Dramatic torque reversals between spin-up and spin-down have been observed in half of the persistent

The formation of millisecond pulsars is addressed. Evolutionary scenarios involving the spinning up of pulsars by accretion disks are discussed, and the implications of the P(dot)-P diagram for a large sample of radio pulsars are examined. 13 references.

The accreting pulsar GX 301-2 (P = 680 s) has been observed continuously by the large-area detectors

We report here a study of the long term properties of Quasi Periodic Oscillations (QPO) in an unusual accreting X-ray pulsar, 4U 1626-67. This is a unique accretion powered X-ray pulsar in which we have found the QPOs to be present during all sufficiently long X-ray observations with a wide range of X-ray observatories. In the present ...

We report here a study of the long-term properties of quasiperiodic oscillations (QPOs) in an unusual accreting X-ray pulsar, 4U 1626-67. This is a unique accretion-powered X-ray pulsar in which we have found the QPOs to be present during all sufficiently long X-ray observations with a wide range of X-ray observatories. In the present spin-down era of this ...

We present a timing and spectral analysis of the variable X-ray source 3A 1954+319. Our analysis is mainly based on an outburst serendipitously observed during INTEGRAL Key Program observations of the Cygnus region in 2008 fall and on the Swift/BAT longterm light curve. Previous observations, though sparse, have identified the source to be one of only nine known symbiotic X-ray binaries, i.e., ...

We report here results of spectropolarimetric observations of the ?8 Myr classical T Tauri star (cTTS) TW Hya carried out with ESPaDOnS at the Canada-France-Hawaii Telescope in the framework of the 'Magnetic Protostars and Planets' programme, and obtained at two different epochs (2008 March and 2010 March). Obvious Zeeman signatures are detected at all times, both in photospheric lines and in ...

Over the past decade our understanding of accreting neutron stars has been revolutionized. Observations with NASA's Rossi X-ray Timing Explorer (RXTE) have resulted in the discovery of fast, coherent X-ray intensity oscillations (hereafter, ``burst oscillations'') during thermonuclear X-ray bursts from 13 low mass X-ray binaries (LMXBs). Although many of their detailed ...

We study the process of spinning up black holes by accretion from slim disks for a wide range of accretion rates. We show that for super-Eddington accretion rates and low values of the viscosity parameter ? ( ? 0.01) the limiting value of the dimensionless spin parameter a? can reach values ...

The highest efficiency of converting rest mass into energy by accreting matter into a Kerr black hole is approximately 31% (Thorne 1974). We propose a new process in which periods of accretion from a thin disk, and the associated spin-up of the black hole, alternate with the periods of no accretion and magnetic ...

Millisecond pulsars are neutron stars that are thought to have been spun-up by mass accretion from a stellar companion. It is not known whether there is a natural brake for this process, or if it continues until the centrifugal breakup limit is reached at submillisecond periods. Many neutron stars that are accreting mass from a companion star exhibit ...

V407 Vul (RX J1914.4+2456) is a candidate double-degenerate binary with a putative 1.756 mHz (9.5 minute) orbital frequency. In a previous timing study using archival ROSAT and ASCA data, we reported evidence for an increase of this frequency at a rate consistent with expectations for gravitational radiation from a detached ultracompact binary system. Here we report the results of new Chandra ...

We review recent results from the X-ray timing of accreting millisecond pulsars in LMXBs. This is the first time a timing analysis is performed on accreting millisecond pulsars, and for the first time we can obtain information on the behavior of a very fast pulsar subject to accretion torques. We find both spin-up ...

It is demonstrated that existing theories of mixing in accreting white dwarfs encounter difficulties when confronted with observations of enrichments in nova ejecta. Arguments are presented, based on the Ekman spin-up process, which suggest that angular momentum transport from the accreted material to the white dwarf is more efficient ...

We review recent results from the X-ray timing of accreting millisecond pulsars in LMXBs. This is the first time a timing analysis is performed on accreting millisecond pulsars, and for the first time we can obtain information on the behavior of a very fast pulsar subject to accretion torques. We find both spin-up ...

We review recent results from the X-ray timing of accreting millisecond pulsars in LMXBs. This is the first time a timing analysis is performed on accreting millisecond pulsars, and for the first time we can obtain information on the behavior of a very fast pulsar subject to accretion torques. We find both spin-up ...

) #12;IV: Fueling AGN: Hot vs. Cold Gas Accretion #12;Hot vs. Cold Accretion Bondi accretion vs. jet power: accretion flow or jet? � The 3CRR sample of radio galaxies � An accretion-flow mode dichotomy in RL AGN � Fueling AGN: Cold vs. hot gas ...

We review recent results of our group on X-ray timing of accreting millisecond pulsars in LMXBs. The good quality of the RXTE data allow us to obtain information on the behavior of a very fast pulsar subject to accretion torques. We find both spin-up and spin-down behaviors, from which, using available models for the ...

... Accession Number : ADP001669. Title : Mechanisms for Ice Bonding in Wet Snow Accretions on Power Lines,. Corporate ...

High Energy Astrophysics: Accretion Disks I 1/60 Accretion Disks I References: Accretion Power in Astrophysics, J. Frank, A. King and D. Raine. High Energy Astrophysics, Vol. 2, M.S. Longair, Cambridge Astrophysics: Accretion Disks I 2/60 1 Overview Accretion disks are ...

Topics covered include young rapidly spinning pulsars; static gaps in outer magnetospheres; dynamic gaps in pulsar outer magnetospheres; pulse structure of energetic radiation sustained by outer gap pair production; outer gap radiation, Crab pulsar; outer gap radiation, the Vela pulsar; radioemission; and high energy radiation during the accretion spin-up ...

Support and Separation Mechanism. 3. 1.00. 0.05. 3.15. Support structure. 1. 2.54. 0.25. 2.79. ARC Solid KS40B Thrusters (spin-up) ...

This paper extends our previous study of planet/brown dwarf accretion by giant stars to solar-mass stars located on the red giant branch. The model assumes that the planet is dissipated at the bottom of the convective envelope of the giant star. The evolution of the giant is then followed in detail. We analyse the effects of different accretion rates and ...

Context. Timing analysis of accretion-powered millisecond pulsars (AMPs) is a powerful tool for probing the physics of compact objects. The recently discovered IGR J17511-3057 was the twelfth discovered of the 13 AMPs known. The Rossi XTE satellite provided an extensive coverage of the 25 days-long observation of the source outburst. Aims: Our goal is to ...

We use a combination of a cosmological N-body simulation of the concordance ? cold dark matter paradigm and a semi-analytic model of galaxy formation to investigate the spin development of central supermassive black holes (BHs) and its relation to the BH host galaxy properties. In order to compute BH spins, we use the ? model of Shakura & Sunyaev and consider the King et al. warped disc ...

