Ahmedov Bobomurat

Institute of Nuclear Physics Uzbekistan Academy of Sciences

Ohm's Law for Plasma in General Relativity and
Cowling's Antidynamo Theorem in Kerr Space

Asghar Qadir

Department of Mathematics Quaid-I-Azam University

Belinski Valodia

Rome University "La Sapienza" and ICRA, Italy

Belousova Irina

Astrophysics Institute of MEPhI

Spectra of GRBs in the model of optically thick extended shell

     We suppose that nonthermal spectra of radiation in gamma-ray bursts (GRBs) are formed by optically thick spherical plasma shells that extand with relativistic velocities. The temperature of the shell decreases as power low. We discuss results of calculations which show that radiation spectrum of such shell is similar to observed spectra of GRBs. This model allows to define some characteristics of emitting areas.

Bertone Gianfranco

ICRA, Italy

Physical and Astrophysical Parameters of Relativistic White Dwarfs

Beskin Vasily

Lebedev Physical Institute,Moscow, RUSSIA

On the Grad-Shafranov approach to the black hole magnetosphere

     The Grad-Shafranov approach to the problem of the structure of the black hole magnetosphere is discussed. Being the most complicated version, this approach contains as well its own intrinsic difficulties.In particular, in general case it is impossible to solve the direct problem (to determine the flow structure from physical boundary conditions) because the position of critical surfaces are unknown. On the other hand, even the number of the boundary conditions can give us very important information e.g. that the angular velocity of a flow is to be determined from the solution

Bicak Jiri

Department of Theoretical Physics Faculty of Mathematics and Physics Charles University Praga

RBlack holes in external fieldsS

     The work on black holes immersed in external stationary magnetic or electric fields will be reviewed in both test-field approximation and within exact solutions. In particular, we shall pay attention to the effect of the expulsion of the flux of external fields across black holes which are approaching extremal states. Recently this effect has been shown to play an important role in the string theories. In the second part of the talk we shall summarize our recent work on rotating black holes accelerated due to the "strings" along the axis of symmetry ("rotating C-metric").

Bini Donato

CNR of Naples, Italy

Circular Orbits in Rotating Black Hole Spacetimes

(R. Jantzen & D. Bini)

Bruno Nicola  Rossano

ICRA, Italy

Camenzind Max

Magnetohydrodynamic Processes near Rapidly Rotating Compact Objects

(Max Camenzind & Ramon Khanna)

     Rapidly rotating Black Holes and neutron stars are relativistic objects requiring a fully general relativistic modelling of hydrodynamic and magnetohydrodynamic processes. While the theory of stationary and axisymmetric MHD for such objects is well understood, a time-dependent description must be based on Numerical simulations. In view of the complexity of this subject, progress is very slow. We discuss relativistic effects for accreting millisecond neutron stars in LMXBs, with particular emphasis on the origin of the twin-kilohertz QPO found By RXTE. The frame--dragging effects are probably also relevant for these types of objects.Magnetic accretion onto rotating Black Holes is different from neutron star accretion. We demonstrate a particular realisation of the Blandford-Znajek process. In the second part, we rely on numerical simulations of the time-dependent evolution of magnetic fields near Black Holes (kinematic induction equation) and show in particular that Cowling's theorem is not valid in Kerr geometry. The differential rotation of absolute space drives a current system near the horizon which powers the outflow. As is found for all magnetically driven outflows, most of this current system is closed near the Alfven surface, and only some fraction can escape into the jet region.

Chakrabarti Sandip K.

S.N. Bose National Centre for Basic Sciences, JD-Block, Sector-III, Salt Lake, CAlcutta-700091

First Talk:
Global Inflow-Outflow solution (GIOS) from
Shock-Compressed accretion disks around Black Holes

     Shocks and more generally centrifugal barrier dominated boundary layer produced around a black hole are the most exciting regions of an accretion disk. Matter is compressed, heated, and become denser in these regions. This region is the source of hard X-rays. QPO is produced because of the oscillation of this region. Now we show that the outflows and jets are also produced primarily from this region of the accretion disk.

