michael; O'Shaughnessy, Richard; Klein, Antoine; Berti, Emanuele; Sperhake, Ulrich; Trifirò, Daniele

2015-10-02

Binary black holes on quasicircular orbits with spins aligned with their orbital angular momentum have been test beds for analytic and numerical relativity for decades, not least because symmetry ensures that such configurations are equilibrium solutions to the spin-precession equations. In this work, we show that these solutions can be unstable when the spin of the higher-mass black hole is aligned with the orbital angular momentum and the spin of the lower-mass black hole is antialigned. Spins in these configurations are unstable to precession to large misalignment when the binary separation r is between the values r(ud±)=(√(χ(1))±√(qχ(2)))(4)(1-q)(-2)M, where M is the total mass, q≡m(2)/m(1) is the mass ratio, and χ(1) (χ(2)) is the dimensionless spin of the more (less) massive black hole. This instability exists for a wide range of spin magnitudes and mass ratios and can occur in the strong-field regime near the merger. We describe the origin and nature of the instability using recently developed analytical techniques to characterize fully generic spin precession. This instability provides a channel to circumvent astrophysical spin alignment at large binary separations, allowing significant spin precession prior to merger affecting both gravitational-wave and electromagnetic signatures of stellar-mass and supermassive binary black holes.

Electrical control of single hole spins in nanowire quantum dots.

Science.gov (United States)

Pribiag, V S; Nadj-Perge, S; Frolov, S M; van den Berg, J W G; van Weperen, I; Plissard, S R; Bakkers, E P A M; Kouwenhoven, L P

2013-03-01

The development of viable quantum computation devices will require the ability to preserve the coherence of quantum bits (qubits). Single electron spins in semiconductor quantum dots are a versatile platform for quantum information processing, but controlling decoherence remains a considerable challenge. Hole spins in III-V semiconductors have unique properties, such as a strong spin-orbit interaction and weak coupling to nuclear spins, and therefore, have the potential for enhanced spin control and longer coherence times. A weaker hyperfine interaction has previously been reported in self-assembled quantum dots using quantum optics techniques, but the development of hole-spin-based electronic devices in conventional III-V heterostructures has been limited by fabrication challenges. Here, we show that gate-tunable hole quantum dots can be formed in InSb nanowires and used to demonstrate Pauli spin blockade and electrical control of single hole spins. The devices are fully tunable between hole and electron quantum dots, which allows the hyperfine interaction strengths, g-factors and spin blockade anisotropies to be compared directly in the two regimes.

Stability of black hole accretion disks

Directory of Open Access Journals (Sweden)

Czerny B.

2012-12-01

Full Text Available We discuss the issues of stability of accretion disks that may undergo the limit-cycle oscillations due to the two main types of thermal-viscous instabilities. These are induced either by the domination of radiation pressure in the innermost regions close to the central black hole, or by the partial ionization of hydrogen in the zone of appropriate temperatures. These physical processes may lead to the intermittent activity in AGN on timescales between hundreds and millions of years. We list a number of observational facts that support the idea of the cyclic activity in high accretion rate sources. We conclude however that the observed features of quasars may provide only indirect signatures of the underlying instabilities. Also, the support from the sources with stellar mass black holes, whose variability timescales are observationally feasible, is limited to a few cases of the microquasars. Therefore we consider a number of plausible mechanisms of stabilization of the limit cycle oscillations in high accretion rate accretion disks. The newly found is the stabilizing effect of the stochastic viscosity fluctuations.

DISCOVERY OF AN Hα EMITTING DISK AROUND THE SUPERMASSIVE BLACK HOLE OF M31

International Nuclear Information System (INIS)

Menezes, R. B.; Steiner, J. E.; Ricci, T. V.

2013-01-01

Due to its proximity, the mass of the supermassive black hole in the nucleus of the Andromeda galaxy (M31), the most massive black hole in the Local Group of galaxies, has been measured by several methods involving the kinematics of a stellar disk which surrounds it. We report here the discovery of an eccentric Hα emitting disk around the black hole at the center of M31 and show how modeling this disk can provide an independent determination of the mass of the black hole. Our model implies a mass of 5.0 +0.8 –1.0 × 10 7 M ☉ for the central black hole, consistent with the average of determinations by methods involving stellar dynamics, and compatible (at 1σ level) with measurements obtained from the most detailed models of the stellar disk around the central black hole. This value is also consistent with the M-σ relation. In order to make a comparison, we applied our simulation on the stellar kinematics in the nucleus of M31 and concluded that the parameters obtained for the stellar disk are not formally compatible with the parameters obtained for the Hα emitting disk. This result suggests that the stellar and the Hα emitting disks are intrinsically different from each other. A plausible explanation is that the Hα emission is associated with a gaseous disk. This hypothesis is supported by the detection of traces of weaker nebular lines in the nuclear region of M31. However, we cannot exclude the possibility that the Hα emission is, at least partially, generated by stars.

Galactic nuclei evolution with spinning black holes: method and implementation

Science.gov (United States)

Fiacconi, Davide; Sijacki, Debora; Pringle, J. E.

2018-04-01

Supermassive black holes at the centre of galactic nuclei mostly grow in mass through gas accretion over cosmic time. This process also modifies the angular momentum (or spin) of black holes, both in magnitude and in orientation. Despite being often neglected in galaxy formation simulations, spin plays a crucial role in modulating accretion power, driving jet feedback, and determining recoil velocity of coalescing black hole binaries. We present a new accretion model for the moving-mesh code AREPO that incorporates (i) mass accretion through a thin α-disc, and (ii) spin evolution through the Bardeen-Petterson effect. We use a diverse suite of idealised simulations to explore the physical connection between spin evolution and larger scale environment. We find that black holes with mass ≲ 107 M⊙ experience quick alignment with the accretion disc. This favours prolonged phases of spin-up, and the spin direction evolves according to the gas inflow on timescales as short as ≲ 100 Myr, which might explain the observed jet direction distribution in Seyfert galaxies. Heavier black holes (≳ 108 M⊙) are instead more sensitive to the local gas kinematic. Here we find a wider distribution in spin magnitudes: spin-ups are favoured if gas inflow maintains a preferential direction, and spin-downs occur for nearly isotropic infall, while the spin direction does not change much over short timescales ˜100 Myr. We therefore conclude that supermassive black holes with masses ≳ 5 × 108 M⊙ may be the ideal testbed to determine the main mode of black hole fuelling over cosmic time.

THE DISK-WIND-JET CONNECTION IN THE BLACK HOLE H 1743–322

International Nuclear Information System (INIS)

Miller, J. M.; King, A. L.; Raymond, J.; Fabian, A. C.; Reynolds, C. S.; Kallman, T. R.; Cackett, E. M.; Van der Klis, M.; Steeghs, D. T. H.

2012-01-01

X-ray disk winds are detected in spectrally soft, disk-dominated phases of stellar-mass black hole outbursts. In contrast, compact, steady, relativistic jets are detected in spectrally hard states that are dominated by non-thermal X-ray emission. Although these distinctive outflows appear to be almost mutually exclusive, it is possible that a disk wind persists in hard states but cannot be detected via X-ray absorption lines owing to very high ionization. Here, we present an analysis of a deep, 60 ks Chandra/HETGS observation of the black hole candidate H 1743–322 in the low/hard state. The spectrum shows no evidence of a disk wind, with tight limits, and within the range of ionizing flux levels that were measured in prior Chandra observations wherein a wind was clearly detected. In H 1743–322, at least, disk winds are actually diminished in the low/hard state, and disk winds and jets are likely state dependent and anti-correlated. These results suggest that although the launching radii of winds and jets may differ by orders of magnitude, they may both be tied to a fundamental property of the inner accretion flow, such as the mass accretion rate and/or the magnetic field topology of the disk. We discuss these results in the context of disk winds and jets in other stellar-mass black holes, and possible launching mechanisms for black hole outflows.

A SPITZER c2d LEGACY SURVEY TO IDENTIFY AND CHARACTERIZE DISKS WITH INNER DUST HOLES

International Nuclear Information System (INIS)

Merin, Bruno; Brown, Joanna M.; Herczeg, Gregory J.; Van Dishoeck, Ewine F.; Oliveira, Isa; Lahuis, Fred; Bottinelli, Sandrine; Augereau, Jean-Charles; Olofsson, Johan; Evans, Neal J.; Harvey, Paul M.; Cieza, Lucas; Spezzi, Loredana; Prusti, Timo; Alcala, Juan M.; Blake, Geoffrey A.; Bayo, Amelia; Geers, Vincent G.; Walter, Frederick M.; Chiu, Kuenley

2010-01-01

Understanding how disks dissipate is essential to studies of planet formation. However, identifying exactly how dust and gas dissipate is complicated due to the difficulty of finding objects that are clearly in the transition phase of losing their surrounding material. We use Spitzer Infrared Spectrograph (IRS) spectra to examine 35 photometrically selected candidate cold disks (disks with large inner dust holes). The infrared spectra are supplemented with optical spectra to determine stellar and accretion properties and 1.3 mm photometry to measure disk masses. Based on detailed spectral energy distribution modeling, we identify 15 new cold disks. The remaining 20 objects have IRS spectra that are consistent with disks without holes, disks that are observed close to edge-on, or stars with background emission. Based on these results, we determine reliable criteria to identify disks with inner holes from Spitzer photometry, and examine criteria already in the literature. Applying these criteria to the c2d surveyed star-forming regions gives a frequency of such objects of at least 4% and most likely of order 12% of the young stellar object population identified by Spitzer. We also examine the properties of these new cold disks in combination with cold disks from the literature. Hole sizes in this sample are generally smaller than in previously discovered disks and reflect a distribution in better agreement with exoplanet orbit radii. We find correlations between hole size and both disk and stellar masses. Silicate features, including crystalline features, are present in the overwhelming majority of the sample, although the 10 μm feature strength above the continuum declines for holes with radii larger than ∼7 AU. In contrast, polycyclic aromatic hydrocarbons are only detected in 2 out of 15 sources. Only a quarter of the cold disk sample shows no signs of accretion, making it unlikely that photoevaporation is the dominant hole-forming process in most cases.

ON THE HIGH-FREQUENCY QUASI-PERIODIC OSCILLATIONS FROM BLACK HOLES

International Nuclear Information System (INIS)

Erkut, M. Hakan

2011-01-01

We apply the global mode analysis, which has been recently developed for the modeling of kHz quasi-periodic oscillations (QPOs) from neutron stars, to the inner region of an accretion disk around a rotating black hole. Within a pseudo-Newtonian approach that keeps the ratio of the radial epicyclic frequency κ to the orbital frequency Ω the same as the corresponding ratio for a Kerr black hole, we determine the innermost disk region where the hydrodynamic modes grow in amplitude. We find that the radiation flux emerging from the inner disk has the highest values within the same region. Using the flux-weighted averages of the frequency bands over this region we identify the growing modes with highest frequency branches Ω + κ and Ω to be the plausible candidates for the high-frequency QPO pairs observed in black hole systems. The observed frequency ratio around 1.5 can therefore be understood naturally in terms of the global free oscillations in the innermost region of a viscous accretion disk around a black hole without invoking a particular resonance to produce black hole QPOs. Although the frequency ratio (Ω + κ)/(Ω) is found to be not sensitive to the black hole's spin which is good for explaining the high-frequency QPOs, it may work as a limited diagnostic of the spin parameter to distinguish black holes with very large spin from the slowly rotating ones. Within our model we estimate the frequency ratio of a high-frequency QPO pair to be greater than 1.5 if the black hole is a slow rotator. For fast rotating black holes, we expect the same ratio to be less than 1.5.

Self-consistent hole motion and spin excitations in a quantum antiferromagnet

International Nuclear Information System (INIS)

Su, Z.B.; Yu, L.; Li, Y.M.; Lai, W.Y.

1989-12-01

A new quantum Bogoliubov-de Gennes (BdeG) formalism is developed to study the self-consistent motion of holes and spin excitations in a quantum antiferromagnet within the generalized t-J model. On the one hand, the effects of local distortion of spin configurations and the renormalization of the hole motion due to virtual excitations of the distorted spin background are treated on an equal footing to obtain the hole wave function and its spectrum, as well as the effective mass for a propagating hole. On the other hand, the change of the spin excitation spectrum and the spin correlations due to the presence of dynamical holes are studied within the same adiabatic approximation. The stability of the hole states with respect to such changes justifies the self-consistency of the proposed formalism. (author). 25 refs, 6 figs, 1 tab

DISCOVERY OF AN H{alpha} EMITTING DISK AROUND THE SUPERMASSIVE BLACK HOLE OF M31

Energy Technology Data Exchange (ETDEWEB)

Menezes, R. B.; Steiner, J. E.; Ricci, T. V., E-mail: robertobm@astro.iag.usp.br [Instituto de Astronomia Geofisica e Ciencias Atmosfericas, Universidade de Sao Paulo, Rua do Matao 1226, Cidade Universitaria, Sao Paulo, SP CEP 05508-090 (Brazil)

2013-01-10

Due to its proximity, the mass of the supermassive black hole in the nucleus of the Andromeda galaxy (M31), the most massive black hole in the Local Group of galaxies, has been measured by several methods involving the kinematics of a stellar disk which surrounds it. We report here the discovery of an eccentric H{alpha} emitting disk around the black hole at the center of M31 and show how modeling this disk can provide an independent determination of the mass of the black hole. Our model implies a mass of 5.0{sup +0.8}{sub -1.0} Multiplication-Sign 10{sup 7} M{sub Sun} for the central black hole, consistent with the average of determinations by methods involving stellar dynamics, and compatible (at 1{sigma} level) with measurements obtained from the most detailed models of the stellar disk around the central black hole. This value is also consistent with the M-{sigma} relation. In order to make a comparison, we applied our simulation on the stellar kinematics in the nucleus of M31 and concluded that the parameters obtained for the stellar disk are not formally compatible with the parameters obtained for the H{alpha} emitting disk. This result suggests that the stellar and the H{alpha} emitting disks are intrinsically different from each other. A plausible explanation is that the H{alpha} emission is associated with a gaseous disk. This hypothesis is supported by the detection of traces of weaker nebular lines in the nuclear region of M31. However, we cannot exclude the possibility that the H{alpha} emission is, at least partially, generated by stars.

Distinguishing spin-aligned and isotropic black hole populations with gravitational waves.

Science.gov (United States)

Farr, Will M; Stevenson, Simon; Miller, M Coleman; Mandel, Ilya; Farr, Ben; Vecchio, Alberto

2017-08-23

The direct detection of gravitational waves from merging binary black holes opens up a window into the environments in which binary black holes form. One signature of such environments is the angular distribution of the black hole spins. Binary systems that formed through dynamical interactions between already-compact objects are expected to have isotropic spin orientations (that is, the spins of the black holes are randomly oriented with respect to the orbit of the binary system), whereas those that formed from pairs of stars born together are more likely to have spins that are preferentially aligned with the orbit. The best-measured combination of spin parameters for each of the four likely binary black hole detections GW150914, LVT151012, GW151226 and GW170104 is the 'effective' spin. Here we report that, if the magnitudes of the black hole spins are allowed to extend to high values, the effective spins for these systems indicate a 0.015 odds ratio against an aligned angular distribution compared to an isotropic one. When considering the effect of ten additional detections, this odds ratio decreases to 2.9 × 10 -7 against alignment. The existing preference for either an isotropic spin distribution or low spin magnitudes for the observed systems will be confirmed (or overturned) confidently in the near future.

SPIN-PRECESSION: BREAKING THE BLACK HOLE-NEUTRON STAR DEGENERACY

Energy Technology Data Exchange (ETDEWEB)

Chatziioannou, Katerina; Cornish, Neil; Klein, Antoine; Yunes, Nicolás [Department of Physics, Montana State University, Bozeman, MT 59717 (United States)

2015-01-01

Mergers of compact stellar remnants are prime targets for the LIGO/Virgo gravitational wave detectors. The gravitational wave signals from these merger events can be used to study the mass and spin distribution of stellar remnants, and provide information about black hole horizons and the material properties of neutron stars. However, it has been suggested that degeneracies in the way that the star's mass and spin are imprinted in the waveforms may make it impossible to distinguish between black holes and neutron stars. Here we show that the precession of the orbital plane due to spin-orbit coupling breaks the mass-spin degeneracy, and allows us to distinguish between standard neutron stars and alternative possibilities, such as black holes or exotic neutron stars with large masses and spins.

Strong disk winds traced throughout outbursts in black-hole X-ray binaries.

Science.gov (United States)

Tetarenko, B E; Lasota, J-P; Heinke, C O; Dubus, G; Sivakoff, G R

2018-02-01

Recurring outbursts associated with matter flowing onto compact stellar remnants (such as black holes, neutron stars and white dwarfs) in close binary systems provide a way of constraining the poorly understood accretion process. The light curves of these outbursts are shaped by the efficiency of angular-momentum (and thus mass) transport in the accretion disks, which has traditionally been encoded in a viscosity parameter, α. Numerical simulations of the magneto-rotational instability that is believed to be the physical mechanism behind this transport yield values of α of roughly 0.1-0.2, consistent with values determined from observations of accreting white dwarfs. Equivalent viscosity parameters have hitherto not been estimated for disks around neutron stars or black holes. Here we report the results of an analysis of archival X-ray light curves of 21 outbursts in black-hole X-ray binaries. By applying a Bayesian approach to a model of accretion, we determine corresponding values of α of around 0.2-1.0. These high values may be interpreted as an indication either of a very high intrinsic rate of angular-momentum transport in the disk, which could be sustained by the magneto-rotational instability only if a large-scale magnetic field threads the disk, or that mass is being lost from the disk through substantial outflows, which strongly shape the outburst in the black-hole X-ray binary. The lack of correlation between our estimates of α and the accretion state of the binaries implies that such outflows can remove a substantial fraction of the disk mass in all accretion states and therefore suggests that the outflows correspond to magnetically driven disk winds rather than thermally driven ones, which require specific radiative conditions.

Strong disk winds traced throughout outbursts in black-hole X-ray binaries

Science.gov (United States)

Tetarenko, B. E.; Lasota, J.-P.; Heinke, C. O.; Dubus, G.; Sivakoff, G. R.

2018-02-01

Recurring outbursts associated with matter flowing onto compact stellar remnants (such as black holes, neutron stars and white dwarfs) in close binary systems provide a way of constraining the poorly understood accretion process. The light curves of these outbursts are shaped by the efficiency of angular-momentum (and thus mass) transport in the accretion disks, which has traditionally been encoded in a viscosity parameter, α. Numerical simulations of the magneto-rotational instability that is believed to be the physical mechanism behind this transport yield values of α of roughly 0.1–0.2, consistent with values determined from observations of accreting white dwarfs. Equivalent viscosity parameters have hitherto not been estimated for disks around neutron stars or black holes. Here we report the results of an analysis of archival X-ray light curves of 21 outbursts in black-hole X-ray binaries. By applying a Bayesian approach to a model of accretion, we determine corresponding values of α of around 0.2–1.0. These high values may be interpreted as an indication either of a very high intrinsic rate of angular-momentum transport in the disk, which could be sustained by the magneto-rotational instability only if a large-scale magnetic field threads the disk, or that mass is being lost from the disk through substantial outflows, which strongly shape the outburst in the black-hole X-ray binary. The lack of correlation between our estimates of α and the accretion state of the binaries implies that such outflows can remove a substantial fraction of the disk mass in all accretion states and therefore suggests that the outflows correspond to magnetically driven disk winds rather than thermally driven ones, which require specific radiative conditions.

Investigating Supermassive Black Hole Spin at Different Redshift

Science.gov (United States)

Sinanan-Singh, Jasmine

2018-01-01

Supermassive black hole (SMBH) spin encodes vital information about the history of SMBH growth. High spins indicate a history of growth through large mass accretion events, which spin-up the black hole; Intermediate spins indicate a history of galactic mergers, which don't tend to systemcatically spin-up or spin-down black holes; low spins are attributed to successive, small accretion events with random orientations. Examining spin over different redshifts will help us understand the relative growth of SMBHs by mergers or accretion over cosmic time, an important part of understanding how SMBHs and their host galaxies co-evolved over time. To study spin, we compute the Fe K alpha emission line from the X-ray spectra of AGN sources in the Chandra-COSMOS Legacy Survey. We stack rest frame AGN spectra to improve the signal-to-noise ratio since the photon counts are low for individual spectra, and then average the spectra using an unwieghted mean. Our method is derived from Corral et al. (2008). We test our method on the two brightest sources in the COSMOS Survey and compute the rest frame average Fe K alpha emission line for different redshift bins. The SAO REU program is funded by the National Science Foundation REU and Department of Defense ASSURE programs under NSF Grant AST-1659473, and by the Smithsonian Institution.

Gravitomagnetic Acceleration of Black Hole Accretion Disk Matter to Polar Jets

Science.gov (United States)

Poirier, John; Mathews, Grant

2015-04-01

It is shown that the motion of the neutral masses in an accretion disk orbiting a black hole creates a magnetic-like (gravitomagnetic) field that vertically accelerates neutral particles near the accretion disk away from the disk and then inward toward the axis of the accretion disk. Moreover, as the accelerated material nears the axis, a frame-dragging effect twists the trajectories around the axis thus contributing to the formation of a narrow polar jet emanating from the poles.

Relaxation of nuclear spin on holes in semiconductors

International Nuclear Information System (INIS)

Gr'ncharova, E.I.; Perel', V.I.

1977-01-01

The longitudienal relaxation time T 1 of nuclear spins due to dipole-dipole interaction with holes in semiconductors is calculated. Expressions for T 1 in cubic and uniaxial semiconductors are obtained for non-degenerate and degenerate cases. On the basis of comparison with available experimental data for silicon the agreement with the theoretical results is obtained. It is demonstrated that in uniaxial semiconductors the time of relaxation on holes for a nuclear spin directed along the c axis is considerably greater than that for a spin in the normal direction

Attempt to explain black hole spin in X-ray binaries by new physics

International Nuclear Information System (INIS)

Bambi, Cosimo

2015-01-01

It is widely believed that the spin of black holes in X-ray binaries is mainly natal. A significant spin-up from accretion is not possible. If the secondary has a low mass, the black hole spin cannot change too much even if the black hole swallows the whole stellar companion. If the secondary has a high mass, its lifetime is too short to transfer the necessary amount of matter and spin the black hole up. However, while black holes formed from the collapse of a massive star with solarmetallicity are expected to have low birth spin, current spin measurements show that some black holes in X-ray binaries are rotating very rapidly. Here we show that, if these objects are not the Kerr black holes of general relativity, the accretion of a small amount of matter (∝2 M s un) can make them look like very fast-rotating Kerr black holes. Such a possibility is not in contradiction with any observation and it can explain current spin measurements in a very simple way. (orig.)

Effects of rolling friction on a spinning coin or disk

Science.gov (United States)

Cross, Rod

2018-05-01

Experimental and theoretical results are presented concerning the motion of a spinning disk on a horizontal surface. The disk precesses about a vertical axis while falling either quickly or slowly onto the surface depending on the coefficient of rolling friction. The rate of fall also depends on the offset distance, in the rolling direction, between the centre of mass and the line of action of the normal reaction force. Euler’s angular momentum equations are solved to obtain estimates of both the coefficient of friction and the offset distance for a 50.6 mm diameter brass disk spinning on three different surfaces. The fall times varied from about 3 s on P800 emery paper to about 30 s on glass.

The Quasar Accretion Disk Size-Black Hole Mass Relation

Science.gov (United States)

Morgan, Christopher W.; Kochanek, C. S.; Morgan, Nicholas D.; Falco, Emilio E.

2010-04-01

We use the microlensing variability observed for 11 gravitationally lensed quasars to show that the accretion disk size at a rest-frame wavelength of 2500 Å is related to the black hole mass by log(R 2500/cm) = (15.78 ± 0.12) + (0.80 ± 0.17)log(M BH/109 M sun). This scaling is consistent with the expectation from thin-disk theory (R vprop M 2/3 BH), but when interpreted in terms of the standard thin-disk model (T vprop R -3/4), it implies that black holes radiate with very low efficiency, log(η) = -1.77 ± 0.29 + log(L/L E), where η =L/(\\dot{M}c^2). Only by making the maximum reasonable shifts in the average inclination, Eddington factors, and black hole masses can we raise the efficiency estimate to be marginally consistent with typical efficiency estimates (η ≈ 10%). With one exception, these sizes are larger by a factor of ~4 than the size needed to produce the observed 0.8 μm quasar flux by thermal radiation from a thin disk with the same T vprop R -3/4 temperature profile. While scattering a significant fraction of the disk emission on large scales or including a large fraction of contaminating line emission can reduce the size discrepancy, resolving it also appears to require that accretion disks have flatter temperature/surface brightness profiles. Based on observations obtained with the Small and Moderate Aperture Research Telescope System (SMARTS) 1.3 m, which is operated by the SMARTS Consortium, the Apache Point Observatory 3.5 m telescope, which is owned and operated by the Astrophysical Research Consortium, the WIYN Observatory which is owned and operated by the University of Wisconsin, Indiana University, Yale University, and the National Optical Astronomy Observatories (NOAO), the 6.5 m Magellan Baade telescope, which is a collaboration between the observatories of the Carnegie Institution of Washington (OCIW), University of Arizona, Harvard University, University of Michigan, and Massachusetts Institute of Technology, and observations made

Yield surface investigation of alloys during model disk spin tests

Directory of Open Access Journals (Sweden)

E. P. Kuzmin

2014-01-01

Full Text Available Gas-turbine engines operate under heavy subsequently static loading conditions. Disks of gas-turbine engine are high loaded parts of irregular shape having intensive stress concentrators wherein a 3D stress strain state occurs. The loss of load-carrying capability or burst of disk can lead to severe accident or disaster. Therefore, development of methods to assess deformations and to predict burst is one of the most important problems.Strength assessment approaches are used at all levels of engine creation. In recent years due to actively developing numerical method, particularly FEA, it became possible to investigate load-carrying capability of irregular shape disks, to use 3D computing schemes including flow theory and different options of force and deformation failure criteria. In spite of a wide progress and practical use of strength assessment approaches, there is a lack of detailed research data on yield surface of disk alloys. The main purpose of this work is to validate the use of basis hypothesis of flow theory and investigate the yield surface of disk alloys during the disks spin test.The results of quasi-static numerical simulation of spin tests of model disk made from high-temperature forged alloy are presented. To determine stress-strain state of disk during loading finite element analysis is used. Simulation of elastic-plastic strain fields was carried out using incremental theory of plasticity with isotropic hardening. Hardening function was taken from the results of specimens tensile test. Specimens were cut from a sinkhead of model disk. The paper investigates the model sensitivity affected by V.Mises and Tresca yield criteria as well as the Hosford model. To identify the material model parameters the eddy current sensors were used in the experimental approach to measure rim radial displacements during the load-unload of spin test. The results of calculation made using different material models were compared with the

Thin accretion disk signatures of slowly rotating black holes in Horava gravity

International Nuclear Information System (INIS)

Harko, Tiberiu; Kovacs, Zoltan; Lobo, Francisco S N

2011-01-01

In this work, we consider the possibility of observationally testing Horava gravity by using the accretion disk properties around slowly rotating black holes of the Kehagias-Sfetsos (KS) solution in asymptotically flat spacetimes. The energy flux, temperature distribution, the emission spectrum as well as the energy conversion efficiency are obtained, and compared to the standard slowly rotating general relativistic Kerr solution. Comparing the mass accretion in a slowly rotating KS geometry in Horava gravity with the one of a slowly rotating Kerr black hole, we verify that the intensity of the flux emerging from the disk surface is greater for the slowly rotating Kehagias-Sfetsos solution than for rotating black holes with the same geometrical mass and accretion rate. We also present the conversion efficiency of the accreting mass into radiation, and show that the rotating KS solution provides a much more efficient engine for the transformation of the accreting mass into radiation than the Kerr black holes. Thus, distinct signatures appear in the electromagnetic spectrum, leading to the possibility of directly testing Horava gravity models by using astrophysical observations of the emission spectra from accretion disks.

Thin accretion disk signatures of slowly rotating black holes in Horava gravity

Energy Technology Data Exchange (ETDEWEB)

Harko, Tiberiu; Kovacs, Zoltan [Department of Physics and Center for Theoretical and Computational Physics, University of Hong Kong, Pok Fu Lam Road (Hong Kong); Lobo, Francisco S N, E-mail: harko@hkucc.hku.hk, E-mail: zkovacs@hku.hk, E-mail: flobo@cii.fc.ul.pt [Centro de Astronomia e Astrofisica da Universidade de Lisboa, Campo Grande, Ed. C8 1749-016 Lisboa (Portugal)

2011-08-21

In this work, we consider the possibility of observationally testing Horava gravity by using the accretion disk properties around slowly rotating black holes of the Kehagias-Sfetsos (KS) solution in asymptotically flat spacetimes. The energy flux, temperature distribution, the emission spectrum as well as the energy conversion efficiency are obtained, and compared to the standard slowly rotating general relativistic Kerr solution. Comparing the mass accretion in a slowly rotating KS geometry in Horava gravity with the one of a slowly rotating Kerr black hole, we verify that the intensity of the flux emerging from the disk surface is greater for the slowly rotating Kehagias-Sfetsos solution than for rotating black holes with the same geometrical mass and accretion rate. We also present the conversion efficiency of the accreting mass into radiation, and show that the rotating KS solution provides a much more efficient engine for the transformation of the accreting mass into radiation than the Kerr black holes. Thus, distinct signatures appear in the electromagnetic spectrum, leading to the possibility of directly testing Horava gravity models by using astrophysical observations of the emission spectra from accretion disks.

Ultrafast superresolution fluorescence imaging with spinning disk confocal microscope optics.

Science.gov (United States)

Hayashi, Shinichi; Okada, Yasushi

2015-05-01

Most current superresolution (SR) microscope techniques surpass the diffraction limit at the expense of temporal resolution, compromising their applications to live-cell imaging. Here we describe a new SR fluorescence microscope based on confocal microscope optics, which we name the spinning disk superresolution microscope (SDSRM). Theoretically, the SDSRM is equivalent to a structured illumination microscope (SIM) and achieves a spatial resolution of 120 nm, double that of the diffraction limit of wide-field fluorescence microscopy. However, the SDSRM is 10 times faster than a conventional SIM because SR signals are recovered by optical demodulation through the stripe pattern of the disk. Therefore a single SR image requires only a single averaged image through the rotating disk. On the basis of this theory, we modified a commercial spinning disk confocal microscope. The improved resolution around 120 nm was confirmed with biological samples. The rapid dynamics of micro-tubules, mitochondria, lysosomes, and endosomes were observed with temporal resolutions of 30-100 frames/s. Because our method requires only small optical modifications, it will enable an easy upgrade from an existing spinning disk confocal to a SR microscope for live-cell imaging. © 2015 Hayashi and Okada. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

Dance of Two Monster Black Holes

Science.gov (United States)

Kohler, Susanna

2016-03-01

than two dozen ground-based optical telescopes and the Swift/XRT satellite to observe OJ 287 in this time frame. The outburst occurred right on schedule, peaking on 5 December 2015, and the results of the observing campaign are now presented in a study led by Mauri Valtonen (University of Turku).Optical photometry of OJ 287 from October to December 2015, showing the outburst that resulted from the secondary black hole crossing the disk. [Valtonen et al. 2016]Because the secondary black holes orbit is affected by the spin of the primary black hole, Valtonen and collaborators were able to use the timing of the outburst to measure the spin of OJ 287s primary black hole to remarkably high precision. They find that its Kerr parameter is 0.313 0.01 which means its spinning at about a third of the maximum rate allowed by general relativity.The outburst timing also confirmed several general-relativistic properties of the system, including its loss of energy to gravitational waves. Remarkably, the energy lost as the secondary black hole punches through the accretion disk is still ten thousand times smaller than the amount of energy it loses through gravitational waves!The observations from this outburst have provided important black-hole measurements and tests of general relativity which are especially relevant in this new era of gravitational wave detections. And we may be able to perform still more tests on the secondarys next pass through the disk, which should occur in 2019.BonusCheck out this awesome animation of the orbits in a system similar to OJ 287! The secondarys orbit precesses around the primary due to general-relativistic effects. The sound you hearis an audio representation of the increasing frequency as the two black holes inspiral. You can find more information about this animation here. [Steve Drasco Curt Cutler]CitationM. J. Valtonen et al 2016 ApJ 819 L37. doi:10.3847/2041-8205/819/2/L37

Planet Formation in Disks with Inclined Binary Companions: Can Primordial Spin-Orbit Misalignment be Produced?

Science.gov (United States)

Zanazzi, J. J.; Lai, Dong

2018-04-01

Many hot Jupiter (HJ) systems have been observed to have their stellar spin axis misaligned with the planet's orbital angular momentum axis. The origin of this spin-orbit misalignment and the formation mechanism of HJs remain poorly understood. A number of recent works have suggested that gravitational interactions between host stars, protoplanetary disks, and inclined binary companions may tilt the stellar spin axis with respect to the disk's angular angular momentum axis, producing planetary systems with misaligned orbits. These previous works considered idealized disk evolution models and neglected the gravitational influence of newly formed planets. In this paper, we explore how disk photoevaporation and planet formation and migration affect the inclination evolution of planet-star-disk-binary systems. We take into account planet-disk interactions and the gravitational spin-orbit coupling between the host star and the planet. We find that the rapid depletion of the inner disk via photoevaporation reduces the excitation of stellar obliquities. Depending on the formation and migration history of HJs, the spin-orbit coupling between the star and the planet may reduces and even completely suppress the excitation of stellar obliquities. Our work constrains the formation/migration history of HJs. On the other hand, planetary systems with "cold" Jupiters or close-in super-earths may experience excitation of stellar obliquities in the presence of distant inclined companions.

Basic properties of a stationary accretion disk surrounding a black hole

International Nuclear Information System (INIS)

Hoshi, Reiun

1977-01-01

The structure of a stationary accretion disk surrounding a black hole is studied by means of newly developed basic equations. The basic equations are derived under the assumption that the vertical distribution of disk matter is given by a polytrope. For a Keplerian accretion disk, basic equations reduce to a differential equation of the first order. We have found that solutions of an optically thick accretion disk converge to a limiting value, irrespective of the outer boundary condition. This gives the happy consequence that the inner structure of an optically thick accretion disk is determined irrespective of the outer boundary condition. On the contrary, an optically thin accretion disk shows bimodal behavior, that is, two physically distinct states exist depending on the outer boundary condition imposed at the outer edge of the accretion disk. (auth.)

Perturbation of a Schwarzschild Black Hole Due to a Rotating Thin Disk

Energy Technology Data Exchange (ETDEWEB)

Čížek, P.; Semerák, O., E-mail: oldrich.semerak@mff.cuni.cz [Institute of Theoretical Physics, Faculty of Mathematics and Physics, Charles University, Prague (Czech Republic)

2017-09-01

Will, in 1974, treated the perturbation of a Schwarzschild black hole due to a slowly rotating, light, concentric thin ring by solving the perturbation equations in terms of a multipole expansion of the mass-and-rotation perturbation series. In the Schwarzschild background, his approach can be generalized to perturbation by a thin disk (which is more relevant astrophysically), but, due to rather bad convergence properties, the resulting expansions are not suitable for specific (numerical) computations. However, we show that Green’s functions, represented by Will’s result, can be expressed in closed form (without multipole expansion), which is more useful. In particular, they can be integrated out over the source (a thin disk in our case) to yield good converging series both for the gravitational potential and for the dragging angular velocity. The procedure is demonstrated, in the first perturbation order, on the simplest case of a constant-density disk, including the physical interpretation of the results in terms of a one-component perfect fluid or a two-component dust in a circular orbit about the central black hole. Free parameters are chosen in such a way that the resulting black hole has zero angular momentum but non-zero angular velocity, as it is just carried along by the dragging effect of the disk.

The superradiant instability regime of the spinning Kerr black hole

Science.gov (United States)

Hod, Shahar

2016-07-01

Spinning Kerr black holes are known to be superradiantly unstable to massive scalar perturbations. We here prove that the instability regime of the composed Kerr-black-hole-massive-scalar-field system is bounded from above by the dimensionless inequality Mμ r+ is the dimensionless ratio between the horizon radii of the black hole. It is further shown that this analytically derived upper bound on the superradiant instability regime of the spinning Kerr black hole agrees with recent numerical computations of the instability resonance spectrum.

Particle accelerators inside spinning black holes.

Science.gov (United States)

Lake, Kayll

2010-05-28

On the basis of the Kerr metric as a model for a spinning black hole accreting test particles from rest at infinity, I show that the center-of-mass energy for a pair of colliding particles is generically divergent at the inner horizon. This shows not only that classical black holes are internally unstable, but also that Planck-scale physics is a characteristic feature within black holes at scales much larger that the Planck length. The novel feature of the divergence discussed here is that the phenomenon is present only for black holes with rotation, and in this sense it is distinct from the well-known Cauchy horizon instability.

Simulations of nearly extremal binary black holes

Science.gov (United States)

Giesler, Matthew; Scheel, Mark; Hemberger, Daniel; Lovelace, Geoffrey; Kuper, Kevin; Boyle, Michael; Szilagyi, Bela; Kidder, Lawrence; SXS Collaboration

2015-04-01

Astrophysical black holes could have nearly extremal spins; therefore, nearly extremal black holes could be among the binaries that current and future gravitational-wave observatories will detect. Predicting the gravitational waves emitted by merging black holes requires numerical-relativity simulations, but these simulations are especially challenging when one or both holes have mass m and spin S exceeding the Bowen-York limit of S /m2 = 0 . 93 . Using improved methods we simulate an unequal-mass, precessing binary black hole coalescence, where the larger black hole has S /m2 = 0 . 99 . We also use these methods to simulate a nearly extremal non-precessing binary black hole coalescence, where both black holes have S /m2 = 0 . 994 , nearly reaching the Novikov-Thorne upper bound for holes spun up by thin accretion disks. We demonstrate numerical convergence and estimate the numerical errors of the waveforms; we compare numerical waveforms from our simulations with post-Newtonian and effective-one-body waveforms; and we compare the evolution of the black-hole masses and spins with analytic predictions.

Truncation of the Inner Accretion Disk Around a Black Hole at Low Luminosity

Science.gov (United States)

Tomsick, John A.; Yamoka, Kazutaka; Corbel, Stephane; Kaaret, Philip; Kalemci, Emrah; Migliari, Simone

2011-01-01

Most black hole binaries show large changes in X-ray luminosity caused primarily by variations in mass accretion rate. An important question for understanding black hole accretion and jet production is whether the inner edge of the accretion disk recedes at low accretion rate. Measurements of the location of the inner edge (R(sub in)) can be made using iron emission lines that arise due to fluorescence of iron in the disk, and these indicate that R(sub in) is very close to the black hole at high and moderate luminosities (greater than or equal to 1% of the Eddington luminosity, L(sub Edd). Here, we report on X-ray observations of the black hole GX 339-4 in the hard state by Suzaku and the Rossi X-ray Timing Explorer that extend iron line studies to 0.14% L(sub Edd) and show that R(sub in) increases by a factor of greater than 27 over the value found when GX 339-4 was bright. The exact value of R(sub in) depends on the inclination of the inner disk (i), and we derive 90% confidence limits of R(sub in) greater than 35 R(sub g) at i = 0 degrees and R(sub in) greater than 175 R(sub g) at i = 30 degrees. This provides direct evidence that the inner portion of the disk is not present at low luminosity, allowing for the possibility that the inner disk is replaced by advection- or magnetically dominated accretion flows.

The Dynamics of Truncated Black Hole Accretion Disks. I. Viscous Hydrodynamic Case

Energy Technology Data Exchange (ETDEWEB)

Hogg, J. Drew; Reynolds, Christopher S. [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States)

2017-07-10

Truncated accretion disks are commonly invoked to explain the spectro-temporal variability in accreting black holes in both small systems, i.e., state transitions in galactic black hole binaries (GBHBs), and large systems, i.e., low-luminosity active galactic nuclei (LLAGNs). In the canonical truncated disk model of moderately low accretion rate systems, gas in the inner region of the accretion disk occupies a hot, radiatively inefficient phase, which leads to a geometrically thick disk, while the gas in the outer region occupies a cooler, radiatively efficient phase that resides in the standard geometrically thin disk. Observationally, there is strong empirical evidence to support this phenomenological model, but a detailed understanding of the dynamics of truncated disks is lacking. We present a well-resolved viscous, hydrodynamic simulation that uses an ad hoc cooling prescription to drive a thermal instability and, hence, produce the first sustained truncated accretion disk. With this simulation, we perform a study of the dynamics, angular momentum transport, and energetics of a truncated disk. We find that the time variability introduced by the quasi-periodic transition of gas from efficient cooling to inefficient cooling impacts the evolution of the simulated disk. A consequence of the thermal instability is that an outflow is launched from the hot/cold gas interface, which drives large, sub-Keplerian convective cells into the disk atmosphere. The convective cells introduce a viscous θ − ϕ stress that is less than the generic r − ϕ viscous stress component, but greatly influences the evolution of the disk. In the truncated disk, we find that the bulk of the accreted gas is in the hot phase.

Structure and stability of accretion-disk around a black-hole

Energy Technology Data Exchange (ETDEWEB)

Shibazaki, N; Hoshi, R [Rikkyo Univ., Tokyo (Japan). Dept. of Physics

1975-09-01

Structure and stability of a stationary thin-disk formed around a black-hole are studied using the conventional formula for the viscous stress. The disk is classified into an optically thick case, an optically thin case and an intermediate case in which the comptonization plays an important role. Thermal and secular stabilities are examined in each of the above three cases. High temperatures in excess of 10sup(9 0)K are expected in the optically thin case and in the comptonization dominant case. However, it is shown that in these cases the disk is unstable for the thermal perturbation.

The Growth of Central Black Hole and the Ionization Instability of Quasar Disk

Science.gov (United States)

Lu, Ye; Cheng, K. S.; Zhang, S. N.

2003-01-01

A possible accretion model associated with the ionization instability of quasar disks is proposed to address the growth of the central black hole harbored in the host galaxy. The evolution of quasars in cosmic time is assumed to change from a highly active state to a quiescent state triggered by the S-shaped ionization instability of the quasar accretion disk. For a given external mass transfer rate supplied by the quasar host galaxy, ionization instability can modify accretion rate in the disk and separates the accretion flows of the disk into three different phases, like a S-shape. We suggest that the bright quasars observed today are those quasars with disks in the upper branch of S-shaped instability, and the faint or 'dormant' quasars are simply the system in the lower branch. The middle branch is the transition state which is unstable. We assume the quasar disk evolves according to the advection-dominated inflow-outflow solutions (ADIOS) configuration in the stable lower branch of S-shaped instability, and Eddington accretion rate is used to constrain the accretion rate in each phase. The mass ratio between black hole and its host galactic bulge is a nature consequence of ADIOS. Our model also demonstrates that a seed black hole (BH) similar to those found in spiral galaxies today is needed to produce a BH with a final mass 2 x 10(exp 8) solar mases.

Spinning test particles in the field of a black hole

Energy Technology Data Exchange (ETDEWEB)

Tod, K P; de Felice, F [Padua Univ. (Italy); Calvani, M [Padua Univ. (Italy). Istituto di Astronomia

1976-08-11

It is studied the motion of spinning test bodies in the gravitational field of a rotating black hole, confining the examination of the pole-dipole approximation and of the special case of motion in the equatorial plane with the spin vector perpendicular to it. The study also provides the locus of the turning points for the equatorial orbits and also the exact limits of validity of the pole-dipole approximation for any given set of particle parameters. The innermost stable circular orbits are studied in details, and it is found that opposite spinning accreting particles are separated by the gravitational field of the black hole and that the fraction of energy ''at infinity'' which can be extracted when the particle spin is opposite to that of the black hole can be as high as 100%.

Measuring the spin of black holes in binary systems using gravitational waves.

Science.gov (United States)

Vitale, Salvatore; Lynch, Ryan; Veitch, John; Raymond, Vivien; Sturani, Riccardo

2014-06-27

Compact binary coalescences are the most promising sources of gravitational waves (GWs) for ground-based detectors. Binary systems containing one or two spinning black holes are particularly interesting due to spin-orbit (and eventual spin-spin) interactions and the opportunity of measuring spins directly through GW observations. In this Letter, we analyze simulated signals emitted by spinning binaries with several values of masses, spins, orientations, and signal-to-noise ratios, as detected by an advanced LIGO-Virgo network. We find that for moderate or high signal-to-noise ratio the spin magnitudes can be estimated with errors of a few percent (5%-30%) for neutron star-black hole (black hole-black hole) systems. Spins' tilt angle can be estimated with errors of 0.04 rad in the best cases, but typical values will be above 0.1 rad. Errors will be larger for signals barely above the threshold for detection. The difference in the azimuth angles of the spins, which may be used to check if spins are locked into resonant configurations, cannot be constrained. We observe that the best performances are obtained when the line of sight is perpendicular to the system's total angular momentum and that a sudden change of behavior occurs when a system is observed from angles such that the plane of the orbit can be seen both from above and below during the time the signal is in band. This study suggests that direct measurement of black hole spin by means of GWs can be as precise as what can be obtained from x-ray binaries.

An Extreme X-ray Disk Wind in the Black Hole Candidate IGR J17091-3624

Science.gov (United States)

King, A. L.; Miller, J. M.; Raymond, J.; Fabian, A. C.; Reynolds, C. S.; Kallman, T. R.; Maitra, D.; Cackett, E. M.; Rupen, M. P.

2012-01-01

Chandra spectroscopy of transient stellar-mass black holes in outburst has clearly revealed accretion disk winds in soft, disk-dominated states, in apparent anti-correlation with relativistic jets in low/hard states. These disk winds are observed to be highly ionized. dense. and to have typical velocities of approx 1000 km/s or less projected along our line of sight. Here. we present an analysis of two Chandra High Energy Transmission Grating spectra of the Galactic black hole candidate IGR J17091-3624 and contemporaneous EVLA radio observations. obtained in 2011. The second Chandra observation reveals an absorption line at 6.91+/-0.01 keV; associating this line with He-like Fe XXV requires a blue-shift of 9300(+500/-400) km/ s (0.03c. or the escape velocity at 1000 R(sub schw)). This projected outflow velocity is an order of magnitude higher than has previously been observed in stellar-mass black holes, and is broadly consistent with some of the fastest winds detected in active galactic nuclei. A potential feature at 7.32 keV, if due to Fe XXVI, would imply a velocity of approx 14600 km/s (0.05c), but this putative feature is marginal. Photoionization modeling suggests that the accretion disk wind in IGR J17091-3624 may originate within 43,300 Schwarzschild radii of the black hole, and may be expelling more gas than accretes. The contemporaneous EVLA observations strongly indicate that jet activity was indeed quenched at the time of our Chandra observations. We discuss the results in the context of disk winds, jets, and basic accretion disk physics in accreting black hole systems

Matched filtering of numerical relativity templates of spinning binary black holes

International Nuclear Information System (INIS)

Vaishnav, Birjoo; Hinder, Ian; Herrmann, Frank; Shoemaker, Deirdre

2007-01-01

Tremendous progress has been made towards the solution of the binary-black-hole problem in numerical relativity. The waveforms produced by numerical relativity will play a role in gravitational wave detection as either test beds for analytic template banks or as template banks themselves. As the parameter space explored by numerical relativity expands, the importance of quantifying the effect that each parameter has on first the detection of gravitational waves and then the parameter estimation of their sources increases. In light of this, we present a study of equal-mass, spinning binary-black-hole evolutions through matched filtering techniques commonly used in data analysis. We study how the match between two numerical waveforms varies with numerical resolution, initial angular momentum of the black holes, and the inclination angle between the source and the detector. This study is limited by the fact that the spinning black-hole binaries are oriented axially and the waveforms only contain approximately two and a half orbits before merger. We find that for detection purposes, spinning black holes require the inclusion of the higher harmonics in addition to the dominant mode, a condition that becomes more important as the black-hole spins increase. In addition, we conduct a preliminary investigation of how well a template of fixed spin and inclination angle can detect target templates of arbitrary but nonprecessing spin and inclination for the axial case considered here

Estimation of Nonconservative Aerodynamic Pressure Leading to Flutter of Spinning Disks

DEFF Research Database (Denmark)

Hansen, Morten Hartvig; Raman, A; Mote Jr., C.D.