The standard model of an accretion disk is considered. The temperature in the inner region is computed. It is assumed that the radiated power derives from comptonized photons, produced in a homogeneous single temperature plasma, supported by radiation pre...

Aug 4, 2011 ... Propagating fluctuations in the mass accretion rate of a precessing flow as a power spectral model for black hole binaries ...

Jan 22, 2010 ... Many astrophysical objects, including neutron stars and accretion disks, are powered by a combination of very strong magnetic fields and ...

In this paper we discuss the spin equilibrium of accreting neutron stars in low-mass X-ray binaries (LMXBs). We demonstrate that, when combined with a naive spin-up torque, the observed data lead to inferred magnetic fields which are at variance with those of Galactic millisecond radio pulsars. This indicates the need for either additional spin-down ...

We present the results of the long-term hard X-ray monitoring of the high-mass X-ray binary 2S 0114+65 with INTEGRAL/IBIS from 2003 to 2008. 2S 0114+65 is a variable hard X-ray source with X-ray luminosities of 1035-4 � 1036 erg s-1 from 20 to 100 keV due to accretion rate changes in different orbital phases. In several observations when 2S 0114+65 was bright, we found a ...

In this Letter we present a new analysis of the torques acting on the accreting millisecond X-ray pulsars SAX J1808.4-3658 and XTE J1814-338, and show how our results can be used to constrain theoretical models of the spin evolution. In particular, we find upper limits on any spin-up/down phase of XTE J1814-338 of |\\dot{\

Mar 12, 2005 ... Accretion Disk Simulation Credit: Michael Owen, John Blondin ... Such accretion disks power bright x-ray sources within our own galaxy. ...

The experimental study of snow accretion on overhead power transmission lines was carried out to obtain data on accretion rates using the artificial snow accretion test equipment and a high speed camera. We evaluated the accretion rate relative to temperature and wind velocity under simulated ...

The angular momentum of matter accreting onto the neutron star produces significant spin-up torque. Effective braking mechanism must exist to balance it in order to explain the existence of slowly-rotating X-ray pulsars. The efficiency of breaking steeply decreases with the rotational frequency and the magnetic field strength. Slowly rotating sources like ...

A continuous monitoring of the neutron star spin period in Her X-1 and its X-ray luminosity performed with Swift/BAT over the last five years revealed unexpected behavior of the pulsar that appears to switch between two different regimes of the angular momentum exchange between the neutron star and accretion disc. A smooth spin-up of the neutron star is ...

We study accretion-induced collapse of magnetized white dwarfs as an origin of millisecond pulsars. We apply magnetized accretion disk models to the precollapse accreting magnetic white dwarfs and calculate the white dwarf spin evolution. If the pulsar magnetic field results solely from the flux-frozen fossil white dwarf field, a ...

Accretion disks are invoked to explain a host of astrophysical phenomena, from protostellar objects to AGN. And yet the mechanism allowing accretion disks to operate are completely unknown. This proposal seeks to observe the ``smoking gun'' signature of magnetically-driven viscosity in accretion disks. Magnetically-induced viscosity is ...

After about 18 yr of steadily spinning down, the accretion-powered pulsar 4U 1626-67 experienced a new torque reversal at the beginning of 2008. For the present study, we have used all available Fermi/Gamma-ray Burst Monitor data since its launch in 2008 June 11 and over 5 yr of hard X-ray Swift/Burst Alert Telescope observations (starting from 2004 October up to the present ...

We present phase-resolved infrared and optical spectrophotometry of the intermediate polar EX Hya supplemented by archival ultraviolet data. The spin-modulated emission from the accretion funnel and the emission from the accretion disk or ring contain substantial optically thin components. The white dwarf dominates the unmodulated flux in the ultraviolet ...

Recent three-dimensional simulations of core-collapse supernovae have revealed the existence of non-axisymmetric modes of the Spherical Accretion Shock Instability, or SASI. Here we investigate the growth of these modes using two-dimensional simulations of the accretion flow in the equatorial plane of a core-collapse supernova. By perturbing a steady-state ...

We present an analysis of the spin and orbital properties of the newly discovered accreting pulsar IGR J17480-2446, located in the globular cluster Terzan 5. Considering the pulses detected by the Rossi X-ray Timing Explorer at a period of 90.539645(2) ms, we derive a solution for the 21.27454(8) hr binary system. The binary mass function is estimated to be 0.021275(5) M?, ...

... universe. They are thought to be powered by the accretion of gas onto super-massive black holes at the centers of galaxies. ...

... They are generally identified from their radio emission, thought to be powered by accretion of matter onto supermassive black holes in the nuclei of ...

... They are generally identified from their radio emission, thought to be powered by accretion of matter onto supermassive black holes in the nuclei of ...

An approximation theory of the acceleration of particles in low-density shear flows is developed and is applied to a number of astrophysical flows including accretion disks, radial accretion, and convective turbulence. In the disk application, the theory suggests a mechanism by which the bulk of the accretion power ...

The current status of the physics of accretion disks in close binary stars is reviewed, with an emphasis on the hydrodynamic overreflection instability, which is a factor leading to the accretion disk turbulence. The estimated turbulent viscosity coefficients are in good agreement with observations and explain the high angular momentum transfer rate and ...

Low-resolution, ultraviolet spectra of the pre-main-sequence objects Z Canis Majoris, V1057 Cygni, and FU Orionis are presented. Ultraviolet absorption features indicate spectral types of A5 I for FU Ori and F5 I for Z CMa. These results are in reasonable agreement with predictions of simple accretion disk models. The lack of significant veiling of ultraviolet absorption ...

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 ...

Context. Stellar rotation is a crucial parameter driving stellar magnetism, activity and mixing of chemical elements. Measuring rotational velocities of young stars can give additional insight in the initial conditions of the star formation process. Furthermore, the evolution of stellar rotation is coupled to the evolution of circumstellar disks. Disk-braking mechanisms are believed to be ...

We propose to continue tests of magnetospheric models for sub-Hz quasi-periodic oscillations (QPOs) by completing a series of brief pointed observations of the disk-fed X-ray pulsar Cen X-3 that began in cycle 1. A key test of such models is the comparison of the QPO frequencies observed when the pulsar is spinning up and when it is spinning down. We will ...

Darwin's (1980) theory of lunar formation from the earth by means of a rotationally driven dynamic fission instability is presently considered in view of viscous shear's maintenance of solid body rotation throughout the protoearth's accretion phase. Assuming the appropriateness of a polytropic account of the protoearth, it is unlikely that dynamic ...