Second Talk:
Global Solution of Dirac Equations in Kerr Black Hole Geometry

Chardonnet Pascal

Cherubini Christian

ICRA, Italy

Introduction to the usage of MapleV for advanced problems in Black Hole Physics

     In this talk we show the quick way of manipulating difficult objects in GR.We can easily verify the Kerr-Newman solution and compute all the relevant quantities.Using the previous program we show the full derivation of the Wald solution and introducing the ZAMO's we obtain the form of Wald solution in this frame.Then we introduce the Newman-Penrose formalism, we transform the K-N solution and we obtain all the well known NP quantities.In the second part of this talk we study the perturbative equations for K-N found by C.H.Lee.We use MapleV to separate the equations in the case of Kerr obtaining the well known Teukolsky equationfor spin 1 and 2.Then we show in the case of Reissner-Nordstrom the separation and the full decoupling of the radial differential equations.At this point we obtain the small Q/M,a/M and a*omega expansion for KN and we compare our results with the linearized equations found by Lee.Our program can immediately give us the higher orders in this expansion so we briefily discuss the possibility of an extension of Lee's work.In our programs all results are obtained with all parameters free.

Christodoulou   D.

Princeton University, USA

Coppi Bruno

MIT, USA

Coroniti Ferdinand V.

University of California, Los Angeles, USA

Cristiani Stefano

Space Telescope-European Coordinating Facility European Southern Observatory Karl-Schwarzschild

Damour Thibault

IHES, Paris, France

Del Giudice Emilio

INFN- Milan

Dorodnitsyn Anton

Institute for Cosmic Research (IKI), Moscow, Russia

Using the Galerkin method to calculate stability
and collapse of relativistic star

     An approximate approach is suggested for studying equilibrium stellar models, relativistic collapse problem and black hole formation on the basis of the Galerkin method. Some results of its simplified version - the energetic method - are reviewed, and equations of general Galerkin method are presented.

Fang Li Zhi

University of Arizona, Tucson, USA

Fedotov Alexander

Department of Theoretical Physics Moscow State Engineering Physical Institute (MEPHI)

Quantum Field in Rindler space

(N.Narozhny, A.Fedotov, B.Karnakov, V.Mur & V. Belinski)

     By considering quantum theory of the free field in Minkowski and Rindler spacetimes we show that conventional derivation of the Unruh effect is not correct since boundary conditions for the fields in these spacetimes are different. We also show that algebraic approach to this problem leads to the same conclusion.

Filippi Simonetta

ICRA, Italy

Fleischmann Martin

University of Southampton

Gadri Mohamed

Al-Fatah-Tripoli Libia

Germani Cristiano

ICRA, Italy

Gurovich Victor

Gurzadyan Vahe

Halpern Leopold

Hirotani Kouichi

National Astronomical Observatory, JAPAN

Collimation of MHD Disturbances around
a Kerr Black Hole

     Nonstationary and nonaxisymmetric perturbations of an MHD accretion onto a Kerr black hole is investigated. Assuming a magnetically dominated accretion, we find that the fluid becomes highly variable slightly within the fast-magnetosonic surface. Since the accretion is expected to be efficient near the equatorial plane, the fast surface will be prolate. In this case, only the waves that propagatetoward the equator can escape from the super-fast region and collimate poleward as they propagate outward in the sub-fast regions.We further discuss the capabilities of such collimated waves in accelerating particles due to cyclotron resonance in an electron-positron plasma

Insu Yi

Department of Physucs Ewha Woman's University 11-1 Daehyun-dong, Seodaemun-ku Seoul 120-750, KOREA

Statistics of Nonstandard models on Gamma-Ray Bursts:
Source Density Evolution and Relativistic Beaming