2001-01-01

theories described herein. It is shown analytically and experimentally that the few parameters of this model may be extracted from frequency response functions of the spinning disk. Parameters for a steel disk in air (with a near vacuum experiment as reference) are estimated at increasing rotation speeds...

Regulation of black-hole accretion by a disk wind during a violent outburst of V404 Cygni.

Science.gov (United States)

Muñoz-Darias, T; Casares, J; Mata Sánchez, D; Fender, R P; Armas Padilla, M; Linares, M; Ponti, G; Charles, P A; Mooley, K P; Rodriguez, J

2016-06-02

Accretion of matter onto black holes is universally associated with strong radiative feedback and powerful outflows. In particular, black-hole transients have outflows whose properties are strongly coupled to those of the accretion flow. This includes X-ray winds of ionized material, expelled from the accretion disk encircling the black hole, and collimated radio jets. Very recently, a distinct optical variability pattern has been reported in the transient stellar-mass black hole V404 Cygni, and interpreted as disrupted mass flow into the inner regions of its large accretion disk. Here we report observations of a sustained outer accretion disk wind in V404 Cyg, which is unlike any seen hitherto. We find that the outflowing wind is neutral, has a large covering factor, expands at one per cent of the speed of light and triggers a nebular phase once accretion drops sharply and the ejecta become optically thin. The large expelled mass (>10(-8) solar masses) indicates that the outburst was prematurely ended when a sizeable fraction of the outer disk was depleted by the wind, detaching the inner regions from the rest of the disk. The luminous, but brief, accretion phases shown by transients with large accretion disks imply that this outflow is probably a fundamental ingredient in regulating mass accretion onto black holes.

Spin relaxation in InGaN quantum disks in GaN nanowires

KAUST Repository

Banerjee, Animesh; Dog,; Heo, Junseok; Manchon, Aurelien; Guo, Wei; Bhattacharya, Pallab K.

2011-01-01

The spin relaxation time of photoinduced conduction electrons has been measured in InGaN quantum disks in GaN nanowires as a function of temperature and In composition in the disks. The relaxation times are of the order of ∼100 ps at 300 K and are weakly dependent on temperature. Theoretical considerations show that the Elliott-Yafet scattering mechanism is essentially absent in these materials and the results are interpreted in terms of the D'yakonov-Perel' relaxation mechanism in the presence of Rashba spin-orbit coupling of the wurtzite structure. The calculated spin relaxation times are in good agreement with the measured values. © 2011 American Chemical Society.

Spin relaxation in InGaN quantum disks in GaN nanowires

KAUST Repository

Banerjee, Animesh

2011-12-14

The spin relaxation time of photoinduced conduction electrons has been measured in InGaN quantum disks in GaN nanowires as a function of temperature and In composition in the disks. The relaxation times are of the order of ∼100 ps at 300 K and are weakly dependent on temperature. Theoretical considerations show that the Elliott-Yafet scattering mechanism is essentially absent in these materials and the results are interpreted in terms of the D\\'yakonov-Perel\\' relaxation mechanism in the presence of Rashba spin-orbit coupling of the wurtzite structure. The calculated spin relaxation times are in good agreement with the measured values. © 2011 American Chemical Society.

Preliminary Investigations of Eddy Current Effects on a Spinning Disk

International Nuclear Information System (INIS)

Piggott, W T; Walston, S; Mayhall, D

2006-01-01

The design of the positron source target for the International Linear Collider (ILC) envisions a Ti6Al4V wheel rotating in a large magnetic field (5-10 Tesla) being impacted by a photon beam to produce positrons. One of the many challenges for this system is determining how large a motor will be needed to spin the shaft. The wheel spinning in the magnetic field induces an eddy current in the wheel, which retards the spinning motion of the wheel. Earlier calculations by Mayhall [1] have shown that those eddy forces could be quite large, and resulted in the preliminary design being moved from a solid disk to a rim and spoke design, as shown in Figure 1. A series of experiments with a spinning metal disk were run at the Stanford Linear Accelerator Center (SLAC) to provide experimental validation of the Maxwell 3D simulations. This report will give a brief outline of the experimental setup and results. In addition, earlier work by Smythe [2] will be used to compare with the experimental results

Disk accretion onto a black hole at subcritical luminosity

International Nuclear Information System (INIS)

Bisnovatyi-Kogan, G.S.; Blinnikov, S.I.

1977-01-01

The influence of radiation pressure on the structure of an accretion disk is considered when the total luminosity L approaches the Eddington limit Lsub(c). The motion of particles in the disk radiation field and gravitational field of a nonrotating black hole is investigated. It is shown that the disk accretion is destroyed when L approximately equal to (0.6 / 1.0) Lsub(c). Matter outflow from the central parts of the disk to infinity then sets in. We conclude that the luminosity cannot significantly exceed the Eddington limit. We show that for L > approximately 0.1 Lsub(c) the plasma in the upper layers of the central region of the disk is heated up to temperatures T approximately 10 9 K and the disk becomes thicker as compared with the standard theory. It is shown that the radiative force can generate magnetic fields B approximately 100 G. We find that convection is the main energy transfer mechanism along z-coordinate in the central parts of the disk. The convection generates an acoustic flux which dissipates in the upper, optically thin layers of the disk and heats them. The comptonization of soft photons going from layers to the hot upper layers and variable accretion rate may explain the spectrum and variations of X-ray emission of the CygX-1. (orig.) [de

A SPATIALLY RESOLVED INNER HOLE IN THE DISK AROUND GM AURIGAE

International Nuclear Information System (INIS)

Hughes, A. Meredith; Andrews, Sean M.; Wilner, David J.; Qi Chunhua; Espaillat, Catherine; Calvet, Nuria; D'Alessio, Paola; Williams, Jonathan P.; Hogerheijde, Michiel R.

2009-01-01

We present 0.''3 resolution observations of the disk around GM Aurigae with the Submillimeter Array (SMA) at a wavelength of 860 μm and with the Plateau de Bure Interferometer at a wavelength of 1.3 mm. These observations probe the distribution of disk material on spatial scales commensurate with the size of the inner hole predicted by models of the spectral energy distribution (SED). The data clearly indicate a sharp decrease in millimeter optical depth at the disk center, consistent with a deficit of material at distances less than ∼20 AU from the star. We refine the accretion disk model of Calvet et al. based on the unresolved SED and demonstrate that it reproduces well the spatially resolved millimeter continuum data at both available wavelengths. We also present complementary SMA observations of CO J = 3-2 and J = 2-1 emission from the disk at 2'' resolution. The observed CO morphology is consistent with the continuum model prediction, with two significant deviations: (1) the emission displays a larger CO J = 3-2/J = 2-1 line ratio than predicted, which may indicate additional heating of gas in the upper disk layers; and (2) the position angle of the kinematic rotation pattern differs by 11 deg. ± 2 deg. from that measured at smaller scales from the dust continuum, which may indicate the presence of a warp. We note that photoevaporation, grain growth, and binarity are unlikely mechanisms for inducing the observed sharp decrease in opacity or surface density at the disk center. The inner hole plausibly results from the dynamical influence of a planet on the disk material. Warping induced by a planet could also potentially explain the difference in position angle between the continuum and CO data sets.

Consequences of Spin-Orbit Coupling at the Single Hole Level: Spin-Flip Tunneling and the Anisotropic g Factor.

Science.gov (United States)

Bogan, A; Studenikin, S A; Korkusinski, M; Aers, G C; Gaudreau, L; Zawadzki, P; Sachrajda, A S; Tracy, L A; Reno, J L; Hargett, T W

2017-04-21

Hole transport experiments were performed on a gated double quantum dot device defined in a p-GaAs/AlGaAs heterostructure with a single hole occupancy in each dot. The charging diagram of the device was mapped out using charge detection confirming that the single hole limit is reached. In that limit, a detailed study of the two-hole spin system was performed using high bias magnetotransport spectroscopy. In contrast to electron systems, the hole spin was found not to be conserved during interdot resonant tunneling. This allows one to fully map out the two-hole energy spectrum as a function of the magnitude and the direction of the external magnetic field. The heavy-hole g factor was extracted and shown to be strongly anisotropic, with a value of 1.45 for a perpendicular field and close to zero for an in-plane field as required for hybridizing schemes between spin and photonic quantum platforms.

Large-scale dynamo of accretion disks around supermassive nonrotating black holes

Directory of Open Access Journals (Sweden)

Poplavsky A.L.

2006-01-01

Full Text Available In this paper one presents an analytical model of accretion disk magnetosphere dynamics around supermassive nonrotating black holes in the centers of active galactic nuclei. Based on general relativistic equations of magneto hydrodynamics, the nonstationary solutions for time-dependent dynamo action in the accretion disks, spatial and temporal distribution of magnetic field are found. It is shown that there are two distinct stages of dynamo process: the transient and the steady-state regimes, the induction of magnetic field at t > 6:6665 x 1011GM/c3 s becomes stationary, magnetic field is located near the innermost stable circular orbit, and its value rises up to ~ 105 G. Applications of such systems with nonrotating black holes in real active galactic nuclei are discussed.

EARTH, MOON, SUN, AND CV ACCRETION DISKS

International Nuclear Information System (INIS)

Montgomery, M. M.

2009-01-01

Net tidal torque by the secondary on a misaligned accretion disk, like the net tidal torque by the Moon and the Sun on the equatorial bulge of the spinning and tilted Earth, is suggested by others to be a source to retrograde precession in non-magnetic, accreting cataclysmic variable (CV) dwarf novae (DN) systems that show negative superhumps in their light curves. We investigate this idea in this work. We generate a generic theoretical expression for retrograde precession in spinning disks that are misaligned with the orbital plane. Our generic theoretical expression matches that which describes the retrograde precession of Earths' equinoxes. By making appropriate assumptions, we reduce our generic theoretical expression to those generated by others, or to those used by others, to describe retrograde precession in protostellar, protoplanetary, X-ray binary, non-magnetic CV DN, quasar, and black hole systems. We find that spinning, tilted CV DN systems cannot be described by a precessing ring or by a precessing rigid disk. We find that differential rotation and effects on the disk by the accretion stream must be addressed. Our analysis indicates that the best description of a retrogradely precessing spinning, tilted, CV DN accretion disk is a differentially rotating, tilted disk with an attached rotating, tilted ring located near the innermost disk annuli. In agreement with the observations and numerical simulations by others, we find that our numerically simulated CV DN accretion disks retrogradely precess as a unit. Our final, reduced expression for retrograde precession agrees well with our numerical simulation results and with selective observational systems that seem to have main-sequence secondaries. Our results suggest that a major source to retrograde precession is tidal torques like that by the Moon and the Sun on the Earth. In addition, these tidal torques should be common to a variety of systems where one member is spinning and tilted, regardless if

Anisotropic Pauli Spin Blockade of Holes in a GaAs Double Quantum Dot

Science.gov (United States)

Wang, Qingwen; Klochan, Oleh; Hung, Jo-Tzu; Culcer, Dimitrie; Farrer, Ian; Ritchie, David; Hamilton, Alex

Electrically defined semiconductor quantum dots are appealing systems for spin manipulation and quantum information processing. Thanks to the weak hyperfine interaction and the strong spin-orbit interaction, heavy-holes in GaAs are promising candidates for all-electrical spin manipulation. However, making stable quantum dots in GaAs has only become possible recently, mainly because of difficulties in device fabrication and device stability. Here we present electrical transport measurements of heavy-holes in a lateral double quantum dot based on a GaAs /AlxGa1 - x As heterostructure. We observe clear Pauli spin blockade and show that the lifting of the spin blockade by an external magnetic field is extremely anisotropic. Numerical calculations of heavy-hole transport through a double quantum dot in the presence of strong spin-orbit interaction demonstrate quantitative agreement with experimental results, which indicates that the observed anisotropy can be explained by the anisotropic hole g-factor and the surface Dresselhaus spin-orbit coupling.

Superresolution upgrade for confocal spinning disk systems using image scanning microscopy (Conference Presentation)

Science.gov (United States)

Isbaner, Sebastian; Hähnel, Dirk; Gregor, Ingo; Enderlein, Jörg

2017-02-01

Confocal Spinning Disk Systems are widely used for 3D cell imaging because they offer the advantage of optical sectioning at high framerates and are easy to use. However, as in confocal microscopy, the imaging resolution is diffraction limited, which can be theoretically improved by a factor of 2 using the principle of Image Scanning Microscopy (ISM) [1]. ISM with a Confocal Spinning Disk setup (CSDISM) has been shown to improve contrast as well as lateral resolution (FWHM) from 201 +/- 20 nm to 130 +/- 10 nm at 488 nm excitation. A minimum total acquisition time of one second per ISM image makes this method highly suitable for 3D live cell imaging [2]. Here, we present a multicolor implementation of CSDISM for the popular Micro-Manager Open Source Microscopy platform. Since changes in the optical path are not necessary, this will allow any researcher to easily upgrade their standard Confocal Spinning Disk system at remarkable low cost ( 5000 USD) with an ISM superresolution option. [1]. Müller, C.B. and Enderlein, J. Image Scanning Microscopy. Physical Review Letters 104, (2010). [2]. Schulz, O. et al. Resolution doubling in fluorescence microscopy with confocal spinning-disk image scanning microscopy. Proceedings of the National Academy of Sciences of the United States of America 110, 21000-5 (2013).

Supermassive black hole spin-flip during the inspiral

International Nuclear Information System (INIS)

Gergely, Laszlo A; Biermann, Peter L; Caramete, Laurentiu I

2010-01-01

During post-Newtonian evolution of a compact binary, a mass ratio ν different from 1 provides a second small parameter, which can lead to unexpected results. We present a statistics of supermassive black hole candidates, which enables us first to derive their mass distribution, and then to establish a logarithmically even probability in ν of the mass ratios at their encounter. In the mass ratio range ν in (1/30, 1/3) of supermassive black hole mergers representing 40% of all possible cases, the combined effect of spin-orbit precession and gravitational radiation leads to a spin-flip of the dominant spin during the inspiral phase of the merger. This provides a mechanism for explaining a large set of observations on X-shaped radio galaxies. In another 40% with mass ratios ν in (1/30, 1/1000) a spin-flip never occurs, while in the remaining 20% of mergers with mass ratios ν in (1/3, 1) it may occur during the plunge. We analyze the magnitude of the spin-flip angle occurring during the inspiral as a function of the mass ratio and original relative orientation of the spin and orbital angular momentum. We also derive a formula for the final spin at the end of the inspiral in this mass ratio range.

Macrospicule Jets in On-Disk Coronal Holes

Science.gov (United States)

Adams, M. L.; Sterling, A. C.; Moore, R. L.

2014-01-01

We examine the magnetic structure and dynamics of multiple jets found in coronal holes close to or on disk center. All data are from the Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager (HMI) of the Solar Dynamics Observatory (SDO). We report on observations of six jets in an equatorial coronal hole spanning 2011 February 27 and 28. We show the evolution of these jets in AIA 193 A, examine the magnetic field configuration, and postulate the probable trigger mechanism of these events. We recently reported on another jet in the same coronal hole on 2011 February 27, approximately 13:04 Universal Time (Adams et al 2014, Astrophysical Journal, 783: 11); this jet is a previously-unrecognized variety of blowout jet. In this variety, the reconnection bright point is not made by interchange reconnection of initially-closed erupting field in the base of the jet with ambient open field. Instead, there is a miniature filament-eruption flare arcade made by internal reconnection of the legs of the erupting field.

Hole dynamics and spin currents after ionization in strong circularly polarized laser fields

International Nuclear Information System (INIS)

Barth, Ingo; Smirnova, Olga

2014-01-01

We apply the time-dependent analytical R-matrix theory to develop a movie of hole motion in a Kr atom upon ionization by strong circularly polarized field. We find rich hole dynamics, ranging from rotation to swinging motion. The motion of the hole depends on the final energy and the spin of the photoelectron and can be controlled by the laser frequency and intensity. Crucially, hole rotation is a purely non-adiabatic effect, completely missing in the framework of quasistatic (adiabatic) tunneling theories. We explore the possibility to use hole rotation as a clock for measuring ionization time. Analyzing the relationship between the relative phases in different ionization channels we show that in the case of short-range electron-core interaction the hole is always initially aligned along the instantaneous direction of the laser field, signifying zero delays in ionization. Finally, we show that strong-field ionization in circular fields creates spin currents (i.e. different flow of spin-up and spin-down density in space) in the ions. This phenomenon is intimately related to the production of spin-polarized electrons in strong laser fields Barth and Smirnova (2013 Phys. Rev. A 88 013401). We demonstrate that rich spin dynamics of electrons and holes produced during strong field ionization can occur in typical experimental conditions and does not require relativistic intensities or strong magnetic fields. (paper)

Static spin-3/2 perturbations of two-black hole system

International Nuclear Information System (INIS)

Embacher, F.; Aichelburg, P.C.

1984-01-01

We construct the most general static regular, non-gauge spin-3/2 perturbations on the Majumdar-Papapetrou background for two black holes. The construction applies a limiting procedure by combining Killing spinors and spacetime perturbations. The supercharge associated with the spin-3/2 field is proportional to the difference of the mass parameters, implying that a system of two equal black holes has zero supercharge. (Author)

NuSTARand Swift observations of the very high state in GX 339-4: Weighing the black hole with X-rays

DEFF Research Database (Denmark)

Parker, M. L.; Tomsick, J. A.; Kennea, J. A.

2016-01-01

We present results from spectral fitting of the very high state of GX 339-4 with Nuclear Spectroscopic Telescope Array (NuSTAR) and Swift. We use relativistic reflection modeling to measure the spin of the black hole and inclination of the inner disk and find a spin of a = 0.95(-0.08)(+0.02) and ......We present results from spectral fitting of the very high state of GX 339-4 with Nuclear Spectroscopic Telescope Array (NuSTAR) and Swift. We use relativistic reflection modeling to measure the spin of the black hole and inclination of the inner disk and find a spin of a = 0...

The Accretion Disk Wind in the Black Hole GRS 1915 + 105

Science.gov (United States)

Miller, J.M.; Raymond, J.; Fabian, A. C.; Gallo, E.; Kaastra, J.; Kallman, T.; King, A. L.; Proga, D.; Reynolds, C. S.; Zoghbi, A.

2016-01-01

We report on a 120 kiloseconds Chandra/HETG spectrum of the black hole GRS 1915+105. The observation was made during an extended and bright soft state in 2015 June. An extremely rich disk wind absorption spectrum is detected, similar to that observed at lower sensitivity in 2007. The very high resolution of the third-order spectrum reveals four components to the disk wind in the Fe K band alone; the fastest has a blueshift of v = 0.03 c (velocity equals 0.03 the speed of light). Broadened reemission from the wind is also detected in the first-order spectrum, giving rise to clear accretion disk P Cygni profiles. Dynamical modeling of the re-emission spectrum gives wind launching radii of r approximately equal to 10 (sup 2-4) GM (Gravitational constant times Mass) divided by c (sup 2) (the speed of light squared). Wind density values of n approximately equal to 10 (sup 13-16) per cubic centimeter are then required by the ionization parameter formalism. The small launching radii, high density values, and inferred high mass outflow rates signal a role for magnetic driving. With simple, reasonable assumptions, the wind properties constrain the magnitude of the emergent magnetic field to be B approximately equal to 10 (sup 3-4) G (Gravitational constant) if the wind is driven via magnetohydrodynamic (MHD) pressure from within the disk and B approximately equal to 10 (sup 4-5) G (Gravitational constant) if the wind is driven by magnetocentrifugal acceleration. The MHD estimates are below upper limits predicted by the canonical alpha-disk model. We discuss these results in terms of fundamental disk physics and black hole accretion modes.

Spin Interaction under the Collision of Two Kerr-(Anti-de Sitter Black Holes

Directory of Open Access Journals (Sweden)

Bogeun Gwak

2017-12-01

Full Text Available We investigate herein the spin interaction during collisions between Kerr-(anti-de Sitter black holes. The spin interaction potential depends on the relative rotation directions of the black holes, and this potential can be released as gravitational radiation upon collision. The energy of the radiation depends on the cosmological constant and corresponds to the spin interaction potential in the limit that one of the black holes has negligibly small mass and angular momentum. We then determine the approximate overall behaviors of the upper bounds on the radiation using thermodynamics. The results indicate that the spin interaction can consistently contribute to the radiation. In addition, the radiation depends on the stability of the black hole produced by the collision.

Accuracy of binary black hole waveform models for aligned-spin binaries

Science.gov (United States)

Kumar, Prayush; Chu, Tony; Fong, Heather; Pfeiffer, Harald P.; Boyle, Michael; Hemberger, Daniel A.; Kidder, Lawrence E.; Scheel, Mark A.; Szilagyi, Bela

2016-05-01

Coalescing binary black holes are among the primary science targets for second generation ground-based gravitational wave detectors. Reliable gravitational waveform models are central to detection of such systems and subsequent parameter estimation. This paper performs a comprehensive analysis of the accuracy of recent waveform models for binary black holes with aligned spins, utilizing a new set of 84 high-accuracy numerical relativity simulations. Our analysis covers comparable mass binaries (mass-ratio 1 ≤q ≤3 ), and samples independently both black hole spins up to a dimensionless spin magnitude of 0.9 for equal-mass binaries and 0.85 for unequal mass binaries. Furthermore, we focus on the high-mass regime (total mass ≳50 M⊙ ). The two most recent waveform models considered (PhenomD and SEOBNRv2) both perform very well for signal detection, losing less than 0.5% of the recoverable signal-to-noise ratio ρ , except that SEOBNRv2's efficiency drops slightly for both black hole spins aligned at large magnitude. For parameter estimation, modeling inaccuracies of the SEOBNRv2 model are found to be smaller than systematic uncertainties for moderately strong GW events up to roughly ρ ≲15 . PhenomD's modeling errors are found to be smaller than SEOBNRv2's, and are generally irrelevant for ρ ≲20 . Both models' accuracy deteriorates with increased mass ratio, and when at least one black hole spin is large and aligned. The SEOBNRv2 model shows a pronounced disagreement with the numerical relativity simulation in the merger phase, for unequal masses and simultaneously both black hole spins very large and aligned. Two older waveform models (PhenomC and SEOBNRv1) are found to be distinctly less accurate than the more recent PhenomD and SEOBNRv2 models. Finally, we quantify the bias expected from all four waveform models during parameter estimation for several recovered binary parameters: chirp mass, mass ratio, and effective spin.

Thermodynamics of higher spin black holes in AdS3

Science.gov (United States)

de Boer, Jan; Jottar, Juan I.

2014-01-01

We discuss the thermodynamics of recently constructed three-dimensional higher spin black holes in SL( N, ) × SL( N, ) Chern-Simons theory with generalized asymptotically-anti-de Sitter boundary conditions. From a holographic perspective, these bulk theories are dual to two-dimensional CFTs with WN symmetry algebras, and the black hole solutions are dual to thermal states with higher spin chemical potentials and charges turned on. Because the notion of horizon area is not gauge-invariant in the higher spin theory, the traditional approaches to the computation of black hole entropy must be reconsidered. One possibility, explored in the recent literature, involves demanding the existence of a partition function in the CFT, and consistency with the first law of thermodynamics. This approach is not free from ambiguities, however, and in particular different definitions of energy result in different expressions for the entropy. In the present work we show that there are natural definitions of the thermodynamically conjugate variables that follow from careful examination of the variational principle, and moreover agree with those obtained via canonical methods. Building on this intuition, we derive general expressions for the higher spin black hole entropy and free energy which are written entirely in terms of the Chern-Simons connections, and are valid for both static and rotating solutions. We compare our results to other proposals in the literature, and provide a new and efficient way to determine the generalization of the Cardy formula to a situation with higher spin charges.

Ringed Accretion Disks: Evolution of Double Toroidal Configurations

Energy Technology Data Exchange (ETDEWEB)

Pugliese, D.; Stuchlík, Z., E-mail: daniela.pugliese@fpf.slu.cz, E-mail: zdenek.stuchlik@physics.cz [Institute of Physics and Research Centre of Theoretical Physics and Astrophysics, Faculty of Philosophy and Science, Silesian University in Opava, Bezručovo náměstí 13, CZ-74601 Opava (Czech Republic)

2017-04-01

We investigate ringed accretion disks composed of two tori (rings) orbiting on the equatorial plane of a central supermassive Kerr black hole. We discuss the emergence of the instability phases of each ring of the macro-configuration (ringed disk) according to the Paczynski violation of mechanical equilibrium. In the full general relativistic treatment, we consider the effects of the geometry of the Kerr spacetimes relevant to the characterization of the evolution of these configurations. The discussion of ring stability in different spacetimes enables us to identify particular classes of central Kerr attractors depending on their dimensionless spin. As a result of this analysis, we set constraints on the evolutionary schemes of the ringed disks relative to the torus morphology and on their rotation relative to the central black hole and to each other. The dynamics of the unstable phases of this system is significant for the high-energy phenomena related to accretion onto supermassive black holes in active galactic nuclei and the extremely energetic phenomena in quasars, which could be observed in their X-ray emission.

Thermodynamics of higher spin black holes in AdS3

International Nuclear Information System (INIS)

Boer, Jan de; Jottar, Juan I.

2014-01-01

We discuss the thermodynamics of recently constructed three-dimensional higher spin black holes in SL(N,ℝ)×SL(N,ℝ) Chern-Simons theory with generalized asymptotically-anti-de Sitter boundary conditions. From a holographic perspective, these bulk theories are dual to two-dimensional CFTs with W N symmetry algebras, and the black hole solutions are dual to thermal states with higher spin chemical potentials and charges turned on. Because the notion of horizon area is not gauge-invariant in the higher spin theory, the traditional approaches to the computation of black hole entropy must be reconsidered. One possibility, explored in the recent literature, involves demanding the existence of a partition function in the CFT, and consistency with the first law of thermodynamics. This approach is not free from ambiguities, however, and in particular different definitions of energy result in different expressions for the entropy. In the present work we show that there are natural definitions of the thermodynamically conjugate variables that follow from careful examination of the variational principle, and moreover agree with those obtained via canonical methods. Building on this intuition, we derive general expressions for the higher spin black hole entropy and free energy which are written entirely in terms of the Chern-Simons connections, and are valid for both static and rotating solutions. We compare our results to other proposals in the literature, and provide a new and efficient way to determine the generalization of the Cardy formula to a situation with higher spin charges

Hole spin coherence in a Ge/Si heterostructure nanowire

DEFF Research Database (Denmark)

Higginbotham, Andrew P; Larsen, Thorvald Wadum; Yao, Jun

2014-01-01

Relaxation and dephasing of hole spins are measured in a gate-defined Ge/Si nanowire double quantum dot using a fast pulsed-gate method and dispersive readout. An inhomogeneous dephasing time T2(*)≈ 0.18 μs exceeds corresponding measurements in III-V semiconductors by more than an order of magnit......Relaxation and dephasing of hole spins are measured in a gate-defined Ge/Si nanowire double quantum dot using a fast pulsed-gate method and dispersive readout. An inhomogeneous dephasing time T2(*)≈ 0.18 μs exceeds corresponding measurements in III-V semiconductors by more than an order...

Improved gravitational waveforms from spinning black hole binaries

International Nuclear Information System (INIS)

Porter, Edward K.; Sathyaprakash, B.S.

2005-01-01

The standard post-Newtonian approximation to gravitational waveforms, called T-approximants, from nonspinning black hole binaries are known not to be sufficiently accurate close to the last stable orbit of the system. A new approximation, called P-approximants, is believed to improve the accuracy of the waveforms rendering them applicable up to the last stable orbit. In this study we apply P-approximants to the case of a test particle in equatorial orbit around a Kerr black hole parameterized by a spin-parameter q that takes values between -1 and 1. In order to assess the performance of the two approximants we measure their effectualness (i.e., larger overlaps with the exact signal), and faithfulness (i.e., smaller biases while measuring the parameters of the signal) with the exact (numerical) waveforms. We find that in the case of prograde orbits, that is orbits whose angular momentum is in the same sense as the spin angular momentum of the black hole, T-approximant templates obtain an effectualness of ∼0.99 for spins q 0.99 for all spins up to q=0.95. The bias in the estimation of parameters is much lower in the case of P-approximants than T-approximants. We find that P-approximants are both effectual and faithful and should be more effective than T-approximants as a detection template family when q>0. For q<0 both T- and P-approximants perform equally well so that either of them could be used as a detection template family

Observables and Microcospic Entropy of Higher Spin Black Holes

NARCIS (Netherlands)

Compère, G.; Jottar, J.I.; Song, W.

2013-01-01

In the context of recently proposed holographic dualities between higher spin theories in AdS3 and (1 + 1)-dimensional CFTs with W symmetry algebras, we revisit the definition of higher spin black hole thermodynamics and the dictionary between bulk fields and dual CFT operators. We build a canonical

Spinning up black holes with super-critical accretion flows

Czech Academy of Sciences Publication Activity Database

Sądowski, A.; Bursa, Michal; Abramowicz, M. A.; Kluzniak, W.; Lasota, J.-P.; Moderski, R.; Safarzadeh, M.

2011-01-01

Roč. 532, August (2011), A41/1-A41/11 ISSN 0004-6361 Institutional research plan: CEZ:AV0Z10030501 Keywords : black hole physics * accretion * accretion disks Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 4.587, year: 2011

Observables and microscopic entropy of higher spin black holes

Science.gov (United States)

Compère, Geoffrey; Jottar, Juan I.; Song, Wei

2013-11-01

In the context of recently proposed holographic dualities between higher spin theories in AdS3 and (1 + 1)-dimensional CFTs with symmetry algebras, we revisit the definition of higher spin black hole thermodynamics and the dictionary between bulk fields and dual CFT operators. We build a canonical formalism based on three ingredients: a gauge-invariant definition of conserved charges and chemical potentials in the presence of higher spin black holes, a canonical definition of entropy in the bulk, and a bulk-to-boundary dictionary aligned with the asymptotic symmetry algebra. We show that our canonical formalism shares the same formal structure as the so-called holomorphic formalism, but differs in the definition of charges and chemical potentials and in the bulk-to-boundary dictionary. Most importantly, we show that it admits a consistent CFT interpretation. We discuss the spin-2 and spin-3 cases in detail and generalize our construction to theories based on the hs[ λ] algebra, and on the sl( N,[InlineMediaObject not available: see fulltext.]) algebra for any choice of sl(2 ,[InlineMediaObject not available: see fulltext.]) embedding.

AN ENERGETIC AGN OUTBURST POWERED BY A RAPIDLY SPINNING SUPERMASSIVE BLACK HOLE OR AN ACCRETING ULTRAMASSIVE BLACK HOLE

International Nuclear Information System (INIS)

McNamara, B. R.; Kazemzadeh, F.; Kirkpatrick, C. C.; Rafferty, D. A.; Birzan, L.; Nulsen, P. E. J.; Wise, M. W.

2009-01-01

Powering the 10 62 erg nuclear outburst in the MS0735.6+7421 cluster central galaxy by accretion with a 10% mass-to-energy conversion efficiency implies that its putative supermassive black hole (SMBH) grew by ∼6 x 10 8 M sun over the past 100 Myr. Guided by data at several wavelengths, we place upper limits on the amount of cold gas and star formation near the nucleus of 9 M sun and sun yr -1 , respectively. These limits imply that an implausibly large fraction of the preexisting cold gas in the inner several kpc must have been consumed by its SMBH at the rate of ∼3-5 M sun yr -1 during the past 100 Myr while leaving no trace of star formation. Such a high accretion rate would be difficult to maintain by stellar accretion or the Bondi mechanism, unless the black hole mass approaches 10 11 M sun . Furthermore, its feeble nuclear luminosities in the UV, I, and X-ray bands compared to its enormous mechanical power are inconsistent with rapid accretion onto a ∼5 x 10 9 M sun black hole. We suggest instead that the active galactic nucleus (AGN) outburst is powered by angular momentum released from a rapidly spinning black hole. The rotational energy and power available from a spinning black hole are consistent with the cavity and shock energetics inferred from X-ray observations. A maximally spinning 10 9 M sun black hole contains enough rotational energy, ∼10 62 erg, to quench a cooling flow over its lifetime and to contribute significantly to the excess entropy found in the hot atmospheres of groups and clusters. Two modes of AGN feedback may be quenching star formation in elliptical galaxies centered in cooling halos at late times. An accretion mode that operates in gas-rich systems, and a spin mode operating at modest accretion rates. The spin conjecture may be avoided in MS0735 by appealing to Bondi accretion onto a central black hole whose mass greatly exceeds 10 10 M sun . The host galaxy's unusually large 3.8 kpc stellar core radius (light deficit) may

Renormalized Stress-Energy Tensor of an Evaporating Spinning Black Hole.

Science.gov (United States)

Levi, Adam; Eilon, Ehud; Ori, Amos; van de Meent, Maarten

2017-04-07

We provide the first calculation of the renormalized stress-energy tensor (RSET) of a quantum field in Kerr spacetime (describing a stationary spinning black hole). More specifically, we employ a recently developed mode-sum regularization method to compute the RSET of a minimally coupled massless scalar field in the Unruh vacuum state, the quantum state corresponding to an evaporating black hole. The computation is done here for the case a=0.7M, using two different variants of the method: t splitting and φ splitting, yielding good agreement between the two (in the domain where both are applicable). We briefly discuss possible implications of the results for computing semiclassical corrections to certain quantities, and also for simulating dynamical evaporation of a spinning black hole.

Constraints on the evolution of black hole spin due to magnetohydrodynamic accretion

International Nuclear Information System (INIS)

Takahashi, Masaaki; Tomimatsu, Akira

2008-01-01

Stationary and axisymmetric ideal magnetohydrodynamic (MHD) accretion onto a black hole is studied analytically. The accreting plasma ejected from a plasma source with low velocity must be superfast magnetosonic before passing through the event horizon. We work out and apply a trans-fast magnetosonic solution without detailed analysis of the regularity conditions at the magnetosonic point, by introducing the bending angle β of the magnetic field line, which is the ratio of the toroidal and poloidal components of the magnetic field. To accrete onto a black hole, the trans-magnetosonic solution has some restrictions on β, which are related to the field-aligned parameters of the MHD flows. One of the restrictions gives the boundary condition at the event horizon for the inclination of a magnetic field line. We find that this inclination is related to the energy and angular momentum transport to the black hole. Then, we discuss the spin-up/down process of a rotating black hole by cold MHD inflows in a secular evolution time scale. There are two asymptotic states for the spin evolution. One is that the angular velocity of the black hole approaches to that of the magnetic field line, and the other is that the spin-up effect by the positive angular momentum influx and the spin-down effect by the energy influx (as the mass-energy influx) are canceled. We also show that the MHD inflows prevents the evolution to the maximally rotating black hole.

Measuring spin of black holes in the universe

Indian Academy of Sciences (India)

First page Back Continue Last page Overview Graphics. Measuring spin of black holes in the universe. Department of Physics Indian Institute of Science Bangalore. Notes: 74th Annual Meeting of Indian Academy of Science.

STRUCTURE AND EVOLUTION OF CIRCUMBINARY DISKS AROUND SUPERMASSIVE BLACK HOLE BINARIES

International Nuclear Information System (INIS)

Rafikov, Roman R.

2013-01-01

We explore properties of circumbinary disks around supermassive black hole (SMBH) binaries in centers of galaxies by reformulating standard viscous disk evolution in terms of the viscous angular momentum flux F J . If the binary stops gas inflow and opens a cavity in the disk, then the inner disk evolves toward a constant-F J (rather than a constant M-dot ) state. We compute disk properties in different physical regimes relevant for SMBH binaries, focusing on the gas-assisted evolution of systems starting at separations 10 –4 – 10 –2 pc, and find the following. (1) Mass pileup at the inner disk edge caused by the tidal barrier accelerates binary inspiral. (2) Binaries can be forced to merge even by a disk with a mass below that of the secondary. (3) Torque on the binary is set non-locally, at radii far larger than the binary semi-major axis; its magnitude does not reflect disk properties in the vicinity of the binary. (4) Binary inspiral exhibits hysteresis—it depends on the past evolution of the disk. (5) The Eddington limit can be important for circumbinary disks even if they accrete at sub-Eddington rates, but only at late stages of the inspiral. (6) Gas overflow across the orbit of the secondary can be important for low secondary mass, high- M-dot systems, but mainly during the inspiral phase dominated by the gravitational wave emission. (7) Circumbinary disks emit more power and have harder spectra than constant M-dot disks; their spectra are very sensitive to the amount of overflow across the secondary orbit

Hole-y Debris Disks, Batman! Where are the planets?

Science.gov (United States)

Bailey, V.; Meshkat, T.; Hinz, P.; Kenworthy, M.; Su, K. Y. L.

2014-03-01

Giant planets at wide separations are rare and direct imaging surveys are resource-intensive, so a cheaper marker for the presence of giant planets is desirable. One intriguing possibility is to use the effect of planets on their host stars' debris disks. Theoretical studies indicate giant planets can gravitationally carve sharp boundaries and gaps in their disks; this has been seen for HR 8799, β Pic, and tentatively for HD 95086 (Su et al. 2009, Lagrange et al. 2010, Moor et al. 2013). If more broadly demonstrated, this link could help guide target selection for next generation direct imaging surveys. Using Spitzer MIPS/IRS spectral energy distributions (SEDs), we identify several dozen systems with two-component and/or large inner cavity disks (aka Hole-y Debris Disks). With LBT/LBTI, VLT/NaCo, GeminiS/NICI, MMT/Clio and Magellan/Clio, we survey a subset these SEDselected targets (~20). In contrast to previous disk-selected planet surveys (e.g.: Janson et al. 2013, Wahhaj et al. 2013) we image primarily in the thermal IR (L'-band), where planet-to-star contrast is more favorable and background contaminants less numerous. Thus far, two of our survey targets host planet-mass companions, both of which were discovered in L'-band after they were unrecognized or undetectable in H-band. For each system in our sample set, we will investigate whether the known companions and/or companions below our detection threshold could be responsible for the disk architecture. Ultimately, we will increase our effective sample size by incorporating detection limits from surveys that have independently targeted some of our systems of interest. In this way we will refine the conditions under which disk SED-based target selection is likely to be useful and valid.

Higher spin black holes with soft hair

Energy Technology Data Exchange (ETDEWEB)

Grumiller, Daniel [Institute for Theoretical Physics, TU Wien,Wiedner Hauptstrasse 8-10/136, Vienna, A-1040 (Austria); Pérez, Alfredo [Centro de Estudios Científicos (CECs),Av. Arturo Prat 514, Valdivia (Chile); Prohazka, Stefan [Institute for Theoretical Physics, TU Wien,Wiedner Hauptstrasse 8-10/136, Vienna, A-1040 (Austria); Tempo, David; Troncoso, Ricardo [Centro de Estudios Científicos (CECs),Av. Arturo Prat 514, Valdivia (Chile)

2016-10-21

We construct a new set of boundary conditions for higher spin gravity, inspired by a recent “soft Heisenberg hair”-proposal for General Relativity on three-dimensional Anti-de Sitter space. The asymptotic symmetry algebra consists of a set of affine û(1) current algebras. Its associated canonical charges generate higher spin soft hair. We focus first on the spin-3 case and then extend some of our main results to spin-N, many of which resemble the spin-2 results: the generators of the asymptotic W{sub 3} algebra naturally emerge from composite operators of the û(1) charges through a twisted Sugawara construction; our boundary conditions ensure regularity of the Euclidean solutions space independently of the values of the charges; solutions, which we call “higher spin black flowers”, are stationary but not necessarily spherically symmetric. Finally, we derive the entropy of higher spin black flowers, and find that for the branch that is continuously connected to the BTZ black hole, it depends only on the affine purely gravitational zero modes. Using our map to W-algebra currents we recover well-known expressions for higher spin entropy. We also address higher spin black flowers in the metric formalism and achieve full consistency with previous results.

More Macrospicule Jets in On-Disk Coronal Holes

Science.gov (United States)

Adams, M. L.; Sterling, A. C.; Moore, R. L.

2015-01-01

We examine the magnetic structure and dynamics of multiple jets found in coronal holes close to or on disk center. All data are from the Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager (HMI) of the Solar Dynamics Observatory (SDO). We report on observations of about ten jets in an equatorial coronal hole spanning 2011 February 27 and 28. We show the evolution of these jets in AIA 193 A, examine the magnetic field configuration and flux changes in the jet area, and discuss the probable trigger mechanism of these events. We reported on another jet in this same coronal hole on 2011 February 27, (is) approximately 13:04 UT (Adams et al 2014, ApJ, 783: 11). That jet is a previously-unrecognized variety of blowout jet, in which the base-edge bright point is a miniature filament-eruption flare arcade made by internal reconnection of the legs of the erupting field. In contrast, in the presently-accepted 'standard' picture for blowout jets, the base-edge bright point is made by interchange reconnection of initially-closed erupting jet-base field with ambient open field. This poster presents further evidence of the production of the base-edge bright point in blowout jets by internal reconnection. Our observations suggest that most of the bigger and brighter EUV jets in coronal holes are blowout jets of the new-found variety.

CHAOTIC MOTION OF CHARGED PARTICLES IN AN ELECTROMAGNETIC FIELD SURROUNDING A ROTATING BLACK HOLE

International Nuclear Information System (INIS)

Takahashi, Masaaki; Koyama, Hiroko

2009-01-01

The observational data from some black hole candidates suggest the importance of electromagnetic fields in the vicinity of a black hole. Highly magnetized disk accretion may play an importance rule, and large-scale magnetic field may be formed above the disk surface. Then, we expect that the nature of the black hole spacetime would be revealed by magnetic phenomena near the black hole. We will start investigating the motion of a charged test particle which depends on the initial parameter setting in the black hole dipole magnetic field, which is a test field on the Kerr spacetime. Particularly, we study the spin effects of a rotating black hole on the motion of the charged test particle trapped in magnetic field lines. We make detailed analysis for the particle's trajectories by using the Poincare map method, and show the chaotic properties that depend on the black hole spin. We find that the dragging effects of the spacetime by a rotating black hole weaken the chaotic properties and generate regular trajectories for some sets of initial parameters, while the chaotic properties dominate on the trajectories for slowly rotating black hole cases. The dragging effects can generate the fourth adiabatic invariant on the particle motion approximately.

Dual jets from binary black holes.

Science.gov (United States)

Palenzuela, Carlos; Lehner, Luis; Liebling, Steven L

2010-08-20

The coalescence of supermassive black holes--a natural outcome when galaxies merge--should produce gravitational waves and would likely be associated with energetic electromagnetic events. We have studied the coalescence of such binary black holes within an external magnetic field produced by the expected circumbinary disk surrounding them. Solving the Einstein equations to describe black holes interacting with surrounding plasma, we present numerical evidence for possible jets driven by these systems. Extending the process described by Blandford and Znajek for a single, spinning black hole, the picture that emerges suggests that the electromagnetic field extracts energy from the orbiting black holes, which ultimately merge and settle into the standard Blandford-Znajek scenario. Emissions along these jets could potentially be observable at large distances.

Optical spin orientation of minority holes in a modulation-doped GaAs/(Ga,Al)As quantum well

Science.gov (United States)

Koudinov, A. V.; Dzhioev, R. I.; Korenev, V. L.; Sapega, V. F.; Kusrayev, Yu. G.

2016-04-01

The optical spin orientation effect in a GaAs/(Ga,Al)As quantum well containing a high-mobility two-dimensional electron gas was found to be due to spin-polarized minority carriers, the holes. The observed oscillations of both the intensity and polarization of the photoluminescence in a magnetic field are well described in a model whose main elements are resonant absorption of the exciting light by the Landau levels and mixing of the heavy- and light-hole subbands. After subtraction of these effects, the observed influence of magnetic fields on the spin polarization can be well interpreted by a standard approach of the optical orientation method. The spin relaxation of holes is controlled by the Dyakonov-Perel' mechanism. Deceleration of the spin relaxation by the magnetic field occurs through the Ivchenko mechanism—due to the cyclotron motion of holes. Mobility of holes was found to be two orders of magnitude smaller than that of electrons, being determined by the scattering of holes by the electron gas.

Assessing the Detectability of Gravitational Waves from Coalescing Binary Black Holes with Precessing Spin

Science.gov (United States)

Frederick, Sara; Privitera, Stephen; Weinstein, Alan J.; LIGO Scientific Collaboration

2015-01-01

The Advanced LIGO and Virgo gravitational wave detectors will come online within the year and are expected to outperform the strain sensitivity of initial LIGO/Virgo detectors by an order of magnitude and operate with greater bandwidth, possibly to frequencies as low as 10 Hz. Coalescing binary black holes (BBH) are anticipated to be among the most likely sources of gravitational radiation observable by the detectors. Searches for such systems benefit greatly from the use of accurate predictions for the gravitational wave signal to filter the data. The component black holes of these systems are predicted to have substantial spin, which greatly influences the gravitational waveforms from these sources; however, recent LIGO/Virgo searches have made use of banks of waveform models which neglect the effects of the component spins. The inclusion of spinning components is relatively simplified when the spins are taken to be aligned with the orbital angular momentum, though the difficult task of including precession (allowing for mis-aligned component spins) remains a goal of this work. We aim to assess the ability of the GSTLAL gravitational wave search pipeline using IMR aligned-spin template waveforms to recover signals from generically spinning black hole binaries injected into simulated Advanced LIGO and Virgo detector noise. If black holes are highly spinning as predicted, use of aligned-spin template banks in upcoming searches could increase the detection rate of these systems in Advanced LIGO and Virgo data, providing the opportunity for a deeper understanding of the sources.

Coherence properties of holes subject to a fluctuating spin chirality

International Nuclear Information System (INIS)

Wheatley, J.M.; Hong, T.M.

1991-01-01

The coherence properties of holes coupled to short-ranged chiral spin fluctuations with a characteristic chiral spin fluctuation time τ ch =ω ch -1 are investigated in two dimensions. At temperatures kT much-lt 4π 2 left-angle φ 2 right-angle -1 ℎω ch hole quasiparticles exist and propagate with a renormalized mass m * /m=1+left-angle φ 2 right-angle ℎ/16πma 0 2 ω ch . $langle phi sup 2 rangle--- is the amplitude of the local fictitious flux fluctuation and a 0 is a lattice cutoff. At temperatures kT much-gt 4π 2 left-angle φ 2 right-angle -1 ℎω ch an effective-mass approximation is invalid and we find that the hole diffuses according to a logarithmic diffusion law in the quasistatic chiral field. The unusual diffusion law is a consequence of the long-ranged nature of the gauge field. The result shows that the holes do not form a coherent quantum fluid in the quasistatic regime

Measuring Parameters of Massive Black Hole Binaries with Partially Aligned Spins

Science.gov (United States)

Lang, Ryan N.; Hughes, Scott A.; Cornish, Neil J.

2011-01-01

The future space-based gravitational wave detector LISA will be able to measure parameters of coalescing massive black hole binaries, often to extremely high accuracy. Previous work has demonstrated that the black hole spins can have a strong impact on the accuracy of parameter measurement. Relativistic spin-induced precession modulates the waveform in a manner which can break degeneracies between parameters, in principle significantly improving how well they are measured. Recent studies have indicated, however, that spin precession may be weak for an important subset of astrophysical binary black holes: those in which the spins are aligned due to interactions with gas. In this paper, we examine how well a binary's parameters can be measured when its spins are partially aligned and compare results using waveforms that include higher post-Newtonian harmonics to those that are truncated at leading quadrupole order. We find that the weakened precession can substantially degrade parameter estimation, particularly for the "extrinsic" parameters sky position and distance. Absent higher harmonics, LISA typically localizes the sky position of a nearly aligned binary about an order of magnitude less accurately than one for which the spin orientations are random. Our knowledge of a source's sky position will thus be worst for the gas-rich systems which are most likely to produce electromagnetic counterparts. Fortunately, higher harmonics of the waveform can make up for this degradation. By including harmonics beyond the quadrupole in our waveform model, we find that the accuracy with which most of the binary's parameters are measured can be substantially improved. In some cases, the improvement is such that they are measured almost as well as when the binary spins are randomly aligned.

Black-hole driven winds

International Nuclear Information System (INIS)

Punsly, B.M.