Black holes grow by accreting matter from their surroundings. However, angular momentum provides an efficient natural barrier to accretion and so only the lowest angular momentum material will be available to feed the black holes. The standard subgrid model for black hole accretion in galaxy formation simulations - based on the ...

The central region of the Galaxy is considered and the density of stars and interstellar matter is estimated. The power owed to accretion by neutron stars is calculated for an r.m.s. velocity of ~160 km/s as from the virial theorem. An upper limit for the accretion luminosity at x-ray wavelengths is proposed. The limit is ...

Accreting millisecond X-ray pulsars like IGR J00291+5934 are important because they can be used to test theories of pulsar formation and evolution. They give also the possibility of constraining gravitational wave emission theories and the equation of state of ultra-dense matter. Particularly crucial to our understanding is the measurement of the long-term spin evolution of ...

The ROSAT observations were part of an extensive multiwavelength campaign of the X-ray, pulsar system Her X-1/HZ Her conducted in 1993 August. The source was found in an anomalous low state detected only once before. Characteristics observed during anomalous low states include a substantial, unexpected drop in flux at X-ray energies, with no change in absorbing column density; an increase in the ...

This work discusses a black hole accretion disk dynamo model for Active Galactic Nuclei (AGN) sources of the cosmic X-ray and ..gamma.. ray backgrounds which involves both thermal and nonthermal accretion disk processes around greater than or equal to 10/sup 8/M/sub sun/ Kerr black holes. Before black hole spin-up to the Kerr metric ...

Accretion disks around supermassive black holes are expected to be the power sources in all AGNS, including blazars. To date, though, little direct evidence for such disks exists in AGN observations. In blazars, the intense relativistic beaming would mask...

ries containing weakly magnetized neutron stars, and to recently suggested models of accretion-powered emission from anomalous X-ray pulsars. ...

Wet snow accretion has caused major loss of overhead line power supplies in various parts of the United Kingdom at different times. As a consequence the electricity boards are systematically refurbishing and strengthening the overhead line system at all v...

We compare accretion and black hole spin as potential energy sources for outbursts from active galactic nuclei (AGNs) in brightest cluster galaxies (BCGs). Based on our adopted spin model, we find that the distribution of AGN power estimated from X-ray cavities is consistent with a broad range of both spin parameters and accretion ...

Recent work has raised the exciting possibility that r-modes (Rossby waves) in rotating neutron star cores might be strong gravitational-wave sources. We estimate the effect of a solid crust on their viscous damping rate and show that the dissipation rate in the viscous boundary layer between the oscillating fluid and the nearly static crust is more than 105 times higher than that from the shear ...

One of the most important and uncertain stages in binary evolution is the common envelope (CE) event. Significant attention has been devoted in the literature so far to the energy balance expected to determine the outcome during the CE event. However, this question is intrinsically coupled with the problem of what is left from the donor star after the CE and its immediate evolution. In this paper ...

We present X-ray and optical data on the Be/X-ray binary (BeXRB) pulsar IGR J 01054-7253= SXP11.5 in the Small Magellanic Cloud (SMC). Rossi X-ray Timing Explorer (RXTE) observations of this source in a large X-ray outburst reveal an 11.483 � 0.002 s pulse period and show both the accretion-driven spin-up of the neutron star and the motion of the neutron ...

A stalled spherical accretion shock, such as that arising in core-collapse supernovae, is unstable to non-spherical perturbations. In three dimensions, this Standing Accretion Shock Instability can develop spiral modes that spin-up the protoneutron star. Here, we study these non-axisymmetric modes by combining linear stability analysis and ...

Rapid rotation in field red giant stars is a relatively rare but well-studied phenomenon; here we investigate the potential role of planet accretion in spinning up these stars. Using Zahn's theory of tidal friction and stellar evolution models, we compute the decay of a planet's orbit into its evolving host star and ...

Context: Monitoring of pulse period variations in accreting binary pulsars is an important tool to study the interaction between the magnetosphere of the neutron star and the accretion disk. While the X-ray flux of the brightest X-ray pulsars have been successfully monitored over many years (e.g. with RXTE/ASM, CGRO/BATSE, Swift/BAT), the possibility to ...

We present a novel method to measure the accretion rate of radio emitting X-ray binaries (XRBs) and active galactic nuclei (AGN) independently of the X-ray luminosity. The radio emission of the jet is used as a tracer for the accretion rate and is normalized using sources of known accretion rates: island state neutron stars (NSs) and ...

Although the powering mechanism for quasars is now widely recognized to be the accretion of matter in a geometrically thin disk, the transport of matter to the inner region of the disk where luminosity is emitted remains an unsolved question. Miralda-Escud� & Kollmeier (2005) proposed a model whereby quasars are fuelled when stars are captured by the ...

Black holes are most often detected by the radiation produced when they gravitationally pull in surrounding gas, in a process called accretion. The efficiency with which the hot gas radiates its thermal energy strongly influences the geometry and dynamics of the accretion flow. Both radiatively efficient thin disks and radiatively inefficient thick disks ...

Accretion disks are invoked to explain a host of astrophysical phenomena, from protostellar objects to AGN. And yet the mechanism allowing accretion disks to operate are completely unknown. This proposal seeks to observe the smoking gun signature of magnetically--driven viscosity in accretion disks. Magnetically--induced viscosity is a ...

and Roland Svensson, eds. How do Bright Accretion Disks Shine? Eric Agol and Julian Krolik Department the disk to shine? 2. MHD Turbulence in Accretion Disks In the 1990's, much progress has been made Shine? 429 still a matter of debate among the simulators. The power spectrum of the tur� bulence

We investigate further a model of the accreting millisecond X-ray pulsars we proposed earlier. In this model, the X-ray-emitting regions of these pulsars are near their spin axes but move. This is to be expected if the magnetic poles of these stars are close to their spin axes, so that accreting gas is channeled there. As the accretion ...

Accretion discs are composed of ionized gas in motion around a central object. Sometimes, the disc is the source of powerful bipolar jets along its rotation axis. Theoretical models invoke the existence of a bipolar magnetic field crossing the disc and require two conditions to produce powerful jets: field lines need to be bent enough ...

We study the absorption spectrum of a two-dimensional electron gas (2DEG) in a magnetic field. We find that at low temperatures, when the 2DEG is spin polarized, the absorption spectra, which correspond to the creation of spin up or spin down electrons, differ in magnitude, linewidth, and filling factor dependence. We show that these differences can be ...

The Kondo effect in a Luttinger liquid composed of right-moving, spin-up electrons and left-moving, spin-down electrons is mapped exactly onto the Kondo effect in a Fermi liquid. The transformation generates anisotropy in the exchange coupling, which explains the two most notable features of the Kondo effect in a full Luttinger liquid: the quenching of the impurity moment for ...

From observations collected with the ESPaDOnS spectropolarimeter at the Canada-France-Hawaii Telescope (CFHT) and with the NARVAL spectropolarimeter at the T�lescope Bernard Lyot (TBL), we report the detection of Zeeman signatures on the prototypical classical T Tauri star AA Tau, both in photospheric lines and accretion-powered emission lines. Using time series of ...

X-ray timing of the accretion-powered pulsations during the 2003 outburst of the accreting millisecond pulsar XTE J1814-338 has revealed variation in the pulse time of arrival residuals. These can be interpreted in several ways, including spin-down and wandering of the fuel impact point around the magnetic pole. In this Letter we show that the burst ...

The illumination of companion stars in very low mass X-ray binaries by various kinds of radiation from the neighborhood of the neutron star after accretion has terminated or during accretion is considered. If a neutron star's spun-up period approaches 0.001 s, pulsar kHz radiation can quench accretion by pushing surrounding ...

Jun 1, 2010 ... The black holes are surrounded and nourished by disks of gas and dust, called accretion disks. Powerful jets stream out from below and above ...

The 2002 outburst of the accretionpowered millisecond pulsar SAX J1808.43658. Askar Ibragimov and prof. Juri Poutanen. University of Oulu, Finland ...

Over 5 years of daily hard X-ray (>20 keV) monitoring of the 2 minute accretion-powered pulsar GX

Dec 31, 2008 ... A particularly powerful diagnostic is possible with very rapidly rotating black holes: the accretion disk capable of producing line emission ...

Accreting high magnetic field neutron stars are observed as X-ray pulsars. ... An examination of a power spectrum of the pulsed emission shows that the peak ...

Evidence is mounting that cataclysmic variables are weak sources of synchrotron emission. If true, it demonstrates that accretion powered interacting binaries produce such emission whether their primaries are white dwarfs, neutron stars, or black holes.

Accreting high magnetic field neutron stars are observed as X-ray pulsars. ... An examination of a power spectrum of the pulsed emission shows that the peak ...

The rotation period of classical T Tauri stars (CTTS) represents a longstanding puzzle. While young low-mass stars show a wide range of rotation periods, many CTTS are slow rotators, spinning at a small fraction of breakup, and their rotation period does not seem to shorten, despite the fact that they are actively accreting and contracting. Matt & Pudritz proposed that the ...

We have explored the dynamics of the stalled accretion shock in core collapse supernovae using large-scale three-dimensional hydrodynamics simulations on the Cray X1 at the National Center for Computational Sciences (Oak Ridge National Laboratory). We confirmed the dominance of the l=1 mode of the SASI in the linear regime, as first seen in two-dimensional simulations. ...

The influence of gas accretion in determining the shape of the initial stellar mass function is investigated. Stars are assumed to form from protostellar condensations which, having fragmented out of a gas cloud, begin to accrete material from their environment. Within protocluster clouds this accretion phase is assumed to continue ...

We have shown previously that many of the properties of persistent accretion-powered millisecond pulsars can be understood if their X-ray emitting areas are near their spin axes and move as the accretion rate and structure of the inner disk vary. Here, we show that this 'nearly aligned moving spot model' may also explain the intermittent ...

We performed a study of 93 radio sources belonging to the same 3CRR sample but characterized by different radio and optical classifications. Two main results are presented: 1) FRI sources are less efficient than FRII in converting gravitational energy into radiation; 2) The accretion flow is an important X-ray component in all the FRII radio sources except for Low Excitation ...

We study the statistics of 61 measured masses of neutron stars (NSs) in binary pulsar systems, including 18 double NS (DNS) systems, 26 radio pulsars (10 in our Galaxy) with white dwarf (WD) companions, 3 NSs with main-sequence companions, 13 NSs in X-ray binaries, and one undetermined system. We derive a mean value of M = 1.46 � 0.30 M?. When the 46 NSs with measured spin periods are divided ...

In this paper we extend our previous works on spherically symmetric accretion onto black holes and superspinars to the case in which the fluid has a finite angular momentum initially. We run 2.5D and 3D general relativistic hydrodynamic simulations of the accretion of a fat disk. We study how the accretion process changes by changing ...

A model involving binary mass transfer and accretion onto main sequence stars is developed to explain the brightest known stars in external galaxies, the Hubble-Sandage variables. The similarity in spectral properties between the Hubble-Sandage variables and cataclysmic variables and the extreme disparity in their luminosities are presented as evidence for the essential ...

We study the power spectra of the variability of seven intermediate polars containing magnetized asynchronous accreting white dwarfs, XSS J00564+4548, IGR J00234+6141, DO Dra, V1223 Sgr, IGR J15094-6649, IGR J16500-3307 and IGR J17195-4100, in the optical band and demonstrate that their variability can be well described by a model based on fluctuations ...

We propose a simplified model of outflow/jet driven by the Blandford-Payne (BP) process from advection-dominated accretion flows (ADAF) and derive the expressions of the BP power and disk luminosity based on the conservation laws of mass, angular momentum and energy. We fit the 2-10 keV luminosity and kinetic power of 15 active ...

This paper reports the analysis of variability data for the Seyfert 1 type active galaxy NGC 4151. It covers the optical flux history for the last 90 years and X-ray flux for last 27 years. It presents the power spectrum density and structure function, and, based on the features in these functions, discusses the properties of the accretion flow onto a ...

The (U-B), (B-V) and (V-R) colour indexes from accretion disks, and sources with power-law spectra, are calculated. They take into account interstellar extinction, in detail. Results are given on two-colour diagrams (U-B)-(B-V) and (B-V)-(V-R). Applications to Nova Vul 1988 and A0620-00 are discussed shortly.

through it. In the X-ray band is where we see most of the accretion power coming from these sources population, a stellar population, would make high mass binaries. If you look at the population sources in X-rays you really see that they have different characteristics. Which X-ray sources interest you the most

A one-zone model is developed for analysis of properties of nuclear shell flashes on accreting degenerate dwarfs and neutron stars. The model provides a description of a steady-state nuclear burning and a linear stability analysis with a small number of algebraic equations. Time evolution of the accreted layer is described with two first order ordinary ...

Using Chandra X-ray observations of nine nearby, X-ray luminous elliptical galaxies with good optical velocity dispersion measurements, we show that a tight correlation exists between the Bondi accretion rates calculated from the observed gas temperature and density profiles and estimated black hole masses, and the power emerging from these systems in ...

A supermassive black hole in the nucleus of an elliptical galaxy at the centre of a cool-core group or cluster of galaxies is immersed in hot gas. Bondi accretion should occur at a rate determined by the properties of the gas at the Bondi radius and the mass of the black hole. X-ray observations of massive nearby elliptical galaxies, including M87 in the Virgo cluster, ...