1988-01-01

This dissertation is a study of the physical mechanism that allows a large scale magnetic field to torque a rapidly rotating, supermassive black hole. This is an interesting problem as it has been conjectured that rapidly rotating black holes are the central engines that power the observed extragalactic double radio sources. Axisymmetric solutions of the curved space-time version of Maxwell's equations in the vacuum do not torque black holes. Plasma must be introduced for the hole to mechanically couple to the field. The dynamical aspect of rotating black holes that couples the magnetic field to the hole is the following. A rotating black hole forces the external geometry of space-time to rotate (the dragging of inertial frames). Inside of the stationary limit surface, the ergosphere, all physical particle trajectories must appear to rotate in the same direction as the black hole as viewed by the stationary observers at asymptotic infinity. In the text, it is demonstrated how plasma that is created on field lines that thread both the ergosphere and the equatorial plane will be pulled by gravity toward the equator. By the aforementioned properties of the ergosphere, the disk must rotate. Consequently, the disk acts like a unipolar generator. It drives a global current system that supports the toroidal magnetic field in an outgoing, magnetically dominated wind. This wind carries energy (mainly in the form of Poynting flux) and angular momentum towards infinity. The spin down of the black hole is the ultimate source of this energy and angular momentum flux

Moving mode shape function approach for spinning disk and asymmetric disc brake squeal

Science.gov (United States)

Kang, Jaeyoung

2018-06-01

The solution approach of an asymmetric spinning disk under stationary friction loads requires the mode shape function fixed in the disk in the assumed mode method when the equations of motion is described in the space-fixed frame. This model description will be termed the 'moving mode shape function approach' and it allows us to formulate the stationary contact load problem in both the axisymmetric and asymmetric disk cases. Numerical results show that the eigenvalues of the time-periodic axisymmetric disk system are time-invariant. When the axisymmetry of the disk is broken, the positive real parts of the eigenvalues highly vary with the rotation of the disk in the slow speeds in such application as disc brake squeal. By using the Floquet stability analysis, it is also shown that breaking the axisymmetry of the disc alters the stability boundaries of the system.

Electron-Hole Asymmetry of Spin Injection and Transport in Single-Layer Graphene

OpenAIRE

Han, Wei; Wang, W. H.; Pi, K.; McCreary, K. M.; Bao, W.; Li, Yan; Miao, F.; Lau, C. N.; Kawakami, R. K.

2009-01-01

Spin-dependent properties of single-layer graphene (SLG) have been studied by non-local spin valve measurements at room temperature. Gate voltage dependence shows that the non-local magnetoresistance (MR) is proportional to the conductivity of the SLG, which is the predicted behavior for transparent ferromagnetic/nonmagnetic contacts. While the electron and hole bands in SLG are symmetric, gate voltage and bias dependence of the non-local MR reveal an electron-hole asymmetry in which the non-...

Hole pairing induced by antiferromagnetic spin fluctuations

International Nuclear Information System (INIS)

Su, Z.B.; Yu Lu; Dong, J.M.; Tosatti, E.

1987-08-01

The effective interaction induced by antiferromagnetic spin fluctuations is considered in the random phase approximation in the context of the recently discovered high T c oxide superconductors. This effective attraction favours a triplet pairing of holes. The implications of such pairing mechanism are discussed in connection with the current experimental observations. (author). 30 refs, 2 figs

Note: Time-gated 3D single quantum dot tracking with simultaneous spinning disk imaging

International Nuclear Information System (INIS)

DeVore, M. S.; Stich, D. G.; Keller, A. M.; Phipps, M. E.; Hollingsworth, J. A.; Goodwin, P. M.; Werner, J. H.; Cleyrat, C.; Lidke, D. S.; Wilson, B. S.

2015-01-01

We describe recent upgrades to a 3D tracking microscope to include simultaneous Nipkow spinning disk imaging and time-gated single-particle tracking (SPT). Simultaneous 3D molecular tracking and spinning disk imaging enable the visualization of cellular structures and proteins around a given fluorescently labeled target molecule. The addition of photon time-gating to the SPT hardware improves signal to noise by discriminating against Raman scattering and short-lived fluorescence. In contrast to camera-based SPT, single-photon arrival times are recorded, enabling time-resolved spectroscopy (e.g., measurement of fluorescence lifetimes and photon correlations) to be performed during single molecule/particle tracking experiments

Note: Time-gated 3D single quantum dot tracking with simultaneous spinning disk imaging

Energy Technology Data Exchange (ETDEWEB)

DeVore, M. S.; Stich, D. G.; Keller, A. M.; Phipps, M. E.; Hollingsworth, J. A.; Goodwin, P. M.; Werner, J. H., E-mail: jwerner@lanl.gov [Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Mail Stop G755, Los Alamos, New Mexico 87545 (United States); Cleyrat, C.; Lidke, D. S.; Wilson, B. S. [Department of Pathology and Cancer Research and Treatment Center, University of New Mexico, Albuquerque, New Mexico 87131 (United States)

2015-12-15

We describe recent upgrades to a 3D tracking microscope to include simultaneous Nipkow spinning disk imaging and time-gated single-particle tracking (SPT). Simultaneous 3D molecular tracking and spinning disk imaging enable the visualization of cellular structures and proteins around a given fluorescently labeled target molecule. The addition of photon time-gating to the SPT hardware improves signal to noise by discriminating against Raman scattering and short-lived fluorescence. In contrast to camera-based SPT, single-photon arrival times are recorded, enabling time-resolved spectroscopy (e.g., measurement of fluorescence lifetimes and photon correlations) to be performed during single molecule/particle tracking experiments.

Post-Newtonian Dynamics in Dense Star Clusters: Highly Eccentric, Highly Spinning, and Repeated Binary Black Hole Mergers.

Science.gov (United States)

Rodriguez, Carl L; Amaro-Seoane, Pau; Chatterjee, Sourav; Rasio, Frederic A

2018-04-13

We present models of realistic globular clusters with post-Newtonian dynamics for black holes. By modeling the relativistic accelerations and gravitational-wave emission in isolated binaries and during three- and four-body encounters, we find that nearly half of all binary black hole mergers occur inside the cluster, with about 10% of those mergers entering the LIGO/Virgo band with eccentricities greater than 0.1. In-cluster mergers lead to the birth of a second generation of black holes with larger masses and high spins, which, depending on the black hole natal spins, can sometimes be retained in the cluster and merge again. As a result, globular clusters can produce merging binaries with detectable spins regardless of the birth spins of black holes formed from massive stars. These second-generation black holes would also populate any upper mass gap created by pair-instability supernovae.

Post-Newtonian Dynamics in Dense Star Clusters: Highly Eccentric, Highly Spinning, and Repeated Binary Black Hole Mergers

Science.gov (United States)

Rodriguez, Carl L.; Amaro-Seoane, Pau; Chatterjee, Sourav; Rasio, Frederic A.

2018-04-01

We present models of realistic globular clusters with post-Newtonian dynamics for black holes. By modeling the relativistic accelerations and gravitational-wave emission in isolated binaries and during three- and four-body encounters, we find that nearly half of all binary black hole mergers occur inside the cluster, with about 10% of those mergers entering the LIGO/Virgo band with eccentricities greater than 0.1. In-cluster mergers lead to the birth of a second generation of black holes with larger masses and high spins, which, depending on the black hole natal spins, can sometimes be retained in the cluster and merge again. As a result, globular clusters can produce merging binaries with detectable spins regardless of the birth spins of black holes formed from massive stars. These second-generation black holes would also populate any upper mass gap created by pair-instability supernovae.

RECOILING SUPERMASSIVE BLACK HOLES IN SPIN-FLIP RADIO GALAXIES

International Nuclear Information System (INIS)

Liu, F. K.; Wang Dong; Chen Xian

2012-01-01

Numerical relativity simulations predict that coalescence of supermassive black hole (SMBH) binaries leads not only to a spin flip but also to a recoiling of the merger remnant SMBHs. In the literature, X-shaped radio sources are popularly suggested to be candidates for SMBH mergers with spin flip of jet-ejecting SMBHs. Here we investigate the spectral and spatial observational signatures of the recoiling SMBHs in radio sources undergoing black hole spin flip. Our results show that SMBHs in most spin-flip radio sources have mass ratio q ∼> 0.3 with a minimum possible value q min ≅ 0.05. For major mergers, the remnant SMBHs can get a kick velocity as high as 2100 km s –1 in the direction within an angle ∼< 40° relative to the spin axes of remnant SMBHs, implying that recoiling quasars are biased to be with high Doppler-shifted broad emission lines while recoiling radio galaxies are biased to large apparent spatial off-center displacements. We also calculate the distribution functions of line-of-sight velocity and apparent spatial off-center displacements for spin-flip radio sources with different apparent jet reorientation angles. Our results show that the larger the apparent jet reorientation angle is, the larger the Doppler-shifting recoiling velocity and apparent spatial off-center displacement will be. We investigate the effects of recoiling velocity on the dust torus in spin-flip radio sources and suggest that recoiling of SMBHs would lead to 'dust-poor' active galactic nuclei. Finally, we collect a sample of 19 X-shaped radio objects and for each object give the probability of detecting the predicted signatures of recoiling SMBH.

Accretion in Radiative Equipartition (AiRE) Disks

Energy Technology Data Exchange (ETDEWEB)

Yazdi, Yasaman K.; Afshordi, Niayesh, E-mail: yyazdi@pitp.ca, E-mail: nafshordi@pitp.ca [Perimeter Institute for Theoretical Physics, 31 Caroline Street N, Waterloo, ON N2L 2Y5 (Canada)

2017-07-01

Standard accretion disk theory predicts that the total pressure in disks at typical (sub-)Eddington accretion rates becomes radiation pressure dominated. However, radiation pressure dominated disks are thermally unstable. Since these disks are observed in approximate steady state over the instability timescale, our accretion models in the radiation-pressure-dominated regime (i.e., inner disk) need to be modified. Here, we present a modification to the Shakura and Sunyaev model, where the radiation pressure is in equipartition with the gas pressure in the inner region. We call these flows accretion in radiative equipartition (AiRE) disks. We introduce the basic features of AiRE disks and show how they modify disk properties such as the Toomre parameter and the central temperature. We then show that the accretion rate of AiRE disks is limited from above and below, by Toomre and nodal sonic point instabilities, respectively. The former leads to a strict upper limit on the mass of supermassive black holes as a function of cosmic time (and spin), while the latter could explain the transition between hard and soft states of X-ray binaries.

Resolution doubling in fluorescence microscopy with confocal spinning-disk image scanning microscopy.

Science.gov (United States)

Schulz, Olaf; Pieper, Christoph; Clever, Michaela; Pfaff, Janine; Ruhlandt, Aike; Kehlenbach, Ralph H; Wouters, Fred S; Großhans, Jörg; Bunt, Gertrude; Enderlein, Jörg

2013-12-24

We demonstrate how a conventional confocal spinning-disk (CSD) microscope can be converted into a doubly resolving image scanning microscopy (ISM) system without changing any part of its optical or mechanical elements. Making use of the intrinsic properties of a CSD microscope, we illuminate stroboscopically, generating an array of excitation foci that are moved across the sample by varying the phase between stroboscopic excitation and rotation of the spinning disk. ISM then generates an image with nearly doubled resolution. Using conventional fluorophores, we have imaged single nuclear pore complexes in the nuclear membrane and aggregates of GFP-conjugated Tau protein in three dimensions. Multicolor ISM was shown on cytoskeletal-associated structural proteins and on 3D four-color images including MitoTracker and Hoechst staining. The simple adaptation of conventional CSD equipment allows superresolution investigations of a broad variety of cell biological questions.

Expanding the catalog of binary black-hole simulations: aligned-spin configurations

Science.gov (United States)

Chu, Tony; Pfeiffer, Harald; Scheel, Mark; Szilagyi, Bela; SXS Collaboration

2015-04-01

A major goal of numerical relativity is to model the inspiral and merger of binary black holes through sufficiently accurate and long simulations, to enable the successful detection of gravitational waves. However, covering the full parameter space of binary configurations is a computationally daunting task. The SXS Collaboration has made important progress in this direction recently, with a catalog of 174 publicly available binary black-hole simulations [black-holes.org/waveforms]. Nevertheless, the parameter-space coverage remains sparse, even for non-precessing binaries. In this talk, I will describe an addition to the SXS catalog to improve its coverage, consisting of 95 new simulations of aligned-spin binaries with moderate mass ratios and dimensionless spins as high as 0.9. Some applications of these new simulations will also be mentioned.

Pairing versus phase coherence of doped holes in distinct quantum spin backgrounds

Science.gov (United States)

Zhu, Zheng; Sheng, D. N.; Weng, Zheng-Yu

2018-03-01

We examine the pairing structure of holes injected into two distinct spin backgrounds: a short-range antiferromagnetic phase versus a symmetry protected topological phase. Based on density matrix renormalization group (DMRG) simulation, we find that although there is a strong binding between two holes in both phases, phase fluctuations can significantly influence the pair-pair correlation depending on the spin-spin correlation in the background. Here the phase fluctuation is identified as an intrinsic string operator nonlocally controlled by the spins. We show that while the pairing amplitude is generally large, the coherent Cooper pairing can be substantially weakened by the phase fluctuation in the symmetry-protected topological phase, in contrast to the short-range antiferromagnetic phase. It provides an example of a non-BCS mechanism for pairing, in which the paring phase coherence is determined by the underlying spin state self-consistently, bearing an interesting resemblance to the pseudogap physics in the cuprate.

Universality, maximum radiation, and absorption in high-energy collisions of black holes with spin.

Science.gov (United States)

Sperhake, Ulrich; Berti, Emanuele; Cardoso, Vitor; Pretorius, Frans

2013-07-26

We explore the impact of black hole spins on the dynamics of high-energy black hole collisions. We report results from numerical simulations with γ factors up to 2.49 and dimensionless spin parameter χ=+0.85, +0.6, 0, -0.6, -0.85. We find that the scattering threshold becomes independent of spin at large center-of-mass energies, confirming previous conjectures that structure does not matter in ultrarelativistic collisions. It has further been argued that in this limit all of the kinetic energy of the system may be radiated by fine tuning the impact parameter to threshold. On the contrary, we find that only about 60% of the kinetic energy is radiated for γ=2.49. By monitoring apparent horizons before and after scattering events we show that the "missing energy" is absorbed by the individual black holes in the encounter, and moreover the individual black-hole spins change significantly. We support this conclusion with perturbative calculations. An extrapolation of our results to the limit γ→∞ suggests that about half of the center-of-mass energy of the system can be emitted in gravitational radiation, while the rest must be converted into rest-mass and spin energy.

Recoil velocity at second post-Newtonian order for spinning black hole binaries

International Nuclear Information System (INIS)

Racine, Etienne; Buonanno, Alessandra; Kidder, Larry

2009-01-01

We compute the flux of linear momentum carried by gravitational waves emitted from spinning binary black holes at second post-Newtonian (2PN) order for generic orbits. In particular we provide explicit expressions of three new types of terms, namely, next-to-leading order spin-orbit terms at 1.5 post-Newtonian (1.5PN) order, spin-orbit tail terms at 2PN order, and spin-spin terms at 2PN order. Restricting ourselves to quasicircular orbits, we integrate the linear-momentum flux over time to obtain the recoil velocity as function of orbital frequency. We find that in the so-called superkick configuration the higher-order spin corrections can increase the recoil velocity up to a factor ∼3 with respect to the leading-order PN prediction. Whereas the recoil velocity computed in PN theory within the adiabatic approximation can accurately describe the early inspiral phase, we find that its fast increase during the late inspiral and plunge, and the arbitrariness in determining until when it should be trusted, makes the PN predictions for the total recoil not very accurate and robust. Nevertheless, the linear-momentum flux at higher PN orders can be employed to build more reliable resummed expressions aimed at capturing the nonperturbative effects until merger. Furthermore, we provide expressions valid for generic orbits, and accurate at 2PN order, for the energy and angular momentum carried by gravitational waves emitted from spinning binary black holes. Specializing to quasicircular orbits we compute the spin-spin terms at 2PN order in the expression for the evolution of the orbital frequency and found agreement with Mikoczi, Vasuth, and Gergely. We also verified that in the limit of extreme mass ratio our expressions for the energy and angular momentum fluxes match the ones of Tagoshi, Shibata, Tanaka, and Sasaki obtained in the context of black hole perturbation theory.

F-Theory, spinning black holes and multi-string branches

International Nuclear Information System (INIS)

Haghighat, Babak; Murthy, Sameer; Vafa, Cumrun; Vandoren, Stefan

2016-01-01

We study 5d supersymmetric black holes which descend from strings of generic N=(1,0) supergravity in 6d. These strings have an F-theory realization in 6d as D3 branes wrapping smooth genus g curves in the base of elliptic 3-folds. They enjoy (0,4) worldsheet supersymmetry with an extra SU(2) L current algebra at level g realized on the left-movers. When the smooth curves degenerate they lead to multi-string branches and we find that the microscopic worldsheet theory flows in the IR to disconnected 2d CFTs having different central charges. The single string sector is the one with maximal central charge, which when wrapped on a circle, leads to a 5d spinning BPS black hole whose horizon volume agrees with the leading entropy prediction from the Cardy formula. However, we find new phenomena where this branch meets other branches of the CFT. These include multi-string configurations which have no bound states in 6 dimensions but are bound through KK momenta when wrapping a circle, as well as loci where the curves degenerate to spheres. These loci lead to black hole configurations which can have total angular momentum relative to a Taub-Nut center satisfying J 2 >M 3 and whose number of states, though exponentially large, grows much slower than those of the large spinning black hole.

Higher spins tunneling from a time dependent and spherically symmetric black hole

International Nuclear Information System (INIS)

Siahaan, Haryanto M.

2016-01-01

The discussions of Hawking radiation via tunneling method have been performed extensively in the case of scalar particles. Moreover, there are also several works in discussing the tunneling method for Hawking radiation by using higher spins, e.g. neutrino, photon, and gravitino, in the background of static black holes. Interestingly, it is found that the Hawking temperature for static black holes using the higher spins particles has no difference compared to the one computed using scalars. In this paper, we study the Hawking radiation for a spherically symmetric and time dependent black holes using the tunneling of Dirac particles, photon, and gravitino. We find that the obtained Hawking temperature is similar to the one derived in the tunneling method by using scalars. (orig.)

Higher spins tunneling from a time dependent and spherically symmetric black hole

Energy Technology Data Exchange (ETDEWEB)

Siahaan, Haryanto M. [Parahyangan Catholic University, Physics Department, Bandung (Indonesia)

2016-03-15

The discussions of Hawking radiation via tunneling method have been performed extensively in the case of scalar particles. Moreover, there are also several works in discussing the tunneling method for Hawking radiation by using higher spins, e.g. neutrino, photon, and gravitino, in the background of static black holes. Interestingly, it is found that the Hawking temperature for static black holes using the higher spins particles has no difference compared to the one computed using scalars. In this paper, we study the Hawking radiation for a spherically symmetric and time dependent black holes using the tunneling of Dirac particles, photon, and gravitino. We find that the obtained Hawking temperature is similar to the one derived in the tunneling method by using scalars. (orig.)

Dirac equation of spin particles and tunneling radiation from a Kinnersly black hole

Energy Technology Data Exchange (ETDEWEB)

Li, Guo-Ping; Zu, Xiao-Tao [University of Electronic Science and Technology of China, School of Physical Electronics, Chengdu (China); Feng, Zhong-Wen [University of Electronic Science and Technology of China, School of Physical Electronics, Chengdu (China); China West Normal University, College of Physics and Space Science, Nanchong (China); Li, Hui-Ling [University of Electronic Science and Technology of China, School of Physical Electronics, Chengdu (China); Shenyang Normal University, College of Physics Science and Technology, Shenyang (China)

2017-04-15

In curved space-time, the Hamilton-Jacobi equation is a semi-classical particle equation of motion, which plays an important role in the research of black hole physics. In this paper, starting from the Dirac equation of spin 1/2 fermions and the Rarita-Schwinger equation of spin 3/2 fermions, respectively, we derive a Hamilton-Jacobi equation for the non-stationary spherically symmetric gravitational field background. Furthermore, the quantum tunneling of a charged spherically symmetric Kinnersly black hole is investigated by using the Hamilton-Jacobi equation. The result shows that the Hamilton-Jacobi equation is helpful to understand the thermodynamic properties and the radiation characteristics of a black hole. (orig.)

Tidal deformations of spinning black holes in Bowen–York initial data

International Nuclear Information System (INIS)

Cabero, Miriam; Krishnan, Badri

2015-01-01

We study the tidal deformations of the shape of a spinning black hole horizon due to a binary companion in the Bowen–York initial data set. We use the framework of quasi-local horizons and identify a black hole by marginally outer trapped surfaces. The intrinsic horizon geometry is specified by a set of mass and angular-momentum multipole moments M n and J n , respectively. The tidal deformations are described by the change in these multipole moments caused by an external perturbation. This leads us to define two sets of dimensionless numbers, the tidal coefficients for M n and J n , which specify the deformations of a black hole with a binary companion. We compute these tidal coefficients in a specific model problem, namely the Bowen–York initial data set for binary black holes. We restrict ourselves to axisymmetric situations and to small spins. Within this approximation, we analytically compute the conformal factor, the location of the marginally trapped surfaces, and finally the multipole moments and the tidal coefficients. (paper)

Correlation effects on spin-polarized electron-hole quantum bilayer

Energy Technology Data Exchange (ETDEWEB)

Saini, L. K., E-mail: drlalitsaini75@gmail.com; Sharma, R. O., E-mail: sharmarajesh0387@gmail.com [Department of Applied Physics, S. V. National Institute of Technology, Surat – 395 007 (India); Nayak, Mukesh G. [Department of Physics, Silvassa College (Silvassa Institute of Higher Learning), Silvassa 396 230 (India)

2016-05-06

We present a numerical calculation for the intra- and interlayer pair-correlation functions, g{sub ll’}(r), of spin-polarized electron-hole quantum bilayers at zero temperature. The calculations of g{sub ll’}(r) are performed by including electron correlations within the dynamical version of the self-consistent mean-field approximation of Singwi, Tosi, Land and Sjölander (qSTLS). Our study reveals that the critical layer density decreases (increases) due to the inclusion of finite width (mass-asymmetry) effect during the phase-transition from charge-density wave to Wigner crystal ground-state by yielding the pronounced oscillatory behavior ing{sub ll}(r). The results are compared with recent findings of spin-polarized electron-hole quantum bilayers with mass-symmetry and zero width effects. To highlight the importance of dynamical character of correlations, we have also compared our results with the STLS results.

PRECISE BLACK HOLE MASSES FROM MEGAMASER DISKS: BLACK HOLE-BULGE RELATIONS AT LOW MASS

International Nuclear Information System (INIS)

Greene, Jenny E.; Peng, Chien Y.; Kim, Minjin; Kuo, Cheng-Yu; Braatz, James A.; Impellizzeri, C. M. Violette; Condon, James J.; Lo, K. Y.; Henkel, Christian; Reid, Mark J.

2010-01-01

The black hole (BH)-bulge correlations have greatly influenced the last decade of efforts to understand galaxy evolution. Current knowledge of these correlations is limited predominantly to high BH masses (M BH ∼>10 8 M sun ) that can be measured using direct stellar, gas, and maser kinematics. These objects, however, do not represent the demographics of more typical L 2 O megamasers in circumnuclear disks. The masers trace the Keplerian rotation of circumnuclear molecular disks starting at radii of a few tenths of a pc from the central BH. Modeling of the rotation curves, presented by Kuo et al., yields BH masses with exquisite precision. We present stellar velocity dispersion measurements for a sample of nine megamaser disk galaxies based on long-slit observations using the B and C spectrograph on the Dupont telescope and the Dual Imaging Spectrograph on the 3.5 m telescope at Apache Point. We also perform bulge-to-disk decomposition of a subset of five of these galaxies with Sloan Digital Sky Survey imaging. The maser galaxies as a group fall below the M BH -σ * relation defined by elliptical galaxies. We show, now with very precise BH mass measurements, that the low-scatter power-law relation between M BH and σ * seen in elliptical galaxies is not universal. The elliptical galaxy M BH -σ * relation cannot be used to derive the BH mass function at low mass or the zero point for active BH masses. The processes (perhaps BH self-regulation or minor merging) that operate at higher mass have not effectively established an M BH -σ * relation in this low-mass regime.

The response of relativistic outflowing gas to the inner accretion disk of a black hole.

Science.gov (United States)

Parker, Michael L; Pinto, Ciro; Fabian, Andrew C; Lohfink, Anne; Buisson, Douglas J K; Alston, William N; Kara, Erin; Cackett, Edward M; Chiang, Chia-Ying; Dauser, Thomas; De Marco, Barbara; Gallo, Luigi C; Garcia, Javier; Harrison, Fiona A; King, Ashley L; Middleton, Matthew J; Miller, Jon M; Miniutti, Giovanni; Reynolds, Christopher S; Uttley, Phil; Vasudevan, Ranjan; Walton, Dominic J; Wilkins, Daniel R; Zoghbi, Abderahmen

2017-03-01

The brightness of an active galactic nucleus is set by the gas falling onto it from the galaxy, and the gas infall rate is regulated by the brightness of the active galactic nucleus; this feedback loop is the process by which supermassive black holes in the centres of galaxies may moderate the growth of their hosts. Gas outflows (in the form of disk winds) release huge quantities of energy into the interstellar medium, potentially clearing the surrounding gas. The most extreme (in terms of speed and energy) of these-the ultrafast outflows-are the subset of X-ray-detected outflows with velocities higher than 10,000 kilometres per second, believed to originate in relativistic (that is, near the speed of light) disk winds a few hundred gravitational radii from the black hole. The absorption features produced by these outflows are variable, but no clear link has been found between the behaviour of the X-ray continuum and the velocity or optical depth of the outflows, owing to the long timescales of quasar variability. Here we report the observation of multiple absorption lines from an extreme ultrafast gas flow in the X-ray spectrum of the active galactic nucleus IRAS 13224-3809, at 0.236 ± 0.006 times the speed of light (71,000 kilometres per second), where the absorption is strongly anti-correlated with the emission of X-rays from the inner regions of the accretion disk. If the gas flow is identified as a genuine outflow then it is in the fastest five per cent of such winds, and its variability is hundreds of times faster than in other variable winds, allowing us to observe in hours what would take months in a quasar. We find X-ray spectral signatures of the wind simultaneously in both low- and high-energy detectors, suggesting a single ionized outflow, linking the low- and high-energy absorption lines. That this disk wind is responding to the emission from the inner accretion disk demonstrates a connection between accretion processes occurring on very different

THE MOST MASSIVE ACTIVE BLACK HOLES AT z ∼ 1.5-3.5 HAVE HIGH SPINS AND RADIATIVE EFFICIENCIES

International Nuclear Information System (INIS)

Trakhtenbrot, Benny

2014-01-01

The radiative efficiencies (η) of 72 luminous unobscured active galactic nuclei at z ∼ 1.5-3.5, powered by some of the most massive black holes (BHs), are constrained. The analysis is based on accretion disk (AD) models, which link the continuum luminosity at rest-frame optical wavelengths and the BH mass (M BH ) to the accretion rate through the AD, M-dot AD . The data are gathered from several literature samples with detailed measurements of the Hβ emission line complex, observed at near-infrared bands. When coupled with standard estimates of bolometric luminosities (L bol ), the analysis suggests high radiative efficiencies, with most of the sources showing η > 0.2, that is, higher than the commonly assumed value of 0.1, and the expected value for non-spinning BHs (η = 0.057). Even under more conservative assumptions regarding L bol (i.e., L bol = 3 × L 5100 ), most of the extremely massive BHs in the sample (i.e., M BH ≳ 3 × 10 9 M ☉ ) show radiative efficiencies which correspond to very high BH spins (a * ), with typical values well above a * ≅ 0.7. These results stand in contrast to the predictions of a ''spin-down'' scenario, in which a series of randomly oriented accretion episodes leads to a * ∼ 0. Instead, the analysis presented here strongly supports a ''spin-up'' scenario, which is driven by either prolonged accretion or a series of anisotropically oriented accretion episodes. Considering the fact that these extreme BHs require long-duration or continuous accretion to account for their high masses, it is argued that the most probable scenario for the super-massive black holes under study is that of an almost continuous sequence of randomly yet not isotropically oriented accretion episodes

Outbursts from the secondary component in OJ 287 and the secondary spin-up

Directory of Open Access Journals (Sweden)

Pihajoki P.

2012-12-01

Full Text Available At the end of March 2012 a prominent optical outburst was observed in the binary black hole system OJ 287. It does not fit the expected sequence of outbursts from the primary component and the bremsstrahlung outbursts from the accretion disk impacts of the secondary component. These occur in a well established pattern repeated with an approximately 12 year interval. In this work we discuss the possibility that the outburst originates from the secondary black hole. The timing of the 2012 outburst relative to the expected sequence would make it a counterpart of the precursor outbursts in 1993 and 2004, which occured before the main pattern of outbursts. If so, it appears that a precursor occurs when the secondary reaches a constant level above the mean accretion disk level of the primary component. It may be that this encounter induces an outburst in the secondary which is nearly as prominent as the outbursts in the expected sequence. The strength of these outbursts depends strongly on the spin of the secondary. In this work we investigate the limits on the secondary spin-up and spin alignment from interaction with the accretion disk of the primary component and its magnetic field.

Skyrmion dynamics in single-hole Neel ordered doped two-dimensional antiferromagnets with arbitrary spin

International Nuclear Information System (INIS)

Moura, A.R.; Pereira, A.R.; Moura-Melo, W.A.; Pires, A.S.T.

2008-01-01

We develop an effective theory to study the skyrmion dynamics in the presence of a hole (removed spins from the lattice) in Neel ordered two-dimensional antiferromagnets with arbitrary spin value S. The general equation of motion for the 'mass center' of this structure is obtained. The frequency of small amplitude oscillations of pinned skyrmions around the defect center is calculated. It is proportional to the hole size and inversely proportional to the square of the skyrmion size

Reprocessing of Soft X-ray Emission Lines in Black Hole Accretion Disks

International Nuclear Information System (INIS)

Mauche, C W; Liedahl, D A; Mathiesen, B F; Jimenez-Garate, M A; Raymond, J C

2003-01-01

By means of a Monte Carlo code that accounts for Compton scattering and photoabsorption followed by recombination, we have investigated the radiation transfer of Lyα, Heα, and recombination continua photons of H- and He-like C, N, O, and Ne produced in the photoionized atmosphere of a relativistic black hole accretion disk. We find that photoelectric opacity causes significant attenuation of photons with energies above the O VIII K-edge; that the conversion efficiencies of these photons into lower-energy lines and recombination continua are high; and that accounting for this reprocessing significantly (by factors of 21% to 105%) increases the flux of the Lyα and Heα emission lines of H- and He-like C and O escaping the disk atmosphere

Constructing binary black hole initial data with high mass ratios and spins

Science.gov (United States)

Ossokine, Serguei; Foucart, Francois; Pfeiffer, Harald; Szilagyi, Bela; Simulating Extreme Spacetimes Collaboration

2015-04-01

Binary black hole systems have now been successfully modelled in full numerical relativity by many groups. In order to explore high-mass-ratio (larger than 1:10), high-spin systems (above 0.9 of the maximal BH spin), we revisit the initial-data problem for binary black holes. The initial-data solver in the Spectral Einstein Code (SpEC) was not able to solve for such initial data reliably and robustly. I will present recent improvements to this solver, among them adaptive mesh refinement and control of motion of the center of mass of the binary, and will discuss the much larger region of parameter space this code can now address.

Hole-spin dynamics in p-doped GaAs/AlGaAs heterostructures; Lochspindynamik in p-dotierten GaAs/AlGaAs-Heterostrukturen

Energy Technology Data Exchange (ETDEWEB)

Kugler, Michael

2012-11-15

This work investigates the spin dynamics of holes in p-doped GaAs/AlGaAs quantum wells (QW) at low temperatures. To examine the energetic structure of the used samples, PL and PLE-spectroscopy were employed. Time resolved Kerr and Faraday-Rotation (TRKR/FR) and 'Resonant Spin Amplification' (RSA) were used to analyse the spin dynamics. First, the signal formation in TRKR/FR and RSA experiments is discussed taking into account the interconnected charge carrier dynamics and spin dynamics of electrons and holes. An excitation energy dependent sign change of the Kerr signal amplitude could be observed, whose energetic position corresponds to an absorption maximum in PLE experiments. This behavior could be explained by an energy dependent splitting of the spin niveaus, which leads to an energy dependence of the Faraday and Kerr signal. Furthermore, two initialization processes were investigated, which could be used to transfer optically generated spin information into the resident hole spin system. This could be achieved by either applying a magnetic field, or by rapid dephasing of hole spins immediately after excitation. Changes in excitation energy, excitation density or temperature could be used to influence the fast dephasing processes and therefore the initial ratio of hole to electron spins. The complex, interconnected charge carrier and spin dynamics of electrons and holes could be accurately reproduced using a rate equation model. This allowed for the extraction of physically relevant parameters like spin lifetimes and g-factors from RSA and TRKR/FR data. An analytical model that was developed at the Wroclaw University of Technology delivered matching results. In the second part of the experimental work, the dependence of the hole spin lifetime and the hole g-factor on various parameters was analysed. Here, the RSA method could for the first time be applied to two-dimensional hole systems, allowing for new insights into the regime of long lived hole

The spinning Kerr-black-hole-mirror bomb: A lower bound on the radius of the reflecting mirror

Science.gov (United States)

Hod, Shahar

2016-10-01

The intriguing superradiant amplification phenomenon allows an orbiting scalar field to extract rotational energy from a spinning Kerr black hole. Interestingly, the energy extraction rate can grow exponentially in time if the black-hole-field system is placed inside a reflecting mirror which prevents the field from radiating its energy to infinity. This composed Kerr-black-hole-scalar-field-mirror system, first designed by Press and Teukolsky, has attracted the attention of physicists over the last four decades. Previous numerical studies of this spinning black-hole bomb have revealed the interesting fact that the superradiant instability shuts down if the reflecting mirror is placed too close to the black-hole horizon. In the present study we use analytical techniques to explore the superradiant instability regime of this composed Kerr-black-hole-linearized-scalar-field-mirror system. In particular, it is proved that the lower bound rm/r+ >1/2 (√{ 1 +8M/r- } - 1) provides a necessary condition for the development of the exponentially growing superradiant instabilities in this composed physical system, where rm is the radius of the confining mirror and r± are the horizon radii of the spinning Kerr black hole. We further show that, in the linearized regime, this analytically derived lower bound on the radius of the confining mirror agrees with direct numerical computations of the superradiant instability spectrum which characterizes the spinning black-hole-mirror bomb.

RINGED ACCRETION DISKS: INSTABILITIES

Energy Technology Data Exchange (ETDEWEB)

Pugliese, D.; Stuchlík, Z., E-mail: d.pugliese.physics@gmail.com, E-mail: zdenek.stuchlik@physics.cz [Institute of Physics and Research Centre of Theoretical Physics and Astrophysics, Faculty of Philosophy and Science, Silesian University in Opava, Bezručovo náměstí 13, CZ-74601 Opava (Czech Republic)

2016-04-01

We analyze the possibility that several instability points may be formed, due to the Paczyński mechanism of violation of mechanical equilibrium, in the orbiting matter around a supermassive Kerr black hole. We consider a recently proposed model of a ringed accretion disk, made up by several tori (rings) that can be corotating or counter-rotating relative to the Kerr attractor due to the history of the accretion process. Each torus is governed by the general relativistic hydrodynamic Boyer condition of equilibrium configurations of rotating perfect fluids. We prove that the number of the instability points is generally limited and depends on the dimensionless spin of the rotating attractor.

Exchange electron-hole interaction of two-dimensional magnetoexcitons under the influence of the Rashba spin-orbit coupling

International Nuclear Information System (INIS)

Moskalenko, S.A.; Podlesny, I.V.; Lelyakov, I.A.; Novikov, B.V.; Kiselyova, E.S.; Gherciu, L.

2011-01-01

The Rashba spin-orbit coupling (RSOC) in the case of two-dimensional (2D) electrons and holes in a strong perpendicular magnetic field was studied. The spinor-type wave functions are characterized by different numbers of Landau levels in different spin projections. For electrons they differ by 1 as was established earlier by Rashba, whereas for holes they differ by 3. Two lowest electron states and four lowest hole states of Landau quantization give rise to eight 2D magnetoexciton states. The exchange electron-hole interaction in the frame of these states is investigated.

Free Vibration Analysis of a Spinning Flexible DISK-SPINDLE System Supported by Ball Bearing and Flexible Shaft Using the Finite Element Method and Substructure Synthesis

Science.gov (United States)

JANG, G. H.; LEE, S. H.; JUNG, M. S.

2002-03-01

Free vibration of a spinning flexible disk-spindle system supported by ball bearing and flexible shaft is analyzed by using Hamilton's principle, FEM and substructure synthesis. The spinning disk is described by using the Kirchhoff plate theory and von Karman non-linear strain. The rotating spindle and stationary shaft are modelled by Rayleigh beam and Euler beam respectively. Using Hamilton's principle and including the rigid body translation and tilting motion, partial differential equations of motion of the spinning flexible disk and spindle are derived consistently to satisfy the geometric compatibility in the internal boundary between substructures. FEM is used to discretize the derived governing equations, and substructure synthesis is introduced to assemble each component of the disk-spindle-bearing-shaft system. The developed method is applied to the spindle system of a computer hard disk drive with three disks, and modal testing is performed to verify the simulation results. The simulation result agrees very well with the experimental one. This research investigates critical design parameters in an HDD spindle system, i.e., the non-linearity of a spinning disk and the flexibility and boundary condition of a stationary shaft, to predict the free vibration characteristics accurately. The proposed method may be effectively applied to predict the vibration characteristics of a spinning flexible disk-spindle system supported by ball bearing and flexible shaft in the various forms of computer storage device, i.e., FDD, CD, HDD and DVD.

Detection and Control of Spin-Orbit Interactions in a GaAs Hole Quantum Point Contact

Science.gov (United States)

Srinivasan, A.; Miserev, D. S.; Hudson, K. L.; Klochan, O.; Muraki, K.; Hirayama, Y.; Reuter, D.; Wieck, A. D.; Sushkov, O. P.; Hamilton, A. R.

2017-04-01

We investigate the relationship between the Zeeman interaction and the inversion-asymmetry-induced spin-orbit interactions (Rashba and Dresselhaus SOIs) in GaAs hole quantum point contacts. The presence of a strong SOI results in the crossing and anticrossing of adjacent spin-split hole subbands in a magnetic field. We demonstrate theoretically and experimentally that the anticrossing energy gap depends on the interplay between the SOI terms and the highly anisotropic hole g tensor and that this interplay can be tuned by selecting the crystal axis along which the current and magnetic field are aligned. Our results constitute the independent detection and control of the Dresselhaus and Rashba SOIs in hole systems, which could be of importance for spintronics and quantum information applications.

A SPITZER CENSUS OF TRANSITIONAL PROTOPLANETARY DISKS WITH AU-SCALE INNER HOLES

International Nuclear Information System (INIS)

Muzerolle, James; Allen, Lori E.; Megeath, S. Thomas; Hernandez, Jesus; Gutermuth, Robert A.

2010-01-01

Protoplanetary disks with AU-scale inner clearings, often referred to as transitional disks, provide a unique sample for understanding disk dissipation mechanisms and possible connections to planet formation. Observations of young stellar clusters with the Spitzer Space Telescope have amassed mid-infrared (IR) spectral energy distributions (SEDs) for thousands of star-disk systems from which transition disks can be identified. From a sample of eight relatively nearby young regions (d ∼ 0) to select for robust optically thick outer disks, and 3.6-5.8 μm spectral slope and 5.8 μm continuum excess limits to select for optically thin or zero continuum excess from the inner few AU of the disks. We also identified two additional categories representing more ambiguous cases: 'warm excess' objects with transition-like SEDs but moderate excess at 5.8 μm, and 'weak excess' objects with smaller 24 μm excess that may be optically thin or exhibit advanced dust grain growth and settling. From existing Hα emission measurements, we find evidence for different accretion activity among the three categories, with a majority of the classical and warm excess transition objects still accreting gas through their inner holes and onto the central stars, while a smaller fraction of the weak transition objects are accreting at detectable rates. We find a possible age dependence on the frequency of classical transition objects, with fractions relative to the total population of disks in a given region of a few percent at 1-2 Myr rising to 10%-20% at 3-10 Myr. The trend is even stronger if the weak and warm excess objects are included. This relationship may be due to a dependence of the outer disk clearing timescale with stellar age, suggesting a variety of clearing mechanisms working at different times, or it may reflect that a smaller fraction of all disks actually undergo an inner clearing phase at younger ages. Classical transition disks appear to be less common, and weak transition

CIRCUMBINARY MAGNETOHYDRODYNAMIC ACCRETION INTO INSPIRALING BINARY BLACK HOLES

Energy Technology Data Exchange (ETDEWEB)

Noble, Scott C.; Mundim, Bruno C.; Nakano, Hiroyuki; Campanelli, Manuela; Zlochower, Yosef [Center for Computational Relativity and Gravitation, Rochester Institute of Technology, Rochester, NY 14623 (United States); Krolik, Julian H. [Physics and Astronomy Department, Johns Hopkins University, Baltimore, MD 21218 (United States); Yunes, Nicolas, E-mail: scn@astro.rit.edu [Department of Physics, Montana State University, Bozeman, MT 59717 (United States)

2012-08-10

We have simulated the magnetohydrodynamic evolution of a circumbinary disk surrounding an equal-mass binary comprising two non-spinning black holes during the period in which the disk inflow time is comparable to the binary evolution time due to gravitational radiation. Both the changing spacetime and the binary orbital evolution are described by an innovative technique utilizing high-order post-Newtonian approximations. Prior to the beginning of the inspiral, the structure of the circumbinary disk is predicted well by extrapolation from Newtonian results: a gap of roughly two binary separation radii is cleared, and matter piles up at the outer edge of this gap as inflow is retarded by torques exerted by the binary; the accretion rate is roughly half its value at large radius. During inspiral, the inner edge of the disk initially moves inward in coordination with the shrinking binary, but-as the orbital evolution accelerates-the inward motion of the disk edge falls behind the rate of binary compression. In this stage, the binary torque falls substantially, but the accretion rate decreases by only 10%-20%. When the binary separation is tens of gravitational radii, the rest-mass efficiency of disk radiation is a few percent, suggesting that supermassive binary black holes could be very luminous at this stage of their evolution. Inner disk heating is modulated at a beat frequency comparable to the binary orbital frequency. However, a disk with sufficient surface density to be luminous may be optically thick, suppressing periodic modulation of the luminosity.

Probing the Accretion Geometry of Black Holes with X-Ray Polarization

Science.gov (United States)

Schnitman, Jeremy D.

2011-01-01

In the coming years, new space missions will be able to measure X-ray polarization at levels of 1% or better in the approx.1-10 keV energy band. In particular, X-ray polarization is an ideal tool for determining the nature of black hole (BH) accretion disks surrounded by hot coronae. Using a Monte Carlo radiation transport code in full general relativity, we calculate the spectra and polarization features of these BH systems. At low energies, the signal is dominated by the thermal flux coming directly from the optically thick disk. At higher energies, the thermal seed photons have been inverse-Compton scattered by the corona, often reflecting back off the disk before reaching the observer, giving a distinctive polarization signature. By measuring the degree and angle of this X-ray polarization, we can infer the BH inclination, the emission geometry of the accretion flow, and also determine the spin of the black hole.

Drude weight and optical conductivity of a two-dimensional heavy-hole gas with k-cubic spin-orbit interactions

Energy Technology Data Exchange (ETDEWEB)

Mawrie, Alestin; Ghosh, Tarun Kanti [Department of Physics, Indian Institute of Technology-Kanpur, Kanpur 208 016 (India)

2016-01-28

We present a detailed theoretical study on zero-frequency Drude weight and optical conductivity of a two-dimensional heavy-hole gas (2DHG) with k-cubic Rashba and Dresselhaus spin-orbit interactions. The presence of k-cubic spin-orbit couplings strongly modifies the Drude weight in comparison to the electron gas with k-linear spin-orbit couplings. For large hole density and strong k-cubic spin-orbit couplings, the density dependence of Drude weight deviates from the linear behavior. We establish a relation between optical conductivity and the Berry connection. Unlike two-dimensional electron gas with k-linear spin-orbit couplings, we explicitly show that the optical conductivity does not vanish even for equal strength of the two spin-orbit couplings. We attribute this fact to the non-zero Berry phase for equal strength of k-cubic spin-orbit couplings. The least photon energy needed to set in the optical transition in hole gas is one order of magnitude smaller than that of electron gas. Types of two van Hove singularities appear in the optical spectrum are also discussed.

Spin relaxation dynamics of holes in intrinsic GaAs quantum wells studied by transient circular dichromatic absorption spectroscopy at room temperature.

Science.gov (United States)

Fang, Shaoyin; Zhu, Ruidan; Lai, Tianshu

2017-03-21

Spin relaxation dynamics of holes in intrinsic GaAs quantum wells is studied using time-resolved circular dichromatic absorption spectroscopy at room temperature. It is found that ultrafast dynamics is dominated by the cooperative contributions of band filling and many-body effects. The relative contribution of the two effects is opposite in strength for electrons and holes. As a result, transient circular dichromatic differential transmission (TCD-DT) with co- and cross-circularly polarized pump and probe presents different strength at several picosecond delay time. Ultrafast spin relaxation dynamics of excited holes is sensitively reflected in TCD-DT with cross-circularly polarized pump and probe. A model, including coherent artifact, thermalization of nonthermal carriers and the cooperative contribution of band filling and many-body effects, is developed, and used to fit TCD-DT with cross-circularly polarized pump and probe. Spin relaxation time of holes is achieved as a function of excited hole density for the first time at room temperature, and increases with hole density, which disagrees with a theoretical prediction based on EY spin relaxation mechanism, implying that EY mechanism may be not dominant hole spin relaxation mechanism at room temperature, but DP mechanism is dominant possibly.

Relativistic Outflows from Advection-dominated Accretion Disks around Black Holes

Science.gov (United States)

Becker, Peter A.; Subramanian, Prasad; Kazanas, Demosthenes

2001-05-01

Advection-dominated accretion flows (ADAFs) have a positive Bernoulli parameter and are therefore gravitationally unbound. The Newtonian ADAF model has been generalized recently to obtain the ADIOS model that includes outflows of energy and angular momentum, thereby allowing accretion to proceed self-consistently. However, the utilization of a Newtonian gravitational potential limits the ability of this model to describe the inner region of the disk, where any relativistic outflows are likely to originate. In this paper we modify the ADIOS scenario to incorporate a pseudo-Newtonian potential, which approximates the effects of general relativity. The analysis yields a unique, self-similar solution for the structure of the coupled disk/wind system. Interesting features of the new solution include the relativistic character of the outflow in the vicinity of the radius of marginal stability, which represents the inner edge of the quasi-Keplerian disk in our model. Hence, our self-similar solution may help to explain the origin of relativistic jets in active galaxies. At large distances the radial dependence of the accretion rate approaches the unique form M~r1/2, with an associated density variation given by ρ~r-1. This density variation agrees with that implied by the dependence of the hard X-ray time lags on the Fourier frequency for a number of accreting galactic black hole candidates. While intriguing, the predictions made using our self-similar solution need to be confirmed in the future using a detailed model that includes a physical description of the energization mechanism that drives the outflow, which is likely to be powered by the shear of the underlying accretion disk.

Study of the round edge disk hole's effects on the frequency and wakefield in disc structure

International Nuclear Information System (INIS)

Wang Lanfa; Hou Mi; Zhang Chuang

2001-01-01

The effects of the round edge beam hole on the frequency and wake field are studied using variational method, which allows for rounded iris disk hole without any approximation in shape treatment. The frequencies and wake fields of accelerating mode and dipole mode are studied for different edge radius cases, including the flat edge shape that is often used to approximately represent the actual structure geometry. The edge hole shape has weak effect on the frequency, but strong effect on the wakefield. The study shows that the amounts of wake fields are not precise enough with the assumption of the flat edge beam hole as of round edge. The shape assumption brings loss factor 15% err for the most dangerous EH 16 mode

Collisional spin-oriented Sherman function in electron-hole semiconductor plasmas: Landau damping effect

Science.gov (United States)

Lee, Myoung-Jae; Jung, Young-Dae

2018-04-01

The influence of Landau damping on the spin-oriented collisional asymmetry is investigated in electron-hole semiconductor plasmas. The analytical expressions of the spin-singlet and the spin-triplet scattering amplitudes as well as the spin-oriented asymmetry Sherman function are obtained as functions of the scattering angle, the Landau parameter, the effective Debye length, and the collision energy. It is found that the Landau damping effect enhances the spin-singlet and spin-triplet scattering amplitudes in the forward and back scattering domains, respectively. It is also found that the Sherman function increases with an increase in the Landau parameter. In addition, the spin-singlet scattering process is found to be dominant rather than the spin-triplet scattering process in the high collision energy domain.

Thermodynamics of Higher Spin Black Holes in AdS3

NARCIS (Netherlands)

de Boer, J.; Jottar, J.I.

2014-01-01

We discuss the thermodynamics of recently constructed three-dimensional higher spin black holes in SL(N, R) × SL(N, R) Chern-Simons theory with generalized asymptotically-anti-de Sitter boundary conditions. From a holographic perspective, these bulk theories are dual to two-dimensional CFTs with WN

TRANSITIONAL DISKS AS SIGNPOSTS OF YOUNG, MULTIPLANET SYSTEMS

International Nuclear Information System (INIS)

Dodson-Robinson, Sarah E.; Salyk, Colette

2011-01-01

Although there has yet been no undisputed discovery of a still-forming planet embedded in a gaseous protoplanetary disk, the cleared inner holes of transitional disks may be signposts of young planets. Here, we show that the subset of accreting transitional disks with wide, optically thin inner holes of 15 AU or more can only be sculpted by multiple planets orbiting inside each hole. Multiplanet systems provide two key ingredients for explaining the origins of transitional disks. First, multiple planets can clear wide inner holes where single planets open only narrow gaps. Second, the confined, non-axisymmetric accretion flows produced by multiple planets provide a way for an arbitrary amount of mass transfer to occur through an apparently optically thin hole without overproducing infrared excess flux. Rather than assuming that the gas and dust in the hole are evenly and axisymmetrically distributed, one can construct an inner hole with apparently optically thin infrared fluxes by covering a macroscopic fraction of the hole's surface area with locally optically thick tidal tails. We also establish that other clearing mechanisms, such as photoevaporation, cannot explain our subset of accreting transitional disks with wide holes. Transitional disks are therefore high-value targets for observational searches for young planetary systems.

Numerical Analysis of The Effect of Hydrodynamics and Operating Conditions on Biodiesel Synthesis in a Rotor-Stator Spinning Disk Reactor

Directory of Open Access Journals (Sweden)

Wen Zhuqing

2017-06-01

Full Text Available A rotor-stator spinning disk reactor for intensified biodiesel synthesis is described and numerically simulated in the present research. The reactor consists of two flat disks, located coaxially and parallel to each other with a gap ranging from 0.1 mm to 0.2 mm between the disks. The upper disk is located on a rotating shaft while the lower disk is stationary. The feed liquids, triglycerides (TG and methanol are injected into the reactor from centres of rotating disk and stationary disk, respectively. Fluid hydrodynamics in the reactor for synthesis of biodiesel from TG and methanol in the presence of a sodium hydroxide catalyst are simulated, using convection-diffusion-reaction multicomponent transport model with the CFD software ANSYS©Fluent v. 13.0. Effect of operating conditions on TG conversion is particularly investigated. Simulation results indicate that there is occurrence of back flow close to the stator at the outlet zone. Small gap size and fast rotational speed generally help to intensify mixing among reagents, and consequently enhance TG conversion. However, increasing rotational speed of spinning disk leads to more backflow, which decreases TG conversion. Large flow rate of TG at inlet is not recommended as well because of the short mean residence time of reactants inside the reactor.

The accretion disk and ionized absorber of the 9.7 hr dipping black hole binary MAXI J1305–704

Energy Technology Data Exchange (ETDEWEB)

Shidatsu, M.; Ueda, Y.; Hori, T.; Yoshikawa, T. [Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502 (Japan); Nakahira, S.; Matsuoka, M. [ISS Science Project Office, Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), 2-1-1 Sengen, Tsukuba, Ibaraki 305-8505 (Japan); Done, C. [Department of Physics, University of Durham, South Road, Durham, DH1 3LE (United Kingdom); Morihana, K. [Nishi-Harima Astronomical Observatory, Sayo-cho, Hyogo 6 79-5313 (Japan); Sugizaki, M.; Mihara, T.; Serino, M. [MAXI team, Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Negoro, H. [Department of Physics, Nihon University, 1-8-14 Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8308 (Japan); Kawai, N. [Department of Physics, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551 (Japan); Yamaoka, K. [Solar-Terrestrial Environment Laboratory, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601 (Japan); Ebisawa, K. [Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), 3-1-1 Yoshino-dai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Nagayama, T. [Department of Astrophysics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602 (Japan); Matsunaga, N., E-mail: shidatsu@kusastro.kyoto-u.ac.jp [Department of Astronomy, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)

2013-12-10

We report the results from X-ray studies of the newly discovered black hole candidate MAXI J1305–704 based on Suzaku and Swift observations in the low/hard and high/soft states, respectively. The long Suzaku observation shows two types of clear absorption dips, both of which recur on a dip interval of 9.74 ± 0.04 hr, which we identify with the orbital period. There is also partially ionized absorption in the nondip (persistent) emission in both the high/soft state and, very unusually, the low/hard state. However, this absorption (in both states) has substantially lower ionization than that seen in other high inclination systems, where the material forms a homogeneous disk wind. Here instead the absorption is most likely associated with clumpy, compact structures associated with the dipping material, which we see uniquely in this source likely because we view it at a very large inclination angle. A large inclination angle is also favored, together with a low black hole mass, to explain the high disk temperature seen in the fairly low luminosity high/soft state, as Doppler boosting enhances the disk temperature at high inclination. The disk radius inferred from these data is significantly smaller than that of the soft component seen in the low/hard state, supporting models where the disk is truncated at low luminosities. We find, however, that the lack of variability power on timescales of ∼50 s in the Suzaku low/hard state data is difficult to explain, even with a low-mass black hole.

A debris disk around an isolated young neutron star.

Science.gov (United States)

Wang, Zhongxiang; Chakrabarty, Deepto; Kaplan, David L

2006-04-06

Pulsars are rotating, magnetized neutron stars that are born in supernova explosions following the collapse of the cores of massive stars. If some of the explosion ejecta fails to escape, it may fall back onto the neutron star or it may possess sufficient angular momentum to form a disk. Such 'fallback' is both a general prediction of current supernova models and, if the material pushes the neutron star over its stability limit, a possible mode of black hole formation. Fallback disks could dramatically affect the early evolution of pulsars, yet there are few observational constraints on whether significant fallback occurs or even the actual existence of such disks. Here we report the discovery of mid-infrared emission from a cool disk around an isolated young X-ray pulsar. The disk does not power the pulsar's X-ray emission but is passively illuminated by these X-rays. The estimated mass of the disk is of the order of 10 Earth masses, and its lifetime (> or = 10(6) years) significantly exceeds the spin-down age of the pulsar, supporting a supernova fallback origin. The disk resembles protoplanetary disks seen around ordinary young stars, suggesting the possibility of planet formation around young neutron stars.

Thermalization with chemical potentials, and higher spin black holes

International Nuclear Information System (INIS)

Mandal, Gautam; Sinha, Ritam; Sorokhaibam, Nilakash

2015-01-01

We study the long time behaviour of local observables following a quantum quench in 1+1 dimensional conformal field theories possessing additional conserved charges besides the energy. We show that the expectation value of an arbitrary string of local observables supported on a finite interval exponentially approaches an equilibrium value. The equilibrium is characterized by a temperature and chemical potentials defined in terms of the quenched state. For an infinite number of commuting conserved charges, the equilibrium ensemble is a generalized Gibbs ensemble (GGE). We compute the thermalization rate in a systematic perturbation in the chemical potentials, using a new technique to sum over an infinite number of Feynman diagrams. The above technique also allows us to compute relaxation times for thermal Green’s functions in the presence of an arbitrary number of chemical potentials. In the context of a higher spin (hs[λ]) holography, the partition function of the final equilibrium GGE is known to agree with that of a higher spin black hole. The thermalization rate from the CFT computed in our paper agrees with the quasinormal frequency of a scalar field in this black hole.

RINGED ACCRETION DISKS: EQUILIBRIUM CONFIGURATIONS

Energy Technology Data Exchange (ETDEWEB)

Pugliese, D.; Stuchlík, Z., E-mail: d.pugliese.physics@gmail.com, E-mail: zdenek.stuchlik@physics.cz [Institute of Physics and Research Centre of Theoretical Physics and Astrophysics, Faculty of Philosophy and Science, Silesian University in Opava, Bezručovo náměstí 13, CZ-74601 Opava (Czech Republic)

2015-12-15

We investigate a model of a ringed accretion disk, made up by several rings rotating around a supermassive Kerr black hole attractor. Each toroid of the ringed disk is governed by the general relativity hydrodynamic Boyer condition of equilibrium configurations of rotating perfect fluids. Properties of the tori can then be determined by an appropriately defined effective potential reflecting the background Kerr geometry and the centrifugal effects. The ringed disks could be created in various regimes during the evolution of matter configurations around supermassive black holes. Therefore, both corotating and counterrotating rings have to be considered as being a constituent of the ringed disk. We provide constraints on the model parameters for the existence and stability of various ringed configurations and discuss occurrence of accretion onto the Kerr black hole and possible launching of jets from the ringed disk. We demonstrate that various ringed disks can be characterized by a maximum number of rings. We present also a perturbation analysis based on evolution of the oscillating components of the ringed disk. The dynamics of the unstable phases of the ringed disk evolution seems to be promising in relation to high-energy phenomena demonstrated in active galactic nuclei.

Spin excitations in hole-overdoped iron-based superconductors.

Science.gov (United States)

Horigane, K; Kihou, K; Fujita, K; Kajimoto, R; Ikeuchi, K; Ji, S; Akimitsu, J; Lee, C H

2016-09-12

Understanding the overall features of magnetic excitation is essential for clarifying the mechanism of Cooper pair formation in iron-based superconductors. In particular, clarifying the relationship between magnetism and superconductivity is a central challenge because magnetism may play a key role in their exotic superconductivity. BaFe2As2 is one of ideal systems for such investigation because its superconductivity can be induced in several ways, allowing a comparative examination. Here we report a study on the spin fluctuations of the hole-overdoped iron-based superconductors Ba1-xKxFe2As2 (x = 0.5 and 1.0; Tc = 36 K and 3.4 K, respectively) over the entire Brillouin zone using inelastic neutron scattering. We find that their spin spectra consist of spin wave and chimney-like dispersions. The chimney-like dispersion can be attributed to the itinerant character of magnetism. The band width of the spin wave-like dispersion is almost constant from the non-doped to optimum-doped region, which is followed by a large reduction in the overdoped region. This suggests that the superconductivity is suppressed by the reduction of magnetic exchange couplings, indicating a strong relationship between magnetism and superconductivity in iron-based superconductors.

Effects of different operating parameters on the particle size of silver chloride nanoparticles prepared in a spinning disk reactor

Science.gov (United States)

Dabir, Hossein; Davarpanah, Morteza; Ahmadpour, Ali

2015-07-01

The aim of this research was to present an experimental method for large-scale production of silver chloride nanoparticles using spinning disk reactor. Silver nitrate and sodium chloride were used as the reactants, and the protecting agent was gelatin. The experiments were carried out in a continuous mode by injecting the reactants onto the surface of the spinning disk, where a chemical precipitation reaction took place to form AgCl particles. The effects of various operating variables, including supersaturation, disk rotational speed, reactants flow rate, disk diameter, and excess ions, on the particle size of products were investigated. In addition, the AgCl nanoparticles were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. According to the results, smaller AgCl particles are obtained under higher supersaturations and also higher disk rotation speeds. Moreover, in the range of our investigation, the use of lower reactants flow rates and larger disk diameter can reduce the particle size of products. The non-stoichiometric condition of reactants has a significant influence on the reduction in particle aggregation. It was also found that by optimizing the operating conditions, uniform AgCl nanoparticles with the mean size of around 37 nm can be produced.

Displacement of fovea toward optic disk after macular hole surgery with internal limiting membrane peeling.

Science.gov (United States)

Ohta, Kouichi; Sato, Atsuko; Senda, Nami; Fukui, Emi

2017-01-01

The purpose of this study was to demonstrate a displacement of the foveal depression toward the optic disk after idiopathic macular hole (MH) surgery with internal limiting membrane (ILM) peeling. Two patients with a unilateral MH developed an MH in the fellow eyes. Vitrectomy with ILM peeling was performed on the fellow eye to close the MH. Images of spectral-domain optical coherence tomography (SD-OCT) were used to measure the disk-to-fovea distances pre MH formation, after MH formation, and 6 months after the closure of the MH. The disk-to-fovea distance was shorter at 6 months than after the development of the MH (4,109 µm and 4,174 µm in Case 1 and 4,001 µm and 4,051 µm in Case 2). These results indicate that the fovea moves nasally after the MH surgery with ILM peeling.

ILLUMINATING BLACK HOLE BINARY FORMATION CHANNELS WITH SPINS IN ADVANCED LIGO

Energy Technology Data Exchange (ETDEWEB)

Rodriguez, Carl L. [MIT-Kavli Institute for Astrophysics and Space Research, 77 Massachusetts Avenue, 37-664H, Cambridge, MA 02139 (United States); Zevin, Michael; Pankow, Chris; Kalogera, Vasilliki; Rasio, Frederic A. [Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astronomy, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (United States)

2016-11-20

The recent detections of the binary black hole mergers GW150914 and GW151226 have inaugurated the field of gravitational-wave astronomy. For the two main formation channels that have been proposed for these sources, isolated binary evolution in galactic fields and dynamical formation in dense star clusters, the predicted masses and merger rates overlap significantly, complicating any astrophysical claims that rely on measured masses alone. Here, we examine the distribution of spin–orbit misalignments expected for binaries from the field and from dense star clusters. Under standard assumptions for black hole natal kicks, we find that black hole binaries similar to GW150914 could be formed with significant spin–orbit misalignment only through dynamical processes. In particular, these heavy-black hole binaries can only form with a significant spin–orbit anti -alignment in the dynamical channel. Our results suggest that future detections of merging black hole binaries with measurable spins will allow us to identify the main formation channel for these systems.

Black Hole Accretion in Gamma Ray Bursts

Directory of Open Access Journals (Sweden)

Agnieszka Janiuk

2017-02-01

Full Text Available We study the structure and evolution of the hyperaccreting disks and outflows in the gamma ray bursts central engines. The torus around a stellar mass black hole is composed of free nucleons, Helium, electron-positron pairs, and is cooled by neutrino emission. Accretion of matter powers the relativistic jets, responsible for the gamma ray prompt emission. The significant number density of neutrons in the disk and outflowing material will cause subsequent formation of heavier nuclei. We study the process of nucleosynthesis and its possible observational consequences. We also apply our scenario to the recent observation of the gravitational wave signal, detected on 14 September 2015 by the two Advanced LIGO detectors, and related to an inspiral and merger of a binary black hole system. A gamma ray burst that could possibly be related with the GW150914 event was observed by the Fermi satellite. It had a duration of about 1 s and appeared about 0.4 s after the gravitational-wave signal. We propose that a collapsing massive star and a black hole in a close binary could lead to the event. The gamma ray burst was powered by a weak neutrino flux produced in the star remnant’s matter. Low spin and kick velocity of the merged black hole are reproduced in our simulations. Coincident gravitational-wave emission originates from the merger of the collapsed core and the companion black hole.

Retrograde versus Prograde Models of Accreting Black Holes

Directory of Open Access Journals (Sweden)

David Garofalo

2013-01-01

Full Text Available There is a general consensus that magnetic fields, accretion disks, and rotating black holes are instrumental in the generation of the most powerful sources of energy in the known universe. Nonetheless, because magnetized accretion onto rotating black holes involves both the complications of nonlinear magnetohydrodynamics that currently cannot fully be treated numerically, and uncertainties about the origin of magnetic fields that at present are part of the input, the space of possible solutions remains less constrained. Consequently, the literature still bears witness to the proliferation of rather different black hole engine models. But the accumulated wealth of observational data is now sufficient to meaningfully distinguish between them. It is in this light that this critical paper compares the recent retrograde framework with standard “spin paradigm” prograde models.

Tailoring Cu Nanoparticle Catalyst for Methanol Synthesis Using the Spinning Disk Reactor

Directory of Open Access Journals (Sweden)

Christian Ahoba-Sam

2018-01-01

Full Text Available Cu nanoparticles are known to be very active for methanol (MeOH synthesis at relatively low temperatures, such that smaller particle sizes yield better MeOH productivity. We aimed to control Cu nanoparticle (NP size and size distribution for catalysing MeOH synthesis, by using the spinning disk reactor. The spinning disk reactor (SDR, which operates based on shear effect and plug flow in thin films, can be used to rapidly micro-mix reactants in order to control nucleation and particle growth for uniform particle size distribution. This could be achieved by varying both physical and chemical operation conditions in a precipitation reaction on the SDR. We have used the SDR for a Cu borohydride reduction to vary Cu NP size from 3 nm to about 55 nm. XRD and TEM characterization confirmed the presence of Cu2O and Cu crystallites when the samples were dried. This technique is readily scalable for Cu NP production by processing continuously over a longer duration than the small-scale tests. However, separation of the nanoparticles from solution posed a challenge as the suspension hardly settled. The Cu NPs produced were tested to be active catalyst for MeOH synthesis at low temperature and MeOH productivity increased with decreasing particle size.

MODERATE-LUMINOSITY GROWING BLACK HOLES FROM 1.25 < z < 2.7: VARIED ACCRETION IN DISK-DOMINATED HOSTS

Energy Technology Data Exchange (ETDEWEB)

Simmons, B. D.; Glikman, E. [Astronomy Department, Yale University, New Haven, CT 06511 (United States); Urry, C. M.; Schawinski, K. [Yale Center for Astronomy and Astrophysics, Physics Department, Yale University, New Haven, CT 06511 (United States); Cardamone, C., E-mail: brooke.simmons@astro.ox.ac.uk [Sheridan Center for Teaching and Learning, Brown University, 96 Waterman St., Providence RI 02912 (United States)

2012-12-10

We compute black hole masses and bolometric luminosities for 57 active galactic nuclei (AGNs) in the redshift range 1.25 {<=} z {<=} 2.67, selected from the GOODS-South deep multi-wavelength survey field via their X-ray emission. We determine host galaxy morphological parameters by separating the galaxies from their central point sources in deep Hubble Space Telescope images, and host stellar masses and colors by multi-wavelength spectral energy distribution fitting. Of GOODS AGNs at these redshifts, 90% have detected rest-frame optical nuclear point sources; bolometric luminosities range from 2 Multiplication-Sign 10{sup 43} to 2 Multiplication-Sign 10{sup 46} erg s{sup -1}. The black holes are growing at a range of accretion rates, with {approx}> 50% of the sample having L/L{sub Edd} < 0.1. Of the host galaxies, 70% have stellar masses M{sub *} > 10{sup 10} M{sub Sun }, with a range of colors suggesting a complex star formation history. We find no evolution of AGN bolometric luminosity within the sample, and no correlation between AGN bolometric luminosity and host stellar mass, color, or morphology. Fully half the sample of host galaxies are disk-dominated, with another 25% having strong disk components. Fewer than 15% of the systems appear to be at some stage of a major merger. These moderate-luminosity AGN hosts are therefore inconsistent with a dynamical history dominated by mergers strong enough to destroy disks, indicating that minor mergers or secular processes dominate the coevolution of galaxies and their central black holes at z {approx} 2.

RADIATION PRESSURE-SUPPORTED ACCRETION DISKS: VERTICAL STRUCTURE, ENERGY ADVECTION, AND CONVECTIVE STABILITY

International Nuclear Information System (INIS)

Gu Weimin

2012-01-01

By taking into account the local energy balance per unit volume between the viscous heating and the advective cooling plus the radiative cooling, we investigate the vertical structure of radiation pressure-supported accretion disks in spherical coordinates. Our solutions show that the photosphere of the disk is close to the polar axis and therefore the disk seems to be extremely thick. However, the density profile implies that most of the accreted matter exists in a moderate range around the equatorial plane. We show that the well-known polytropic relation between the pressure and the density is unsuitable for describing the vertical structure of radiation pressure-supported disks. More importantly, we find that the energy advection is significant even for slightly sub-Eddington accretion disks. We argue that the non-negligible advection may help us understand why the standard thin disk model is likely to be inaccurate above ∼0.3 Eddington luminosity, which was found by some works on black hole spin measurement. Furthermore, the solutions satisfy the Solberg-Høiland conditions, which indicate the disk to be convectively stable. In addition, we discuss the possible link between our disk model and ultraluminous X-ray sources.

Sporadic mass loss, spin-down, and element redistribution in young disk galaxies

International Nuclear Information System (INIS)

Charlton, J.C.; Salpeter, E.E.

1989-01-01

Violent conditions in young spiral disks may be conducive to the high-velocity ejection of large blobs of material powered by the concerted action of supernovae. Using explicit numerical Monte Carlo models, treating ejected bobs as galactic cannonballs traveling with little interaction through the corona, several important consequences for galactic evolution are found. Preferential escape from the galaxy or objects with high specific angular momenta lead to a significant spin-down of the disk. In addition, this process may contribute to the production of an exponential column density distribution, and a metallicity gradient. The models predict a reversal in the sign of the metallicity gradient at large radii because the metal-rich objects that return to such a low column density region suffer relatively little dilution. 39 refs

Spin currents, relativistic effects and the Darwin interaction in the theory of hole superconductivity

International Nuclear Information System (INIS)

Hirsch, J.E.

2005-01-01

The existence of macroscopic spin currents in the ground state of superconductors is predicted within the theory of hole superconductivity. Here it is shown that the electromagnetic Darwin interaction is attractive for spin currents and repulsive for charge currents. It is also shown that the mere existence of spin currents implies that some electrons are moving at relativistic speeds in macroscopic superconductors, which in turn implies that the Darwin interaction plays a fundamental role in stabilizing the superconducting state

Simultaneous differential spinning disk fluorescence optical sectioning microscopy and nanomechanical mapping atomic force microscopy

International Nuclear Information System (INIS)

Miranda, Adelaide; De Beule, Pieter A. A.; Martins, Marco

2015-01-01

Combined microscopy techniques offer the life science research community a powerful tool to investigate complex biological systems and their interactions. Here, we present a new combined microscopy platform based on fluorescence optical sectioning microscopy through aperture correlation microscopy with a Differential Spinning Disk (DSD) and nanomechanical mapping with an Atomic Force Microscope (AFM). The illumination scheme of the DSD microscope unit, contrary to standard single or multi-point confocal microscopes, provides a time-independent illumination of the AFM cantilever. This enables a distortion-free simultaneous operation of fluorescence optical sectioning microscopy and atomic force microscopy with standard probes. In this context, we discuss sample heating due to AFM cantilever illumination with fluorescence excitation light. Integration of a DSD fluorescence optical sectioning unit with an AFM platform requires mitigation of mechanical noise transfer of the spinning disk. We identify and present two solutions to almost annul this noise in the AFM measurement process. The new combined microscopy platform is applied to the characterization of a DOPC/DOPS (4:1) lipid structures labelled with a lipophilic cationic indocarbocyanine dye deposited on a mica substrate

Simultaneous differential spinning disk fluorescence optical sectioning microscopy and nanomechanical mapping atomic force microscopy

Energy Technology Data Exchange (ETDEWEB)

Miranda, Adelaide; De Beule, Pieter A. A., E-mail: pieter.de-beule@inl.int [Applied Nano-Optics Laboratory, International Iberian Nanotechnology Laboratory, Avenida Mestre José Veiga, s/n, 4715-330 Braga (Portugal); Martins, Marco [Nano-ICs Group, International Iberian Nanotechnology Laboratory, Avenida Mestre José Veiga, s/n, 4715-330 Braga (Portugal)

2015-09-15

Combined microscopy techniques offer the life science research community a powerful tool to investigate complex biological systems and their interactions. Here, we present a new combined microscopy platform based on fluorescence optical sectioning microscopy through aperture correlation microscopy with a Differential Spinning Disk (DSD) and nanomechanical mapping with an Atomic Force Microscope (AFM). The illumination scheme of the DSD microscope unit, contrary to standard single or multi-point confocal microscopes, provides a time-independent illumination of the AFM cantilever. This enables a distortion-free simultaneous operation of fluorescence optical sectioning microscopy and atomic force microscopy with standard probes. In this context, we discuss sample heating due to AFM cantilever illumination with fluorescence excitation light. Integration of a DSD fluorescence optical sectioning unit with an AFM platform requires mitigation of mechanical noise transfer of the spinning disk. We identify and present two solutions to almost annul this noise in the AFM measurement process. The new combined microscopy platform is applied to the characterization of a DOPC/DOPS (4:1) lipid structures labelled with a lipophilic cationic indocarbocyanine dye deposited on a mica substrate.

Spinning Kerr black holes with stationary massive scalar clouds: the large-coupling regime

Energy Technology Data Exchange (ETDEWEB)

Hod, Shahar [Marine sciences, The Ruppin Academic Center,Ruppin, Emeq Hefer 40250 (Israel); Biotechnology, The Hadassah Academic College,37 Hanevi’im St., Jerusalem 9101001 (Israel)

2017-01-09

We study analytically the Klein-Gordon wave equation for stationary massive scalar fields linearly coupled to spinning Kerr black holes. In particular, using the WKB approximation, we derive a compact formula for the discrete spectrum of scalar field masses which characterize the stationary composed Kerr-black-hole-massive-scalar-field configurations in the large-coupling regime Mμ≫1 (here M and μ are respectively the mass of the central black hole and the proper mass of the scalar field). We confirm our analytically derived formula for the Kerr-scalar-field mass spectrum with numerical data that recently appeared in the literature.

Irradiation of an Accretion Disc by a Jet: General Properties and Implications for Spin Measurements of Black Holes

Science.gov (United States)

T.Dauser; Garcia, J.; Wilms, J.; Boeck, M.; Brenneman, L. W.; Falanga, M.; Fukumura, Keigo; Reynolds, C. S.

2013-01-01

X-ray irradiation of the accretion disc leads to strong reflection features, which are then broadened and distorted by relativistic effects. We present a detailed, general relativistic approach to model this irradiation for different geometries of the primary X-ray source. These geometries include the standard point source on the rotational axis as well as more jet-like sources, which are radially elongated and accelerating. Incorporating this code in the RELLINE model for relativistic line emission, the line shape for any configuration can be predicted. We study how different irradiation geometries affect the determination of the spin of the black hole. Broad emission lines are produced only for compact irradiating sources situated close to the black hole. This is the only case where the black hole spin can be unambiguously determined. In all other cases the line shape is narrower, which could either be explained by a low spin or an elongated source. We conclude that for those cases and independent of the quality of the data, no unique solution for the spin exists and therefore only a lower limit of the spin value can be given

Many-body dynamics of holes in a driven, dissipative spin chain of Rydberg superatoms

Science.gov (United States)

Letscher, Fabian; Petrosyan, David; Fleischhauer, Michael

2017-11-01

Strong, long-range interactions between atoms in high-lying Rydberg states can suppress multiple Rydberg excitations within a micron-sized trapping volume and yield sizable Rydberg level shifts at larger distances. Ensembles of atoms in optical microtraps then form Rydberg superatoms with collectively enhanced transition rates to the singly excited state. These superatoms can represent mesoscopic, strongly interacting spins. We study a regular array of such effective spins driven by a laser field tuned to compensate the interaction-induced level shifts between neighboring superatoms. During the initial transient, a few excited superatoms seed a cascade of resonantly facilitated excitation of large clusters of superatoms. Due to spontaneous decay, the system then relaxes to the steady state having nearly universal Rydberg excitation density {ρ }{{R}}=2/3. This state is characterized by highly non-trivial equilibrium dynamics of quasi-particles—excitation holes in the lattice of Rydberg excited superatoms. We derive an effective many-body model that accounts for hole mobility as well as continuous creation and annihilation of holes upon collisions with each other. We find that holes exhibit a nearly incompressible liquid phase with highly sub-Poissonian number statistics and finite-range density-density correlations.

Hawking radiation of spin-1 particles from a three-dimensional rotating hairy black hole

Energy Technology Data Exchange (ETDEWEB)

Sakalli, I.; Ovgun, A., E-mail: ali.ovgun@emu.edu.tr [Eastern Mediterranean University Famagusta, North Cyprus, Department of Physics (Turkey)

2015-09-15

We study the Hawking radiation of spin-1 particles (so-called vector particles) from a three-dimensional rotating black hole with scalar hair using a Hamilton–Jacobi ansatz. Using the Proca equation in the WKB approximation, we obtain the tunneling spectrum of vector particles. We recover the standard Hawking temperature corresponding to the emission of these particles from a rotating black hole with scalar hair.

Observation of Rashba zero-field spin splitting in a strained germanium 2D hole gas

International Nuclear Information System (INIS)

Morrison, C.; Rhead, S. D.; Foronda, J.; Leadley, D. R.; Myronov, M.; Wiśniewski, P.

2014-01-01

We report the observation, through Shubnikov-de Haas oscillations in the magnetoresistance, of spin splitting caused by the Rashba spin-orbit interaction in a strained Ge quantum well epitaxially grown on a standard Si(001) substrate. The Shubnikov-de Haas oscillations display a beating pattern due to the spin split Landau levels. The spin-orbit parameter and Rashba spin-splitting energy are found to be 1.0 × 10 −28   eVm 3 and 1.4 meV, respectively. This energy is comparable to 2D electron gases in III-V semiconductors, but substantially larger than in Si, and illustrates the suitability of Ge for modulated hole spin transport devices.

Direct imaging rapidly-rotating non-Kerr black holes

Energy Technology Data Exchange (ETDEWEB)

Bambi, Cosimo, E-mail: Cosimo.Bambi@physik.uni-muenchen.de [Arnold Sommerfeld Center for Theoretical Physics, Ludwig-Maximilians-Universitaet Muenchen, 80333 Munich (Germany); Caravelli, Francesco, E-mail: fcaravelli@perimeterinstitute.ca [Max Planck Institute for Gravitational Physics, Albert Einstein Institute, 14476 Golm (Germany); Department of Physics, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5 (Canada); Modesto, Leonardo, E-mail: lmodesto@perimeterinstitute.ca [Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5 (Canada)

2012-05-01

Recently, two of us have argued that non-Kerr black holes in gravity theories different from General Relativity may have a topologically non-trivial event horizon. More precisely, the spatial topology of the horizon of non-rotating and slow-rotating objects would be a 2-sphere, like in Kerr space-time, while it would change above a critical value of the spin parameter. When the topology of the horizon changes, the black hole central singularity shows up. The accretion process from a thin disk can potentially overspin these black holes and induce the topology transition, violating the Weak Cosmic Censorship Conjecture. If the astrophysical black hole candidates are not the black holes predicted by General Relativity, we might have the quite unique opportunity to see their central region, where classical physics breaks down and quantum gravity effects should appear. Even if the quantum gravity region turned out to be extremely small, at the level of the Planck scale, the size of its apparent image would be finite and potentially observable with future facilities.

Accretion disks in active galactic nuclei

International Nuclear Information System (INIS)

Shields, G.A.

1989-01-01

Active galactic nuclei (AGN) have taunted astrophysicists for a quarter century. How do these objects produce huge luminosities---in some cases, far outshining our galaxy---from a region perhaps no larger than the solar system? Accretion onto supermassive black holes has been widely considered the best buy in theories of AGN. Much work has gone into accretion disk theory, searches for black holes in galactic nuclei, and observational tests. These efforts have not proved the disk model, but there is progress. Evidence for black holes in the nuclei of nearby galaxies is provided by observations of stellar velocities, and radiation from the disk's hot surface may be observed in the ultraviolet (UV) and neighboring spectral bands. In the review, the author describe some of the recent work on accretion disks in AGN, with an emphasis on points of contact between theory and observation

Premixed direct injection disk

Science.gov (United States)

York, William David; Ziminsky, Willy Steve; Johnson, Thomas Edward; Lacy, Benjamin; Zuo, Baifang; Uhm, Jong Ho

2013-04-23

A fuel/air mixing disk for use in a fuel/air mixing combustor assembly is provided. The disk includes a first face, a second face, and at least one fuel plenum disposed therebetween. A plurality of fuel/air mixing tubes extend through the pre-mixing disk, each mixing tube including an outer tube wall extending axially along a tube axis and in fluid communication with the at least one fuel plenum. At least a portion of the plurality of fuel/air mixing tubes further includes at least one fuel injection hole have a fuel injection hole diameter extending through said outer tube wall, the fuel injection hole having an injection angle relative to the tube axis. The invention provides good fuel air mixing with low combustion generated NOx and low flow pressure loss translating to a high gas turbine efficiency, that is durable, and resistant to flame holding and flash back.

Dusty disks around young stars

NARCIS (Netherlands)

Verhoeff, A.

2009-01-01

Stars are formed through the collapse of giant molecular clouds. During this contraction the matter spins up and naturally forms a circumstellar disk. Once accretion comes to a halt, these disks are relatively stable. Some disks are known to last up to 10 Myrs. Most disks however, dissipate on

Conductivity of a spin-polarized two-dimensional hole gas at very low temperature

Energy Technology Data Exchange (ETDEWEB)

Dlimi, S., E-mail: kaaouachi21@yahoo.fr; Kaaouachi, A. El, E-mail: kaaouachi21@yahoo.fr; Limouny, L., E-mail: kaaouachi21@yahoo.fr; Sybous, A.; Narjis, A.; Errai, M.; Daoudi, E. [Research Group ESNPS , Physics department, University Ibn Zohr, Faculty of Sciences, B.P 8106, Hay Dakhla, 80000 Agadir (Morocco); Idrissi, H. El [Faculté des Sciences et Techniques de Mohammedia, Département de physique. BP 146 Quartier Yasmina Mohammedia (Morocco); Zatni, A. [Laboratoire MSTI. Ecole de technologied' Agadir, B.P33/S Agadir (Morocco)

2014-01-27

In the ballistic regime where k{sub B}Tτ / ħ ≥1, the temperature dependence of the metallic conductivity in a two-dimensional hole system of gallium arsenide, is found to change non-monotonically with the degree of spin polarization. In particular, it fades away just before the onset of complete spin polarization, but reappears again in the fully spin-polarized state, being, however, suppressed relative to the zero magnetic field case. The analysis of the degree of suppression can distinguish between screening and interaction-based theories. We show that in a fully polarized spin state, the effects of disorder are dominant and approach a strong localization regime, which is contrary to the behavior of 2D electron systems in a weakly disordered unpolarized state. It was found that the elastic relaxation time correction, depending on the temperature, changed significantly with the degree of spin polarization, to reach a minimum just below the start of the spin-polarized integer, where the conductivity is practically independent of temperature.

Spinning-disk confocal microscopy: present technology and future trends.

Science.gov (United States)

Oreopoulos, John; Berman, Richard; Browne, Mark

2014-01-01

Live-cell imaging requires not only high temporal resolution but also illumination powers low enough to minimize photodamage. Traditional single-point laser scanning confocal microscopy (LSCM) is generally limited by both the relatively slow speed at which it can acquire optical sections by serial raster scanning (a few Hz) and the higher potential for phototoxicity. These limitations have driven the development of rapid, parallel forms of confocal microscopy, the most popular of which is the spinning-disk confocal microscope (SDCM). Here, we briefly introduce the SDCM technique, discuss its strengths and weaknesses against LSCM, and update the reader on some recent developments in SDCM technology that improve its performance and expand its utility for life science research now and in the future. © 2014 Elsevier Inc. All rights reserved.

Accretion Disk Assembly During Common Envelope Evolution: Implications for Feedback and LIGO Binary Black Hole Formation

Energy Technology Data Exchange (ETDEWEB)

Murguia-Berthier, Ariadna; Ramirez-Ruiz, Enrico; Antoni, Andrea; Macias, Phillip [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); MacLeod, Morgan, E-mail: armurgui@ucsc.edu [School of Natural Sciences, Institute for Advanced Study, 1 Einstein Drive, Princeton, NJ 08540 (United States)

2017-08-20

During a common envelope (CE) episode in a binary system, the engulfed companion spirals to tighter orbital separations under the influence of drag from the surrounding envelope material. As this object sweeps through material with a steep radial gradient of density, net angular momentum is introduced into the flow, potentially leading to the formation of an accretion disk. The presence of a disk would have dramatic consequences for the outcome of the interaction because accretion might be accompanied by strong, polar outflows with enough energy to unbind the entire envelope. Without a detailed understanding of the necessary conditions for disk formation during CE, therefore, it is difficult to accurately predict the population of merging compact binaries. This paper examines the conditions for disk formation around objects embedded within CEs using the “wind tunnel” formalism developed by MacLeod et al. We find that the formation of disks is highly dependent on the compressibility of the envelope material. Disks form only in the most compressible of stellar envelope gas, found in envelopes’ outer layers in zones of partial ionization. These zones are largest in low-mass stellar envelopes, but comprise small portions of the envelope mass and radius in all cases. We conclude that disk formation and associated accretion feedback in CE is rare, and if it occurs, transitory. The implication for LIGO black hole binary assembly is that by avoiding strong accretion feedback, CE interactions should still result in the substantial orbital tightening needed to produce merging binaries.

Thin accretion disks in stationary axisymmetric wormhole spacetimes

International Nuclear Information System (INIS)

Harko, Tiberiu; Kovacs, Zoltan; Lobo, Francisco S. N.

2009-01-01

In this paper, we study the physical properties and the equilibrium thermal radiation emission characteristics of matter forming thin accretion disks in stationary axially symmetric wormhole spacetimes. The thin disk models are constructed by taking different values of the wormhole's angular velocity, and the time averaged energy flux, the disk temperature, and the emission spectra of the accretion disks are obtained. Comparing the mass accretion in a rotating wormhole geometry with the one of a Kerr black hole, we verify that the intensity of the flux emerging from the disk surface is greater for wormholes than for rotating black holes with the same geometrical mass and accretion rate. We also present the conversion efficiency of the accreting mass into radiation, and show that the rotating wormholes provide a much more efficient engine for the transformation of the accreting mass into radiation than the Kerr black holes. Therefore specific signatures appear in the electromagnetic spectrum of thin disks around rotating wormholes, thus leading to the possibility of distinguishing wormhole geometries by using astrophysical observations of the emission spectra from accretion disks.

Photooxidative Removal of p -Nitrophenol by UV/H 2 O 2 Process in a Spinning Disk Photoreactor: Influence of Operating Parameters

Directory of Open Access Journals (Sweden)

H. Dadkhah

2017-10-01

Full Text Available In this paper, spinning disk photoreactor (SDP has been used for the removal of a refractory pollutant, namely p-nitrophenol (PNP, in UV/H2O2 process. The effect of various parameters such as the plate type in the SDP, concentration of oxidant (H2O2, fluid volume, initial concentration of PNP, distance of the lamps from the spinning disk, distance of the lamps from each other, pH, and rotation speed of the spinning disk in the removal efficiency has been investigated. The results indicated that the use of scrobiculate disc instead of flat disc significantly increased the removal percentage of PNP from 46 to 100 % for the irradiation time of 20 min; it also increased with increasing H2O2 concentration, but the increase in fluid volume and the initial concentration of PNP reduced the removal percentage of PNP in the SDP. The increase in the distance of UV lamps from each other and from disc surface in the SDP reduced the removal percentage of PNP. However, the increase in pH to 5.5 increased removal efficiency while increasing pH above 5.5 reduced PNP removal efficiency. The disk rotation speed from 0 to 90 rpm increased the removal percentage from 49 to 70 % for the irradiation time of 5 min, but increasing the rotation speed to more than 90 rpm reduced the removal efficiency.

OPTICAL VARIABILITY OF THE ACCRETION DISK AROUND THE INTERMEDIATE-MASS BLACK HOLE ESO 243-49 HLX-1 DURING THE 2012 OUTBURST

Energy Technology Data Exchange (ETDEWEB)

Webb, N. A.; Godet, O.; Barret, D. [Université de Toulouse, UPS-OMP, IRAP, Toulouse (France); Wiersema, K. [University of Leicester, University Road, Leicester LE1 7RH (United Kingdom); Lasota, J.-P. [Institut d' Astrophysique de Paris, UMR 7095, CNRS, UPMC Université Paris 06, 98bis Boulevard Arago, F-75014 Paris (France); Farrell, S. A. [Sydney Institute for Astronomy, School of Physics, The University of Sydney, NSW 2006 (Australia); Maccarone, T. J. [Department of Physics, Box 41051, Texas Tech University, Lubbock TX 79409-1051 (United States); Servillat, M., E-mail: natalie.webb@irap.omp.eu [Laboratoire AIM (CEA/DSM/IRFU/SAp, CNRS, Université Paris Diderot), CEA Saclay, Bat. 709, F-91191 Gif-sur-Yvette (France)

2014-01-01

We present dedicated quasi-simultaneous X-ray (Swift) and optical (Very Large Telescope, V-, and R-band) observations of the intermediate-mass black hole candidate HLX-1 before and during the 2012 outburst. We show that the V-band magnitudes vary with time, thus proving that a portion of the observed emission originates in the accretion disk. Using the first quiescent optical observations of HLX-1, we show that the stellar population surrounding HLX-1 is fainter than V ∼ 25.1 and R ∼ 24.2. We show that the optical emission may increase before the X-ray emission consistent with the scenario proposed by Lasota et al. in which the regular outbursts could be related to the passage at periastron of a star circling the intermediate-mass black hole in an eccentric orbit, which triggers mass transfer into a quasi-permanent accretion disk around the black hole. Further, if there is indeed a delay in the X-ray emission we estimate the mass-transfer delivery radius to be ∼10{sup 11} cm.

Measuring Parameters of Massive Black Hole Binaries with Partially-Aligned Spins

Science.gov (United States)

Lang, Ryan N.; Hughes, Scott A.; Cornish, Neil J.

2010-01-01

It is important to understand how well the gravitational-wave observatory LISA can measure parameters of massive black hole binaries. It has been shown that including spin precession in the waveform breaks degeneracies and produces smaller expected parameter errors than a simpler, precession-free analysis. However, recent work has shown that gas in binaries can partially align the spins with the orbital angular momentum, thus reducing the precession effect. We show how this degrades the earlier results, producing more pessimistic errors in gaseous mergers. However, we then add higher harmonics to the signal model; these also break degeneracies, but they are not affected by the presence of gas. The harmonics often restore the errors in partially-aligned binaries to the same as, or better than/ those that are obtained for fully precessing binaries with no harmonics. Finally, we investigate what LISA measurements of spin alignment can tell us about the nature of gas around a binary,

Application of the Landau-Zener-Stückelberg-Majorana dynamics to the electrically driven flip of a hole spin

Science.gov (United States)

Pasek, W. J.; Maialle, M. Z.; Degani, M. H.

2018-03-01

An idea of employing the Landau-Zener-Stückelberg-Majorana dynamics to flip a spin of a single ground state hole is introduced and explored by a time-dependent simulation. This configuration interaction study considers a hole confined in a quantum molecule formed in an InSb 〈111 〉 quantum wire by application of an electrostatic potential. An up-down spin-mixing avoided crossing is formed by nonaxial terms in the Kohn-Luttinger Hamiltonian and the Dresselhaus spin-orbit one. Manipulation of the system is possible by the dynamic change of an external vertical electric field, which enables the consecutive driving of the hole through two anticrossings. Moreover, a simple model of the power-law-type noise that impedes precise electric control of the system is included in the form of random telegraph noise to estimate the limitations of the working conditions. We show that in principle the process is possible, but it requires precise control of the parameters of the driving impulse.

On Estimating the Mass of Keplerian Accretion Disks in H2O Maser Galaxies

Science.gov (United States)

Kuo, C. Y.; Reid, M. J.; Braatz, J. A.; Gao, F.; Impellizzeri, C. M. V.; Chien, W. T.

2018-06-01

H2O maser disks with Keplerian rotation in active galactic nuclei offer a clean way to determine accurate black hole mass and the Hubble constant. An important assumption made in using a Keplerian H2O maser disk for measuring black hole mass and the Hubble constant is that the disk mass is negligible compared to the black hole mass. A simple and useful model of Huré et al. can be used to test this assumption. In that work, the authors apply a linear disk model to a position–dynamical mass diagram and re-analyze position–velocity data from H2O maser disks associated with active galactic nuclei. They claim that a maser disk with nearly perfect Keplerian rotation could have a disk mass comparable to the black hole mass. This would imply that ignoring the effects of disk self-gravity can lead to large systematic errors in the measurement of black hole mass and the Hubble constant. We examine their methods and find that their large estimated disk masses of Keplerian disks are likely the result of their use of projected instead of three-dimensional position and velocity information. To place better constraints on the disk masses of Keplerian maser systems, we incorporate disk self-gravity into a three-dimensional Bayesian modeling program for maser disks and also evaluate constraints based on the physical conditions for disks that support water maser emission. We find that there is little evidence that disk masses are dynamically important at the ≲1% level compared to the black holes.

Tuning of the hole spin relaxation time in single self-assembled In{sub 1−x}Ga{sub x}As/GaAs quantum dots by electric field

Energy Technology Data Exchange (ETDEWEB)

Wei, Hai; Guo, Guang-Can; He, Lixin, E-mail: helx@ustc.edu.cn [Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026 (China); Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026 (China)

2014-11-28

We investigate the electric field tuning of the phonon-assisted hole spin relaxation in single self-assembled In{sub 1−x}Ga{sub x}As/GaAs quantum dots (QDs), using an atomistic empirical pseudopotential method. We find that the electric field along the growth direction can tune the hole spin relaxation time for more than one order of magnitude. The electric field can prolong or shorten the hole spin lifetime and the tuning shows an asymmetry in terms of the field direction. The asymmetry is more pronounced for the taller dot. The results show that the electric field is an effective way to tune the hole spin-relaxation in self-assembled QDs.

Primordial black holes as seeds of magnetic fields in the universe

Science.gov (United States)

Safarzadeh, Mohammadtaher

2018-06-01

Although it is assumed that magnetic fields in accretion disks are dragged from the interstellar medium, the idea is likely not applicable to primordial black holes (PBHs) formed in the early universe. Here we show that magnetic fields can be generated in initially unmagnetized accretion disks around PBHs through the Biermann battery mechanism, and therefore provide the small scale seeds of magnetic field in the universe. The radial temperature and vertical density profiles of these disks provide the necessary conditions for the battery to operate naturally. The generated seed fields have a toroidal structure with opposite sign in the upper and lower half of the disk. In the case of a thin accretion disk around a rotating PBH, the field generation rate increases with increasing PBH spin. At a fixed r/risco, where r is the radial distance from the PBH and risco is the radius of the innermost stable circular orbit, the battery scales as M-9/4, where M is the PBH's mass. The very weak dependency of the battery on accretion rate, makes this mechanism a viable candidate to provide seed fields in an initially unmagnetized accretion disk, following which the magnetorotational instability could take over.

Over spinning a black hole?

Energy Technology Data Exchange (ETDEWEB)

Bouhmadi-Lopez, Mariam; Cardoso, Vitor; Nerozzi, Andrea; Rocha, Jorge V, E-mail: mariam.bouhmadi@ist.utl.pt, E-mail: vitor.cardoso@ist.utl.pt, E-mail: andrea.nerozzi@ist.utl.pt, E-mail: jorge.v.rocha@ist.utl.pt [CENTRA, Department de Fisica, Instituto Superior Tecnico, Av. Rovisco Pais 1, 1049 Lisboa (Portugal)

2011-09-22

A possible process to destroy a black hole consists on throwing point particles with sufficiently large angular momentum into the black hole. In the case of Kerr black holes, it was shown by Wald that particles with dangerously large angular momentum are simply not captured by the hole, and thus the event horizon is not destroyed. Here we reconsider this gedanken experiment for black holes in higher dimensions. We show that this particular way of destroying a black hole does not succeed and that Cosmic Censorship is preserved.

ON THE TRANSITIONAL DISK CLASS: LINKING OBSERVATIONS OF T TAURI STARS AND PHYSICAL DISK MODELS

International Nuclear Information System (INIS)

Espaillat, C.; Andrews, S.; Qi, C.; Wilner, D.; Ingleby, L.; Calvet, N.; Hernández, J.; Furlan, E.; D'Alessio, P.; Muzerolle, J.