A supermassive black hole in the nucleus of an elliptical galaxy at the centre of a cool-core group or cluster of galaxies is immersed in hot gas. Bondi accretion should occur at a rate determined by the properties of the gas at the Bondi radius and the mass of the black hole. X-ray observations of massive nearby elliptical galaxies, including M87 in the Virgo cluster, ...

Stellar black-hole candidates and active galactic nuclei are believed to contain accretion disks around black holes. Their X-ray variability is characterized by power spectra with a power law dependence on the variability frequency. The power slope beta is in the range between 1 and 2 and its most typical value is ...

The protostellar mass function (PMF) is the present-day mass function of the protostars in a region of star formation. It is determined by the initial mass function weighted by the accretion time. The PMF thus depends on the accretion history of protostars and in principle provides a powerful tool for observationally distinguishing ...

Galactic nuclei should contain a cluster of stars and compact objects in the vicinity of the central supermassive black hole due to stellar evolution, minor mergers and gravitational dynamical friction. By analogy with protoplanetary migration, nuclear cluster objects (NCOs) can migrate in the accretion discs that power active galactic nuclei (AGN) by ...

By performing electrolysis in seawater a concrete-like accretion of precipitating aragonite (one crystalline form of CaCO3) and brucite (Mg(OH) 2) slowly develops onto the cathode. The accretion forms by high pH conditions caused by the reduction reactions occurring at the cathode. A solid casing of accretions over a preformed cathodic ...

The dynamics and structure of accretion disks, which accumulate a vertical magnetic field in their centers, are investigated using two- and three-dimensional MHD simulations. The central field can be built up to the equipartition level, where it disrupts a nearly axisymmetric outer accretion disk inside a magnetospheric radius, forming a magnetically ...

In the ``competitive accretion" picture, the high-mass end of the stellar initial mass function (IMF) results from continuing accretion onto the central star from a gas reservoir. Most simulations to date have been conducted assuming formation in a cluster gravitational potential. In this contribution we report a set of numerical simulations aimed at ...

We present an analytical description of the energetics of the population of cosmic accretion shocks, for a concordance cosmology. We calculate how the shock-processed accretion power and mass current are distributed among different shock Mach numbers, and how they evolve with cosmic time. We calculate the cumulative energy input of ...

We present an analytical description of the energetics of the population of cosmic accretion shocks, for a concordance cosmology (?m+??=1). We calculate how the shock-processed accretion power and mass current are distributed among different shock Mach numbers and how they evolve with cosmic time. We calculate the cumulative energy ...

I summarize recent work on two aspects of nuclear burning on accreting neutron stars that are particularly sensitive to the details of the rp-process: the lightcurves of Type I X-ray bursts which show long tails powered by rp-process burning, and "superbursts", which are long duration and energetic bursts powered by ignition of carbon ...

We present the analysis of RXTE monitoring data obtained during the January 2009 outburst of the hard X-ray transient 1A 1118-61. Using these observations the broadband (3.5-120 keV) spectrum of the source was measured for the first time ever. We have found that the broadband continuum spectrum of the source is similar to other accreting pulsars and is well described by ...

We present the analysis of RXTE monitoring data obtained during the 2009 January outburst of the hard X-ray transient 1A 1118-61. Using these observations the broadband (3.5-120 keV) spectrum of the source was measured for the first time ever. We have found that the broadband continuum spectrum of the source is similar to other accreting pulsars and is well described by ...

We have put on CDS a catalog containing 561 evolutionary models of binaries: J/A+A/487/1129 (Van Rensbergen+, 2008). The catalog covers a grid of binaries with a B-type primary at birth, different values for the initial mass ratio and a wide range of initial orbital periods. The evolution was calculated with the Brussels code in which we introduced the spinning ...

The time variability of the x ray binary pulsars is discussed. It is found that the observed power spectral density of the aperiodic time variability of the x ray pulsar can be approximated by a power law spectrum which changes its slope at the coherent p...

The effect that the injection of a high-power electron cyclotron (EC) wave has on the dynamics of a tokamak plasma through its ponderomotive force is studied. A plasma rotation mechanism is analyzed, produced by the EC wave propagating perpendicular to the magnetic field, exhibiting its effect on the charged particles directly. It is shown that a particle flow in the poloidal ...

We describe the development of both multilevel two-dimensional and grid-based three-dimensional illumination systems for volumetric particle image velocimetry (PIV) that uses a single camera and an arbitrary number of low powered lasers. This flexible system is robust and capable of capturing results over a range of spatiotemporal scales determined by the choice of camera, the ...

We describe the development of both multilevel two-dimensional and grid-based three-dimensional illumination systems for volumetric particle image velocimetry (PIV) that uses a single camera and an arbitrary number of low powered lasers. This flexible system is robust and capable of capturing results over a range of spatiotemporal scales determined by the choice of camera, the ...

Classical T Tauri stars offer a unique window into star+disk systems that are still in the accretion/outflow phase yet are no longer surrounded by an opaque circumstellar envelope. These objects hold the key to understanding how magnetospheric accretion occurs, how accretion powers outflows, and what the physical ...

Wet snow icing accretion on power lines is a real problem in Italy, causing failures on high and medium voltage power supplies during the cold season. The phenomenon is a process in which many large and local scale variables contribute in a complex way and not completely understood. A numerical weather forecast can be used to select ...

On the basis of data from an energy-conserving three-dimensional general relativistic MHD simulation, we predict the statistical character of variability in the coronal luminosity from accreting black holes. When the inner boundary of the corona is defined to be the electron scattering photosphere, its location depends only on the mass accretion rate in ...

This paper discusses a search for the centrifugal barrier in transient X-ray pulsars with RXTE. The RXTE observation associated with this research involved monitoring the X-ray intensities and pulse profiles of six transient x-ray pulsars on five different occasions. The goal was to determine whether the so-called "centrifugal barrier" effects exists for accretion-powered ...

A powerful new method to determine the structure of effectively optically thin accretion disks is described. The method reduces the set of equations needed to be numerically solved to the microphysical equations only and reduces the dimension of the parameter space needed to be explored from three to two. It is shown why proton optical depth and ...

A powerful new method to determine the structure of effectively optically thin accretion disks is described. The method reduces the set of equations needed to be numerically solved to the microphysical equations only and reduces the dimension of the parameter space needed to be explored from three to two. It is shown why proton optical depth and ...