2012-01-01

Two decades ago 'transitional disks' (TDs) described spectral energy distributions (SEDs) of T Tauri stars with small near-IR excesses, but significant mid- and far-IR excesses. Many inferred this indicated dust-free holes in disks possibly cleared by planets. Recently, this term has been applied disparately to objects whose Spitzer SEDs diverge from the expectations for a typical full disk (FD). Here, we use irradiated accretion disk models to fit the SEDs of 15 such disks in NGC 2068 and IC 348. One group has a 'dip' in infrared emission while the others' continuum emission decreases steadily at all wavelengths. We find that the former have an inner disk hole or gap at intermediate radii in the disk and we call these objects 'transitional disks' and 'pre-transitional disks' (PTDs), respectively. For the latter group, we can fit these SEDs with FD models and find that millimeter data are necessary to break the degeneracy between dust settling and disk mass. We suggest that the term 'transitional' only be applied to objects that display evidence for a radical change in the disk's radial structure. Using this definition, we find that TDs and PTDs tend to have lower mass accretion rates than FDs and that TDs have lower accretion rates than PTDs. These reduced accretion rates onto the star could be linked to forming planets. Future observations of TDs and PTDs will allow us to better quantify the signatures of planet formation in young disks.

Superluminous Transients at AGN Centers from Interaction between Black Hole Disk Winds and Broad-line Region Clouds

Energy Technology Data Exchange (ETDEWEB)

Moriya, Takashi J.; Tanaka, Masaomi; Ohsuga, Ken [Division of Theoretical Astronomy, National Astronomical Observatory of Japan, National Institutes of Natural Sciences, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Morokuma, Tomoki, E-mail: takashi.moriya@nao.ac.jp [Institute of Astronomy, Graduate School of Science, The University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan)

2017-07-10

We propose that superluminous transients that appear at central regions of active galactic nuclei (AGNs) such as CSS100217:102913+404220 (CSS100217) and PS16dtm, which reach near- or super-Eddington luminosities of the central black holes, are powered by the interaction between accretion-disk winds and clouds in broad-line regions (BLRs) surrounding them. If the disk luminosity temporarily increases by, e.g., limit–cycle oscillations, leading to a powerful radiatively driven wind, strong shock waves propagate in the BLR. Because the dense clouds in the AGN BLRs typically have similar densities to those found in SNe IIn, strong radiative shocks emerge and efficiently convert the ejecta kinetic energy to radiation. As a result, transients similar to SNe IIn can be observed at AGN central regions. Since a typical black hole disk-wind velocity is ≃0.1 c , where c is the speed of light, the ejecta kinetic energy is expected to be ≃10{sup 52} erg when ≃1 M {sub ⊙} is ejected. This kinetic energy is transformed to radiation energy in a timescale for the wind to sweep up a similar mass to itself in the BLR, which is a few hundred days. Therefore, both luminosities (∼10{sup 44} erg s{sup −1}) and timescales (∼100 days) of the superluminous transients from AGN central regions match those expected in our interaction model. If CSS100217 and PS16dtm are related to the AGN activities triggered by limit–cycle oscillations, they become bright again in coming years or decades.

Mergers of Black-Hole Binaries with Aligned Spins: Waveform Characteristics

Science.gov (United States)

Kelly, Bernard J.; Baker, John G.; vanMeter, James R.; Boggs, William D.; McWilliams, Sean T.; Centrella, Joan

2011-01-01

"We apply our gravitational-waveform analysis techniques, first presented in the context of nonspinning black holes of varying mass ratio [1], to the complementary case of equal-mass spinning black-hole binary systems. We find that, as with the nonspinning mergers, the dominant waveform modes phases evolve together in lock-step through inspiral and merger, supporting the previous model of the binary system as an adiabatically rigid rotator driving gravitational-wave emission - an implicit rotating source (IRS). We further apply the late-merger model for the rotational frequency introduced in [1], along with a new mode amplitude model appropriate for the dominant (2, plus or minus 2) modes. We demonstrate that this seven-parameter model performs well in matches with the original numerical waveform for system masses above - 150 solar mass, both when the parameters are freely fit, and when they are almost completely constrained by physical considerations."

The entropy of Garfinkle-Horne dilaton black hole due to arbitrary spin fields

Institute of Scientific and Technical Information of China (English)

SHEN; Yougen(沈有根)

2002-01-01

Using the membrane model which is based on brick wall model, we calculated the free energy and entropy of Garfinkle-Horne dilatonic black hole due to arbitrary spin fields. The result shows that the entropy of scalar field and the entropy of Fermionic field have similar formulas. There is only a coefficient between them.

Propulsion health monitoring of a turbine engine disk using spin test data

Science.gov (United States)

Abdul-Aziz, Ali; Woike, Mark; Oza, Nikunj; Matthews, Bryan; Baakilini, George

2010-03-01

is expected to present a select evaluation of online health monitoring of a rotating disk using these high caliber sensors and test the capability of the in-house spin system.

SUPERMASSIVE BLACK HOLES IN A STAR-FORMING GASEOUS CIRCUMNUCLEAR DISK

Energy Technology Data Exchange (ETDEWEB)

Del Valle, L.; Escala, A.; Molina, J. [Departamento de Astronomía, Universidad de Chile (Chile); Maureira-Fredes, C.; Amaro-Seoane, P. [Max Planck Institut fur Gravitationsphysik (Albert-Einstein-Institut), D-14476 Potsdam (Germany); Cuadra, J., E-mail: ldelvalleb@gmail.com [Instituto de Astrofísica, Pontificia Universidad Catolica de Chile (Chile)

2015-09-20

Using N-body/smoothed particle hydrodynamics simulations we study the evolution of the separation of a pair of supermassive black holes (SMBHs) embedded in a star-forming circumnuclear disk (CND). This type of disk is expected to be formed in the central kiloparsec of the remnant of gas-rich galaxy mergers. Our simulations indicate that orbital decay of the SMBHs occurs more quickly when the mean density of the CND is higher, due to increased dynamical friction. However, in simulations where the CND is fragmented in high-density gaseous clumps (clumpy CND), the orbits of the SMBHs are erratically perturbed by the gravitational interaction with these clumps, delaying, in some cases, the orbital decay of the SMBHs. The densities of these gaseous clumps in our simulations and in recent studies of clumpy CNDs are two orders of magnitude higher than the observed density of molecular clouds in isolated galaxies or ultraluminous infrared galaxies (ULIRGs), thus, we expect that SMBH orbits are perturbed less in real CNDs than in the simulated CNDs of this study and other recent studies. We also find that the migration timescale has a weak dependence on the star formation rate of the CND. Furthermore, the migration timescale of an SMBH pair in a star-forming clumpy CND is at most a factor of three longer than the migration timescale of a pair of SMBHs in a CND modeled with more simple gas physics. Therefore, we estimate that the migration timescale of the SMBHs in a clumpy CND is on the order of 10{sup 7} years.

STRONGER REFLECTION FROM BLACK HOLE ACCRETION DISKS IN SOFT X-RAY STATES

International Nuclear Information System (INIS)

Steiner, James F.; Remillard, Ronald A.; García, Javier A.; McClintock, Jeffrey E.

2016-01-01

We analyze 15,000 spectra of 29 stellar-mass black hole (BH) candidates collected over the 16 year mission lifetime of Rossi X-ray Timing Explorer using a simple phenomenological model. As these BHs vary widely in luminosity and progress through a sequence of spectral states, which we broadly refer to as hard and soft, we focus on two spectral components: the Compton power law and the reflection spectrum it generates by illuminating the accretion disk. Our proxy for the strength of reflection is the equivalent width of the Fe–K line as measured with respect to the power law. A key distinction of our work is that for all states we estimate the continuum under the line by excluding the thermal disk component and using only the component that is responsible for fluorescing the Fe–K line, namely, the Compton power law. We find that reflection is several times more pronounced (∼3) in soft compared to hard spectral states. This is most readily caused by the dilution of the Fe line amplitude from Compton scattering in the corona, which has a higher optical depth in hard states. Alternatively, this could be explained by a more compact corona in soft (compared to hard) states, which would result in a higher reflection fraction.

STRONGER REFLECTION FROM BLACK HOLE ACCRETION DISKS IN SOFT X-RAY STATES

Energy Technology Data Exchange (ETDEWEB)

Steiner, James F.; Remillard, Ronald A. [MIT Kavli Institute for Astrophysics and Space Research, MIT, 70 Vassar Street, Cambridge, MA 02139 (United States); García, Javier A.; McClintock, Jeffrey E., E-mail: jsteiner@mit.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

2016-10-01

We analyze 15,000 spectra of 29 stellar-mass black hole (BH) candidates collected over the 16 year mission lifetime of Rossi X-ray Timing Explorer using a simple phenomenological model. As these BHs vary widely in luminosity and progress through a sequence of spectral states, which we broadly refer to as hard and soft, we focus on two spectral components: the Compton power law and the reflection spectrum it generates by illuminating the accretion disk. Our proxy for the strength of reflection is the equivalent width of the Fe–K line as measured with respect to the power law. A key distinction of our work is that for all states we estimate the continuum under the line by excluding the thermal disk component and using only the component that is responsible for fluorescing the Fe–K line, namely, the Compton power law. We find that reflection is several times more pronounced (∼3) in soft compared to hard spectral states. This is most readily caused by the dilution of the Fe line amplitude from Compton scattering in the corona, which has a higher optical depth in hard states. Alternatively, this could be explained by a more compact corona in soft (compared to hard) states, which would result in a higher reflection fraction.

Compact objects and accretion disks

NARCIS (Netherlands)

Blandford, Roger; Agol, Eric; Broderick, Avery; Heyl, Jeremy; Koopmans, Leon; Lee, Hee-Won

2002-01-01

Recent developments in the spectropolarimetric study of compact objects, specifically black holes (stellar and massive) and neutron stars are reviewed. The lectures are organized around five topics: disks, jets, outflows, neutron stars and black holes. They emphasize physical mechanisms and are

Possibility to determine the radius of accretion disk by gravitational waves

International Nuclear Information System (INIS)

Sotani, H; Saijo, M

2007-01-01

We investigate gravitational waves from a dust disk around a Schwarzschild black hole to focus on whether we can extract any of its physical properties from a direct detection of gravitational waves. We adopt a black hole perturbation approach in a time domain, which is a satisfactory approximation to illustrate a dust disk in a supermassive black hole. We find that we can determine the radius of the disk by using the power spectrum of gravitational waves and that our method to extract the radius works for a disk of arbitrary density distribution. Therefore we believe a possibility exists for determining the radius of the disk from a direct observation of gravitational waves detected by the Laser Interferometer Space Antenna

A Be-type star with a black-hole companion.

Science.gov (United States)

Casares, J; Negueruela, I; Ribó, M; Ribas, I; Paredes, J M; Herrero, A; Simón-Díaz, S

2014-01-16

Stellar-mass black holes have all been discovered through X-ray emission, which arises from the accretion of gas from their binary companions (this gas is either stripped from low-mass stars or supplied as winds from massive ones). Binary evolution models also predict the existence of black holes accreting from the equatorial envelope of rapidly spinning Be-type stars (stars of the Be type are hot blue irregular variables showing characteristic spectral emission lines of hydrogen). Of the approximately 80 Be X-ray binaries known in the Galaxy, however, only pulsating neutron stars have been found as companions. A black hole was formally allowed as a solution for the companion to the Be star MWC 656 (ref. 5; also known as HD 215227), although that conclusion was based on a single radial velocity curve of the Be star, a mistaken spectral classification and rough estimates of the inclination angle. Here we report observations of an accretion disk line mirroring the orbit of MWC 656. This, together with an improved radial velocity curve of the Be star through fitting sharp Fe II profiles from the equatorial disk, and a refined Be classification (to that of a B1.5-B2 III star), indicates that a black hole of 3.8 to 6.9 solar masses orbits MWC 656, the candidate counterpart of the γ-ray source AGL J2241+4454 (refs 5, 6). The black hole is X-ray quiescent and fed by a radiatively inefficient accretion flow giving a luminosity less than 1.6 × 10(-7) times the Eddington luminosity. This implies that Be binaries with black-hole companions are difficult to detect in conventional X-ray surveys.

Reflection Spectra of the Black Hole Binary Candidate MAXI J1535-571 in the Hard State Observed by NuSTAR

Science.gov (United States)

Xu, Yanjun; Harrison, Fiona A.; García, Javier A.; Fabian, Andrew C.; Fürst, Felix; Gandhi, Poshak; Grefenstette, Brian W.; Madsen, Kristin K.; Miller, Jon M.; Parker, Michael L.; Tomsick, John A.; Walton, Dominic J.

2018-01-01

We report on a Nuclear Spectroscopic Telescope Array (NuSTAR) observation of the recently discovered bright black hole candidate MAXI J1535-571. NuSTAR observed the source on MJD 58003 (five days after the outburst was reported). The spectrum is characteristic of a black hole binary in the hard state. We observe clear disk reflection features, including a broad Fe Kα line and a Compton hump peaking around 30 keV. Detailed spectral modeling reveals a narrow Fe Kα line complex centered around 6.5 keV on top of the strong relativistically broadened Fe Kα line. The narrow component is consistent with distant reflection from moderately ionized material. The spectral continuum is well described by a combination of cool thermal disk photons and a Comptonized plasma with the electron temperature {{kT}}{{e}}=19.7+/- 0.4 keV. An adequate fit can be achieved for the disk reflection features with a self-consistent relativistic reflection model that assumes a lamp-post geometry for the coronal illuminating source. The spectral fitting measures a black hole spin a> 0.84, inner disk radius {R}{in}lamp-post height h={7.2}-2.0+0.8 {r}{{g}} (statistical errors, 90% confidence), indicating no significant disk truncation and a compact corona. Although the distance and mass of this source are not currently known, this suggests the source was likely in the brighter phases of the hard state during this NuSTAR observation.

Optical pumping of a single hole spin in a p-doped quantum dot coupled to a metallic nanoparticle

Science.gov (United States)

Antón, M. A.; Carreño, F.; Melle, Sonia; Calderón, Oscar G.; Cabrera-Granado, E.; Singh, Mahi R.

2013-05-01

The preparation of quantum states with a defined spin is analyzed in a hybrid system consisting of a p-doped semiconductor quantum dot (QD) coupled to a metallic nanoparticle. The quantum dot is described as a four-level atom-like system using the density matrix formalism. The lower levels are Zeeman-split hole spin states and the upper levels correspond to positively charged excitons containing a spin-up, spin-down hole pair and a spin electron. A metallic nanoparticle with spheroidal geometry is placed in close proximity to the quantum dot, and its effects are considered in the quasistatic approximation. A linearly polarized laser field drives two of the optical transitions of the QD and produces localized surface plasmons in the nanoparticle which act back upon the QD. The frequencies of these localized plasmons are very different along the two principal axes of the nanoparticle, thus producing an anisotropic modification of the spontaneous emission rates of the allowed optical transitions which is accompanied by local-field corrections. This effect translates into a preferential acceleration of some of the optical pathways and therefore into a fast initialization of the QD by excitation with a short optical pulse. The population transfer between the lower levels of the QD and the fidelity is analyzed as a function of the nanoparticle's aspect ratio, the external magnetic field, and the Rabi frequency of the driving field. It is also shown that the main effect of the local-field corrections is a lengthening of the time elapsed to reach the steady-state. The hole spin is predicted to be successfully cooled from 5 to 0.04 K at a magnetic field of 4.6 T applied in the Voigt geometry.

HUBBLE provides multiple views of how to feed a black hole

Science.gov (United States)

1998-05-01

Although the cause-and-effect relationships are not yet clear, the views provided by complementary images from two instruments aboard the Hubble Space Telescope are giving astronomers new insights into the powerful forces being exerted in this complex maelstrom. Researchers believe these forces may even have shifted the axis of the massive black hole from its expected orientation. The Hubble wide-field camera visible image of the merged Centaurus A galaxy, also called NGC 5128, shows in sharp clarity a dramatic dark lane of dust girdling the galaxy. Blue clusters of newborn stars are clearly resolved, and silhouettes of dust filaments are interspersed with blazing orange-glowing gas. Located only 10 million light-years away, this peculiar-looking galaxy contains the closest active galactic nucleus to Earth and has long been considered an example of an elliptical galaxy disrupted by a recent collision with a smaller companion spiral galaxy. Using the infrared vision of Hubble, astronomers have penetrated this wall of dust for the first time to see a twisted disk of hot gas swept up in the black hole's gravitational whirlpool. The suspected black hole is so dense it contains the mass of perhaps a billion stars, compacted into a small region of space not much larger than our Solar System. Resolving features as small as seven light-years across, Hubble has shown astronomers that the hot gas disk is tilted in a different direction from the black hole's axis -- like a wobbly wheel around an axle. The black hole's axis is identified by the orientation of a high-speed jet of material, glowing in X-rays and radio frequencies, blasted from the black hole at 1/100th the speed of light. This gas disk presumably fueling the black hole may have formed so recently it is not yet aligned to the black hole's spin axis, or it may simply be influenced more by the galaxy's gravitational tug than by the black hole's. "This black hole is doing its own thing. Aside from receiving fresh

Constraints on Mass, Spin and Magnetic Field of Microquasar H 1743-322 from Observations of QPOs

Science.gov (United States)

Tursunov, A. A.; Kološ, M.

2018-03-01

The study of quasi-periodic oscillations (QPOs) of X-ray flux observed in many microquasars can provide a powerful tool for testing of the phenomena occurring in strong gravity regime. QPOs phenomena can be well related to the oscillations of charged particles in accretion disks orbiting Kerr black holes immersed in external large-scalemagnetic fields. In the present paper we study the model ofmagnetic relativistic precession and provide estimations of the mass and spin of the central object of the microquasar H 1743-322 which is a candidate for a black hole. Moreover, we discuss the possible values of external magnetic field and study its influence on the motion of charged particles around rotating black hole.

Consequences of Relativistic Neutron Outflow beyond the Accretion Disks of Active Galaxies

Science.gov (United States)

Ekejiuba, I. E.; Okeke, P. N.

1993-05-01

Three channels of relativistic electron injection in the jets of extragalactic radio sources (EGRSs) are discussed. With the assumption that an active galactic nucleus (AGN) is powered by a spinning supermassive black hole of mass ~ 10(8) M_⊙ which sits at the center of the nucleus and ingests matter and energy through an accretion disk, a model for extracting relativistic neutrons from the AGN is forged. In this model, the inelastic proton--proton and proton--photon interactions within the accretion disk, of relativistic protons with background thermal protons and photons, respectively, produce copious amounts of relativistic neutrons. These neutrons travel ballistically for ~ 10(3gamma_n ) seconds and escape from the disk before they decay. The secondary particles produced from the neutron decays then interact with the ambient magnetic field and/or other particles to produce the radio emissions observed in the jets of EGRSs. IEE acknowledges the support of the World Bank and the Federal University of Technology, Yola, Nigeria as well as the hospitality of Georgia State University.

Quantum Black Holes As Elementary Particles

OpenAIRE

Ha, Yuan K.

2008-01-01

Are black holes elementary particles? Are they fermions or bosons? We investigate the remarkable possibility that quantum black holes are the smallest and heaviest elementary particles. We are able to construct various fundamental quantum black holes: the spin-0, spin 1/2, spin-1, and the Planck-charge cases, using the results in general relativity. Quantum black holes in the neighborhood of the Galaxy could resolve the paradox posed by the Greisen-Zatsepin-Kuzmin limit on the energy of cosmi...

Implications of the Low Binary Black Hole Aligned Spins Observed by LIGO

Energy Technology Data Exchange (ETDEWEB)

Hotokezaka, Kenta [Center for Computational Astrophysics, Flatiron Institute, 162 5th Avenue, New York, NY 10010 (United States); Piran, Tsvi [Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 91904 (Israel)

2017-06-20

We explore the implications of the low-spin components along the orbital axis observed in an Advanced LIGO O1 run on binary black hole (BBH) merger scenarios in which the merging BBHs have evolved from field binaries. The coalescence time determines the initial orbital separation of BBHs. This, in turn, determines whether the stars are synchronized before collapse, and hence determines their projected spins. Short coalescence times imply synchronization and large spins. Among known stellar objects, Wolf–Rayet (WR) stars seem to be the only progenitors consistent with the low aligned spins observed in LIGO’s O1, provided that the orbital axis maintains its direction during the collapse. We calculate the spin distribution of BBH mergers in the local universe, and its redshift evolution for WR progenitors. Assuming that the BBH formation rate peaks around a redshift of ∼2–3, we show that BBH mergers in the local universe are dominated by low-spin events. The high-spin population starts to dominate at a redshift of ∼0.5–1.5. WR stars are also progenitors of long gamma-ray bursts that take place at a comparable rate to BBH mergers. We discuss the possible connection between the two phenomena. Additionally, we show that hypothetical Population III star progenitors are also possible. Although WR and Population III progenitors are consistent with the current data, both models predict a non-vanishing fraction of high positive values of the BBHs’ aligned spin. If those are not detected within the coming LIGO/Virgo runs, it will be unlikely that the observed BBHs formed via field binaries.

Series Solution for Steady Three-Dimensional Flow due to Spraying on Inclined Spinning Disk by Homotopy Perturbation Method

Directory of Open Access Journals (Sweden)

Saeed Dinarvand

2012-01-01

Full Text Available The steady three-dimensional flow of condensation or spraying on inclined spinning disk is studied analytically. The governing nonlinear equations and their associated boundary conditions are transformed into the system of nonlinear ordinary differential equations. The series solution of the problem is obtained by utilizing the homotopy perturbation method (HPM. The velocity and temperature profiles are shown and the influence of Prandtl number on the heat transfer and Nusselt number is discussed in detail. The validity of our solutions is verified by the numerical results. Unlike free surface flows on an incline, this through flow is highly affected by the spray rate and the rotation of the disk.

Spin polarized and density modulated phases in symmetric electron-electron and electron-hole bilayers.

Science.gov (United States)

Kumar, Krishan; Moudgil, R K

2012-10-17

We have studied symmetric electron-electron and electron-hole bilayers to explore the stable homogeneous spin phase and the feasibility of inhomogeneous charge-/spin-density ground states. The former is resolved by comparing the ground-state energies in states of different spin polarizations, while the latter is resolved by searching for a divergence in the wavevector-dependent static charge/spin susceptibility. For this endeavour, we have used the dielectric approach within the self-consistent mean-field theory of Singwi et al. We find that the inter-layer interactions tend to change an abrupt spin-polarization transition of an isolated layer into a nearly gradual one, even though the partially spin-polarized phases are not clearly stable within the accuracy of our calculation. The transition density is seen to decrease with a reduction in layer spacing, implying a suppression of spin polarization by inter-layer interactions. Indeed, the suppression shows up distinctly in the spin susceptibility computed from the spin-polarization dependence of the ground-state energy. However, below a critical layer spacing, the unpolarized liquid becomes unstable against a charge-density-wave (CDW) ground state at a density preceding full spin polarization, with the transition density for the CDW state increasing on further reduction in the layer spacing. Due to attractive e-h correlations, the CDW state is found to be more pronounced in the e-h bilayer. On the other hand, the static spin susceptibility diverges only in the long-wavelength limit, which simply represents a transition to the homogeneous spin-polarized phase.

Post-merger evolution of a neutron star-black hole binary with neutrino transport

Science.gov (United States)

Foucart, Francois; O'Connor, Evan; Roberts, Luke; Duez, Matthew D.; Haas, Roland; Kidder, Lawrence E.; Ott, Christian D.; Pfeiffer, Harald P.; Scheel, Mark A.; Szilagyi, Bela

2015-06-01

We present a first simulation of the post-merger evolution of a black hole-neutron star binary in full general relativity using an energy-integrated general-relativistic truncated moment formalism for neutrino transport. We describe our implementation of the moment formalism and important tests of our code, before studying the formation phase of an accretion disk after a black hole-neutron star merger. We use as initial data an existing general-relativistic simulation of the merger of a neutron star of mass 1.4 M⊙ with a black hole of mass 7 M⊙ and dimensionless spin χBH=0.8 . Comparing with a simpler leakage scheme for the treatment of the neutrinos, we find noticeable differences in the neutron-to-proton ratio in and around the disk, and in the neutrino luminosity. We find that the electron neutrino luminosity is much lower in the transport simulations, and that both the disk and the disk outflows are less neutron rich. The spatial distribution of the neutrinos is significantly affected by relativistic effects, due to large velocities and curvature in the regions of strongest emission. Over the short time scale evolved, we do not observe purely neutrino-driven outflows. However, a small amount of material (3 ×10-4M⊙ ) is ejected in the polar region during the circularization of the disk. Most of that material is ejected early in the formation of the disk, and is fairly neutron rich (electron fraction Ye˜0.15 - 0.25 ). Through r-process nucleosynthesis, that material should produce high-opacity lanthanides in the polar region, and could thus affect the light curve of radioactively powered electromagnetic transients. We also show that by the end of the simulation, while the bulk of the disk remains neutron rich (Ye˜0.15 - 0.2 and decreasing), its outer layers have a higher electron fraction: 10% of the remaining mass has Ye>0.3 . As that material would be the first to be unbound by disk outflows on longer time scales, and as composition evolution is

Ion microprobe analyses of oxygen three-isotope ratios of chondrules from the Sayh al Uhaymir 290 CH chondrite using a multiple-hole disk

Digital Repository Service at National Institute of Oceanography (India)

Nakashima, D.; Ushikubo, T.; Gowda, R.N.; Kita, N.T.; Valley, J.W.; Naga, K.

Author version: Meteorit. Planet. Sci., vol.46(6); 2011; 857-874 Ion microprobe analyses of oxygen three isotope ratios of chondrules from the Sayh al Uhaymir 290 CH chondrite using a multiple-hole disk Daisuke Nakashima 1,2,* , Takayuki Ushikubo...

Development of an eddy current inspection technique for sleeved engine disk bolt holes

International Nuclear Information System (INIS)

Palanisamy, R.; Lakin, K.M.

1983-01-01

Recent research programs have concentrated mainly on developing techniques to characterize surface breaking cracks and very little has been done towards characterizing subsurface flaws in conducting materials. Presented in this paper are the results of some initial theoretical work aimed at the development of a reliable eddy current technique to detect and characterize defects in engine disk bolt holes under a 0.05'' stainless steel sleeve. The change in impedance of an absolute eddy current coil with and without ferrite core, and the distribution of eddy currents around a second layer crack with and without a thin insulating film between the two conducting layers have been predicted numerically. The overall system development goals and methods to accomplish them are outlined briefly

Spin-Glass Transition and Giant Paramagnetism in Heavily Hole-Doped Bi2Sr2Co2Oy

Science.gov (United States)

Hsu, Hung Chang; Lee, Wei-Li; Lin, Jiunn-Yuan; Young, Ben-Li; Kung, Hsiang-Hsi; Huang, Jian; Chou, Fang Cheng

2014-02-01

Hole-doped single crystals of misfit-layered cobaltate Bi2-xPbxSr2-zCo2Oy (x = 0-0.61, y = 8.28-8.62, and z = 0.01-0.22) have been successfully grown using the optical floating-zone method. Heavier hole doping has been achieved through both Pb substitution in the Bi site and the more effective Sr vacancy formation. The Co4+ : Co3+ ratio can be raised significantly from its original ˜1 : 1 to 4.5 : 1, as confirmed by iodometric titration. A spin-glass transition temperature of Tg ˜ 70 K is confirmed by ac susceptibility measurement when the Co4+ : Co3+ ratio becomes higher than 2 : 1, presumably owing to the significantly increased probability of triangular geometrical frustration among antiferromagnetically coupled localized Co4+ spins.

On the Observability of Individual Population III Stars and Their Stellar-mass Black Hole Accretion Disks through Cluster Caustic Transits

Science.gov (United States)

Windhorst, Rogier A.; Wyithe, Stuart; Alpaslan, Mehmet; Timmes, F. X.; Andrews, Stephen K.; Kim, Duho; Kelly, Patrick; Coe, Dan A.; Diego, Jose M.; Driver, Simon P.; Dijkstra, Mark

2018-06-01

We summarize panchromatic Extragalactic Background Light data to place upper limits on the integrated near-IR surface brightness (SB) that may come from Population III stars and possible accretion disks around their stellar-mass black holes (BHs) in the epoch of First Light, broadly taken from z=7-17.We outline the physical properties of zero-metallicity Population III stars from MESA stellar evolution models through helium depletion and of BH accretion disks at z>7. We assume that second-generation non-zero-metallicity stars can form at higher multiplicity, so that BH accretion disks may be fed by Roche-lobe overflow from lower-mass companions.We use these near-infrared SB constraints to calculate the number of caustic transits behind lensing clusters that the James Webb Space Telescope and the next-generation ground-based telescopes may observe for both Population III stars and their BH accretion disks. Typical caustic magnifications can be 10^4-10^5x, with rise times of hours and decline times of z~Economia y Competitividad of Spain Consolider Project CSD2010-00064.

Grumblings from an Awakening Black Hole

Science.gov (United States)

Kohler, Susanna

2015-11-01

In June of this year, after nearly three decades of sleep, the black hole V404 Cygni woke up and began grumbling. Scientists across the globe scrambled to observe the sudden flaring activity coming from this previously peaceful black hole. And now were getting the first descriptions of what weve learned from V404 Cygs awakening!Sudden OutburstV404 Cyg is a black hole of roughly nine solar masses, and its in a binary system with a low-mass star. The black hole pulls a stream of gas from the star, which then spirals in around the black hole, forming an accretion disk. Sometimes the material simply accumulates in the disk but every two or three decades, the build-up of gas suddenly rushes toward the black hole as if a dam were bursting.The sudden accretion in these events causes outbursts of activity from the black hole, its flaring easily visible to us. The last time V404 Cyg exhibited such activity was in 1989, and its been rather quiet since then. Our telescopes are of course much more powerful and sensitive now, nearly three decades later so when the black hole woke up and began flaring in June, scientists were delighted at the chance to observe it.The high variability of V404 Cyg is evident in this example set of spectra, where time increases from the bottom panel to the top. [King et al. 2015]Led by Ashley King (Einstein Fellow at Stanford University), a team of scientists observed V404 Cyg with the Chandra X-ray Observatory, obtaining spectra of the black hole during its outbursts. The black hole flared so brightly during its activity that the team had to take precautions to protect the CCDs in their detector from radiation damage! Now the group has released the first results from their analysis.Windy DiskThe primary surprise from V404 Cyg is its winds. Many stellar-mass black holes have outflows of mass, either in the form of directed jets emitted from their centers, or in the form of high-energy winds isotropically emitted from their accretion disks. But V404

Flip-flopping binary black holes.

Science.gov (United States)

Lousto, Carlos O; Healy, James

2015-04-10

We study binary spinning black holes to display the long term individual spin dynamics. We perform a full numerical simulation starting at an initial proper separation of d≈25M between equal mass holes and evolve them down to merger for nearly 48 orbits, 3 precession cycles, and half of a flip-flop cycle. The simulation lasts for t=20 000M and displays a total change in the orientation of the spin of one of the black holes from an initial alignment with the orbital angular momentum to a complete antialignment after half of a flip-flop cycle. We compare this evolution with an integration of the 3.5 post-Newtonian equations of motion and spin evolution to show that this process continuously flip flops the spin during the lifetime of the binary until merger. We also provide lower order analytic expressions for the maximum flip-flop angle and frequency. We discuss the effects this dynamics may have on spin growth in accreting binaries and on the observational consequences for galactic and supermassive binary black holes.

Mergers of black-hole binaries with aligned spins: Waveform characteristics

International Nuclear Information System (INIS)

Kelly, Bernard J.; Baker, John G.; Centrella, Joan; Boggs, William D.; McWilliams, Sean T.

2011-01-01

We conduct a descriptive analysis of the multipolar structure of gravitational-radiation waveforms from equal-mass aligned-spin mergers, following an approach first presented in the complementary context of nonspinning black holes of varying mass ratio [J. G. Baker et al., Phys. Rev. D 78, 044046 (2008).]. We find that, as with the nonspinning mergers, the dominant waveform mode phases evolve together in lock-step through inspiral and merger, supporting the previous waveform description in terms of an adiabatically rigid rotator driving gravitational-wave emission--an implicit rotating source. We further apply the late-time merger-ringdown model for the rotational frequency introduced in [J. G. Baker et al., Phys. Rev. D 78, 044046 (2008).], along with an improved amplitude model appropriate for the dominant (2, ±2) modes. This provides a quantitative description of the merger-ringdown waveforms, and suggests that the major features of these waveforms can be described with reference only to the intrinsic parameters associated with the state of the final black hole formed in the merger. We provide an explicit model for the merger-ringdown radiation, and demonstrate that this model agrees to fitting factors better than 95% with the original numerical waveforms for system masses above ∼150M · . This model may be directly applicable to gravitational-wave detection of intermediate-mass black-hole mergers.

Polarization of Light from Warm Clouds above an Accretion Disk: Effects of Strong Gravity near a Black Hole

Czech Academy of Sciences Publication Activity Database

Horák, Jiří; Karas, Vladimír

2006-01-01

Roč. 58, č. 1 (2006), s. 203-209 ISSN 0004-6264 R&D Projects: GA MŠk(CZ) LC06014; GA ČR(CZ) GP205/06/P415; GA AV ČR IAA300030510; GA ČR GD205/03/H144 Institutional research plan: CEZ:AV0Z10030501 Keywords : accretion disks * black holes * general relativity Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 2.106, year: 2006

Black Holes and Exotic Spinors

Directory of Open Access Journals (Sweden)

J. M. Hoff da Silva

2016-05-01

Full Text Available Exotic spin structures are non-trivial liftings, of the orthogonal bundle to the spin bundle, on orientable manifolds that admit spin structures according to the celebrated Geroch theorem. Exotic spin structures play a role of paramount importance in different areas of physics, from quantum field theory, in particular at Planck length scales, to gravity, and in cosmological scales. Here, we introduce an in-depth panorama in this field, providing black hole physics as the fount of spacetime exoticness. Black holes are then studied as the generators of a non-trivial topology that also can correspond to some inequivalent spin structure. Moreover, we investigate exotic spinor fields in this context and the way exotic spinor fields branch new physics. We also calculate the tunneling probability of exotic fermions across a Kerr-Sen black hole, showing that the exotic term does affect the tunneling probability, altering the black hole evaporation rate. Finally we show that it complies with the Hawking temperature universal law.

Measuring the Innermost Stable Circular Orbits of Supermassive Black Holes

Energy Technology Data Exchange (ETDEWEB)

Chartas, G.; Zalesky, L. [Department of Physics and Astronomy, College of Charleston, Charleston, SC 29424 (United States); Krawczynski, H. [Physics Department and McDonnell Center for the Space Sciences, Washington University in St. Louis, 1 Brookings Drive, CB 1105, St. Louis, MO 63130 (United States); Kochanek, C. S. [Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Dai, X. [Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, Norman, OK 73019 (United States); Morgan, C. W.; Mosquera, A., E-mail: chartasg@cofc.edu [Physics Department, United States Naval Academy, Annapolis, MD 21403 (United States)

2017-03-01

We present a promising new technique, the g -distribution method, for measuring the inclination angle ( i ), the innermost stable circular orbit (ISCO), and the spin of a supermassive black hole. The g -distribution method uses measurements of the energy shifts in the relativistic iron line emitted by the accretion disk of a supermassive black hole due to microlensing by stars in a foreground galaxy relative to the g -distribution shifts predicted from microlensing caustic calculations. We apply the method to the gravitationally lensed quasars RX J1131–1231 ( z {sub s} = 0.658, z {sub l} = 0.295), QJ 0158–4325 ( z {sub s} = 1.294, z {sub l} = 0.317), and SDSS 1004+4112 ( z {sub s} = 1.734, z {sub l} = 0.68). For RX J1131−1231, our initial results indicate that r {sub ISCO} ≲ 8.5 gravitational radii ( r {sub g}) and i ≳ 55° (99% confidence level). We detect two shifted Fe lines in several observations, as predicted in our numerical simulations of caustic crossings. The current Δ E distribution of RX J1131–1231 is sparsely sampled, but further X-ray monitoring of RX J1131–1231 and other lensed quasars will provide improved constraints on the inclination angles, ISCO radii, and spins of the black holes of distant quasars.

COMPARING THE ACCRETION DISK EVOLUTION OF BLACK HOLE AND NEUTRON STAR X-RAY BINARIES FROM LOW TO SUPER-EDDINGTON LUMINOSITY

International Nuclear Information System (INIS)

Weng Shanshan; Zhang Shuangnan

2011-01-01

Low-mass X-ray binaries (LMXBs) are systems in which a low-mass companion transfers mass via Roche-lobe overflow onto a black hole (BH) or a weakly magnetized neutron star (NS). It is believed that both the solid surface and the magnetic field of an NS can affect the accretion flow and show some observable effects. Using the disk emission dominant data, we compare the disk evolution of the two types of systems from low luminosity to super-Eddington luminosity. As the luminosity decreases the disk in the NS LMXB 4U1608-522 begins to leave the innermost stable circular orbit (ISCO) at much higher luminosity (∼0.1 L Edd ), compared with BH LMXBs at much lower luminosity (∼0.03 L Edd ), due to the interaction between the NS magnetosphere and accretion flow. However, as the luminosity increases above a critical luminosity, the disks in BH and NS LMXBs trace the same evolutionary pattern, because the magnetosphere is restricted inside ISCO, and then both the NS surface emission and (dipole) magnetic field do not significantly affect the secular evolution of the accretion disk, which is driven by the increased radiation pressure in the inner region. We further suggest that the NS surface emission provides additional information about the accretion disk not available in BH systems. Through the observed NS surface emission, we argue that the disk thickness H/R is less than 0.3-0.4, and that the significant outflow from the inner disk edge exists at a luminosity close to Eddington luminosity.

Astrophysics of black holes from fundamental aspects to latest developments

CERN Document Server

2016-01-01

This book discusses the state of the art of the basic theoretical and observational topics related to black hole astrophysics. It covers all the main topics in this wide field, from the theory of accretion disks and formation mechanisms of jet and outflows, to their observed electromagnetic spectrum, and attempts to measure the spin of these objects. Black holes are one of the most fascinating predictions of general relativity and are currently a very hot topic in both physics and astrophysics. In the last five years there have been significant advances in our understanding of these systems, and in the next five years it should become possible to use them to test fundamental physics, in particular to predict the general relativity in the strong field regime. The book is both a reference work for researchers and a textbook for graduate students.

THE NATURE OF TRANSITION CIRCUMSTELLAR DISKS. II. SOUTHERN MOLECULAR CLOUDS

Energy Technology Data Exchange (ETDEWEB)

Romero, Gisela A.; Schreiber, Matthias R.; Rebassa-Mansergas, Alberto [Departamento de Fisica y Astronomia, Universidad de Valparaiso, Valparaiso (Chile); Cieza, Lucas A. [Institute for Astronomy, University of Hawaii at Manoa, Honolulu, HI 96822 (United States); Merin, Bruno [Herschel Science Centre, ESAC (ESA), P.O. Box 78, 28691 Villanueva de la Canada, Madrid (Spain); Smith Castelli, Analia V. [Consejo Nacional de Investigaciones Cientificas y Tecnicas, Rivadavia 1917, C1033AAJ Buenos Aires (Argentina); Allen, Lori E. [Department of Astronomy, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721-0065 (United States); Morrell, Nidia [Las Campanas Observatory, Carnegie Observatories, Casilla 601, La Serena (Chile)

2012-04-10

Transition disk objects are pre-main-sequence stars with little or no near-IR excess and significant far-IR excess, implying inner opacity holes in their disks. Here we present a multifrequency study of transition disk candidates located in Lupus I, III, IV, V, VI, Corona Australis, and Scorpius. Complementing the information provided by Spitzer with adaptive optics (AO) imaging (NaCo, VLT), submillimeter photometry (APEX), and echelle spectroscopy (Magellan, Du Pont Telescopes), we estimate the multiplicity, disk mass, and accretion rate for each object in our sample in order to identify the mechanism potentially responsible for its inner hole. We find that our transition disks show a rich diversity in their spectral energy distribution morphology, have disk masses ranging from {approx}<1 to 10 M{sub JUP}, and accretion rates ranging from {approx}<10{sup -11} to 10{sup -7.7} M{sub Sun} yr{sup -1}. Of the 17 bona fide transition disks in our sample, three, nine, three, and two objects are consistent with giant planet formation, grain growth, photoevaporation, and debris disks, respectively. Two disks could be circumbinary, which offers tidal truncation as an alternative origin of the inner hole. We find the same heterogeneity of the transition disk population in Lupus III, IV, and Corona Australis as in our previous analysis of transition disks in Ophiuchus while all transition disk candidates selected in Lupus V, VI turned out to be contaminating background asymptotic giant branch stars. All transition disks classified as photoevaporating disks have small disk masses, which indicates that photoevaporation must be less efficient than predicted by most recent models. The three systems that are excellent candidates for harboring giant planets potentially represent invaluable laboratories to study planet formation with the Atacama Large Millimeter/Submillimeter Array.

THE NATURE OF TRANSITION CIRCUMSTELLAR DISKS. II. SOUTHERN MOLECULAR CLOUDS

International Nuclear Information System (INIS)

Romero, Gisela A.; Schreiber, Matthias R.; Rebassa-Mansergas, Alberto; Cieza, Lucas A.; Merín, Bruno; Smith Castelli, Analía V.; Allen, Lori E.; Morrell, Nidia

2012-01-01

Transition disk objects are pre-main-sequence stars with little or no near-IR excess and significant far-IR excess, implying inner opacity holes in their disks. Here we present a multifrequency study of transition disk candidates located in Lupus I, III, IV, V, VI, Corona Australis, and Scorpius. Complementing the information provided by Spitzer with adaptive optics (AO) imaging (NaCo, VLT), submillimeter photometry (APEX), and echelle spectroscopy (Magellan, Du Pont Telescopes), we estimate the multiplicity, disk mass, and accretion rate for each object in our sample in order to identify the mechanism potentially responsible for its inner hole. We find that our transition disks show a rich diversity in their spectral energy distribution morphology, have disk masses ranging from ∼ JUP , and accretion rates ranging from ∼ –11 to 10 –7.7 M ☉ yr –1 . Of the 17 bona fide transition disks in our sample, three, nine, three, and two objects are consistent with giant planet formation, grain growth, photoevaporation, and debris disks, respectively. Two disks could be circumbinary, which offers tidal truncation as an alternative origin of the inner hole. We find the same heterogeneity of the transition disk population in Lupus III, IV, and Corona Australis as in our previous analysis of transition disks in Ophiuchus while all transition disk candidates selected in Lupus V, VI turned out to be contaminating background asymptotic giant branch stars. All transition disks classified as photoevaporating disks have small disk masses, which indicates that photoevaporation must be less efficient than predicted by most recent models. The three systems that are excellent candidates for harboring giant planets potentially represent invaluable laboratories to study planet formation with the Atacama Large Millimeter/Submillimeter Array.

Dynamically important magnetic fields near accreting supermassive black holes.

Science.gov (United States)

Zamaninasab, M; Clausen-Brown, E; Savolainen, T; Tchekhovskoy, A

2014-06-05

Accreting supermassive black holes at the centres of active galaxies often produce 'jets'--collimated bipolar outflows of relativistic particles. Magnetic fields probably play a critical role in jet formation and in accretion disk physics. A dynamically important magnetic field was recently found near the Galactic Centre black hole. If this is common and if the field continues to near the black hole event horizon, disk structures will be affected, invalidating assumptions made in standard models. Here we report that jet magnetic field and accretion disk luminosity are tightly correlated over seven orders of magnitude for a sample of 76 radio-loud active galaxies. We conclude that the jet-launching regions of these radio-loud galaxies are threaded by dynamically important fields, which will affect the disk properties. These fields obstruct gas infall, compress the accretion disk vertically, slow down the disk rotation by carrying away its angular momentum in an outflow and determine the directionality of jets.

Taking the Pulse of a Black Hole System

Science.gov (United States)

2011-01-01

Using two NASA X-ray satellites, astronomers have discovered what drives the "heartbeats" seen in the light from an unusual black hole system. These results give new insight into the ways that black holes can regulate their intake and severely curtail their growth. This study examined GRS 1915+105 (GRS 1915 for short), a binary system in the Milky Way galaxy containing a black hole about 14 times more massive than the Sun that is feeding off material from a companion star. As this material falls towards the black hole, it forms a swirling disk that emits X-rays. The black hole in GRS 1915 has been estimated to rotate at the maximum possible rate, allowing material in the inner disk to orbit very close to the black hole, at a radius only 20% larger than the event horizon, where the material travels at 50% the speed of light. Using the Chandra X-ray Observatory and the Rossi X-ray Timing Explorer (RXTE), researchers monitored this black hole system over a period of eight hours. As they watched, GRS 1915 gave off a short, bright pulse of X-ray light approximately every 50 seconds, varying in brightness by a factor of about three. This type of rhythmic cycle closely resembles an electrocardiogram of a human heart -- though at a slower pace. "Trying to understand the physics of this 'heartbeat state' is a little like trying to understand how a person's heart beats by watching changes in the blood flow through their veins," said Joey Neilsen, a graduate student at Harvard University, who presented these results from his dissertation at the American Astronomical Society (AAS) meeting in Seattle, Wash. It was previously known that GRS 1915 can develop such heartbeats when its mass consumption rate is very high. After monitoring it with the special combination of Chandra and RXTE, Neilsen and his collaborators realized that they could use the pulses to figure out what controls how much material the black hole consumes. "With each beat, the black hole pumps an enormous

INTERACTION BETWEEN DARK MATTER SUB-HALOS AND A GALACTIC GASEOUS DISK

International Nuclear Information System (INIS)

Kannan, Rahul; Macciò, Andrea V.; Walter, Fabian; Pasquali, Anna; Moster, Benjamin P.

2012-01-01

We investigate the idea that the interaction of dark matter (DM) sub-halos with the gaseous disks of galaxies can be the origin for the observed holes and shells found in their neutral hydrogen (H I) distributions. We use high-resolution hydrodynamic simulations to show that pure DM sub-halos impacting a galactic disk are not able to produce holes; on the contrary, they result in high-density regions in the disk. However, sub-halos containing a small amount of gas (a few percent of the total DM mass of the sub-halo) are able to displace the gas in the disk and form holes and shells. The sizes and lifetimes of these holes depend on the sub-halo gas mass, density, and impact velocity. A DM sub-halo, of mass 10 8 M ☉ and a gas mass fraction of ∼3%, is able to create a kiloparsec-scale hole with a lifetime similar to those observed in nearby galaxies. We also register an increase in the star formation rate at the rim of the hole, again in agreement with observations. Even though the properties of these simulated structures resemble those found in observations, we find that the number of predicted holes (based on mass and orbital distributions of DM halos derived from cosmological N-body simulations) falls short compared to the observations. Only a handful of holes are produced per gigayear. This leads us to conclude that DM halo impact is not the major channel through which these holes are formed.

What stellar orbit is needed to measure the spin of the Galactic centre black hole from astrometric data?

Science.gov (United States)

Waisberg, Idel; Dexter, Jason; Gillessen, Stefan; Pfuhl, Oliver; Eisenhauer, Frank; Plewa, Phillip M.; Bauböck, Michi; Jimenez-Rosales, Alejandra; Habibi, Maryam; Ott, Thomas; von Fellenberg, Sebastiano; Gao, Feng; Widmann, Felix; Genzel, Reinhard

2018-05-01

Astrometric and spectroscopic monitoring of individual stars orbiting the supermassive black hole in the Galactic Center offer a promising way to detect general relativistic effects. While low-order effects are expected to be detected following the periastron passage of S2 in Spring 2018, detecting higher order effects due to black hole spin will require the discovery of closer stars. In this paper, we set out to determine the requirements such a star would have to satisfy to allow the detection of black hole spin. We focus on the instrument GRAVITY, which saw first light in 2016 and which is expected to achieve astrometric accuracies 10-100 μas. For an observing campaign with duration T years, total observations Nobs, astrometric precision σx, and normalized black hole spin χ, we find that a_orb(1-e^2)^{3/4} ≲ 300 R_S √{T/4 {yr}} (N_obs/120)^{0.25} √{10 μ as/σ _x} √{χ /0.9} is needed. For χ = 0.9 and a potential observing campaign with σ _x = 10 μas, 30 observations yr-1 and duration 4-10 yr, we expect ˜0.1 star with K < 19 satisfying this constraint based on the current knowledge about the stellar population in the central 1 arcsec. We also propose a method through which GRAVITY could potentially measure radial velocities with precision ˜50 km s-1. If the astrometric precision can be maintained, adding radial velocity information increases the expected number of stars by roughly a factor of 2. While we focus on GRAVITY, the results can also be scaled to parameters relevant for future extremely large telescopes.