RXTE observations have shown that weak-field neutron stars in low-mass X-ray binary systems (LMXBs) produce three distinct types of millisecond X-ray oscillations. These are generated directly or indirectly by the star's magnetic field and rotation and can therefore be used to determine the spin rates and estimate the magnetic fields of these stars. Periodic accretion-powered ...

Using Chandra X-ray observations of 9 nearby, X-ray luminous ellipticals with good optical velocity dispersion measurements, we show that a tight correlation exists between the Bondi accretion rates calculated from the X-ray data and estimated black hole masses, and the power emerging from these systems in relativistic jets. The jet ...

The detection of quasi-periodic sources of gravitational waves requires the accumulation of signal to noise over long observation times. This represents the most difficult data analysis problem facing experimenters with detectors such as those at LIGO. If not removed, Earth-motion induced Doppler modulations and intrinsic variations of the gravitational-wave frequency make the signals impossible ...

RS Ophiuchi is a recurrent nova system that experiences outbursts every ~20 years, implying accretion at a high rate onto a massive white dwarf. However, previous X-ray observations of the system in quiescence have detected only faint emission that is difficult to reconcile with the high accretion rate (>2 � 10�8 M sun yr�1) predicted by nova ...

: Magnetohydrodynamics (MHD) -- turbulence -- stars: magnetic fields -- accretion, accretion disks 1. Introduction problem. These fields can arise, in principle, by turbulent dynamo generation, from a weak seed field (see that the ensemble of fluctuating motions does not contain waves with # = 0 thus the spectral power of turbulence

An expert system is discussed which assists in deciding the deicing countermeasures against snow accretion on 187KV and 66KV transmission lines. The distinctive features of the system are the application of an expert system to a new field, the completely hierarchical design of the whole system and ranking by messages instead of by a certainty factor. The system has been ...

Several types of cataclysmic events involving stellar-mass compact objects could result in the extreme, transient accretion onto a black hole widely believed to power gamma-ray bursts. We calculate the vertical structure of such thick accretion disks with a semi-analytical model which includes the effects of neutrino transport on the ...

Active galactic nuclei (AGN) are powered by accretion and recent observations indicate the existence of accretion disks around a central black hole of 108 to 1010Msun. A derivation and discussion of the basic equations for the structure of a thin accretion disk around a rotating black hole is presented. Starting ...

Active galactic nuclei are believed to be powered by accretion through a disk onto a super-massive black hole at the center of the host galaxy. Luminous quasars then require accretion rates of one to ten solar masses per year. I will show that this requires disk surface densities of order 400 grams per square centimeter at radii of ...

The radio-loud Narrow-Line Seyfert 1 galaxy PKS 0558-504 is a highly variable, X-ray bright source with super-Eddington accretion rate and a powerful radio jet, and hence represents an ideal laboratory to study the link between accretion and ejection phenomena. Here we present the preliminary results from an ongoing multiwavelength ...

Hyper-accretion discs around black holes emit copious neutrinos and anti-neutrinos. A fraction of the emitted neutrinos convert to electron-positron plasma above the disc through the annihilation reaction ?. This process may drive relativistic jets associated with gamma-ray bursts (GRB) explosions. We calculate the efficiency of energy deposition by neutrinos. Our calculation ...

This page provides a flash simulation of a Stern-Gerlach filters that select spin up electrons. The simulation allows the user to use up to three filters and to change the orientation of each of the filters.

The report describes a method for evaluation of heat seeking missiles and discusses preliminary activities, equipment, and facilities required. Provided are procedures for gyro spin-up time, gyro spin-up current, gyro spin-down time, maximum look angle, r...

NASA Spins Up New Vehicle Rollover Test. 06.14.03. Taking the family car out for a spin has assumed a whole new meaning at NASA's Goddard Space Flight ...

The available data on the forward charge exchange of nucleons on the deuteron up to 2 GeV/nucleon are reviewed. The value of the inclusive nd ? pnn/ np ? pn cross section ratio is sensitive to the fraction of spin-independent neutron-proton backward scattering. The measurements of the polarisation transfer in d( n, p){ nn} or the deuteron analysing power in p{ d, { pp}) n in ...

The authors present a design study for an X-band frequency-doubling magnicon amplifier driven by a 500 keV, 172 A beam from a field-emission diode. This study makes use of steady-state particle simulations employing the realistic fields of magnicon cavities connected by beam tunnels, and includes the effects of finite electron beam diameter. The simulations propagate an electron beam through a ...

The change in the structure of the collective levels with spin angular momentum in atomic nuclei is often expressed in terms of the classical concepts of the kinematic and the dynamic moments of inertia varying with spin. For the well deformed even-even nuclei the kinematic moment of inertia increases with spin up to 10%�20%, at say I? = 12+. However, ...

The black holes in the hearts of bright elliptical galaxies are commonly observed to be associated with powerful relativistic jets. The mechanism by which material entering the accretion radius is converted into jet power remains the subject of much debate. At the same time, the interplay between the relativistic jet and the ...

Accretion onto a black hole can produce enormous power which has a profound influence on its surroundings. The power is emitted in the form of radiation or as a matter outflow such as a jet. Observational evidence of the accretion flow in the immediate vicinity of the black hole where the power ...

We examine the electrodynamic power output from a thin accretion disk surrounding a Kerr black hole. We derive an upper limit for the total power. We find that this limit is only moderately sensitive to most of the relativistic correction factors. In fact, this limit is less sensitive to the change in the black hole spin than one would ...

We investigate the model of disk/coronal accretion into a black hole. We show that the inner regions of an accretion disk in X-ray binaries can transform from a cool standard disk to an advection-dominated flow through the known properties of Coulomb interaction in a two-temperature plasma, viscous heating, radiative processes, and thermal conduction. A ...

Cataclysmic variables provide the most accessible view of accretion physics. They are the most numerous accretion powered X-ray sources, and there are thus many relatively bright, nearby examples. Known examples include several bright eclipsing systems that allow a quantitative determination of the accretion ...

Aperiodic fluctuations with 1/f-like power spectral density (PSD, where f is a frequency) are characteristics of X-ray radiation from accreting compact objects, such as active galactic nuclei and Cyg X-1. To account for such intriguing features, we previously proposed a cellular-automaton model for accretion disks based on the concept ...

We track the coevolution of supermassive black holes (SMBHs) and their host galaxies through cosmic time. The calculation is embedded in the GALFORM semi-analytic model which simulates the formation and evolution of galaxies in a cold dark matter (CDM) universe. The black hole (BH) and galaxy formation models are coupled: during the evolution of the host galaxy, hot and cold gas are added to the ...

... led to accidental spin-up of the spacecraft and loss of attitude control gas . ..... SURVEY" Identifies the producer organization of this data product. ...

... I A Thesis in Mathematics * by Dawn L. Stewart I Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Arts I ...