Monte Carlo studies of thermalization of electron-hole pairs in spin-polarized degenerate electron gas in monolayer graphene

Science.gov (United States)

Borowik, Piotr; Thobel, Jean-Luc; Adamowicz, Leszek

2018-02-01

Monte Carlo method is applied to the study of relaxation of excited electron-hole (e-h) pairs in graphene. The presence of background of spin-polarized electrons, with high density imposing degeneracy conditions, is assumed. To such system, a number of e-h pairs with spin polarization parallel or antiparallel to the background is injected. Two stages of relaxation: thermalization and cooling are clearly distinguished when average particles energy and its standard deviation σ _E are examined. At the very beginning of thermalization phase, holes loose energy to electrons, and after this process is substantially completed, particle distributions reorganize to take a Fermi-Dirac shape. To describe the evolution of and σ _E during thermalization, we define characteristic times τ _ {th} and values at the end of thermalization E_ {th} and σ _ {th}. The dependence of these parameters on various conditions, such as temperature and background density, is presented. It is shown that among the considered parameters, only the standard deviation of electrons energy allows to distinguish between different cases of relative spin polarizations of background and excited electrons.

Voltage- and Light-Controlled Spin Properties of a Two-Dimensional Hole Gas in p-Type GaAs/AlAs Resonant Tunneling Diodes

Science.gov (United States)

Galeti, H. V. A.; Galvão Gobato, Y.; Brasil, M. J. S. P.; Taylor, D.; Henini, M.

2018-03-01

We have investigated the spin properties of a two-dimensional hole gas (2DHG) formed at the contact layer of a p-type GaAs/AlAs resonant tunneling diode (RTD). We have measured the polarized-resolved photoluminescence of the RTD as a function of bias voltage, laser intensity and external magnetic field up to 15T. By tuning the voltage and the laser intensity, we are able to change the spin-splitting from the 2DHG from almost 0 meV to 5 meV and its polarization degree from - 40% to + 50% at 15T. These results are attributed to changes of the local electric field applied to the two-dimensional gas which affects the valence band and the hole Rashba spin-orbit effect.

Evolution of accretion disks in tidal disruption events

Energy Technology Data Exchange (ETDEWEB)

Shen, Rong-Feng [Current address: Racah Institute of Physics, Hebrew University of Jerusalem, Israel. (Israel); Matzner, Christopher D., E-mail: rf.shen@mail.huji.ac.il, E-mail: matzner@astro.utoronto.ca [Department of Astronomy and Astrophysics, University of Toronto, M5S 3H4 (Canada)

2014-04-01

During a stellar tidal disruption event (TDE), an accretion disk forms as stellar debris returns to the disruption site and circularizes. Rather than being confined within the circularizing radius, the disk can spread to larger radii to conserve angular momentum. A spreading disk is a source of matter for re-accretion at rates that may exceed the later stellar fallback rate, although a disk wind can suppress its contribution to the central black hole accretion rate. A spreading disk is detectible through a break in the central accretion rate history or, at longer wavelengths, by its own emission. We model the evolution of TDE disk size and accretion rate by accounting for the time-dependent fallback rate, for the influence of wind losses in the early advective stage, and for the possibility of thermal instability for accretion rates intermediate between the advection-dominated and gas-pressure-dominated states. The model provides a dynamic basis for modeling TDE light curves. All or part of a young TDE disk will precess as a solid body because of the Lense-Thirring effect, and precession may manifest itself as a quasi-periodic modulation of the light curve. The precession period increases with time. Applying our results to the jetted TDE candidate Swift J1644+57, whose X-ray light curve shows numerous quasi-periodic dips, we argue that the data best fit a scenario in which a main-sequence star was fully disrupted by an intermediate mass black hole on an orbit significantly inclined from the black hole equator, with the apparent jet shutoff at t = 500 days corresponding to a disk transition from the advective state to the gas-pressure-dominated state.

EPISODIC RANDOM ACCRETION AND THE COSMOLOGICAL EVOLUTION OF SUPERMASSIVE BLACK HOLE SPINS

International Nuclear Information System (INIS)

Wang Jianmin; Hu Chen; Li Yanrong; Chen Yanmei; Yan Changshuo; Zhang Shu; King, Andrew R.; Marconi, Alessandro; Ho, Luis C.; Staubert, Ruediger

2009-01-01

The growth of supermassive black holes (BHs) located at the centers of their host galaxies comes mainly from the accretion of gas, but how to fuel them remains an outstanding unsolved problem in quasar evolution. This issue can be elucidated by quantifying the radiative efficiency parameter (η) as a function of redshift, which also provides constraints on the average spin of the BHs and its possible evolution with time. We derive a formalism to link η with the luminosity density, BH mass density, and duty cycle of quasars, quantities we can estimate from existing quasars, and galaxy survey data. We find that η has a strong cosmological evolution: at z ∼ 2, η ∼ 0.3, and by z ∼ 0 it has decreased by an order of magnitude, to η ∼ 0.03. We interpret this trend as evolution in BH spin, and we appeal to episodic, random accretion as the mechanism for reducing the spin. The observation that the fraction of radio-loud quasars decreases with increasing redshift is inconsistent with the popular notion that BH spin is a critical factor for generating strong radio jets. In agreement with previous studies, we show that the derived history of BH accretion closely follows the cosmic history of star formation, consistent with other evidence that BHs and their host galaxies co-evolve.

Rotordynamic Analysis and Feasibility Study of a Disk Spin Test Facility for Rotor Health Monitoring

Science.gov (United States)

Sawicki, Jerzy T.

2005-01-01

Recently, National Aeronautics and Space Administration (NASA) initiated a program to achieve the significant improvement in aviation safety. One of the technical challenges is the design and development of accelerated experiments that mimic critical damage cases encountered in engine components. The Nondestructive Evaluation (NDE) Group at the NASA Glenn Research Center (GRC) is currently addressing the goal concerning propulsion health management and the development of propulsion system specific technologies intended to detect potential failures prior to catastrophe. For this goal the unique disk spin simulation system was assembled at NASA GRC, which allows testing of rotors with the spinning speeds up to 10K RPM, and at the elevated temperature environment reaching 540 C (1000 F). It is anticipated that the facility can be employed for detection of Low Cycle Fatigue disk cracking and further High Cycle Fatigue blade vibration. The controlled crack growth studies at room and elevated temperatures can be conducted on the turbine wheels, and various NDE techniques can be integrated and assessed as in-situ damage monitoring tools. Critical rotating parts in advanced gas turbine engines such as turbine disks frequently operate at high temperature and stress for long periods of time. The integrity of these parts must be proven by non-destructive evaluation (NDE) during various machining steps ranging from forging blank to finished shape, and also during the systematic overhaul inspections. Conventional NDE methods, however, have unacceptable limits. Some of these techniques are time-consuming and inconvenient for service aircraft testing. Almost all of these techniques require that the vicinity of the damage is known in advance. These experimental techniques can provide only local information and no indication of the structural strength at a component and/or system level. The shortcomings of currently available NDE methods lead to the requirement of new damage

Imprint of accretion disk-induced migration on gravitational waves from extreme mass ratio inspirals.

Science.gov (United States)

Yunes, Nicolás; Kocsis, Bence; Loeb, Abraham; Haiman, Zoltán

2011-10-21

We study the effects of a thin gaseous accretion disk on the inspiral of a stellar-mass black hole into a supermassive black hole. We construct a phenomenological angular momentum transport equation that reproduces known disk effects. Disk torques modify the gravitational wave phase evolution to detectable levels with LISA for reasonable disk parameters. The Fourier transform of disk-modified waveforms acquires a correction with a different frequency trend than post-Newtonian vacuum terms. Such inspirals could be used to detect accretion disks with LISA and to probe their physical parameters. © 2011 American Physical Society

Energetics and phasing of nonprecessing spinning coalescing black hole binaries

Science.gov (United States)

Nagar, Alessandro; Damour, Thibault; Reisswig, Christian; Pollney, Denis

2016-02-01

We present an improved numerical relativity (NR) calibration of the new effective-one-body (EOB) model for coalescing nonprecessing spinning black hole binaries recently introduced by Damour and Nagar [Phys. Rev. D 90, 044018 (2014), 10.1103/PhysRevD.90.044018]. We do so by comparing the EOB predictions to both the phasing and the energetics provided by two independent sets of NR data covering mass ratios 1 ≤q ≤9.989 and dimensionless spin range -0.95 ≤χ ≤+0.994 . One set of data is a subset of the Simulating eXtreme Spacetimes (SXS) catalog of public waveforms; the other set consists of new simulations obtained with the Llama code plus Cauchy characteristic evolution. We present the first systematic computation of the gauge-invariant relation between the binding energy and the total angular momentum, Eb(j ), for a large sample of, spin-aligned, SXS and Llama data. The dynamics of the EOB model presented here involves only two free functional parameters, one [a6c(ν )] entering the nonspinning sector, as a 5PN effective correction to the interaction potential, and one [c3(a˜1,a˜2,ν )] in the spinning sector, as an effective next-to-next-to-next-to-leading order correction to the spin-orbit coupling. These parameters are determined [together with a third functional parameter Δ tNQC(χ ) entering the waveform] by comparing the EOB phasing with the SXS phasing, the consistency of the energetics being checked afterwards. The quality of the analytical model for gravitational wave data analysis purposes is assessed by computing the EOB/NR faithfulness. Over the NR data sample and when varying the total mass between 20 and 200 M⊙ the EOB/NR unfaithfulness (integrated over the NR frequency range) is found to vary between 99.493% and 99.984% with a median value of 99.944%.

SUBARU IMAGING OF ASYMMETRIC FEATURES IN A TRANSITIONAL DISK IN UPPER SCORPIUS

Energy Technology Data Exchange (ETDEWEB)

Mayama, S. [Center for the Promotion of Integrated Sciences, The Graduate University for Advanced Studies (SOKENDAI), Shonan International Village, Hayama-cho, Miura-gun, Kanagawa 240-0193 (Japan); Hashimoto, J.; Kusakabe, N.; Kuzuhara, M.; Takahashi, Y.; Akiyama, E. [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Muto, T. [Division of Liberal Arts, Kogakuin University, 1-24-2, Nishi-Shinjuku, Shinjuku-ku, Tokyo 163-8677 (Japan); Tsukagoshi, T.; Momose, M. [College of Science, Ibaraki University, 2-1-1 Bunkyo, Mito, Ibaraki 310-8512 (Japan); Kudo, T.; Egner, S. [Subaru Telescope, 650 North A' ohoku Place, Hilo, HI 96720 (United States); Dong, R.; Brandt, T. [Department of Astrophysical Sciences, Princeton University, NJ 08544 (United States); Fukagawa, M. [Department of Earth and Space Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043 (Japan); Takami, M. [Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 106, Taiwan (China); Wisniewski, J. P. [H L Dodge Department of Physics and Astronomy, University of Oklahoma, 440 West Brooks St. Norman, OK 73019 (United States); Follette, K. [Department of Astronomy and Steward Observatory, The University of Arizona, 933 North Cherry Avenue, Rm. N204, Tucson, AZ 85721-0065 (United States); Abe, L. [Laboratoire Hippolyte Fizeau, UMR6525, Universite de Nice Sophia-Antipolis, 28, avenue Valrose, F-06108 Nice Cedex 02 (France); Brandner, W. [Max Planck Institute for Astronomy, Koenigstuhl 17, D-69117 Heidelberg (Germany); Carson, J., E-mail: mayama_satoshi@soken.ac.jp [Department of Physics and Astronomy, College of Charleston, 58 Coming Street, Charleston, SC 29424 (United States); and others

2012-12-01

We report high-resolution (0.07 arcsec) near-infrared polarized intensity images of the circumstellar disk around the star 2MASS J16042165-2130284 obtained with HiCIAO mounted on the Subaru 8.2 m telescope. We present our H-band data, which clearly exhibit a resolved, face-on disk with a large inner hole for the first time at infrared wavelengths. We detect the centrosymmetric polarization pattern in the circumstellar material as has been observed in other disks. Elliptical fitting gives the semimajor axis, semiminor axis, and position angle (P.A.) of the disk as 63 AU, 62 AU, and -14 Degree-Sign , respectively. The disk is asymmetric, with one dip located at P.A.s of {approx}85 Degree-Sign . Our observed disk size agrees well with a previous study of dust and CO emission at submillimeter wavelength with Submillimeter Array. Hence, the near-infrared light is interpreted as scattered light reflected from the inner edge of the disk. Our observations also detect an elongated arc (50 AU) extending over the disk inner hole. It emanates at the inner edge of the western side of the disk, extending inward first, then curving to the northeast. We discuss the possibility that the inner hole, the dip, and the arc that we have observed may be related to the existence of unseen bodies within the disk.

Relativistic, accreting disks

International Nuclear Information System (INIS)

Abramowicz, M.A; Jaroszynski, M.; Sikora, M.

1978-01-01

An analytic theory of the hydrodynamical structure of accreting disks (without self-gravitation but with pressure) orbiting around and axially symmetric, stationary, compact body (e.g. black hole) is presented. The inner edge of the marginally stable accreting disk (i.e. disk with constant angular momentum density) has a sharp cusp located on the equatorial plane between rsub(ms) and rsub(mb). The existence of the cusp is also typical for any angular momentum distribution. The physical importance of the cusp follows from the close analogy with the case of a close binary system (L 1 Lagrange point on the Roche lobe). The existence of the cusp is thus a crucial phenomenon in such problems as boundary condition for the viscous stresses, accretion rate etc. (orig.) [de

On the Observability of Individual Population III Stars and Their Stellar-mass Black Hole Accretion Disks through Cluster Caustic Transits

Science.gov (United States)

Windhorst, Rogier A.; Timmes, F. X.; Wyithe, J. Stuart B.; Alpaslan, Mehmet; Andrews, Stephen K.; Coe, Daniel; Diego, Jose M.; Dijkstra, Mark; Driver, Simon P.; Kelly, Patrick L.; Kim, Duho

2018-02-01

We summarize panchromatic Extragalactic Background Light data to place upper limits on the integrated near-infrared surface brightness (SB) that may come from Population III stars and possible accretion disks around their stellar-mass black holes (BHs) in the epoch of First Light, broadly taken from z ≃ 7–17. Theoretical predictions and recent near-infrared power spectra provide tighter constraints on their sky signal. We outline the physical properties of zero-metallicity Population III stars from MESA stellar evolution models through helium depletion and of BH accretion disks at z≳ 7. We assume that second-generation non-zero-metallicity stars can form at higher multiplicity, so that BH accretion disks may be fed by Roche-lobe overflow from lower-mass companions. We use these near-infrared SB constraints to calculate the number of caustic transits behind lensing clusters that the James Webb Space Telescope and the next-generation ground-based telescopes may observe for both Population III stars and their BH accretion disks. Typical caustic magnifications can be μ ≃ {10}4{--}{10}5, with rise times of hours and decline times of ≲ 1 year for cluster transverse velocities of {v}T≲ 1000 km s‑1. Microlensing by intracluster-medium objects can modify transit magnifications but lengthen visibility times. Depending on BH masses, accretion-disk radii, and feeding efficiencies, stellar-mass BH accretion-disk caustic transits could outnumber those from Population III stars. To observe Population III caustic transits directly may require monitoring 3–30 lensing clusters to {AB}≲ 29 mag over a decade.

BLACK HOLE FORAGING: FEEDBACK DRIVES FEEDING

International Nuclear Information System (INIS)

Dehnen, Walter; King, Andrew

2013-01-01

We suggest a new picture of supermassive black hole (SMBH) growth in galaxy centers. Momentum-driven feedback from an accreting hole gives significant orbital energy, but little angular momentum to the surrounding gas. Once central accretion drops, the feedback weakens and swept-up gas falls back toward the SMBH on near-parabolic orbits. These intersect near the black hole with partially opposed specific angular momenta, causing further infall and ultimately the formation of a small-scale accretion disk. The feeding rates into the disk typically exceed Eddington by factors of a few, growing the hole on the Salpeter timescale and stimulating further feedback. Natural consequences of this picture include (1) the formation and maintenance of a roughly toroidal distribution of obscuring matter near the hole; (2) random orientations of successive accretion disk episodes; (3) the possibility of rapid SMBH growth; (4) tidal disruption of stars and close binaries formed from infalling gas, resulting in visible flares and ejection of hypervelocity stars; (5) super-solar abundances of the matter accreting on to the SMBH; and (6) a lower central dark-matter density, and hence annihilation signal, than adiabatic SMBH growth implies. We also suggest a simple subgrid recipe for implementing this process in numerical simulations

Stellar-Mass Black Holes and their Progenitors

NARCIS (Netherlands)

Miller, J.; Uttley, [No Value; Nandra, [No Value; Barret, [No Value; Matt, [No Value; Paerels, [No Value; Mendez, [No Value; Diaz-Trigo, [No Value; Cappi, [No Value; Kitamoto, [No Value; Nowak, [No Value; Wilms, [No Value; Rothschild, [No Value; Smith, [No Value; Weisskopf, [No Value; Terashima, [No Value; Ueda, [No Value

2009-01-01

If a black hole has a low spin value, it must double its mass to reach a high spin parameter (Volonteri et al. 2005). Although this is easily accomplished through mergers or accretion in the case of supermassive black holes in galactic centers, it is impossible for stellar-mass black holes in X-ray

A Pulsar and a Disk

Science.gov (United States)

Kohler, Susanna

2016-07-01

Recent, unusual X-ray observations from our galactic neighbor, the Small Magellanic Cloud, have led to an interesting model for SXP 214, a pulsar in a binary star system.Artists illustration of the magnetic field lines of a pulsar, a highly magnetized, rotating neutron star. [NASA]An Intriguing BinaryAn X-ray pulsar is a magnetized, rotating neutron star in a binary system with a stellar companion. Material is fed from the companion onto the neutron star, channeled by the objects magnetic fields onto a hotspot thats millions of degrees. This hotspot rotating past our line of sight is what produces the pulsations that we observe from X-ray pulsars.Located in the Small Magellanic Cloud, SXP 214 is a transient X-ray pulsar in a binary with a Be-type star. This star is spinning so quickly that material is thrown off of it to form a circumstellar disk.Recently, a team of authors led by JaeSub Hong (Harvard-Smithsonian Center for Astrophysics) have presented new Chandra X-ray observations of SXP 214, tracking it for 50 ks (~14 hours) in January 2013. These observations reveal some very unexpected behavior for this pulsar.X-ray PuzzleThe energy distribution of the X-ray emission from SXP 214 over time. Dark shades or blue colors indicate high counts, and light shades or yellow colors indicate low counts. Lower-energy X-ray emission appeared only later, after about 20 ks. [Hong et al. 2016]Three interesting pieces of information came from the Chandra observations:SXP 214s rotation period was measured to be 211.5 s an increase in the spin rate since the discovery measurement of a 214-second period. Pulsars usually spin down as they lose angular momentum over time so what caused this one to spin up?Its overall X-ray luminosity steadily increased over the 50 ks of observations.Its spectrum became gradually softer (lower energy) over time; in the first 20 ks, the spectrum only consisted of hard X-ray photons above 3 keV, but after 20 ks, softer X-ray photons below 2 ke

Misaligned Accretion and Jet Production

Science.gov (United States)

King, Andrew; Nixon, Chris

2018-04-01

Disk accretion onto a black hole is often misaligned from its spin axis. If the disk maintains a significant magnetic field normal to its local plane, we show that dipole radiation from Lense–Thirring precessing disk annuli can extract a significant fraction of the accretion energy, sharply peaked toward small disk radii R (as R ‑17/2 for fields with constant equipartition ratio). This low-frequency emission is immediately absorbed by surrounding matter or refracted toward the regions of lowest density. The resultant mechanical pressure, dipole angular pattern, and much lower matter density toward the rotational poles create a strong tendency to drive jets along the black hole spin axis, similar to the spin-axis jets of radio pulsars, also strong dipole emitters. The coherent primary emission may explain the high brightness temperatures seen in jets. The intrinsic disk emission is modulated at Lense–Thirring frequencies near the inner edge, providing a physical mechanism for low-frequency quasi-periodic oscillations (QPOs). Dipole emission requires nonzero hole spin, but uses only disk accretion energy. No spin energy is extracted, unlike the Blandford–Znajek process. Magnetohydrodynamic/general-relativistic magnetohydrodynamic (MHD/GRMHD) formulations do not directly give radiation fields, but can be checked post-process for dipole emission and therefore self-consistency, given sufficient resolution. Jets driven by dipole radiation should be more common in active galactic nuclei (AGN) than in X-ray binaries, and in low accretion-rate states than high, agreeing with observation. In non-black hole accretion, misaligned disk annuli precess because of the accretor’s mass quadrupole moment, similarly producing jets and QPOs.

NUSTAR and Suzaku x-ray spectroscopy of NGC 4151: Evidence for reflection from the inner accretion disk

Energy Technology Data Exchange (ETDEWEB)

Keck, M. L.; Brenneman, L. W.; Ballantyne, D. R.; Bauer, F.; Boggs, S. E.; Christensen, F. E.; Craig, W. W.; Dauser, T.; Elvis, M.; Fabian, A. C.; Fuerst, F.; García, J.; Grefenstette, B. W.; Hailey, C. J.; Harrison, F. A.; Madejski, G.; Marinucci, A.; Matt, G.; Reynolds, C. S.; Stern, D.; Walton, D. J.; Zoghbi, A.

2015-06-15

We present X-ray timing and spectral analyses of simultaneous 150 ks Nuclear Spectroscopic Telescope Array (NuSTAR) and Suzaku X-ray observations of the Seyfert 1.5 galaxy NGC 4151. We disentangle the continuum emission, absorption, and reflection properties of the active galactic nucleus (AGN) by applying inner accretion disk reflection and absorption-dominated models. With a time-averaged spectral analysis, we find strong evidence for relativistic reflection from the inner accretion disk. We find that relativistic emission arises from a highly ionized inner accretion disk with a steep emissivity profile, which suggests an intense, compact illuminating source. We find a preliminary, near-maximal black hole spin $a\\gt 0.9$ accounting for statistical and systematic modeling errors. We find a relatively moderate reflection fraction with respect to predictions for the lamp post geometry, in which the illuminating corona is modeled as a point source. Through a time-resolved spectral analysis, we find that modest coronal and inner disk reflection (IDR) flux variation drives the spectral variability during the observations. We discuss various physical scenarios for the IDR model and we find that a compact corona is consistent with the observed features.

THE KOZAI-LIDOV MECHANISM IN HYDRODYNAMICAL DISKS

International Nuclear Information System (INIS)

Martin, Rebecca G.; Nixon, Chris; Armitage, Philip J.; Lubow, Stephen H.; Price, Daniel J.; Doğan, Suzan; King, Andrew

2014-01-01

We use three-dimensional hydrodynamical simulations to show that a highly misaligned accretion disk around one component of a binary system can exhibit global Kozai-Lidov cycles, where the inclination and eccentricity of the disk are interchanged periodically. This has important implications for accreting systems on all scales, for example, the formation of planets and satellites in circumstellar and circumplanetary disks, outbursts in X-ray binary systems, and accretion onto supermassive black holes

Black Hole Paradox Solved By NASA's Chandra

Science.gov (United States)

2006-06-01

Black holes are lighting up the Universe, and now astronomers may finally know how. New data from NASA's Chandra X-ray Observatory show for the first time that powerful magnetic fields are the key to these brilliant and startling light shows. It is estimated that up to a quarter of the total radiation in the Universe emitted since the Big Bang comes from material falling towards supermassive black holes, including those powering quasars, the brightest known objects. For decades, scientists have struggled to understand how black holes, the darkest objects in the Universe, can be responsible for such prodigious amounts of radiation. Animation of a Black Hole Pulling Matter from Companion Star Animation of a Black Hole Pulling Matter from Companion Star New X-ray data from Chandra give the first clear explanation for what drives this process: magnetic fields. Chandra observed a black hole system in our galaxy, known as GRO J1655-40 (J1655, for short), where a black hole was pulling material from a companion star into a disk. "By intergalactic standards J1655 is in our backyard, so we can use it as a scale model to understand how all black holes work, including the monsters found in quasars," said Jon M. Miller of the University of Michigan, Ann Arbor, whose paper on these results appears in this week's issue of Nature. Gravity alone is not enough to cause gas in a disk around a black hole to lose energy and fall onto the black hole at the rates required by observations. The gas must lose some of its orbital angular momentum, either through friction or a wind, before it can spiral inward. Without such effects, matter could remain in orbit around a black hole for a very long time. Illustration of Magnetic Fields in GRO J1655-40 Illustration of Magnetic Fields in GRO J1655-40 Scientists have long thought that magnetic turbulence could generate friction in a gaseous disk and drive a wind from the disk that carries angular momentum outward allowing the gas to fall inward

Constraints on mass, spin and magnetic field of microquasar H~1743-322 from observations of QPOs

OpenAIRE

Tursunov, Arman; Kološ, Martin

2018-01-01

The study of quasi-periodic oscillations (QPOs) of X-ray flux observed in many microquasars can provide a powerful tool for testing of the phenomena occurring in strong gravity regime. QPOs phenomena can be well related to the oscillations of charged particles in accretion disks orbiting Kerr black holes immersed in external large-scale magnetic fields. In the present paper we study the model of magnetic relativistic precession and provide estimations of the mass and spin of the central objec...

Ballistic hole magnetic microscopy

NARCIS (Netherlands)

Haq, E.; Banerjee, T.; Siekman, M.H.; Lodder, J.C.; Jansen, R.

2005-01-01

A technique to study nanoscale spin transport of holes is presented: ballistic hole magnetic microscopy. The tip of a scanning tunneling microscope is used to inject hot electrons into a ferromagnetic heterostructure, where inelastic decay creates a distribution of electron-hole pairs.

NuSTAR AND Swift Observations of the Very High State in GX 339-4: Weighing the Black Hole With X-Rays

Science.gov (United States)

Parker, M. L.; Tomsick, J. A.; Kennea, J. A.; Miller, J. M.; Harrison, F. A.; Barret, D.; Boggs, S. E.; Christensen, F. E.; Craig, W. W.; Fabian, A. C.;

Height Resolution of Antibody Spots Measured by Spinning-Disk Interferometry on the BioCD

Directory of Open Access Journals (Sweden)

Kevin O’Brien

2016-02-01

Full Text Available Spinning-disc interferometry (SDI is a high-speed laser scanning approach to surface metrology that uses common-path interferometry to measure protein spots on a BioCD disk. The measurement sensitivity depends on the scanning pitch and on the time-base. Based on high-resolution laser scanning images of printed antibody spots, we quantify the protein sensitivity as a function of the scan parameters. For smoothly printed antibody spots scanned with a transverse spatial resolution of 1 μm, the surface height precision for a single 100 μm diameter protein spot is approximately 1 pm. This detection sensitivity sets the fundamental limit of detection for label-free BioCD biosensors performing immunoassays.

Three-Dimensional General-Relativistic Magnetohydrodynamic Simulations of Remnant Accretion Disks from Neutron Star Mergers: Outflows and r-Process Nucleosynthesis.

Science.gov (United States)

Siegel, Daniel M; Metzger, Brian D

2017-12-08

The merger of binary neutron stars, or of a neutron star and a stellar-mass black hole, can result in the formation of a massive rotating torus around a spinning black hole. In addition to providing collimating media for γ-ray burst jets, unbound outflows from these disks are an important source of mass ejection and rapid neutron capture (r-process) nucleosynthesis. We present the first three-dimensional general-relativistic magnetohydrodynamic (GRMHD) simulations of neutrino-cooled accretion disks in neutron star mergers, including a realistic equation of state valid at low densities and temperatures, self-consistent evolution of the electron fraction, and neutrino cooling through an approximate leakage scheme. After initial magnetic field amplification by magnetic winding, we witness the vigorous onset of turbulence driven by the magnetorotational instability (MRI). The disk quickly reaches a balance between heating from MRI-driven turbulence and neutrino cooling, which regulates the midplane electron fraction to a low equilibrium value Y_{e}≈0.1. Over the 380-ms duration of the simulation, we find that a fraction ≈20% of the initial torus mass is unbound in powerful outflows with asymptotic velocities v≈0.1c and electron fractions Y_{e}≈0.1-0.25. Postprocessing the outflows through a nuclear reaction network shows the production of a robust second- and third-peak r process. Though broadly consistent with the results of previous axisymmetric hydrodynamical simulations, extrapolation of our results to late times suggests that the total ejecta mass from GRMHD disks is significantly higher. Our results provide strong evidence that postmerger disk outflows are an important site for the r process.

First Higher-Multipole Model of Gravitational Waves from Spinning and Coalescing Black-Hole Binaries.

Science.gov (United States)

London, Lionel; Khan, Sebastian; Fauchon-Jones, Edward; García, Cecilio; Hannam, Mark; Husa, Sascha; Jiménez-Forteza, Xisco; Kalaghatgi, Chinmay; Ohme, Frank; Pannarale, Francesco

2018-04-20

Gravitational-wave observations of binary black holes currently rely on theoretical models that predict the dominant multipoles (ℓ=2,|m|=2) of the radiation during inspiral, merger, and ringdown. We introduce a simple method to include the subdominant multipoles to binary black hole gravitational waveforms, given a frequency-domain model for the dominant multipoles. The amplitude and phase of the original model are appropriately stretched and rescaled using post-Newtonian results (for the inspiral), perturbation theory (for the ringdown), and a smooth transition between the two. No additional tuning to numerical-relativity simulations is required. We apply a variant of this method to the nonprecessing PhenomD model. The result, PhenomHM, constitutes the first higher-multipole model of spinning and coalescing black-hole binaries, and currently includes the (ℓ,|m|)=(2,2),(3,3),(4,4),(2,1),(3,2),(4,3) radiative moments. Comparisons with numerical-relativity waveforms demonstrate that PhenomHM is more accurate than dominant-multipole-only models for all binary configurations, and typically improves the measurement of binary properties.

First Higher-Multipole Model of Gravitational Waves from Spinning and Coalescing Black-Hole Binaries

Science.gov (United States)

London, Lionel; Khan, Sebastian; Fauchon-Jones, Edward; García, Cecilio; Hannam, Mark; Husa, Sascha; Jiménez-Forteza, Xisco; Kalaghatgi, Chinmay; Ohme, Frank; Pannarale, Francesco

2018-04-01

Gravitational-wave observations of binary black holes currently rely on theoretical models that predict the dominant multipoles (ℓ=2 ,|m |=2 ) of the radiation during inspiral, merger, and ringdown. We introduce a simple method to include the subdominant multipoles to binary black hole gravitational waveforms, given a frequency-domain model for the dominant multipoles. The amplitude and phase of the original model are appropriately stretched and rescaled using post-Newtonian results (for the inspiral), perturbation theory (for the ringdown), and a smooth transition between the two. No additional tuning to numerical-relativity simulations is required. We apply a variant of this method to the nonprecessing PhenomD model. The result, PhenomHM, constitutes the first higher-multipole model of spinning and coalescing black-hole binaries, and currently includes the (ℓ,|m |)=(2 ,2 ),(3 ,3 ),(4 ,4 ),(2 ,1 ),(3 ,2 ),(4 ,3 ) radiative moments. Comparisons with numerical-relativity waveforms demonstrate that PhenomHM is more accurate than dominant-multipole-only models for all binary configurations, and typically improves the measurement of binary properties.

Minidisks in Binary Black Hole Accretion

Energy Technology Data Exchange (ETDEWEB)

Ryan, Geoffrey; MacFadyen, Andrew, E-mail: gsr257@nyu.edu [Center for Cosmology and Particle Physics, Physics Department, New York University, New York, NY 10003 (United States)

2017-02-01

Newtonian simulations have demonstrated that accretion onto binary black holes produces accretion disks around each black hole (“minidisks”), fed by gas streams flowing through the circumbinary cavity from the surrounding circumbinary disk. We study the dynamics and radiation of an individual black hole minidisk using 2D hydrodynamical simulations performed with a new general relativistic version of the moving-mesh code Disco. We introduce a comoving energy variable that enables highly accurate integration of these high Mach number flows. Tidally induced spiral shock waves are excited in the disk and propagate through the innermost stable circular orbit, providing a Reynolds stress that causes efficient accretion by purely hydrodynamic means and producing a radiative signature brighter in hard X-rays than the Novikov–Thorne model. Disk cooling is provided by a local blackbody prescription that allows the disk to evolve self-consistently to a temperature profile where hydrodynamic heating is balanced by radiative cooling. We find that the spiral shock structure is in agreement with the relativistic dispersion relation for tightly wound linear waves. We measure the shock-induced dissipation and find outward angular momentum transport corresponding to an effective alpha parameter of order 0.01. We perform ray-tracing image calculations from the simulations to produce theoretical minidisk spectra and viewing-angle-dependent images for comparison with observations.

Turbulent black holes.

Science.gov (United States)

Yang, Huan; Zimmerman, Aaron; Lehner, Luis

2015-02-27

We demonstrate that rapidly spinning black holes can display a new type of nonlinear parametric instability-which is triggered above a certain perturbation amplitude threshold-akin to the onset of turbulence, with possibly observable consequences. This instability transfers from higher temporal and azimuthal spatial frequencies to lower frequencies-a phenomenon reminiscent of the inverse cascade displayed by (2+1)-dimensional fluids. Our finding provides evidence for the onset of transitory turbulence in astrophysical black holes and predicts observable signatures in black hole binaries with high spins. Furthermore, it gives a gravitational description of this behavior which, through the fluid-gravity duality, can potentially shed new light on the remarkable phenomena of turbulence in fluids.

HIGH-RESOLUTION 25 μM IMAGING OF THE DISKS AROUND HERBIG AE/BE STARS

Energy Technology Data Exchange (ETDEWEB)

Honda, M. [Department of Mathematics and Physics, Kanagawa University, 2946 Tsuchiya, Hiratsuka, Kanagawa 259-1293 (Japan); Maaskant, K. [Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands); Okamoto, Y. K. [Institute of Astrophysics and Planetary Sciences, Faculty of Science, Ibaraki University, 2-1-1 Bunkyo, Mito, Ibaraki 310-8512 (Japan); Kataza, H. [Department of Infrared Astrophysics, Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229-8510 (Japan); Yamashita, T. [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Miyata, T.; Sako, S.; Kamizuka, T. [Institute of Astronomy, School of Science, University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan); Fujiyoshi, T.; Fujiwara, H. [Subaru Telescope, National Astronomical Observatory of Japan, 650 North A’ohoku Place, Hilo, Hawaii 96720 (United States); Sakon, I.; Onaka, T. [Department of Astronomy, School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033 (Japan); Mulders, G. D. [Lunar and Planetary Laboratory, The University of Arizona, Tucson, AZ 85721 (United States); Lopez-Rodriguez, E.; Packham, C. [Department of Physics and Astronomy, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249 (United States)

2015-05-10

We imaged circumstellar disks around 22 Herbig Ae/Be stars at 25 μm using Subaru/COMICS and Gemini/T-ReCS. Our sample consists of an equal number of objects from each of the two categories defined by Meeus et al.; 11 group I (flaring disk) and II (flat disk) sources. We find that group I sources tend to show more extended emission than group II sources. Previous studies have shown that the continuous disk is difficult to resolve with 8 m class telescopes in the Q band due to the strong emission from the unresolved innermost region of the disk. This indicates that the resolved Q-band sources require a hole or gap in the disk material distribution to suppress the contribution from the innermost region of the disk. As many group I sources are resolved at 25 μm, we suggest that many, but not all, group I Herbig Ae/Be disks have a hole or gap and are (pre-)transitional disks. On the other hand, the unresolved nature of many group II sources at 25 μm supports the idea that group II disks have a continuous flat disk geometry. It has been inferred that group I disks may evolve into group II through the settling of dust grains into the mid-plane of the protoplanetary disk. However, considering the growing evidence for the presence of a hole or gap in the disk of group I sources, such an evolutionary scenario is unlikely. The difference between groups I and II may reflect different evolutionary pathways of protoplanetary disks.

HIGH-RESOLUTION 25 μM IMAGING OF THE DISKS AROUND HERBIG AE/BE STARS

International Nuclear Information System (INIS)

Honda, M.; Maaskant, K.; Okamoto, Y. K.; Kataza, H.; Yamashita, T.; Miyata, T.; Sako, S.; Kamizuka, T.; Fujiyoshi, T.; Fujiwara, H.; Sakon, I.; Onaka, T.; Mulders, G. D.; Lopez-Rodriguez, E.; Packham, C.

2015-01-01

We imaged circumstellar disks around 22 Herbig Ae/Be stars at 25 μm using Subaru/COMICS and Gemini/T-ReCS. Our sample consists of an equal number of objects from each of the two categories defined by Meeus et al.; 11 group I (flaring disk) and II (flat disk) sources. We find that group I sources tend to show more extended emission than group II sources. Previous studies have shown that the continuous disk is difficult to resolve with 8 m class telescopes in the Q band due to the strong emission from the unresolved innermost region of the disk. This indicates that the resolved Q-band sources require a hole or gap in the disk material distribution to suppress the contribution from the innermost region of the disk. As many group I sources are resolved at 25 μm, we suggest that many, but not all, group I Herbig Ae/Be disks have a hole or gap and are (pre-)transitional disks. On the other hand, the unresolved nature of many group II sources at 25 μm supports the idea that group II disks have a continuous flat disk geometry. It has been inferred that group I disks may evolve into group II through the settling of dust grains into the mid-plane of the protoplanetary disk. However, considering the growing evidence for the presence of a hole or gap in the disk of group I sources, such an evolutionary scenario is unlikely. The difference between groups I and II may reflect different evolutionary pathways of protoplanetary disks

Relativistic, accreting disks

Energy Technology Data Exchange (ETDEWEB)

Abramowicz, M A; Jaroszynski, M; Sikora, M [Polska Akademia Nauk, Warsaw

1978-02-01

An analytic theory of the hydrodynamical structure of accreting disks (without self-gravitation but with pressure) orbiting around an axially symmetric, stationary, compact body (e.g. black hole) is presented. The inner edge of the marginally stable accreting disk (i.e. disk with constant angular momentum density) has a sharp cusp located on the equatorial plane between r/sub ms/ and r/sub mb/. The existence of the cusp is also typical for any angular momentum distribution. The physical importance of the cusp follows from the close analogy with the case of a close binary system (L/sub 1/ Lagrange point on the Roche lobe). The existence of the cusp is thus a crucial phenomenon in such problems as boundary condition for the viscous stresses, accretion rate, etc.

Chandra Data Reveal Rapidly Whirling Black Holes

Science.gov (United States)

2008-01-01

A new study using results from NASA's Chandra X-ray Observatory provides one of the best pieces of evidence yet that many supermassive black holes are spinning extremely rapidly. The whirling of these giant black holes drives powerful jets that pump huge amounts of energy into their environment and affects galaxy growth. A team of scientists compared leading theories of jets produced by rotating supermassive black holes with Chandra data. A sampling of nine giant galaxies that exhibit large disturbances in their gaseous atmospheres showed that the central black holes in these galaxies must be spinning at near their maximum rates. People Who Read This Also Read... NASA’s Swift Satellite Catches First Supernova in The Act of Exploding Black Holes Have Simple Feeding Habits Jet Power and Black Hole Assortment Revealed in New Chandra Image Erratic Black Hole Regulates Itself "We think these monster black holes are spinning close to the limit set by Einstein's theory of relativity, which means that they can drag material around them at close to the speed of light," said Rodrigo Nemmen, a visiting graduate student at Penn State University, and lead author of a paper on the new results presented at American Astronomical Society in Austin, Texas. The research reinforces other, less direct methods previously used which have indicated that some stellar and supermassive black holes are spinning rapidly. According to Einstein's theory, a rapidly spinning black hole makes space itself rotate. This effect, coupled with gas spiraling toward the black hole, can produce a rotating, tightly wound vertical tower of magnetic field that flings a large fraction of the inflowing gas away from the vicinity of the black hole in an energetic, high-speed jet. Computer simulations by other authors have suggested that black holes may acquire their rapid spins when galaxies merge, and through the accretion of gas from their surroundings. "Extremely fast spin might be very common for large

Observation of orientation- and k-dependent Zeeman spin-splitting in hole quantum wires on (100)-oriented AlGaAs/GaAs heterostructures

International Nuclear Information System (INIS)

Chen, J C H; Klochan, O; Micolich, A P; Hamilton, A R; Martin, T P; Ho, L H; Zuelicke, U; Reuter, D; Wieck, A D

2010-01-01

In this paper, We study the Zeeman spin-splitting in hole quantum wires oriented along the [011] and [01 1-bar] crystallographic axes of a high mobility undoped (100)-oriented AlGaAs/GaAs heterostructure. Our data show that the spin-splitting can be switched 'on' (finite g*) or 'off' (zero g*) by rotating the field from a parallel to a perpendicular orientation with respect to the wire, and the properties of the wire are identical for the two orientations with respect to the crystallographic axes. We also find that the g-factor in the parallel orientation decreases as the wire is narrowed. This is in contrast to electron quantum wires, where the g-factor is enhanced by exchange effects as the wire is narrowed. This is evidence for a k-dependent Zeeman splitting that arises from the spin-3/2 nature of holes.

Black hole spin from wobbling and rotation of the M87 jet and a sign of a magnetically arrested disc

Science.gov (United States)

Sob'yanin, Denis Nikolaevich

2018-06-01

New long-term Very Long Baseline Array observations of the well-known jet in the M87 radio galaxy at 43 GHz show that the jet experiences a sideways shift with an approximately 8-10 yr quasi-periodicity. Such jet wobbling can be indicative of a relativistic Lense-Thirring precession resulting from a tilted accretion disc. The wobbling period together with up-to-date kinematic data on jet rotation opens up the possibility for estimating angular momentum of the central supermassive black hole. In the case of a test-particle precession, the specific angular momentum is J/Mc = (2.7 ± 1.5) × 1014 cm, implying moderate dimensionless spin parameters a = 0.5 ± 0.3 and 0.31 ± 0.17 for controversial gas-dynamic and stellar-dynamic black hole masses. However, in the case of a solid-body-like precession, the spin parameter is much smaller for both masses, 0.15 ± 0.05. Rejecting this value on the basis of other independent spin estimations requires the existence of a magnetically arrested disc in M87.

Chandra Sees Remarkable Eclipse of Black Hole

Science.gov (United States)

2007-04-01

A remarkable eclipse of a supermassive black hole and the hot gas disk around it has been observed with NASA's Chandra X-ray Observatory. This eclipse has allowed two key predictions about the effects of supermassive black holes to be tested. Just as eclipses of the Sun and moon give astronomers rare opportunities to learn about those objects, an alignment in a nearby galaxy has provided a rare opportunity to investigate a supermassive black hole. Illustrations of Black Hole Eclipse Illustrations of Black Hole Eclipse The supermassive black hole is located in NGC 1365, a galaxy 60 million light years from Earth. It contains a so called active galactic nucleus, or AGN. Scientists believe that the black hole at the center of the AGN is fed by a steady stream of material, presumably in the form of a disk. Material just about to fall into a black hole should be heated to millions of degrees before passing over the event horizon, or point of no return. The disk of gas around the central black hole in NGC 1365 produces copious X-rays but is much too small to resolve directly with a telescope. However, the disk was eclipsed by an intervening cloud, so observation of the time taken for the disk to go in and out of eclipse allowed scientists to estimate the size of the disk. Black Hole Animation Black Hole Animation "For years we've been struggling to confirm the size of this X-ray structure," said Guido Risaliti of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass, and the Italian Institute of Astronomy (INAF). "This serendipitous eclipse enabled us to make this breakthrough." The Chandra team directly measured the size of the X-ray source as about seven times the distance between the Sun and the Earth. That means the source of X-rays is about 2 billion times smaller than the host galaxy and only about 10 times larger than the estimated size of the black hole's event horizon, consistent with theoretical predictions. Chandra X-ray Image of NGC 1365

INTRINSIC ELECTROMAGNETIC VARIABILITY IN CELESTIAL OBJECTS CONTAINING RAPIDLY SPINNING BLACK HOLES

Energy Technology Data Exchange (ETDEWEB)

Zhang, Fan, E-mail: fnzhang@bnu.edu.cn [Gravitational Wave and Cosmology Laboratory, Department of Astronomy, Beijing Normal University, Beijing 100875 (China); Department of Physics and Astronomy, West Virginia University, P.O. Box 6315, Morgantown, WV 26506 (United States)

2016-02-10

Analytical studies have raised the concern that a mysterious expulsion of magnetic field lines by a rapidly spinning black hole (dubbed the black hole Meissner effect) would shut down the Blandford–Znajek process and quench the jets of active galactic nuclei and microquasars. This effect is, however, not seen observationally or in numerical simulations. Previous attempts at reconciling the predictions with observations have proposed several mechanisms to evade the Meissner effect. In this paper, we identify a new evasion mechanism and discuss its observational significance. Specifically, we show that the breakdown of stationarity is sufficient to remove the expulsion of the magnetic field at all multipole orders, and that the associated temporal variation is likely turbulent because of the existence of efficient mechanisms for sharing energy across different modes. Such an intrinsic (as opposed to being driven externally by, e.g., changes in the accretion rate) variability of the electromagnetic field can produce the recorded linear correlation between microvariability amplitudes and mean fluxes, help create magnetic randomness and seed sheared magnetic loops in jets, and lead to a better theoretical fit to the X-ray microvariability power spectral density.

Simulating the Growth of a Disk Galaxy and its Supermassive Black Hole in a Cosmological Simulating the Growth of a Disk Galaxy and its Supermassive Black Hole in a Cosmological Context

International Nuclear Information System (INIS)

Levine, Robyn Deborah; JILA, Boulder

2008-01-01

Supermassive black holes (SMBHs) are ubiquitous in the centers of galaxies. Their formation and subsequent evolution is inextricably linked to that of their host galaxies, and the study of galaxy formation is incomplete without the inclusion of SMBHs. The present work seeks to understand the growth and evolution of SMBHs through their interaction with the host galaxy and its environment. In the first part of the thesis (Chap. 2 and 3), we combine a simple semi-analytic model of outflows from active galactic nuclei (AGN) with a simulated dark matter density distribution to study the impact of SMBH feedback on cosmological scales. We find that constraints can be placed on the kinetic efficiency of such feedback using observations of the filling fraction of the Lyα forest. We also find that AGN feedback is energetic enough to redistribute baryons over cosmological distances, having potentially significant effects on the interpretation of cosmological data which are sensitive to the total matter density distribution (e.g. weak lensing). However, truly assessing the impact of AGN feedback in the universe necessitates large-dynamic range simulations with extensive treatment of baryonic physics to first model the fueling of SMBHs. In the second part of the thesis (Chap. 4-6) we use a hydrodynamic adaptive mesh refinement simulation to follow the growth and evolution of a typical disk galaxy hosting a SMBH, in a cosmological context. The simulation covers a dynamical range of 10 million allowing us to study the transport of matter and angular momentum from super-galactic scales all the way down to the outer edge of the accretion disk around the SMBH. Focusing our attention on the central few hundred parsecs of the galaxy, we find the presence of a cold, self-gravitating, molecular gas disk which is globally unstable. The global instabilities drive super-sonic turbulence, which maintains local stability and allows gas to fuel a SMBH without first fragmenting completely

Inferences about Supernova Physics from Gravitational-Wave Measurements: GW151226 Spin Misalignment as an Indicator of Strong Black-Hole Natal Kicks.

Science.gov (United States)

O'Shaughnessy, Richard; Gerosa, Davide; Wysocki, Daniel

2017-07-07

The inferred parameters of the binary black hole GW151226 are consistent with nonzero spin for the most massive black hole, misaligned from the binary's orbital angular momentum. If the black holes formed through isolated binary evolution from an initially aligned binary star, this misalignment would then arise from a natal kick imparted to the first-born black hole at its birth during stellar collapse. We use simple kinematic arguments to constrain the characteristic magnitude of this kick, and find that a natal kick v_{k}≳50  km/s must be imparted to the black hole at birth to produce misalignments consistent with GW151226. Such large natal kicks exceed those adopted by default in most of the current supernova and binary evolution models.