... Descriptors : *EXTERIOR BALLISTICS, *SPIN STABILIZATION, FREQUENCY ... ITERATIONS, Q FACTOR, DECAY SCHEMES, PRECESSION. ...

The GMA provides the helium gas required to spin up the gyroscopes. ... The dewar with cryogenic liquid helium is connected to the ground support equipment, ...

There is a significant non-linear correlation between the Eddington ratio (Lbol/LEdd) and the Eddington-scaled kinetic power (Lkin/LEdd) of jets in low luminosity active galactic nuclei (AGNs). It is believed that these low luminosity AGNs contain advection-dominated accretion flows (ADAFs). We adopt the ADAF model developed by Li & Cao, in which the ...

Scientific data centers comprised of high-powered computing equipment and large capacity disk storage systems consume considerable amount of energy. Dynamic power management techniques (DPM) are commonly used for saving energy in disk systems. These involve powering down disks that exhibit long idle periods and placing them in standby ...

attention has been given to the problem of linear spin-up of a stratified ambient (Holton, 1965; Pedlosky EXPERIMENTAL STRATIFIED SPIN-UP 291 #12;(Phillips, 1954; Pedlosky, 1970). The minimum of the marginal stability�271 (1994). Pedlosky, J., ``The spin-up of a stratified fluid'', J. Fluid Mech. 28, 463�479 (1967). Pedlosky

Although disk accretion onto compact objects-white dwarfs, neutron stars and black holes-is central to much of high-energy astrophysics, the mechanisms that enable this process have remained observationally difficult to determine. Accretion disks must transfer angular momentum in order for matter to travel radially inward onto the compact object. Internal ...

We present a new keplerian accretion disc solution, the so-called Jet Emitting Disc (JED hereafter), which is part of global self-consistent disc-jet MHD structure. In our framework, a large scale, organized vertical magnetic field is threading the JED giving birth, when conditions are met, to stationnary self-collimated non relativistic jets. The main condition is that the ...

We use results from simulations of the production of magnetohydrodynamic jets around black holes to derive the cosmic spin history of the most massive black holes. We assume that the efficiency of jet production is a monotonic function of spin a, as given by the simulations, and that the accretion flow geometry is similarly thick for quasars accreting ...

We discuss the fueling of the central black hole in active galactic nuclei (AGN) in the framework of a clumpy accretion flow. Shocks between elements (clumps) forming the accretion flow are at the origin of the observed radiation. We expect a cascade of shocks, with optically thick shocks giving rise to optical/UV emission and optically thin shocks ...

The galactic black hole candidate Cygnus X-1 is observed to be in one of two X-ray spectral states: either the low/hard (low soft X-ray flux and a flat power-law tail) or high/soft (high blackbody-like soft X-ray flux and a steep power-law tail) state. The physical origin of these two states is unclear. We present here a model of an ionized ...

In this paper, we propose a new plausible mechanism of supernova explosions specific to close binary systems. The starting point is the common envelope phase in the evolution of a binary consisting of a red supergiant and a neutron star. As the neutron star spirals towards the centre of its companion it spins up via disc accretion. ...

continuum power laws, emission lines, and a thermal Big Blue Bump (BBB). ..... in the nuclei of galaxies will yield important information on their overall lifetime and on the .... broad Balmer lines may be an outer extension of the accretion disk. ...

Ice formation and accretion may hinder the operation of many systems critical to national infrastructure, including airplanes, power lines, windmills, ships, and telecommunications equipment. Yet despite the pervasiveness of the icing problem, the fundame...

is in vertical hydrostatic equilibrium or free fall. Hence we conclude that the original Shakura is in vertical hydrostatic equilibrium near the horizon or in free fall. The fact that the original Shakura to provide ideal environments for the shock accel- eration of relativistic particles that can escape to power

Jul 22, 2011 ... Ionized relativistic line (relline profile). ? Bulk emission possibly from Fe XXV/XXVI. ? Reflection from accretion disk ~20-100r ...

A methodology is proposed to transform standard meteorological data into probability-based transmission structure loads at any location within the Pennsylvania Power and Light Company's service area. Proposed accretion models are presented for estimating ...

The photospheres of 25000 K helium white dwarfs should not produce X-rays, while an accretion-powered source should emit much of its emergy in the ROSAT ...

The role of pull aparts and pushups in transcurrent systems, the rotation of faults and blocks within transcurrent fault systems, the role of accretion tectonics in plate boundary deformation, and power law creep behavior and the yielding at plate boundaries were investigated.

The role of pull aparts and pushups in transcurrent systems, the rotation of faults and blocks within transcurrent fault systems, the role of accretion tectonics in plate boundary deformation, and power law creep behavior and the yielding at plate boundar...

The physical mechanisms responsible for production of the non-thermal emission in accreting black holes should be imprinted in the observational appearances of the power law tails in the X-ray spectra from these objects. Variety of spectral states observe...

drift is apparent in the Short High pulses showing that a re ned period can be ... Figure 5 shows a sequence of Uhuru pulses from 3] from a single Main High ...

We use new mid-infrared (mid-IR) photometry from the Spitzer Space Telescope to study the relations between low-frequency radio luminosity density ?, mid-IR (12 ?m rest frame) luminosity ? and optical emission-line ([O II]) luminosity L]O II], for a complete sample of z� 1 radio galaxies from the 3CRR, 6CE, 6C*, 7CRS and TOOT00 surveys. The narrow redshift span of our sample (0.9 < z < ...

The continuum emission from the inner regions of Active Galactic Nuclei (AGN) is discussed. It is emphasized that a thermal UV component is a generic feature of accretion powered sources, and does not necessarily require a 'standard' disc; in particular, ...

A unified description of the properties of 14 X-ray pulsars is presented and compared with the current theoretical understanding of these systems. The sample extends over six orders of magnitude in luminosity, with the only trend in the phase averaged spe...

(Italy) email: foschini@tesre.bo.cnr.it Abstract The existence of large domains of antimatter is still an open of antimatter. This paper presents a discussion about possible effects of the close en� counter of stars and antistars. It is known that the accretion power can be higher in presence of antimatter, because of high

Extended radio galaxies (RGs) have traditionally been classified into Fanaroff-Riley (FR) I/II types, based on the ratio r of the separation between the brightest regions on either sides of the host galaxy and the total size of the radio source. We examine the distribution of various physical properties as a function of r of 1040 extended RGs at z<0.3. About 2/3 of the RGs are lobe dominated ...

A simple model of gas accretion in young galaxy disks suggests that fast turbulent motions can be driven by accretion energy for a time t{sub acc} {approx} 2(epsilon{sup 0.5} GM {sup 2}/xiV {sup 3}){sup 0.5} where epsilon is the fraction of the accretion energy going into disk turbulence, M and V are the galaxy mass and rotation speed, ...

We present new global calculations of X-ray spectra from fully relativistic magneto-hydrodynamic (MHD) simulations of black hole (BH) accretion disks. With a self-consistent radiative transfer code including Compton scattering and returning radiation, we can reproduce the predominant spectral features seen in decades of X-ray observations of stellar-mass BHs: a broad thermal ...

Nuclear-powered oscillations during Type-I X-ray bursts have so far revealed the spin of about twenty accreting millisecond pulsars in low-mass X-ray binaries. We study the properties of such burst oscillations by means of numerical computations of hot spots on the neutron star surface. We use adaptive mesh refinement hydrodynamical simulations to model ...

The transport of photons in steady, spherical, scattering flows is investigated. The moment equations are solved analytically for accretion on to a Schwarzschild black hole, taking full account of relativistic effects. We show that the emergent radiation spectrum is a power law at high frequencies with a spectral index smaller (harder spectrum) than in the ...

We report the discovery of burst oscillations from the intermittent accretion-powered millisecond pulsar (AMP) HETE J1900.1-2455, with a frequency ~1 Hz below the known spin frequency. The burst oscillation properties are far more similar to those of the non-AMPs and Aql X-1 (an intermittent AMP with a far lower duty cycle), than those of the AMPs SAX J1808.4-3658 and XTE ...

I comment on some aspects of accretion and ejection in the prototypical black hole X-ray binay Cygnus X-1. I present evidence indicating that in the hard state, the coronal magnetic field is below equipartition with radiation (suggesting that the corona is not powered by magnetic field dissipation) and that the ion temperature in the corona is ...

We present time-dependent models of the remnant accretion discs created during compact object mergers, focusing on the energy available from accretion at late times and the composition of the disc and its outflows. We calculate the dynamics near the outer edge of the disc, which contains the majority of the disc's mass and determines the ...

By analogy to the different accretion states observed in black-hole X-ray binaries (BHXBs), it appears plausible that accretion disks in active galactic nuclei (AGN) undergo a state transition between a radiatively efficient and inefficient accretion flow. If the radiative efficiency changes at some critical ...

We find long-term evolution of the ? class from the study of X-ray timing and spectral analysis of the Galactic microquasar GRS 1915+105 during two outburst activities, observed by the proportional counter array (PCA) and the High Energy X-ray Timing Experiment on-board Rossi X-ray Timing Explorer. The class is characterized by unusual periodic-like variation in intensity. With the passage of ...

This paper reports on a maintenance information system for overhead power lines that was developed and put into practical use in assuring a stable and reliable supply of electrical power. By using tension sensors, various kinds of meteorological sensors, and TV cameras, this system regularly monitors snow accretion on ...

Active Galactic Nuclei, powered by accretion onto a Supermassive Black Hole (SMBH), emit over the entire electromagnetic spectrum. Besides being sources where high energy physical processes take place, it is now emerging that they are leading actors in the formation and evolution of galaxies and, in general, of cosmic structures in the Universe. Fully ...

The northeast coast of North America is frequently hit by severe ice storms. These freezing rain events can produce large ice accretions that damage structures, frequently power transmission and distribution infrastructure. For this reason, it is highly desirable to model and forecast such icing events, so that the consequent damages can be prevented or ...

We report here the first results of a multi-wavelength campaign focusing on magnetospheric accretion processes within the close binary system V4046 Sgr, hosting two partly convective classical T Tauri stars of masses ?0.9 M&sun; and age ?12 Myr. In this paper, we present time-resolved spectropolarimetric observations collected in 2009 September with ESPaDOnS at the ...

Context. Interpretation of the X-ray spectra of X-ray binaries during their hard states requires a hot, optically thin medium. There are several accretion disc models that account for this aspect. However, none is designed to simultaneously explain powerful jets detected during these states. Aims: A new quasi-Keplerian hot accretion ...

We calculate the quantum radiation power of black holes which are asymptotic to the Einstein de Sitter universe at spatial and null infinities. We consider two limiting mass accretion scenarios, no accretion and significant accretion. We find that the radiation power strongly depends on not ...

It is anticipated that in the near future disk storage systems will surpass application servers and will become the primary consumer of power in the data centers. Shutting down of inactive disks is one of the more widespread solutions to save power consumption of disk systems. This solution involves spinning down or completely shutting off disks that ...

Using Chandra X-ray observations of nine nearby, X-ray luminous elliptical galaxies with good optical velocity dispersion measurements, we show that a tight correlation exists between the Bondi accretion rates calculated from the observed gas temperature and density profiles and estimated black hole masses, and the power emerging from these systems in ...

Slim-disk models describe advective accretion flows at high luminosities, while reducing to the standard thin disk form in the low luminosity limit. We have developed a new spectral model, slimbb, within the framework of XSPEC, which describes fully relativistic slim-disk accretion and includes photon ray-tracing that starts from the disk photosphere, ...

In this paper we continue our study on the accretion process onto superspinning Kerr objects with no event horizon (super-spinars). We discuss the counterpart of the Bondi accretion onto black holes. We first report the results of our numerical simulations. We found a quasi-steady-state configuration for any choice of the parameters of our model. The most ...

This thesis presents quantitative models of the magnetosphere of a magnetic star surrounded by a thin plasma disk. The model is motivated by the currently accepted picture of many accretion-powered pulsars as strongly magnetic neutron stars accreting from disks. It may also be relevant to the luminous galactic bulge X-ray sources that display ...

A small number of active galactic nuclei are known to exhibit prominent double peak emission profiles that are well-fitted by a relativistic accretion disk model. We develop a Monte Carlo code to compute the linear polarization of a double peaked broad emission line arising from Thomson scattering. A Keplerian accretion disk is adopted for the double peak ...

It has long been believed that the optical and infrared (OIR) fluxes of compact accreting sources will not generally show fast, stochastic variability. This is because reprocessing of high energy photons is thought to be the primer driver of the OIR fluxes. In recent work, we have found fast (sub-second) optical variations in accreting black hole and ...

Black holes from stellar to galactic scales are observed to accrete material from their environments and, via an as yet unknown mechanism, produce jets of outflowing plasma. In X-ray binaries (XRBs), the systems display radically different radiative properties depending on the amount of captured gas reaching the event horizon. These modes of behavior (one of which includes ...

The turning point in the relation between the X-ray photon index and the Eddington Ratio for AGN that was recently revealed by Constantin et al. (2009) and Gu & Cao (2009), provides new stimulus for investigating: 1) the role of accretion in powering the ambiguous low luminosity AGN and 2) the proposed analogy between accretion ...