Spin One Hawking Radiation from Dirty Black Holes

OpenAIRE

Petarpa Boonserm; Tritos Ngampitipan; Matt Visser

2013-01-01

A “clean” black hole is a black hole in vacuum such as the Schwarzschild black hole. However in real physical systems, there are matter fields around a black hole. Such a black hole is called a “dirty black hole”. In this paper, the effect of matter fields on the black hole and the greybody factor is investigated. The results show that matter fields make a black hole smaller. They can increase the potential energy to a black hole to obstruct Hawking radiation to propagate. This causes the gre...

Dynamical spin susceptibility of electron-doped high-Tc cuprates. Comparison with hole-doped systems

International Nuclear Information System (INIS)

Suzuki, Atsuo; Mutou, Tetsuya; Tanaka, Syunsuke; Hirashima, Dai S.

2010-01-01

The magnetic excitation spectrum of electron-doped copper oxide superconductors is studied by calculating the dynamical spin susceptibility of the two-dimensional Hubbard model in which a d x2-y2 -wave superconducting order parameter is assumed. The spectrum of electron-doped systems is compared with that of hole-doped systems, and the relationship between the frequency at which a peak grows in the spectrum and the superconducting energy gap at a hot spot is investigated. A peak may be observed even when the magnetic resonance condition is not exactly satisfied. We find that, in the electron-doped systems, the resonance condition is less likely to be satisfied than in the hole-doped systems because of the small density of states around the hot spots, and the peak frequency is close to twice the gap magnitude at the hot spots. (author)

Evolution of the magnetized, neutrino-cooled accretion disk in the aftermath of a black hole-neutron star binary merger

Science.gov (United States)

Hossein Nouri, Fatemeh; Duez, Matthew D.; Foucart, Francois; Deaton, M. Brett; Haas, Roland; Haddadi, Milad; Kidder, Lawrence E.; Ott, Christian D.; Pfeiffer, Harald P.; Scheel, Mark A.; Szilagyi, Bela

2018-04-01

Black hole-torus systems from compact binary mergers are possible engines for gamma-ray bursts (GRBs). During the early evolution of the postmerger remnant, the state of the torus is determined by a combination of neutrino cooling and magnetically driven heating processes, so realistic models must include both effects. In this paper, we study the postmerger evolution of a magnetized black hole-neutron star binary system using the Spectral Einstein Code (SpEC) from an initial postmerger state provided by previous numerical relativity simulations. We use a finite-temperature nuclear equation of state and incorporate neutrino effects in a leakage approximation. To achieve the needed accuracy, we introduce improvements to SpEC's implementation of general-relativistic magnetohydrodynamics (MHD), including the use of cubed-sphere multipatch grids and an improved method for dealing with supersonic accretion flows where primitive variable recovery is difficult. We find that a seed magnetic field triggers a sustained source of heating, but its thermal effects are largely cancelled by the accretion and spreading of the torus from MHD-related angular momentum transport. The neutrino luminosity peaks at the start of the simulation, and then drops significantly over the first 20 ms but in roughly the same way for magnetized and nonmagnetized disks. The heating rate and disk's luminosity decrease much more slowly thereafter. These features of the evolution are insensitive to grid structure and resolution, formulation of the MHD equations, and seed field strength, although turbulent effects are not fully converged.

Magnonic Black Holes.

Science.gov (United States)

Roldán-Molina, A; Nunez, Alvaro S; Duine, R A

2017-02-10

We show that the interaction between the spin-polarized current and the magnetization dynamics can be used to implement black-hole and white-hole horizons for magnons-the quanta of oscillations in the magnetization direction in magnets. We consider three different systems: easy-plane ferromagnetic metals, isotropic antiferromagnetic metals, and easy-plane magnetic insulators. Based on available experimental data, we estimate that the Hawking temperature can be as large as 1 K. We comment on the implications of magnonic horizons for spin-wave scattering and transport experiments, and for magnon entanglement.

Production of spinning black holes at colliders

International Nuclear Information System (INIS)

Park, S. C.; Song, H. S.

2003-01-01

When the Planck scale is as low as TeV, there will be chances to produce Black holes at future colliders. Generally, black holes produced via particle collisions can have non-zero angular momenta. We estimate the production cross-section of rotating Black holes in the context of low energy gravitation theories by taking the effects of rotation into account. The production cross section is shown to be enhanced by a factor of 2 - 3 over the naive estimate σ = π ∼ R S 2 , where R S denotes the Schwarzschild radius of black hole for a given energy. We also point out that the decay spectrum may have a distinguishable angular dependence through the grey-body factor of a rotating black hole. The angular dependence of decaying particles may give a clear signature for the effect of rotating black holes.

Is black-hole ringdown a memory of its progenitor?

Science.gov (United States)

Kamaretsos, Ioannis; Hannam, Mark; Sathyaprakash, B S

2012-10-05

We perform an extensive numerical study of coalescing black-hole binaries to understand the gravitational-wave spectrum of quasinormal modes excited in the merged black hole. Remarkably, we find that the masses and spins of the progenitor are clearly encoded in the mode spectrum of the ringdown signal. Some of the mode amplitudes carry the signature of the binary's mass ratio, while others depend critically on the spins. Simulations of precessing binaries suggest that our results carry over to generic systems. Using Bayesian inference, we demonstrate that it is possible to accurately measure the mass ratio and a proper combination of spins even when the binary is itself invisible to a detector. Using a mapping of the binary masses and spins to the final black-hole spin allows us to further extract the spin components of the progenitor. Our results could have tremendous implications for gravitational astronomy by facilitating novel tests of general relativity using merging black holes.

High-resolution submillimeter and near-infrared studies of the transition disk around Sz 91

Energy Technology Data Exchange (ETDEWEB)

Tsukagoshi, Takashi; Momose, Munetake [College of Science, Ibaraki University, Bunkyo 2-1-1, Mito 310-8512 (Japan); Hashimoto, Jun [Department of Physics and Astronomy, The University of Oklahoma, 440 West Brooks Street, Norman, OK 73019 (United States); Kudo, Tomoyuki; Saito, Masao; Ohashi, Nagayoshi; Kawabe, Ryohei; Akiyama, Eiji [National Astronomical Observatory Japan (NAOJ), Osawa 2-21-1, Mitaka, Tokyo 181-8588 (Japan); Andrews, Sean; Wilner, David [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Kitamura, Yoshimi [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Yoshinodai 3-1-1, Sagamihara, Kanagawa 229-8510 (Japan); Abe, Lyu [Lboratoire Lagrange (UMR 7293), Université de Nice-Sophia Antipolis, CNRS, Observatoire de la Côte d' Azur, 28 avenue Valrose, F-06108 Nice Cedex 2 (France); Brandner, Wolfgang [Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Brandt, Timothy D. [Department of Astrophysical Sciences, Princeton University, Peyton Hall, Ivy Lane, Princeton, NJ 08544 (United States); Carson, Joseph [Department of Physics and Astronomy, College of Charleston, 58 Coming Street, Charleston, SC 29424 (United States); Currie, Thayne [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street M5S 3H4, Toronto, Ontario (Canada); Egner, Sebastian E.; Guyon, Olivier [Subaru Telescope, 650 North A' ohoku Place, Hilo, HI 96720 (United States); Goto, Miwa [Universitäts-Sternwarte München, Ludwig-Maximilians-Universität, Scheinerstr. 1, D-81679 München (Germany); Grady, Carol, E-mail: ttsuka@mx.ibaraki.ac.jp [Exoplanets and Stellar Astrophysics Laboratory, Code 667, Goddard Space Flight Center, Greenbelt, MD 20771 (United States); and others

2014-03-10

To reveal the structures of a transition disk around a young stellar object in Lupus, Sz 91 , we have performed aperture synthesis 345 GHz continuum and CO(3-2) observations with the Submillimeter Array (∼1''-3'' resolution) and high-resolution imaging of polarized intensity at the K{sub s} -band using the HiCIAO instrument on the Subaru Telescope (0.''25 resolution). Our observations successfully resolved the inner and outer radii of the dust disk to be 65 and 170 AU, respectively, which indicates that Sz 91 is a transition disk source with one of the largest known inner holes. The model fitting analysis of the spectral energy distribution reveals an H{sub 2} mass of 2.4 × 10{sup –3} M {sub ☉} in the cold (T < 30 K) outer part at 65 AU 3 × 10{sup –9} M {sub ☉}) of hot (T ∼ 180 K) dust possibly remains inside the inner hole of the disk. The structure of the hot component could be interpreted as either an unresolved self-luminous companion body (not directly detected in our observations) or a narrow ring inside the inner hole. Significant CO(3-2) emission with a velocity gradient along the major axis of the dust disk is concentrated on the Sz 91 position, suggesting a rotating gas disk with a radius of 420 AU. The Sz 91 disk is possibly a rare disk in an evolutionary stage immediately after the formation of protoplanets because of the large inner hole and the lower disk mass than other transition disks studied thus far.

Brightening of an accretion disk due to viscous dissipation of gravitational waves during the coalescence of supermassive black holes.

Science.gov (United States)

Kocsis, Bence; Loeb, Abraham

2008-07-25

Mergers of supermassive black hole binaries release peak power of up to approximately 10(57) erg s(-1) in gravitational waves (GWs). As the GWs propagate through ambient gas, they induce shear and a small fraction of their power is dissipated through viscosity. The dissipated heat appears as electromagnetic (EM) radiation, providing a prompt EM counterpart to the GW signal. For thin accretion disks, the GW heating rate exceeds the accretion power at distances farther than approximately 10(3) Schwarzschild radii, independently of the accretion rate and viscosity coefficient.

Thermodynamics of higher dimensional black holes

International Nuclear Information System (INIS)

Accetta, F.S.; Gleiser, M.

1986-05-01

We discuss the thermodynamics of higher dimensional black holes with particular emphasis on a new class of spinning black holes which, due to the increased number of Casimir invariants, have additional spin degrees of freedom. In suitable limits, analytic solutions in arbitrary dimensions are presented for their temperature, entropy, and specific heat. In 5 + 1 and 9 + 1 dimensions, more general forms for these quantities are given. It is shown that the specific heat for a higher dimensional black hole is negative definite if it has only one non-zero spin parameter, regardless of the value of this parameter. We also consider equilibrium configurations with both massless particles and massive string modes. 16 refs., 3 figs

Thermodynamics of higher dimensional black holes

Energy Technology Data Exchange (ETDEWEB)

Accetta, F.S.; Gleiser, M.

1986-05-01

We discuss the thermodynamics of higher dimensional black holes with particular emphasis on a new class of spinning black holes which, due to the increased number of Casimir invariants, have additional spin degrees of freedom. In suitable limits, analytic solutions in arbitrary dimensions are presented for their temperature, entropy, and specific heat. In 5 + 1 and 9 + 1 dimensions, more general forms for these quantities are given. It is shown that the specific heat for a higher dimensional black hole is negative definite if it has only one non-zero spin parameter, regardless of the value of this parameter. We also consider equilibrium configurations with both massless particles and massive string modes. 16 refs., 3 figs.

EVIDENCE FOR LOW BLACK HOLE SPIN AND PHYSICALLY MOTIVATED ACCRETION MODELS FROM MILLIMETER-VLBI OBSERVATIONS OF SAGITTARIUS A*

Energy Technology Data Exchange (ETDEWEB)

Broderick, Avery E [Canadian Institute for Theoretical Astrophysics, 60 St. George Street, Toronto, ON M5S 3H8 (Canada); Fish, Vincent L; Doeleman, Sheperd S [Massachusetts Institute of Technology, Haystack Observatory, Route 40, Westford, MA 01886 (United States); Loeb, Abraham [Institute for Theory and Computation, Harvard University, Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

2011-07-10

Millimeter very long baseline interferometry (mm-VLBI) provides the novel capacity to probe the emission region of a handful of supermassive black holes on sub-horizon scales. For Sagittarius A* (Sgr A*), the supermassive black hole at the center of the Milky Way, this provides access to the region in the immediate vicinity of the horizon. Broderick et al. have already shown that by leveraging spectral and polarization information as well as accretion theory, it is possible to extract accretion-model parameters (including black hole spin) from mm-VLBI experiments containing only a handful of telescopes. Here we repeat this analysis with the most recent mm-VLBI data, considering a class of aligned, radiatively inefficient accretion flow (RIAF) models. We find that the combined data set rules out symmetric models for Sgr A*'s flux distribution at the 3.9{sigma} level, strongly favoring length-to-width ratios of roughly 2.4:1. More importantly, we find that physically motivated accretion flow models provide a significantly better fit to the mm-VLBI observations than phenomenological models, at the 2.9{sigma} level. This implies that not only is mm-VLBI presently capable of distinguishing between potential physical models for Sgr A*'s emission, but further that it is sensitive to the strong gravitational lensing associated with the propagation of photons near the black hole. Based upon this analysis we find that the most probable magnitude, viewing angle, and position angle for the black hole spin are a = 0.0{sup +0.64+0.86}, {theta}=68{sup o+5o+9o}{sub -20}{sup o}{sub -28}{sup o}, and {xi}=-52{sup o+17o+33o}{sub -15}{sup o}{sub -24}{sup o} east of north, where the errors quoted are the 1{sigma} and 2{sigma} uncertainties.

EVIDENCE FOR LOW BLACK HOLE SPIN AND PHYSICALLY MOTIVATED ACCRETION MODELS FROM MILLIMETER-VLBI OBSERVATIONS OF SAGITTARIUS A*

International Nuclear Information System (INIS)

Broderick, Avery E.; Fish, Vincent L.; Doeleman, Sheperd S.; Loeb, Abraham

2011-01-01

Millimeter very long baseline interferometry (mm-VLBI) provides the novel capacity to probe the emission region of a handful of supermassive black holes on sub-horizon scales. For Sagittarius A* (Sgr A*), the supermassive black hole at the center of the Milky Way, this provides access to the region in the immediate vicinity of the horizon. Broderick et al. have already shown that by leveraging spectral and polarization information as well as accretion theory, it is possible to extract accretion-model parameters (including black hole spin) from mm-VLBI experiments containing only a handful of telescopes. Here we repeat this analysis with the most recent mm-VLBI data, considering a class of aligned, radiatively inefficient accretion flow (RIAF) models. We find that the combined data set rules out symmetric models for Sgr A*'s flux distribution at the 3.9σ level, strongly favoring length-to-width ratios of roughly 2.4:1. More importantly, we find that physically motivated accretion flow models provide a significantly better fit to the mm-VLBI observations than phenomenological models, at the 2.9σ level. This implies that not only is mm-VLBI presently capable of distinguishing between potential physical models for Sgr A*'s emission, but further that it is sensitive to the strong gravitational lensing associated with the propagation of photons near the black hole. Based upon this analysis we find that the most probable magnitude, viewing angle, and position angle for the black hole spin are a = 0.0 +0.64+0.86 , θ=68 o+5 o +9 o -20 o -28 o , and ξ=-52 o+17 o +33 o -15 o -24 o east of north, where the errors quoted are the 1σ and 2σ uncertainties.

Post-Newtonian templates for binary black-hole inspirals: the effect of the horizon fluxes and the secular change in the black-hole masses and spins

Science.gov (United States)

Isoyama, Soichiro; Nakano, Hiroyuki

2018-01-01

Black holes (BHs) in an inspiraling compact binary system absorb the gravitational-wave (GW) energy and angular-momentum fluxes across their event horizons and this leads to the secular change in their masses and spins during the inspiral phase. The goal of this paper is to present ready-to-use, 3.5 post-Newtonian (PN) template families for spinning, non-precessing, binary BH inspirals in quasicircular orbits, including the 2.5 PN and 3.5 PN horizon-flux contributions as well as the correction due to the secular change in the BH masses and spins through 3.5 PN order, respectively, in phase. We show that, for binary BHs observable by Advanced LIGO with high mass ratios (larger than  ∼10) and large aligned-spins (larger than  ∼ 0.7 ), the mismatch between the frequency-domain template with and without the horizon-flux contribution is typically above the 3% mark. For (supermassive) binary BHs observed by LISA, even a moderate mass-ratios and spins can produce a similar level of the mismatch. Meanwhile, the mismatch due to the secular time variations of the BH masses and spins is well below the 1% mark in both cases, hence this is truly negligible. We also point out that neglecting the cubic-in-spin, point-particle phase term at 3.5 PN order would deteriorate the effect of BH absorption in the template.

Rotation of gas above the galactic disk

International Nuclear Information System (INIS)

Gvaramadze, V.V.; Lominadze, D.G.

1988-01-01

The galactic disk is modeled by an oblate spheroid with confocal spherodial isodensity surfaces. An explicit analytic expression is found for the angular velocity of the gas outside the disk. The parameters of a three-component model of a spiral galaxy (oblate spheroid with central hole, bulge, and massive corona) are chosen in such a way as to obtain in the disk a two-hump rotation curve (as in the Galaxy, M 31, and M 81). It is shown that at heights absolute value z ≤ 2 kpc the gas rotates in the same manner as the disk. However, at greater heights the rotation curve ceases to have two humps. Allowance for the pressure gradient of the gas slightly changes the rotation curve directly above the disk (r r/sub disk/)

Astrophysical disks Collective and Stochastic Phenomena

CERN Document Server

Fridman, Alexei M; Kovalenko, Ilya G

2006-01-01

The book deals with collective and stochastic processes in astrophysical discs involving theory, observations, and the results of modelling. Among others, it examines the spiral-vortex structure in galactic and accretion disks , stochastic and ordered structures in the developed turbulence. It also describes sources of turbulence in the accretion disks, internal structure of disk in the vicinity of a black hole, numerical modelling of Be envelopes in binaries, gaseous disks in spiral galaxies with shock waves formation, observation of accretion disks in a binary system and mass distribution of luminous matter in disk galaxies. The editors adaptly brought together collective and stochastic phenomena in the modern field of astrophysical discs, their formation, structure, and evolution involving the methodology to deal with, the results of observation and modelling, thereby advancing the study in this important branch of astrophysics and benefiting Professional Researchers, Lecturers, and Graduate Students.

Boosting jet power in black hole spacetimes.

Science.gov (United States)

Neilsen, David; Lehner, Luis; Palenzuela, Carlos; Hirschmann, Eric W; Liebling, Steven L; Motl, Patrick M; Garrett, Travis

2011-08-02

The extraction of rotational energy from a spinning black hole via the Blandford-Znajek mechanism has long been understood as an important component in models to explain energetic jets from compact astrophysical sources. Here we show more generally that the kinetic energy of the black hole, both rotational and translational, can be tapped, thereby producing even more luminous jets powered by the interaction of the black hole with its surrounding plasma. We study the resulting Poynting jet that arises from single boosted black holes and binary black hole systems. In the latter case, we find that increasing the orbital angular momenta of the system and/or the spins of the individual black holes results in an enhanced Poynting flux.

NuSTAR AND SUZAKU OBSERVATIONS OF THE HARD STATE IN CYGNUS X-1: LOCATING THE INNER ACCRETION DISK

International Nuclear Information System (INIS)

Parker, M. L.; Lohfink, A.; Fabian, A. C.; Alston, W. N.; Kara, E.; Tomsick, J. A.; Boggs, S. E.; Craig, W. W.; Miller, J. M.; Yamaoka, K.; Nowak, M.; Grinberg, V.; Christensen, F. E.; Fürst, F.; Grefenstette, B. W.; Harrison, F. A.; Gandhi, P.; Hailey, C. J.; King, A. L.; Stern, D.

2015-01-01

We present simultaneous Nuclear Spectroscopic Telescope Array (NuSTAR ) and Suzaku observations of the X-ray binary Cygnus X-1 in the hard state. This is the first time this state has been observed in Cyg X-1 with NuSTAR, which enables us to study the reflection and broadband spectra in unprecedented detail. We confirm that the iron line cannot be fit with a combination of narrow lines and absorption features, instead requiring a relativistically blurred profile in combination with a narrow line and absorption from the companion wind. We use the reflection models of García et al. to simultaneously measure the black hole spin, disk inner radius, and coronal height in a self-consistent manner. Detailed fits to the iron line profile indicate a high level of relativistic blurring, indicative of reflection from the inner accretion disk. We find a high spin, a small inner disk radius, and a low source height and rule out truncation to greater than three gravitational radii at the 3σ confidence level. In addition, we find that the line profile has not changed greatly in the switch from soft to hard states, and that the differences are consistent with changes in the underlying reflection spectrum rather than the relativistic blurring. We find that the blurring parameters are consistent when fitting either just the iron line or the entire broadband spectrum, which is well modeled with a Comptonized continuum plus reflection model

X-ray Reflected Spectra from Accretion Disk Models. III. A Complete Grid of Ionized Reflection Calculations

Science.gov (United States)

Garcia, J.; Dauser, T.; Reynolds, C. S.; Kallman, T. R.; McClintock, J. E.; Wilms, J.; Ekmann, W.

2013-01-01

We present a new and complete library of synthetic spectra for modeling the component of emission that is reflected from an illuminated accretion disk. The spectra were computed using an updated version of our code xillver that incorporates new routines and a richer atomic data base. We offer in the form of a table model an extensive grid of reflection models that cover a wide range of parameters. Each individual model is characterized by the photon index Gamma of the illuminating radiation, the ionization parameter zeta at the surface of the disk (i.e., the ratio of the X-ray flux to the gas density), and the iron abundance A(sub Fe) relative to the solar value. The ranges of the parameters covered are: 1.2 <= Gamma <= 3.4, 1 <= zeta <= 104, and 0.5 <= A(sub Fe) <= 10. These ranges capture the physical conditions typically inferred from observations of active galactic nuclei, and also stellar-mass black holes in the hard state. This library is intended for use when the thermal disk flux is faint compared to the incident power-law flux. The models are expected to provide an accurate description of the Fe K emission line, which is the crucial spectral feature used to measure black hole spin. A total of 720 reflection spectra are provided in a single FITS file suitable for the analysis of X-ray observations via the atable model in xspec. Detailed comparisons with previous reflection models illustrate the improvements incorporated in this version of xillver.

Accretion Disk Spectra of the Ultra-Luminous X-Ray Sources in Nearby Spiral Galaxies and Galactic Superluminal Jet Sources

Energy Technology Data Exchange (ETDEWEB)

Mizuno, T

2003-12-11

Ultra-luminous Compact X-ray Sources (ULXs) in nearby spiral galaxies and Galactic superluminal jet sources share the common spectral characteristic that they have unusually high disk temperatures which cannot be explained in the framework of the standard optically thick accretion disk in the Schwarzschild metric. On the other hand, the standard accretion disk around the Kerr black hole might explain the observed high disk temperature, as the inner radius of the Kerr disk gets smaller and the disk temperature can be consequently higher. However, we point out that the observable Kerr disk spectra becomes significantly harder than Schwarzschild disk spectra only when the disk is highly inclined. This is because the emission from the innermost part of the accretion disk is Doppler-boosted for an edge-on Kerr disk, while hardly seen for a face-on disk. The Galactic superluminal jet sources are known to be highly inclined systems, thus their energy spectra may be explained with the standard Kerr disk with known black hole masses. For ULXs, on the other hand, the standard Kerr disk model seems implausible, since it is highly unlikely that their accretion disks are preferentially inclined, and, if edge-on Kerr disk model is applied, the black hole mass becomes unreasonably large (> 300 M{sub solar}). Instead, the slim disk (advection dominated optically thick disk) model is likely to explain the observed super-Eddington luminosities, hard energy spectra, and spectral variations of ULXs. We suggest that ULXs are accreting black holes with a few tens of solar mass, which is not unexpected from the standard stellar evolution scenario, and that their X-ray emission is from the slim disk shining at super-Eddington luminosities.

General relativistic hydrodynamics with Adaptive-Mesh Refinement (AMR) and modeling of accretion disks

Science.gov (United States)

Donmez, Orhan

We present a general procedure to solve the General Relativistic Hydrodynamical (GRH) equations with Adaptive-Mesh Refinement (AMR) and model of an accretion disk around a black hole. To do this, the GRH equations are written in a conservative form to exploit their hyperbolic character. The numerical solutions of the general relativistic hydrodynamic equations is done by High Resolution Shock Capturing schemes (HRSC), specifically designed to solve non-linear hyperbolic systems of conservation laws. These schemes depend on the characteristic information of the system. We use Marquina fluxes with MUSCL left and right states to solve GRH equations. First, we carry out different test problems with uniform and AMR grids on the special relativistic hydrodynamics equations to verify the second order convergence of the code in 1D, 2 D and 3D. Second, we solve the GRH equations and use the general relativistic test problems to compare the numerical solutions with analytic ones. In order to this, we couple the flux part of general relativistic hydrodynamic equation with a source part using Strang splitting. The coupling of the GRH equations is carried out in a treatment which gives second order accurate solutions in space and time. The test problems examined include shock tubes, geodesic flows, and circular motion of particle around the black hole. Finally, we apply this code to the accretion disk problems around the black hole using the Schwarzschild metric at the background of the computational domain. We find spiral shocks on the accretion disk. They are observationally expected results. We also examine the star-disk interaction near a massive black hole. We find that when stars are grounded down or a hole is punched on the accretion disk, they create shock waves which destroy the accretion disk.

EFFECTS OF LOCAL DISSIPATION PROFILES ON MAGNETIZED ACCRETION DISK SPECTRA

International Nuclear Information System (INIS)

Tao, Ted; Blaes, Omer

2013-01-01

We present spectral calculations of non-LTE accretion disk models appropriate for high-luminosity stellar mass black hole X-ray binary systems. We first use a dissipation profile based on scaling the results of shearing box simulations of Hirose et al. to a range of annuli parameters. We simultaneously scale the effective temperature, orbital frequency, and surface density with luminosity and radius according to the standard α-model. This naturally brings increased dissipation to the disk surface layers (around the photospheres) at small radii and high luminosities. We find that the local spectrum transitions directly from a modified blackbody to a saturated Compton scattering spectrum as we increase the effective temperature and orbital frequency while decreasing midplane surface density. Next, we construct annuli models based on the parameters of a L/L Edd = 0.8 disk orbiting a 6.62 solar mass black hole using two modified dissipation profiles that explicitly put more dissipation per unit mass near the disk surface. The new dissipation profiles are qualitatively similar to the one found by Hirose et al., but produce strong near power-law spectral tails. Our models also include physically motivated magnetic acceleration support based once again on scaling the Hirose et al. results. We present three full-disk spectra, each based on one of the dissipation prescriptions. Our most aggressive dissipation profile results in a disk spectrum that is in approximate quantitative agreement with certain observations of the steep power-law spectral states from some black hole X-ray binaries.

Orbit of the OJ287 black hole binary as determined from the General Relativity centenary flare

Science.gov (United States)

Valtonen, Mauri; Gopakumar, Achamveedu; Mikkola, Seppo; Zola, Staszek; Ciprini, Stefano; Matsumoto, Katsura; Sadakane, Kozo; Kidger, Mark; Gazeas, Kosmas; Nilsson, Kari; Berdyugin, Andrei; Piirola, Vilppu; Jermak, Helen; Baliyan, Kiran; Hudec, Rene; Reichart, Daniel

2016-05-01

OJ287 goes through large optical flares twice each 12 years. The times of these flares have been predicted successfully now 5 times using a black hole binary model. In this model a secondary black hole goes around a primary black hole, impacting the accretion disk of the latter twice per orbital period, creating a thermal flare. Together with 6 flares from the historical data base, the set of flare timings determines uniquely the 7 parameters of the model: the two masses, the primary spin, the major axis, eccentricity and the phase of the orbit, plus a time delay parameter that gives the extent of time between accretion disk impacts and the related optical flares. Based on observations by the OJ287-15/16 Collaboration, OJ287 went into the phase of rapid flux rise on November 25, on the centenary of Einstein’s General Relativity, and peaked on December 5. At that time OJ287 was the brightest in over 30 years in optical wavelengths. The flare was of low polarization, and did not extend beyond the optical/UV region of the spectrum. On top of the main flare there were a number of small flares; their excess brightness correlates well with the simultaneous X-ray data. With these properties the main flare qualifies as the marker of the orbit of the secondary going around the primary black hole. Since the orbit solution is strongly over-determined, its parameters are known very accurately, at better than one percent level for the masses and the spin. The next flare is predicted to peak on July 28, 2019.Detailed monitoring of this event should allow us to test, for the first time, the celebrated black hole no-hair theorem for a massive black hole at the 10% level. The present data is consistent with the theorem only at a 30% level. The main difficulty in observing OJ287 from Earth at our predicted epoch is its closeness to the sun. Therefore, it is desirable to monitor OJ287 from a space-based telescope not in the vicinity of Earth. Unfortunately, this unique opportunity

Merger of Multiple Accreting Black Holes Concordant with Gravitational-wave Events

Science.gov (United States)

Tagawa, Hiromichi; Umemura, Masayuki

2018-03-01

Recently, the advanced Laser Interferometer Gravitational-Wave Observatory (aLIGO) has detected black hole (BH) merger events, most of which are sourced by BHs more massive than 30 M ⊙. Especially, the observation of GW170104 suggests dynamically assembled binaries favoring a distribution of misaligned spins. It has been argued that mergers of unassociated BHs can be engendered through a chance meeting in a multiple BH system under gas-rich environments. In this paper, we consider the merger of unassociated BHs, concordant with the massive BH merger events. To that end, we simulate a multiple BH system with a post-Newtonian N-body code incorporating gas accretion and general relativistic effects. As a result, we find that gas dynamical friction effectively promotes a three-body interaction of BHs in dense gas of n gas ≳ 106 cm‑3, so that BH mergers can take place within 30 Myr. This scenario predicts an isotropic distribution of spin tilts. In the concordant models with GW150914, the masses of seed BHs are required to be ≳25 M ⊙. The potential sites of such chance meeting BH mergers are active galactic nucleus (AGN) disks and dense interstellar clouds. Assuming the LIGO O1, we roughly estimate the event rates for PopI BHs and PopIII BHs in AGN disks to be ≃1–2 yr‑1 and ≃1 yr‑1, respectively. Multiple episodes of AGNs may enhance the rates by roughly an order of magnitude. For massive PopI BHs in dense interstellar clouds the rate is ≃0.02 yr‑1. Hence, high-density AGN disks are a more plausible site for mergers of chance meeting BHs.

Observing Mergers of Non-Spinning Black-Hole Binaries

Science.gov (United States)

McWilliams, Sean T.; Boggs, William D.; Baker, John G.; Kelly, Bernard J.

2010-01-01

Advances in the field of numerical relativity now make it possible to calculate the final, most powerful merger phase of binary black-hole coalescence for generic binaries. The state of the art has advanced well beyond the equal-mass case into the unequal-mass and spinning regions of parameter space. We present a study of the nonspinning portion of parameter space, primarily using an analytic waveform model tuned to available numerical data, with an emphasis on observational implications. We investigate the impact of varied m8BS ratio on merger signal-to-noise ratios (SNR) for several detectors, and compare our results with expectations from the test-mass limit. We note a striking similarity of the waveform phasing of the merger waveform across the available mass ratios. Motivated by this, we calculate the match between our equal-mass and 4:1 mass-ratio waveforms during the merger as a function of location on the source sky, using a new formalism for the match that accounts for higher harmonics. This is an indicator of the amount of degeneracy in mass ratio for mergers of moderate mass ratio systems.

Super-entropic black holes and the Kerr-CFT correspondence

Energy Technology Data Exchange (ETDEWEB)

Sinamuli, Musema [Department of Physics and Astronomy, University of Waterloo,200 University Ave., Waterloo, Ontario N2L 3G1 (Canada); Perimeter Institute for Theoretical Physics,31 Caroline St., Waterloo, Ontario, N2L 2Y5 (Canada); Mann, Robert B. [Department of Physics and Astronomy, University of Waterloo,200 University Ave., Waterloo, Ontario N2L 3G1 (Canada)

2016-08-24

We demonstrate that Kerr-CFT duality can be extended to super-entropic black holes, which have non-compact horizons with finite area. We demonstrate that this duality is robust insofar as the ultra-spinning limit of a Kerr-AdS black hole (which yields the super-entropic class) commutes with the near-horizon limit (which yields the Kerr-CFT duality). Consequently the Bekenstein-Hawking and the CFT entropies are equivalent. We show that the duality holds for both singly-spinning super-entropic black holes in 4 dimensions and for doubly-spinning super-entropic black holes of gauged supergravity in 5 dimensions. In both cases we obtain not only the expected left/right temperatures, but also temperatures associated with electric charge and with a new thermodynamic parameter specific to super-entropic black holes.

Super-entropic black holes and the Kerr-CFT correspondence

International Nuclear Information System (INIS)

Sinamuli, Musema; Mann, Robert B.

2016-01-01

We demonstrate that Kerr-CFT duality can be extended to super-entropic black holes, which have non-compact horizons with finite area. We demonstrate that this duality is robust insofar as the ultra-spinning limit of a Kerr-AdS black hole (which yields the super-entropic class) commutes with the near-horizon limit (which yields the Kerr-CFT duality). Consequently the Bekenstein-Hawking and the CFT entropies are equivalent. We show that the duality holds for both singly-spinning super-entropic black holes in 4 dimensions and for doubly-spinning super-entropic black holes of gauged supergravity in 5 dimensions. In both cases we obtain not only the expected left/right temperatures, but also temperatures associated with electric charge and with a new thermodynamic parameter specific to super-entropic black holes.

The force-free magnetosphere of a rotating black hole

Directory of Open Access Journals (Sweden)

Contopoulos Ioannis

2013-12-01

Full Text Available We explore the analogy with pulsars and investigate the structure of the force-free magnetosphere around a Kerr black hole. We propose that the source of the black hole magnetic field is the Poynting-Robertson effect on the plasma electrons at the inner edge of the surrounding accretion disk, the so called Cosmic Battery. The magnetospheric solution is characterized by the distributions of the magnetic field angular velocity and the poloidal electric current. These are not arbitrary. They are determined self-consistently by requiring that magnetic field lines cross smoothly the two singular surfaces of the problem, the inner ‘light surface’ located inside the ergosphere, and the outer ‘light surface’ which is the generalization of the pulsar light cylinder. The black hole forms a relativistic jet only if it is surrounded by a thick disk and/or extended disk outflows.

Two-temperature accretion disks in pair equilibrium

International Nuclear Information System (INIS)

Kusunose, Masaaki; Takahara, Fumio.

1989-01-01

We investigate two-temperature accretion disks with electron-positron pair production, taking account of the bremsstrahlung and Comptonization of soft photons produced by the cyclotron higher harmonics. The properties of the disks are qualitatively the same as those of disks in which bremsstrahlung is the only photon source. For an accretion rate higher than a critical value, M cr , no steady solutions exist for a certain range of radial distance from a central black hole. The critical value increases only slightly with the input of soft photons; the increment is 45%, i.e., M cr ∼ 0.43 M Edd , for the viscosity parameter α = 0.1, where M Edd ≡ L Edd /c 2 = 4πGM BH m p /(σ T c) with M BH being the mass of the central black hole. Furthermore, the disks are unstable against perturbations of the proton temperature. For α ∼ 0.1, the equipartition magnetic field, and a range of accretion rates, emission spectra obey the power law with a spectral index of -0.7 to -0.6, which coincides with the observed universal X-ray spectra of Seyfert galaxies. Brief comments on the model of the γ-ray flare of Cyg X-1 are also given. (author)

Black-hole galactic nuclei: a high-energy perspective

CERN Document Server

Boldt, E; Loewenstein, M

2002-01-01

The gravitational radiation signals to be anticipated from events involving black-hole galactic nuclei depend on the spin of the underlying object. To obtain evidence about the spin of Seyfert AGN black holes, we can rely on future ultra-high resolution spectral/spatial x-ray studies of iron K line fluorescence from the innermost regions of accreting matter. Normal galaxies present more of a challenge. To account for the highest energy cosmic rays, we propose that ultra-relativistic particle acceleration can occur near the event horizons of spun-up supermassive black-holes at the non-active nuclei of giant elliptical galaxies. This conjecture about the black hole spin associated with such nuclei is subject to verification via the characteristic TeV curvature radiation expected to be detected with upcoming gamma-ray observatories.

Generic features of Einstein-Aether black holes

International Nuclear Information System (INIS)

Tamaki, Takashi; Miyamoto, Umpei

2008-01-01

We reconsider spherically symmetric black hole solutions in Einstein-Aether theory with the condition that this theory has identical parametrized post-Newtonian parameters as those for general relativity, which is the main difference from the previous research. In contrast with previous study, we allow superluminal propagation of a spin-0 Aether-gravity wave mode. As a result, we obtain black holes having a spin-0 'horizon' inside an event horizon. We allow a singularity at a spin-0 horizon since it is concealed by the event horizon. If we allow such a configuration, the kinetic term of the Aether field can be large enough for black holes to be significantly different from Schwarzschild black holes with respect to Arnowitt-Deser-Misner mass, innermost stable circular orbit, Hawking temperature, and so on. We also discuss whether or not the above features can be seen in more generic vector-tensor theories

Quantum computing with acceptor spins in silicon.

Science.gov (United States)

Salfi, Joe; Tong, Mengyang; Rogge, Sven; Culcer, Dimitrie

2016-06-17

The states of a boron acceptor near a Si/SiO2 interface, which bind two low-energy Kramers pairs, have exceptional properties for encoding quantum information and, with the aid of strain, both heavy hole and light hole-based spin qubits can be designed. Whereas a light-hole spin qubit was introduced recently (arXiv:1508.04259), here we present analytical and numerical results proving that a heavy-hole spin qubit can be reliably initialised, rotated and entangled by electrical means alone. This is due to strong Rashba-like spin-orbit interaction terms enabled by the interface inversion asymmetry. Single qubit rotations rely on electric-dipole spin resonance (EDSR), which is strongly enhanced by interface-induced spin-orbit terms. Entanglement can be accomplished by Coulomb exchange, coupling to a resonator, or spin-orbit induced dipole-dipole interactions. By analysing the qubit sensitivity to charge noise, we demonstrate that interface-induced spin-orbit terms are responsible for sweet spots in the dephasing time [Formula: see text] as a function of the top gate electric field, which are close to maxima in the EDSR strength, where the EDSR gate has high fidelity. We show that both qubits can be described using the same starting Hamiltonian, and by comparing their properties we show that the complex interplay of bulk and interface-induced spin-orbit terms allows a high degree of electrical control and makes acceptors potential candidates for scalable quantum computation in Si.

Some electromagnetic and gravitational perturbations of black holes

International Nuclear Information System (INIS)

Pollock, M.D.

1978-08-01

The dissertation is concerned with the changes which take place in a Kerr black hole which is subjected to electromagnetic or gravitational perturbations, in particular idealized configurations. A calculation is made of the interaction between a slowly rotating black hole and a uniform, weak magnetic field. The method used is to solve the tensorial Maxwell equations in the background geometry of the hole and then calculate the torque on the sources of the field, hence deducing the spin-down law of the hole. The calculation is extended to include black holes rotating with arbitrary angular velocity by a different method, which is based on Newman-Penrose spinor formalism and applies some work of Chandrasekhar. The analogous gravitational problem, in which the centrally located hole is perturbed by a spinning shell of matter is solved by drawing on the results of Chrzanowski on factorized Green functions and horizon multipole moments. Formulae are presented for the spin-down behaviour of a black hole under these two kinds of perturbation. In addition to these effects produced by the fields, there are also linear precessional effects in the gravitational case, but not in the electromagnetic case. (author)

Hidden Pair of Supermassive Black Holes

Science.gov (United States)

Kohler, Susanna

2015-08-01

Could a pair of supermassive black holes (SMBHs) be lurking at the center of the galaxy Mrk 231? A recent study finds that this may be the case and the unique spectrum of this galaxy could be the key to discovering more hidden binary SMBH systems.Where Are the Binary Supermassive Black Holes?Its believed that most, if not all, galaxies have an SMBH at their centers. As two galaxies merge, the two SMBHs should evolve into a closely-bound binary system before they eventually merge. Given the abundance of galaxy mergers, we would expect to see the kinematic and visual signatures of these binary SMBHs among observed active galactic nuclei yet such evidence for sub-parsec binary SMBH systems remains scarce and ambiguous. This has led researchers to wonder: is there another way that we might detect these elusive systems?A collaboration led by Chang-Shuo Yan (National Astronomical Observatories, Chinese Academy of Sciences) thinks that there is. The group suggests that these systems might have distinct signatures in their optical-to-UV spectra, and they identify a system that might be just such a candidate: Mrk 231.A Binary CandidateProposed model of Mrk 231. Two supermassive black holes, each with their own mini-disk, orbit each other in the center of a circumbinary disk. The secondary black hole has cleared gap in the circumbinary disk as a result of its orbit around the primary black hole. [Yan et al. 2015]Mrk 231 is a galaxy with a disturbed morphology and tidal tails strong clues that it might be in the final stages of a galactic merger. In addition to these signs, Mrk 231 also has an unusual spectrum for a quasar: its continuum emission displays an unexpected drop in the near-UV band.Yan and her collaborators propose that the odd behavior of Mrk 231s spectrum can be explained if the center of the galaxy houses a pair of SMBHs each with its own mini accretion disk surrounded by a circumbinary accretion disk. As the secondary SMBH orbits the primary SMBH (with a

Review of gravitomagnetic acceleration from accretion disks

Science.gov (United States)

Poirier, J.; Mathews, G. J.

2015-11-01

We review the development of the equations of gravitoelectromagnetism and summarize how the motion of the neutral masses in an accretion disk orbiting a black hole creates a general-relativistic magnetic-like (gravitomagnetic) field that vertically accelerates neutral particles near the accretion disk upward and then inward toward the axis of the accretion disk. Even though this gravitomagnetic field is not the only mechanism to produce collimated jets, it is a novel means to identify one general relativistic effect from a much more complicated problem. In addition, as the accelerated material above or below the accretion disk nears the axis with a nearly vertical direction, a frame-dragging effect twists the trajectories around the axis thus contributing to the collimation of the jet.

Radiation transport around Kerr black holes

Science.gov (United States)

Schnittman, Jeremy David

This Thesis describes the basic framework of a relativistic ray-tracing code for analyzing accretion processes around Kerr black holes. We begin in Chapter 1 with a brief historical summary of the major advances in black hole astrophysics over the past few decades. In Chapter 2 we present a detailed description of the ray-tracing code, which can be used to calculate the transfer function between the plane of the accretion disk and the detector plane, an important tool for modeling relativistically broadened emission lines. Observations from the Rossi X-Ray Timing Explorer have shown the existence of high frequency quasi-periodic oscillations (HFQPOs) in a number of black hole binary systems. In Chapter 3, we employ a simple "hot spot" model to explain the position and amplitude of these HFQPO peaks. The power spectrum of the periodic X-ray light curve consists of multiple peaks located at integral combinations of the black hole coordinate frequencies, with the relative amplitude of each peak determined by the orbital inclination, eccentricity, and hot spot arc length. In Chapter 4, we introduce additional features to the model to explain the broadening of the QPO peaks as well as the damping of higher frequency harmonics in the power spectrum. The complete model is used to fit the power spectra observed in XTE J1550-564, giving confidence limits on each of the model parameters. In Chapter 5 we present a description of the structure of a relativistic alpha- disk around a Kerr black hole. Given the surface temperature of the disk, the observed spectrum is calculated using the transfer function mentioned above. The features of this modified thermal spectrum may be used to infer the physical properties of the accretion disk and the central black hole. In Chapter 6 we develop a Monte Carlo code to calculate the detailed propagation of photons from a hot spot emitter scattering through a corona surrounding the black hole. The coronal scattering has two major observable

Electric-field effects in optically generated spin transport

International Nuclear Information System (INIS)

Miah, M. Idrish

2009-01-01

Transport of spin-polarized electrons in semiconductors is studied experimentally. Spins are generated by optical excitation because of the selection rules governing optical transitions from heavy-hole and light-hole states to conduction-band states. Experiments designed for the control of spins in semiconductors investigate the bias-dependent spin transport process and detect the spin-polarized electrons during transport. A strong bias dependence is observed. The electric-field effects on the spin-polarized electron transport are also found to be depended on the excitation photon energy and temperature. Based on a field-dependent spin relaxation mechanism, the electric-field effects in the transport process are discussed.

Electric-field effects in optically generated spin transport

Energy Technology Data Exchange (ETDEWEB)

Miah, M. Idrish [Nanoscale Science and Technology Centre and School of Biomolecular and Physical Sciences, Griffith University, Nathan, Brisbane, QLD 4111 (Australia); Department of Physics, University of Chittagong, Chittagong 4331 (Bangladesh)], E-mail: m.miah@griffith.edu.au

2009-05-25

Transport of spin-polarized electrons in semiconductors is studied experimentally. Spins are generated by optical excitation because of the selection rules governing optical transitions from heavy-hole and light-hole states to conduction-band states. Experiments designed for the control of spins in semiconductors investigate the bias-dependent spin transport process and detect the spin-polarized electrons during transport. A strong bias dependence is observed. The electric-field effects on the spin-polarized electron transport are also found to be depended on the excitation photon energy and temperature. Based on a field-dependent spin relaxation mechanism, the electric-field effects in the transport process are discussed.

Gamma-ray bursts from black hole accretion disks

International Nuclear Information System (INIS)

Strong, I.B.

1975-01-01

The suggestion was first made more than a year ago that gamma-ray bursts might originate in the neighborhood of black holes, based on some rather circumstantial evidence linking Cygnus X-1, the prime black-hole candidate, with two of the then-known gamma-ray bursts. Since then additional evidence makes the idea still more plausible. The evidence is summarized briefly, a physical model for production of gamma-ray bursts is given, and several of the more interesting consequences of such an origin are pointed out. (orig.) [de

Collision of two rotating Hayward black holes

Energy Technology Data Exchange (ETDEWEB)

Gwak, Bogeun [Sejong University, Department of Physics and Astronomy, Seoul (Korea, Republic of)

2017-07-15

We investigate the spin interaction and the gravitational radiation thermally allowed in a head-on collision of two rotating Hayward black holes. The Hayward black hole is a regular black hole in a modified Einstein equation, and hence it can be an appropriate model to describe the extent to which the regularity effect in the near-horizon region affects the interaction and the radiation. If one black hole is assumed to be considerably smaller than the other, the potential of the spin interaction can be analytically obtained and is dependent on the alignment of angular momenta of the black holes. For the collision of massive black holes, the gravitational radiation is numerically obtained as the upper bound by using the laws of thermodynamics. The effect of the Hayward black hole tends to increase the radiation energy, but we can limit the effect by comparing the radiation energy with the gravitational waves GW150914 and GW151226. (orig.)

Semiconductors put spin in spintronics

International Nuclear Information System (INIS)

Weiss, Dieter

2000-01-01

Electrons and holes, which carry the current in semiconductor devices, are quantum-mechanical objects characterized by a set of quantum numbers - the band index, the wave-vector (which is closely related to the electron or hole velocity) and spin. The spin, however, is one of the strangest properties of particles. In simple terms, we can think of the spin as an internal rotation of the electron, but it has no classical counterpart. The spin is connected to a quantized magnetic moment and hence acts as a microscopic magnet. Thus the electron spin can adopt one of two directions (''up'' or ''down'') in a magnetic field. The spin plays no role in conventional electronics and the current in any semiconductor device is made up of a mixture of electrons with randomly oriented spins. However, a new range of electronic devices that transport the spin of the electrons, in addition to their charge, is being developed. But the biggest obstacle to making practical ''spin electronic'' or ''spintronic'' devices so far has been finding a way of injecting spin-polarized electrons or holes into the semiconductor and then detecting them. Recently a team of physicists from the University of Wuerzburg in Germany, and also a collaboration of researchers from Tohoku University in Japan and the University of California at Santa Barbara, have found a way round these problems using either semi-magnetic or ferromagnetic semiconductors as ''spin aligners'' (R Fiederling et al. 1999 Nature 402 787; Y Ohno et al. 1999 Nature 402 790). In this article the author presents the latest breakthrough in spintronics research. (UK)

The Fate of Massive Black Holes in Gas-Rich Galaxy Mergers

Science.gov (United States)

Escala, A.; Larson, R. B.; Coppi, P. S.; Mardones, D.

2006-06-01

Using SPH numerical simulations, we investigate the effects of gas on the inspiral and merger of a massive black hole binary. This study is motivated by the very massive nuclear gas disks observed in the central regions of merging galaxies. Here we present results that expand on the treatment in previous works (Escala et al. 2004, 2005), by studying the evolution of a binary with different black holes masses in a massive gas disk.

Massive disc formation in the tidal disruption of a neutron star by a nearly extremal black hole

International Nuclear Information System (INIS)

Lovelace, Geoffrey; Kidder, Lawrence E; Duez, Matthew D; Foucart, Francois; Pfeiffer, Harald P; Scheel, Mark A; Szilágyi, Béla

2013-01-01

Black hole–neutron star (BHNS) binaries are important sources of gravitational waves for second-generation interferometers, and BHNS mergers are also a proposed engine for short, hard gamma-ray bursts. The behavior of both the spacetime (and thus the emitted gravitational waves) and the neutron-star matter in a BHNS merger depend strongly and nonlinearly on the black hole's spin. While there is a significant possibility that astrophysical black holes could have spins that are nearly extremal (i.e. near the theoretical maximum), to date fully relativistic simulations of BHNS binaries have included black-hole spins only up to S/M 2 = 0.9, which corresponds to the black hole having approximately half as much rotational energy as possible, given the black hole's mass. In this paper, we present a new simulation of a BHNS binary with a mass ratio q = 3 and black-hole spin S/M 2 = 0.97, the highest simulated to date. We find that the black hole's large spin leads to the most massive accretion disc and the largest tidal tail outflow of any fully relativistic BHNS simulations to date, even exceeding the results implied by extrapolating results from simulations with lower black-hole spin. The disc appears to be remarkably stable. We also find that the high black-hole spin persists until shortly before the time of merger; afterward, both merger and accretion spin down the black hole. (paper)

Spin-resolved x-ray photoemission studies of ferromagnetic metals

International Nuclear Information System (INIS)

Klebanoff, L.E.

1996-01-01

Recent spin-resolved x-ray photoelectron spectroscopy (SRXPS) studies of ferromagnetic metals are reviewed. SRXPS studies of metallic Fe, Co, Co 66 Fe 4 Ni 1 B 14 Si 15 , and Ni demonstrate that core-level photoemission, and the itinerant electron response to core-hole creation, are highly spin-dependent. The exchange splitting of the Fe 2p 3/2 level is found to be 0.48±0.05 eV. Lifetime broadening results for the Fe 2p 3/2 N↑ (majority spin) and N↓ (minority spin) components indicate conservation of spin in core-hole filling processes involving the valence band. SRXPS study of the Fe 2p 3/2 peak asymmetry α reveals a dependence of electron endash hole excitation on the spin of the core hole. Spin analysis of the Fe 3s XPS line shape shows it to be a three-component spectrum, rather than the two-component line shape assumed previously. A photon energy dependence of one of the Fe 3s components explains disagreement among previous Fe 3s XPS results. Comparisons of SRXPS from Co metal and Co 66 Fe 4 Ni 1 B 14 Si 15 directly demonstrate the effect of a reduced atomic magnetic moment on the spin dependence of core-level XPS. The behavior of lifetime broadenings for the N↑ and N↓ Co 2p 3/2 components show that the reduced Co magnetic moment found in the Co 66 Fe 4 Ni 1 B 14 Si 15 amorphous glass is due to the transfer of ↑-spin valence electron density to the ↓-spin valence band upon glass formation. SRXPS also allows investigation of spin-dependent core-hole screening processes and satellite production, as demonstrated in SRXPS studies of ferromagnetic Ni. Future directions of SRXPS are also explored. copyright 1996 American Vacuum Society

Childhood to adolescence: dust and gas clearing in protoplanetary disks

Science.gov (United States)

Brown, Joanna Margaret

Disks are ubiquitous around young stars. Over time, disks dissipate, revealing planets that formed hidden by their natal dust. Since direct detection of young planets at small orbital radii is currently impossible, other tracers of planet formation must be found. One sign of disk evolution, potentially linked to planet formation, is the opening of a gap or inner hole in the disk. In this thesis, I have identified and characterized several cold disks with large inner gaps but retaining massive primordial outer disks. While cold disks are not common, with ~5% of disks showing signs of inner gaps, they provide proof that at least some disks evolve from the inside-out. These large gaps are equivalent to dust clearing from inside the Earth's orbit to Neptune's orbit or even the inner Kuiper belt. Unlike more evolved systems like our own, the central star is often still accreting and a large outer disk remains. I identified four cold disks in Spitzer 5-40 μm spectra and modeled these disks using a 2-D radiative transfer code to determine the gap properties. Outer gap radii of 20-45 AU were derived. However, spectrophotometric identification is indirect and model-dependent. To validate this interpretation, I observed three disks with a submillimeter interferometer and obtained the first direct images of the central holes. The images agree well with the gap sizes derived from the spectrophotometry. One system, LkH&alpha 330, has a very steep outer gap edge which seems more consistent with gravitational perturbation rather than gradual processes, such as grain growth and settling. Roughly 70% of cold disks show CO v=1&rarr 0 gas emission from the inner 1 AU and therefore are unlikely to have evolved due to photoevaporation. The derived rotation temperatures are significantly lower for the cold disks than disks without gaps. Unresolved (sub)millimeter photometry shows that cold disks have steeper colors, indicating that they are optically thin at these wavelengths, unlike

DISK FORMATION IN MAGNETIZED CLOUDS ENABLED BY THE HALL EFFECT

International Nuclear Information System (INIS)

Krasnopolsky, Ruben; Shang, Hsien; Li Zhiyun

2011-01-01

Stars form in dense cores of molecular clouds that are observed to be significantly magnetized. A dynamically important magnetic field presents a significant obstacle to the formation of protostellar disks. Recent studies have shown that magnetic braking is strong enough to suppress the formation of rotationally supported disks in the ideal MHD limit. Whether non-ideal MHD effects can enable disk formation remains unsettled. We carry out a first study on how disk formation in magnetic clouds is modified by the Hall effect, the least explored of the three non-ideal MHD effects in star formation (the other two being ambipolar diffusion and Ohmic dissipation). For illustrative purposes, we consider a simplified problem of a non-self-gravitating, magnetized envelope collapsing onto a central protostar of fixed mass. We find that the Hall effect can spin up the inner part of the collapsing flow to Keplerian speed, producing a rotationally supported disk. The disk is generated through a Hall-induced magnetic torque. Disk formation occurs even when the envelope is initially non-rotating, provided that the Hall coefficient is large enough. When the magnetic field orientation is flipped, the direction of disk rotation is reversed as well. The implication is that the Hall effect can in principle produce both regularly rotating and counter-rotating disks around protostars. The Hall coefficient expected in dense cores is about one order of magnitude smaller than that needed for efficient spin-up in these models. We conclude that the Hall effect is an important factor to consider in studying the angular momentum evolution of magnetized star formation in general and disk formation in particular.

Energy level diagrams for black hole orbits

Science.gov (United States)

Levin, Janna

2009-12-01

A spinning black hole with a much smaller black hole companion forms a fundamental gravitational system, like a colossal classical analog to an atom. In an appealing if imperfect analogy with atomic physics, this gravitational atom can be understood through a discrete spectrum of periodic orbits. Exploiting a correspondence between the set of periodic orbits and the set of rational numbers, we are able to construct periodic tables of orbits and energy level diagrams of the accessible states around black holes. We also present a closed-form expression for the rational q, thereby quantifying zoom-whirl behavior in terms of spin, energy and angular momentum. The black hole atom is not just a theoretical construct, but corresponds to extant astrophysical systems detectable by future gravitational wave observatories.

Energy level diagrams for black hole orbits

International Nuclear Information System (INIS)

Levin, Janna

2009-01-01

A spinning black hole with a much smaller black hole companion forms a fundamental gravitational system, like a colossal classical analog to an atom. In an appealing if imperfect analogy with atomic physics, this gravitational atom can be understood through a discrete spectrum of periodic orbits. Exploiting a correspondence between the set of periodic orbits and the set of rational numbers, we are able to construct periodic tables of orbits and energy level diagrams of the accessible states around black holes. We also present a closed-form expression for the rational q, thereby quantifying zoom-whirl behavior in terms of spin, energy and angular momentum. The black hole atom is not just a theoretical construct, but corresponds to extant astrophysical systems detectable by future gravitational wave observatories.

Chaos and order in models of black hole pairs

International Nuclear Information System (INIS)

Levin, Janna

2006-01-01

Chaos in the orbits of black hole pairs has by now been confirmed by several independent groups. While the chaotic behavior of binary black hole orbits is no longer argued, it remains difficult to quantify the importance of chaos to the evolutionary dynamics of a pair of comparable mass black holes. None of our existing approximations are robust enough to offer convincing quantitative conclusions in the most highly nonlinear regime. It is intriguing to note that, in three different approximations to a black hole pair built of a spinning black hole and a nonspinning companion, two approximations exhibit chaos and one approximation does not. The fully relativistic scenario of a spinning test mass around a Schwarzschild black hole shows chaos, as does the post-Newtonian Lagrangian approximation. However, the approximately equivalent post-Newtonian Hamiltonian approximation does not show chaos when only one body spins. It is well known in dynamical systems theory that one system can be regular while an approximately related system is chaotic, so there is no formal conflict. However, the physical question remains: Is there chaos for comparable mass binaries when only one object spins? We are unable to answer this question given the poor convergence of the post-Newtonian approximation to the fully relativistic system. A resolution awaits better approximations that can be trusted in the highly nonlinear regime

SURFACE LAYER ACCRETION IN TRANSITIONAL AND CONVENTIONAL DISKS: FROM POLYCYCLIC AROMATIC HYDROCARBONS TO PLANETS

International Nuclear Information System (INIS)

Perez-Becker, Daniel; Chiang, Eugene

2011-01-01

'Transitional' T Tauri disks have optically thin holes with radii ∼>10 AU, yet accrete up to the median T Tauri rate. Multiple planets inside the hole can torque the gas to high radial speeds over large distances, reducing the local surface density while maintaining accretion. Thus multi-planet systems, together with reductions in disk opacity due to grain growth, can explain how holes can be simultaneously transparent and accreting. There remains the problem of how outer disk gas diffuses into the hole. Here it has been proposed that the magnetorotational instability (MRI) erodes disk surface layers ionized by stellar X-rays. In contrast to previous work, we find that the extent to which surface layers are MRI-active is limited not by ohmic dissipation but by ambipolar diffusion, the latter measured by Am: the number of times a neutral hydrogen molecule collides with ions in a dynamical time. Simulations by Hawley and Stone showed that Am ∼ 100 is necessary for ions to drive MRI turbulence in neutral gas. We calculate that in X-ray-irradiated surface layers, Am typically varies from ∼10 -3 to 1, depending on the abundance of charge-adsorbing polycyclic aromatic hydrocarbons, whose properties we infer from Spitzer observations. We conclude that ionization of H 2 by X-rays and cosmic rays can sustain, at most, only weak MRI turbulence in surface layers 1-10 g cm -2 thick, and that accretion rates in such layers are too small compared to observed accretion rates for the majority of disks.

Evolution of Spin, Orbital, and Superorbital Modulations of 4U 0114+650

International Nuclear Information System (INIS)

Hu, Chin-Ping; Ng, C.-Y.; Chou, Yi; Lin, Lupin Chun-Che; Yen, David Chien-Chang

2017-01-01

We report a systematic analysis of the spin, orbital, and superorbital modulations of 4U 0114+650, a high-mass X-ray binary that consists of one of the slowest spinning neutron stars. Using the dynamic power spectrum, we found that the spin period varied dramatically and is anticorrelated with the long-term X-ray flux variation that can be observed using the Rossi X-ray Timing Explorer ASM, Swift BAT, and the Monitor of All-sky X-ray Image. The spin-up rate over the entire data set is consistent with previously reported values; however, the local spin-up rate is considerably higher. The corresponding local spin-up timescale is comparable to the local spin-up rate of OAO 1657−415, indicating that 4U 0114+650 could also have a transient disk. Moreover, the spin period evolution shows two ∼1000-day spin-down/random-walk epochs that appeared together with depressions of the superorbital modulation amplitude. This implies that the superorbital modulation was closely related to the presence of the accretion disk, which is not favored in the spin-down/random-walk epochs because the accretion is dominated by the direct wind accretion. The orbital period is stable during the entire time span; however, the orbital profile significantly changes with time. We found that the depth of the dip near the inferior conjunction of the companion is highly variable, which disfavors the eclipsing scenario. Moreover, the dip was less obvious during the spin-down/random-walk epochs, indicating its correlation with the accretion disk. Further monitoring in both X-ray and optical bands could reveal the establishment of the accretion disk in this system.

Evolution of Spin, Orbital, and Superorbital Modulations of 4U 0114+650

Science.gov (United States)

Hu, Chin-Ping; Chou, Yi; Ng, C.-Y.; Lin, Lupin Chun-Che; Yen, David Chien-Chang

2017-07-01

We report a systematic analysis of the spin, orbital, and superorbital modulations of 4U 0114+650, a high-mass X-ray binary that consists of one of the slowest spinning neutron stars. Using the dynamic power spectrum, we found that the spin period varied dramatically and is anticorrelated with the long-term X-ray flux variation that can be observed using the Rossi X-ray Timing Explorer ASM, Swift BAT, and the Monitor of All-sky X-ray Image. The spin-up rate over the entire data set is consistent with previously reported values; however, the local spin-up rate is considerably higher. The corresponding local spin-up timescale is comparable to the local spin-up rate of OAO 1657-415, indicating that 4U 0114+650 could also have a transient disk. Moreover, the spin period evolution shows two ˜1000-day spin-down/random-walk epochs that appeared together with depressions of the superorbital modulation amplitude. This implies that the superorbital modulation was closely related to the presence of the accretion disk, which is not favored in the spin-down/random-walk epochs because the accretion is dominated by the direct wind accretion. The orbital period is stable during the entire time span; however, the orbital profile significantly changes with time. We found that the depth of the dip near the inferior conjunction of the companion is highly variable, which disfavors the eclipsing scenario. Moreover, the dip was less obvious during the spin-down/random-walk epochs, indicating its correlation with the accretion disk. Further monitoring in both X-ray and optical bands could reveal the establishment of the accretion disk in this system.

Evolution of Spin, Orbital, and Superorbital Modulations of 4U 0114+650

Energy Technology Data Exchange (ETDEWEB)

Hu, Chin-Ping; Ng, C.-Y. [Department of Physics, The University of Hong Kong, Pokfulam Road (Hong Kong); Chou, Yi [Graduate Institute of Astronomy, National Central University, Jhongli 32001, Taiwan (China); Lin, Lupin Chun-Che [Institute of Astronomy and Astrophysics, Academia Sinica, Taiwan (China); Yen, David Chien-Chang, E-mail: cphu@hku.hk [Department of Mathematics, Fu Jen Catholic University, New Taipei City 24205, Taiwan (China)

2017-07-20

We report a systematic analysis of the spin, orbital, and superorbital modulations of 4U 0114+650, a high-mass X-ray binary that consists of one of the slowest spinning neutron stars. Using the dynamic power spectrum, we found that the spin period varied dramatically and is anticorrelated with the long-term X-ray flux variation that can be observed using the Rossi X-ray Timing Explorer ASM, Swift BAT, and the Monitor of All-sky X-ray Image. The spin-up rate over the entire data set is consistent with previously reported values; however, the local spin-up rate is considerably higher. The corresponding local spin-up timescale is comparable to the local spin-up rate of OAO 1657−415, indicating that 4U 0114+650 could also have a transient disk. Moreover, the spin period evolution shows two ∼1000-day spin-down/random-walk epochs that appeared together with depressions of the superorbital modulation amplitude. This implies that the superorbital modulation was closely related to the presence of the accretion disk, which is not favored in the spin-down/random-walk epochs because the accretion is dominated by the direct wind accretion. The orbital period is stable during the entire time span; however, the orbital profile significantly changes with time. We found that the depth of the dip near the inferior conjunction of the companion is highly variable, which disfavors the eclipsing scenario. Moreover, the dip was less obvious during the spin-down/random-walk epochs, indicating its correlation with the accretion disk. Further monitoring in both X-ray and optical bands could reveal the establishment of the accretion disk in this system.

Determination of elastic stresses in gas-turbine disks

Science.gov (United States)

Manson, S S

1947-01-01

A method is presented for the calculation of elastic stresses in symmetrical disks typical of those of a high-temperature gas turbine. The method is essentially a finite-difference solution of the equilibrium and compatibility equations for elastic stresses in a symmetrical disk. Account can be taken of point-to-point variations in disk thickness, in temperature, in elastic modulus, in coefficient of thermal expansion, in material density, and in Poisson's ratio. No numerical integration or trial-and-error procedures are involved and the computations can be performed in rapid and routine fashion by nontechnical computers with little engineering supervision. Checks on problems for which exact mathematical solutions are known indicate that the method yields results of high accuracy. Illustrative examples are presented to show the manner of treating solid disks, disks with central holes, and disks constructed either of a single material or two or more welded materials. The effect of shrink fitting is taken into account by a very simple device.

Testing the Binary Black Hole Nature of a Compact Binary Coalescence.

Science.gov (United States)

Krishnendu, N V; Arun, K G; Mishra, Chandra Kant

2017-09-01

We propose a novel method to test the binary black hole nature of compact binaries detectable by gravitational wave (GW) interferometers and, hence, constrain the parameter space of other exotic compact objects. The spirit of the test lies in the "no-hair" conjecture for black holes where all properties of a Kerr black hole are characterized by its mass and spin. The method relies on observationally measuring the quadrupole moments of the compact binary constituents induced due to their spins. If the compact object is a Kerr black hole (BH), its quadrupole moment is expressible solely in terms of its mass and spin. Otherwise, the quadrupole moment can depend on additional parameters (such as the equation of state of the object). The higher order spin effects in phase and amplitude of a gravitational waveform, which explicitly contains the spin-induced quadrupole moments of compact objects, hence, uniquely encode the nature of the compact binary. Thus, we argue that an independent measurement of the spin-induced quadrupole moment of the compact binaries from GW observations can provide a unique way to distinguish binary BH systems from binaries consisting of exotic compact objects.

GRAVITATIONAL WAVE SIGNATURES OF HYPERACCRETING COLLAPSAR DISKS

International Nuclear Information System (INIS)

Kotake, Kei; Takiwaki, Tomoya; Harikae, Seiji

2012-01-01

By performing two-dimensional special relativistic (SR) magnetohydrodynamic simulations, we study possible signatures of gravitational waves (GWs) in the context of the collapsar model for long-duration gamma-ray bursts. In our SR simulations, the central black hole is treated as an absorbing boundary. By doing so, we focus on the GWs generated by asphericities in neutrino emission and matter motions in the vicinity of the hyperaccreting disks. We compute nine models by adding initial angular momenta and magnetic fields parametrically to a precollapse core of a 35 M ☉ progenitor star. As for the microphysics, a realistic equation of state is employed and the neutrino cooling is taken into account via a multi-flavor neutrino leakage scheme. To accurately estimate GWs produced by anisotropic neutrino emission, we perform a ray-tracing analysis in general relativity by a post-processing procedure. By employing a stress formula that includes contributions from both magnetic fields and SR corrections, we also study the effects of magnetic fields on the gravitational waveforms. We find that the GW amplitudes from anisotropic neutrino emission show a monotonic increase with time, whose amplitudes are much larger than those from matter motions of the accreting material. We show that the increasing trend of the neutrino GWs stems from the excess of neutrino emission in the direction near parallel to the spin axis illuminated from the hyperaccreting disks. We point out that a recently proposed future space-based interferometer like Fabry-Perot-type DECIGO would permit the detection of these GW signals within ≈100 Mpc.

Stars Form Surprisingly Close to Milky Way's Black Hole

Science.gov (United States)

2005-10-01

The supermassive black hole at the center of the Milky Way has surprisingly helped spawn a new generation of stars, according to observations from NASA's Chandra X-ray Observatory. This novel mode of star formation may solve several mysteries about the supermassive black holes that reside at the centers of nearly all galaxies. "Massive black holes are usually known for violence and destruction," said Sergei Nayakshin of the University of Leicester, United Kingdom, and coauthor of a paper on this research in an upcoming issue of the Monthly Notices of the Royal Astronomical Society. "So it's remarkable that this black hole helped create new stars, not just destroy them." Black holes have earned their fearsome reputation because any material -- including stars -- that falls within the so-called event horizon is never seen again. However, these new results indicate that the immense disks of gas known to orbit many black holes at a "safe" distance from the event horizon can help nurture the formation of new stars. Animation of Stars Forming Around Black Hole Animation of Stars Forming Around Black Hole This conclusion came from new clues that could only be revealed in X-rays. Until the latest Chandra results, astronomers have disagreed about the origin of a mysterious group of massive stars discovered by infrared astronomers to be orbiting less than a light year from the Milky Way's central black hole, a.k.a. Sagittarius A*, or Sgr A*. At such close distances to Sgr A*, the standard model for star formation predicts that gas clouds from which stars form should have been ripped apart by tidal forces from the black hole. Two models to explain this puzzle have been proposed. In the disk model, the gravity of a dense disk of gas around Sgr A* offsets the tidal forces and allows stars to form; in the migration model, the stars formed in a star cluster far away from the black hole and migrated in to form the ring of massive stars. The migration scenario predicts about a

Herniated disk disease

International Nuclear Information System (INIS)

Ross, J.S.; Masaryk, T.J.; Modic, M.T.; Bohlman, H.; Wilber, G.; Carter, J.

1988-01-01

Thirty patients with symptoms of disk herniation and no previous surgery were examined with Gd-DTPA-enhanced MR imaging. Studies obtained before and after administration of Gd-DTPA included the following sequences: sagittal and axial spin echo (SE) 500/17 (repetition time, msec/echo time, msec), sagittal SE 2,000/60, sagittal FLASH 200/13/60. Studies were interpreted separately for presence of extradural disease (EDD) characterized by morphology, mass effect, and enhancement. Post Gd-DTPA diagnoses were: normal, n = 1; herniation, n = 28; neoplasm, n = 1. Tissue diagnosis was obtained in 13. The Gd-DTPA examination correctly changed the diagnosis in one case, provided increased confidence in the diagnosis in four, and was equivalent to the precontrast study in eight. Increased conspicuity of EDD with Gd-DTPA was related to the enhancement of epidural space analogous to IV CT and enhancement of scar surrounding disk herniation. Histologically, this scar was identical to that seen in postoperative spines, Gd-DTPA appears to be a useful adjunct in cervical and thoracic degenerative disk disease

Advanced spinning disk-TIRF microscopy for faster imaging of the cell interior and the plasma membrane.

Science.gov (United States)

Zobiak, Bernd; Failla, Antonio Virgilio

2018-03-01

Understanding the cellular processes that occur between the cytosol and the plasma membrane is an important task for biological research. Till now, however, it was not possible to combine fast and high-resolution imaging of both the isolated plasma membrane and the surrounding intracellular volume. Here, we demonstrate the combination of fast high-resolution spinning disk (SD) and total internal reflection fluorescence (TIRF) microscopy for specific imaging of the plasma membrane. A customised SD-TIRF microscope was used with specific design of the light paths that allowed, for the first time, live SD-TIRF experiments at high acquisition rates. A series of experiments is shown to demonstrate the feasibility and performance of our setup. © 2017 The Authors. Journal of Microscopy published by JohnWiley & Sons Ltd on behalf of Royal Microscopical Society.

Application of off-specular polarized neutron reflectometry to measurements on an array of mesoscopic ferromagnetic disks

International Nuclear Information System (INIS)

Temst, K.; Van Bael, M. J.; Fritzsche, H.

2001-01-01

Using off-specular polarized neutron reflectometry with neutron spin analysis, we determined the magnetic properties of a large array of in-plane magnetized ferromagnetic Co disks. Resonant peaks are clearly observed in the off-specular reflectivity, due to the lateral periodicity of the disk array. Using polarized neutrons, the intensity of the resonant peak in the off-specular reflectivity is studied as a function of the magnetic field applied in the sample plane. Spin analysis of the reflected neutrons reveals the magnetization reversal and saturation within the disks. copyright 2001 American Institute of Physics

From X-ray binaries to quasars black holes on all mass scales black holes on all mass scales

CERN Document Server

Ho, L C; Maccarone, T J

2005-01-01

This volume brings together contributions from many of the world's leading authorities on black hole accretion. The papers within represent part of a new movement to make use of the relative advantages of studying stellar mass and supermassive black holes and to bring together the knowledge gained from the two approaches. The topics discussed here run the gamut of the state of the art in black hole observational and theoretical work-variability, spectroscopy, disk-jet connections, and multi-wavelength campaigns on black holes are all covered. Reprinted from ASTROPHYSICS AND SPACE SCIENCE, 300:1-3 (2005)

Tidal disruption of white dwarfs by intermediate mass black holes

Directory of Open Access Journals (Sweden)

Bode T.

2012-12-01

Full Text Available Modeling ultra-close encounters between a white dwarf and a spinning, intermediate mass black hole requires a full general relativistic treatment of gravity. This paper summarizes results from such a study. Our results show that the disruption process and prompt accretion of the debris strongly depend on the magnitude and orientation of the black hole spin. On the other hand, the late-time accretion onto the black hole follows the same decay, Ṁ ∝  t−5/3, estimated from Newtonian gravity disruption studies. The spectrum of the fallback material peaks in the soft X-rays and sustains Eddington luminosity for 1–3 yrs after the disruption. The orientation of the black hole spin has also a profound effect on how the outflowing debris obscures the central region. The disruption produces a burst of gravitational radiation with characteristic frequencies of ∼3.2 Hz and strain amplitudes of ∼10−18 for galactic intermediate mass black holes.

Further evidence for a supermassive black hole mass-pitch angle relation

Energy Technology Data Exchange (ETDEWEB)

Berrier, Joel C.; Kennefick, Daniel; Kennefick, Julia D.; Hartley, Matthew; Lacy, Claud H. S. [Department of Physics, University of Arkansas, 825 West Dickson Street, Fayetteville, AR 72701 (United States); Davis, Benjamin L.; Barrows, Robert Scott; Shields, Doug [Arkansas Center for Space and Planetary Sciences, University of Arkansas, 202 Old Field House, Fayetteville, AR 72701 (United States); Seigar, Marc S. [Department of Physics and Astronomy, University of Arkansas at Little Rock, 2801 South University Avenue, Little Rock, AR 72204 (United States); Bentz, Misty C. [Department of Physics and Astronomy, Georgia State University, Atlanta, GA 30303 (United States)

2013-06-01

We present new and stronger evidence for a previously reported relationship between galactic spiral arm pitch angle P (a measure of the tightness of spiral structure) and the mass M {sub BH} of a disk galaxy's nuclear supermassive black hole (SMBH). We use an improved method to accurately measure the spiral arm pitch angle in disk galaxies to generate quantitative data on this morphological feature for 34 galaxies with directly measured black hole masses. We find a relation of log (M/M {sub ☉}) = (8.21 ± 0.16) – (0.062 ± 0.009)P. This method is compared with other means of estimating black hole mass to determine its effectiveness and usefulness relative to other existing relations. We argue that such a relationship is predicted by leading theories of spiral structure in disk galaxies, including the density wave theory. We propose this relationship as a tool for estimating SMBH masses in disk galaxies. This tool is potentially superior when compared to other methods for this class of galaxy and has the advantage of being unambiguously measurable from imaging data alone.

Pseudo-particles picture in single-hole-doped two-dimensional Neel ordered antiferromagnet

International Nuclear Information System (INIS)

Pereira, A R; Ercolessi, E; Pires, A S T

2007-01-01

Using the nonlinear σ model on a non-simply connected manifold, we consider the interaction effects between the elementary excitations (magnons and skyrmions) and static spin vacancy (hole) in two-dimensional quantum antiferromagnetic systems. Holes scatter magnons and trap skyrmions. The phase-shifts of the scattered magnons are obtained and used to calculate the zero point energy of spin waves measured with respect to the vacuum. It is suggested that this zero point energy lowers the energy cost of removing spins from the lattice. We also study the problems of the skyrmion-hole interactions and the skyrmion-hole (half-skyrmion-hole) bound states in the presence of magnons. We argue that two adjacent non-magnetic impurities are attracted when they are placed at the centre of half-skyrmions

Probing Black Hole Magnetic Fields with QED

Directory of Open Access Journals (Sweden)

Ilaria Caiazzo

2018-05-01

Full Text Available The effect of vacuum birefringence is one of the first predictions of quantum electrodynamics (QED: the presence of a charged Dirac field makes the vacuum birefringent when threaded by magnetic fields. This effect, extremely weak for terrestrial magnetic fields, becomes important for highly magnetized astrophysical objects, such as accreting black holes. In the X-ray regime, the polarization of photons traveling in the magnetosphere of a black hole is not frozen at emission but is changed by the local magnetic field. We show that, for photons traveling along the plane of the disk, where the field is expected to be partially organized, this results in a depolarization of the X-ray radiation. Because the amount of depolarization depends on the strength of the magnetic field, this effect can provide a way to probe the magnetic field in black-hole accretion disks and to study the role of magnetic fields in astrophysical accretion in general.

WL 17: A Young Embedded Transition Disk

OpenAIRE

Sheehan, Patrick D.; Eisner, Josh A.

2017-01-01

We present the highest spatial resolution ALMA observations to date of the Class I protostar WL 17 in the $\\rho$ Ophiuchus L1688 molecular cloud complex, which show that it has a 12 AU hole in the center of its disk. We consider whether WL 17 is actually a Class II disk being extincted by foreground material, but find that such models do not provide a good fit to the broadband SED and also require such high extinction that it would presumably arise from dense material close to the source such...

Magnonic black holes

OpenAIRE

Roldán-Molina, A.; Nunez, A.S.; Duine, R. A.

2017-01-01

We show that the interaction between spin-polarized current and magnetization dynamics can be used to implement black-hole and white-hole horizons for magnons - the quanta of oscillations in the magnetization direction in magnets. We consider three different systems: easy-plane ferromagnetic metals, isotropic antiferromagnetic metals, and easy-plane magnetic insulators. Based on available experimental data, we estimate that the Hawking temperature can be as large as 1 K. We comment on the imp...

CORRELATIONS OF DISK AND JET EMISSION DEVIATING FROM THE FUNDAMENTAL PLANE

Energy Technology Data Exchange (ETDEWEB)

Lin, Da-Bin; Mu, Hui-Jun; Lu, Zu-Jia; Liang, En-Wei [GXU-NAOC Center for Astrophysics and Space Sciences, Department of Physics, Guangxi University, Nanning 530004 (China); Gu, Wei-Min; Ma, Ren-Yi, E-mail: lindabin@gxu.edu.cn [Department of Astronomy and Institute of Theoretical Physics and Astrophysics, Xiamen University, Xiamen, Fujian 361005 (China)

2015-07-01

The variability of the accretion rate, which is believed to induce the aperiodic variability of X-ray emission from disks, may affect the energy injection into a jet. In this spirit, a correlation between disk emission and jet emission can be formed even if the mean luminosity of disk emission remains constant. In this work, these correlations are found in the situation in which the luminosity of disk emission is variable and kept at a constant mean value. The obtained correlations may be shallower than that of the fundamental plane of black hole activity. In addition, the slope of correlation may increase with increasing observed frequency of jet emission. For the luminosities spaced over three days, the slope of correlation decreases with increasing black hole mass. The deviation of our found correlations from that of the fundamental plane is related to the suppression of variability in the jet emission in comparison with that in the disk emission. This mechanism may work in some sources in which shallower correlations have been reported. Moreover, it implies that luminosities used to estimate the relation of the fundamental plane should cover an appropriate timescale, in which the variability of jet emission is not significantly suppressed.

Black hole fusion in the extreme mass ratio limit

Science.gov (United States)

Emparan, Roberto; Martínez, Marina; Zilhão, Miguel

2018-02-01

We present a simple, general, and accurate construction of the event horizons for the fusion of two neutral, rotating black holes with arbitrary orientation and values of their spins, in the extreme mass ratio limit where one black hole is much larger than the other. We compute several parameters that characterize the fusion and investigate their dependence on the black hole spin and orientation axis. We also exhibit and study the appearance of transient toroidal topology of the horizon. An earlier conjecture about universal critical exponents before and after an axisymmetric pinch is proven.

Site-specific Pt deposition and etching on electrically and thermally isolated SiO2 micro-disk surfaces

International Nuclear Information System (INIS)

Saraf, Laxmikant V

2010-01-01

Electrically and thermally isolated surfaces are crucial for improving the detection sensitivity of microelectronic sensors. The site-specific in situ growth of Pt nano-rods on thermally and electrically isolated SiO 2 micro-disks using wet chemical etching and a focused ion/electron dual beam (FIB-SEM) is demonstrated. Fabrication of an array of micro-cavities on top of a micro-disk is also demonstrated. The FIB source is utilized to fabricate through-holes in the micro-disks. Due to the amorphous nature of SiO 2 micro-disks, the Ga implantation possibly modifies through-hole sidewall surface chemistry rather than affecting its transport properties. Some sensor design concepts based on micro-fabrication of SiO 2 micro-disks utilizing thermally and electrically isolated surfaces are discussed from the viewpoint of applications in photonics and bio-sensing.

The upper bound of radiation energy in the Myers-Perry black hole collision

International Nuclear Information System (INIS)

Gwak, Bogeun; Lee, Bum-Hoon

2016-01-01

We have investigated the upper bound of the radiation energy in the head-on collision of two Myers-Perry black holes. Initially, the two black holes are far away from each other, and they become one black hole after the collision. We have obtained the upper bound of the radiation energy thermodynamically allowed in the process. The upper bound of the radiation energy is obtained in general dimensions. The radiation bound depends on the alignments of rotating axes for a given initial condition due to spin-spin interaction. We have found that the collision may not be occurred for a initially ultra-spinning black hole.

Erratic Black Hole Regulates Itself

Science.gov (United States)

2009-03-01

New results from NASA's Chandra X-ray Observatory have made a major advance in explaining how a special class of black holes may shut off the high-speed jets they produce. These results suggest that these black holes have a mechanism for regulating the rate at which they grow. Black holes come in many sizes: the supermassive ones, including those in quasars, which weigh in at millions to billions of times the mass of the Sun, and the much smaller stellar-mass black holes which have measured masses in the range of about 7 to 25 times the Sun's mass. Some stellar-mass black holes launch powerful jets of particles and radiation, like seen in quasars, and are called "micro-quasars". The new study looks at a famous micro-quasar in our own Galaxy, and regions close to its event horizon, or point of no return. This system, GRS 1915+105 (GRS 1915 for short), contains a black hole about 14 times the mass of the Sun that is feeding off material from a nearby companion star. As the material swirls toward the black hole, an accretion disk forms. This system shows remarkably unpredictable and complicated variability ranging from timescales of seconds to months, including 14 different patterns of variation. These variations are caused by a poorly understood connection between the disk and the radio jet seen in GRS 1915. Chandra, with its spectrograph, has observed GRS 1915 eleven times since its launch in 1999. These studies reveal that the jet in GRS 1915 may be periodically choked off when a hot wind, seen in X-rays, is driven off the accretion disk around the black hole. The wind is believed to shut down the jet by depriving it of matter that would have otherwise fueled it. Conversely, once the wind dies down, the jet can re-emerge. "We think the jet and wind around this black hole are in a sort of tug of war," said Joseph Neilsen, Harvard graduate student and lead author of the paper appearing in the journal Nature. "Sometimes one is winning and then, for reasons we don

Vibration-Based Data Used to Detect Cracks in Rotating Disks

Science.gov (United States)

Gyekenyesi, Andrew L.; Sawicki, Jerzy T.; Martin, Richard E.; Baaklini, George Y.

2004-01-01

Rotor health monitoring and online damage detection are increasingly gaining the interest of aircraft engine manufacturers. This is primarily due to the fact that there is a necessity for improved safety during operation as well as a need for lower maintenance costs. Applied techniques for the damage detection and health monitoring of rotors are essential for engine safety, reliability, and life prediction. Recently, the United States set the ambitious goal of reducing the fatal accident rate for commercial aviation by 80 percent within 10 years. In turn, NASA, in collaboration with the Federal Aviation Administration, other Federal agencies, universities, and the airline and aircraft industries, responded by developing the Aviation Safety Program. This program provides research and technology products needed to help the aerospace industry achieve their aviation safety goal. The Nondestructive Evaluation (NDE) Group of the Optical Instrumentation Technology Branch at the NASA Glenn Research Center is currently developing propulsion-system-specific technologies to detect damage prior to catastrophe under the propulsion health management task. Currently, the NDE group is assessing the feasibility of utilizing real-time vibration data to detect cracks in turbine disks. The data are obtained from radial blade-tip clearance and shaft-clearance measurements made using capacitive or eddy-current probes. The concept is based on the fact that disk cracks distort the strain field within the component. This, in turn, causes a small deformation in the disk's geometry as well as a possible change in the system's center of mass. The geometric change and the center of mass shift can be indirectly characterized by monitoring the amplitude and phase of the first harmonic (i.e., the 1 component) of the vibration data. Spin pit experiments and full-scale engine tests have been conducted while monitoring for crack growth with this detection methodology. Even so, published data are

Nontrivial ac spin response in the effective Luttinger model

International Nuclear Information System (INIS)

Hu Liangbin; Zhong Jiansong; Hu Kaige

2006-01-01

Based on the three-dimensional effective Luttinger Hamiltonian and the exact Heisenberg equations of motion and within a self-consistent semiclassical approximation, we present a theoretical investigation on the nontrivial ac spin responses due to the intrinsic spin-orbit coupling of holes in p-doped bulk semiconductors. We show that the nontrivial ac spin responses induced by the combined action of an ac external electric field and the intrinsic spin-orbit coupling of holes may lead to the generation of a nonvanishing ac spin Hall current in a p-doped bulk semiconductor, which shares some similarities with the dissipationless dc spin Hall current conceived previously and also exhibits some interesting new features that was not found before

On the Theoretical Framework of Magnetized Outflows from Stellar-Mass Black Holes and Related Observations

Science.gov (United States)

Christodoulou, D. M.; Contopoulos, I.; Kazanas, D.; Steiner, J. F.; Papadopoulos, D. B.; Laycock, S. G. T.

2016-01-01

The spins of stellar-mass black holes (BHs) and the power outputs of their jets are measurable quantities. Unfortunately, the currently employed methods do not agree and the results are controversial. Two major issues concern the measurements of BH spin and beam (jet) power. The former issue can be resolved by future observations. But the latter issue can be resolved now, if we pay attention to what is expected from theoretical considerations. The question of whether a correlation has been found between the power outputs of few objects and the spins of their BHs is moot because BH beam power does not scale with the square of the spin of the BH. We show that the theoretical BH beam power is a strongly nonlinear function of spin that cannot be approximated by a quadratic relation, as is generally stated when the influence of the magnetic field is not accounted for in the Blandford & Znajek model. The BH beam power of ballistic jets should scale a lot more steeply with BH spin irrespective of the magnetic field assumed to thread the horizon and the spin range considered. This behavior may already be visible in the analyses of radio observations by Narayan & McClintock and Russell et al. In agreement with previous studies, we also find that the power output that originates in the inner regions of the surrounding accretion disks is higher than that from the BHs and it cannot be ignored in investigations of continuous compact jets from these systems.

The effect of spin-orbit coupling on magnetoresistance in nonmagnetic organic semiconductors

International Nuclear Information System (INIS)

Zhao Jun-Qing; Ding Meng; Zhang Tian-You; Zhang Ning-Yu; Pang Yan-Tao; Ji Yan-Ju; Chen Ying; Wang Feng-Xiang; Fu Gang

2012-01-01

We investigated the effect of spin-orbit coupling on magnetoresistance in nonmagnetic organic semiconductors. A Lorentz-type magnetoresistance is obtained from spin-orbit coupling-dependent spin precession under the condition of a space-charge-limited current. The magnetoresistance depends on the initial spin orientation of the electron with respect to the hole in electron—hole pairs, and the increasing spin-orbit coupling slows down the change in magnetoresistance with magnetic field. The field dependence, the sign and the saturation value of the magnetoresistance are composite effects of recombination and dissociation rate constants of singlet and triplet electron—hole pairs. The simulated magnetoresistance shows good consistency with the experimental results. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

The Cosmogony of Super-Massive Black Holes

International Nuclear Information System (INIS)

Duschl, Wolfgang J; Strittmatter, Peter A

2012-01-01

We summarize our recent results on the evolution of super-massive black holes in the cores of galaxies. Our models are based on the viscous, Eddington-limited evolution of self-gravitating accretion disks. We find that, within this framework, one can explain the growth time scales and the luminosities of individual objects as well as the variation of these quantities for AGN with different black hole masses.

Long-range spin deformations around quasiparticles

International Nuclear Information System (INIS)

Godfrey, M.; Gunn, M.

1989-01-01

The quasi-particle formed by a hole in a Heisenberg antiferromagnet has an associated long-range spin distortion whose amplitude increases with the velocity of the hole. The authors show that the existence and properties of this distortion follow from simple classical arguments based on the long-wavelength equations of motion for the spin system. A similar long-range distortion is found in the quantum-mechanical problem of an electron exchange coupled to a Heisenberg antiferromagnet

Damage detection of engine bladed-disks using multivariate statistical analysis

Science.gov (United States)

Fang, X.; Tang, J.

2006-03-01

The timely detection of damage in aero-engine bladed-disks is an extremely important and challenging research topic. Bladed-disks have high modal density and, particularly, their vibration responses are subject to significant uncertainties due to manufacturing tolerance (blade-to-blade difference or mistuning), operating condition change and sensor noise. In this study, we present a new methodology for the on-line damage detection of engine bladed-disks using their vibratory responses during spin-up or spin-down operations which can be measured by blade-tip-timing sensing technique. We apply a principle component analysis (PCA)-based approach for data compression, feature extraction, and denoising. The non-model based damage detection is achieved by analyzing the change between response features of the healthy structure and of the damaged one. We facilitate such comparison by incorporating the Hotelling's statistic T2 analysis, which yields damage declaration with a given confidence level. The effectiveness of the method is demonstrated by case studies.

Tests of spinning turbine fragment impact on casing models

International Nuclear Information System (INIS)

Wilbeck, J.S.

1984-01-01

Ten 1/11-scale model turbine missile impact tests were conducted at a Naval spin chamber test facility to assess turbine missile effects in nuclear plant design. The objective of the tests was to determine the effects of missile spin, blade crush, and target edge conditions on the impact of turbine disk fragments on the steel casing. The results were intended for use in making realistic estimates for the initial conditions of fragments that might escape the casing in the event of a disk burst in a nuclear plant. The burst of a modified gas turbine rotor in a high-speed spin chamber provided three missiles with the proper rotational and translational velocities of actual steam turbine fragments. Tests of bladed, spinning missiles were compared with previous tests of unbladed, nonspinning missiles. The total residual energy of the spinning missiles, as observed from high-speed photographs of disk burst, was the same as that of the nonspinning missiles launched in a piercing orientation. Tests with bladed missiles showed that for equal burst speeds, the residual energy of bladed missiles is less than that of unbladed missiles. Impacts of missiles near the edge of targets resulted in residual missile velocities greater than for central impact. (orig.)

Diskoseismology: Probing accretion disks. I - Trapped adiabatic oscillations

Science.gov (United States)

Nowak, Michael A.; Wagoner, Robert V.

1991-01-01

The normal modes of acoustic oscillations within thin accretion disks which are terminated by an innermost stable orbit around a slowly rotating black hole or weakly magnetized compact neutron star are analyzed. The dominant relativistic effects which allow modes to be trapped within the inner region of the disk are approximated via a modified Newtonian potential. A general formalism is developed for investigating the adiabatic oscillations of arbitrary unperturbed disk models. The generic behavior is explored by way of an expansion of the Lagrangian displacement about the plane of symmetry and by assuming separable solutions with the same radial wavelength for the horizontal and vertical perturbations. The lowest eigenfrequencies and eigenfunctions of a particular set of radial and quadrupole modes which have minimum motion normal for the plane are obtained. These modes correspond to the standard dispersion relation of disk theory.

Quasinormal modes and absorption probabilities of spin-3 /2 fields in D -dimensional Reissner-Nordström black hole spacetimes

Science.gov (United States)

Chen, C.-H.; Cho, H. T.; Cornell, A. S.; Harmsen, G.; Ngcobo, X.

2018-01-01

In this paper we consider spin-3 /2 fields in a D -dimensional Reissner-Nordström black hole spacetime. As these spacetimes are not Ricci flat, it is necessary to modify the covariant derivative to the supercovariant derivative, by including terms related to the background electromagnetic fields, so as to maintain the gauge symmetry. Using this supercovariant derivative we arrive at the corresponding Rarita-Schwinger equation in a charged black hole background. As in our previous works, we exploit the spherical symmetry of the spacetime and use the eigenspinor vectors on an N sphere to derive the radial equations for both nontransverse-traceless (non-TT) modes and TT modes. We then determine the quasinormal mode and absorption probabilities of the associated gauge-invariant variables using the WKB approximation and the asymptotic iteration method. We then concentrate on how these quantities change with the charge of the black hole, especially when they reach the extremal limits.

Wave function, spectrum and effective mass of holes in 2 D quantum antiferromagnet

Science.gov (United States)

Su, Zhao-bin; Ll, Yan-min; Lai, Wu-yan; Yu, Lu

1989-12-01

A new quantum Bogoliubov-de Gennes (BdeG) formalism is developed to study the self-consistent motion of holes on an quantum antiferromagnetic (QAFM) background within the generalized t- J model. The local distortion of spin configurations and the renormalization of the hole motion due to virtual excitations of the distorted spin background are treated on an equal footing. The hole wave function and its spectrum, as well as the effective mass for a propagating hole are calculated explicitly.

Deformation and Life Analysis of Composite Flywheel Disk and Multi-disk Systems

Science.gov (United States)

Arnold, S. M.; Saleeb, A. F.; AlZoubi, N. R.

2001-01-01

In this study an attempt is made to put into perspective the problem of a rotating disk, be it a single disk or a number of concentric disks forming a unit. An analytical model capable of performing an elastic stress analysis for single/multiple, annular/solid, anisotropic/isotropic disk systems, subjected to both pressure surface tractions, body forces (in the form of temperature-changes and rotation fields) and interfacial misfits is derived and discussed. Results of an extensive parametric study are presented to clearly define the key design variables and their associated influence. In general the important parameters were identified as misfit, mean radius, thickness, material property and/or load gradation, and speed; all of which must be simultaneously optimized to achieve the "best" and most reliable design. Also, the important issue of defining proper performance/merit indices (based on the specific stored energy), in the presence of multiaxiality and material anisotropy is addressed. These merit indices are then utilized to discuss the difference between flywheels made from PMC and TMC materials with either an annular or solid geometry. Finally two major aspects of failure analysis, that is the static and cyclic limit (burst) speeds are addressed. In the case of static limit loads, upper, lower, and out-of-plane bounds for disks with constant thickness are presented for both the case of internal pressure loading (as one would see in a hydroburst test) and pure rotation (as in the case of a free spinning disk). The results (interaction diagrams) are displayed graphically in designer friendly format. For the case of fatigue, a representative fatigue/life master curve is illustrated in which the normalized limit speed versus number of applied cycles is given for a cladded TMC disk application.

Featured Image: Making a Rapidly Rotating Black Hole

Science.gov (United States)

Kohler, Susanna

2017-10-01

These stills from a simulation show the evolution (from left to right and top to bottom) of a high-mass X-ray binary over 1.1 days, starting after the star on the right fails to explode as a supernova and then collapses into a black hole. Many high-mass X-ray binaries like the well-known Cygnus X-1, the first source widely accepted to be a black hole host rapidly spinning black holes. Despite our observations of these systems, however, were still not sure how these objects end up with such high rotation speeds. Using simulations like that shown above, a team of scientists led by Aldo Batta (UC Santa Cruz) has demonstrated how a failed supernova explosion can result in such a rapidly spinning black hole. The authors work shows that in a binary where one star attempts to explode as a supernova and fails it doesnt succeed in unbinding the star the large amount of fallback material can interact with the companion star and then accrete onto the black hole, spinning it up in the process. You can read more about the authors simulations and conclusions in the paper below.CitationAldo Batta et al 2017 ApJL 846 L15. doi:10.3847/2041-8213/aa8506

Spin interactions in InAs quantum dots and molecules

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