     We show that the observed statistics of the BATSE 4B data can be explained by nonstandard effects such as source density evolution and the apparent luminosity distribution (due to beaming). The observed data are classified by several categories based on their hardness ratio (HR23) and duration (T90). We use the <V/Vmax> statistic for each category to compare theoretical models and observed values. From the standard model, the bright bursts with long duration are considered to have low redshift (z<1).However, nonstandard effects can give much larger redshift(z¡­10). With this large redshift, the possibility of gravitational lensing is also discussed

Jantzen Robert

Villanova University, USA

Circular Orbits in Rotating Black Hole Spacetimes

(R.Jantzen and D.Bini)

Jongman Yang

Department of Physics Ewha Woman's University 11-1 Daehyun-dong, Seodaemun-ku Seoul 120-750, KOREA

Test of Evolution Models of QSOs

     To explain the observed comoving space density of QSOs and their luminosity function, we apply the observed spectral states of the Galactic black hole candidates, which has the analogous emission mechanism with QSOs. We explore two types of models which have been suggested and tested. The pure luminosity evolution model supports a scenario which a single generation of long-lived (¡Ã 109 yr) QSO population form at high z and become gradually dimmer while the number of QSOs is conserved throughout the evolution.The density evolution model supports a scenario which the QSOs are composed of many short-lived (¡­107yr) populations and the populations are evolved successively with cosmological time scale. Therefore, we can test which model is more plausible to account the observed QSO luminosities in various energy bands including X-rays.

Jung-Hwan Jun

Department of Physics Chung-Ang University 221 Heuksuk-dong, Dongjak-ku Seoul 156-756, KOREA

Exact Solution of the Cosmological Fluid Equations
for the Newtonian Stars

     We investigate spherically symmetric solutions for nonrelativistic cosmological fluid equations and thermodynamic equation of state for newtonian stars of ideal gas. Using a special ansatz it is shown that the assumption of a ploytrope, $ P_0 =\kappa \rho^\gamma_0$, at the center of the star only suffices to obtain analytic solutions. We discuss stability properties and find collapse behaviour for $\gamma \le 4/3$ and oscillatory behaviour for $\gamma > 4/3.

Khriplovich Iosif.B.

Budker Institute of Nuclear Physics, 630090 Novosibirsk, Russia

Particle creation by charged black holes

     A simple derivation is given for the leading term (n=1) in the Schwinger formula for the pair creation by a constant electric field. The same approach is applied then to the charged particle production by a charged black hole. In this case, as distinct from that of a constant electric field, the probability of the charged particle production depends essentially on the particle energy. The production rate by black holes is found in the nonrelativistic and ultrarelativistic limits. The range of values for the mass and charge of a black hole is indicated where the discussed mechanism of radiation is dominating over the Hawking one.

Kim Sangpyo

Department of Physics Kunsan University 68 Miryong-dong, Kunsan 573-701, KOREA

Thermodynamic Arrow of Time in the Recollapsing Univers

(Jung Kon Kim & Sang Pyo Kim)

     We investigate the thermodynamic arrow of time in a time-symmetrically recollapsing Universe by calculating quantum mechanically the particle and entropy production of either a massive scalar field or an electromagnetic field. It is found that even though the Hamiltonian has a time reversal symmetry with respect to the maximum expansion of the universe, the particle production is generic and the total entropy of the scalar field or the electromagnetic field increases monotonically. We conclude that the thermodynamic arrow of time is a universal phenomenon even in the expanding and subsequently recollapsing universe due to the parametric interaction of matter field with gravity.

Kim Sung-Won

Department of Science Education Ewha Woman's University 11-1 Daehyun-dong, Seodaemun-ku Seoul 120-750, KOREA

Quantum nature of Lorenzian wormhole

     The current status of researcjes on the Lorentzian traversable wormhole physics is represented in this talk. The basic nature,the physical properties, and the necessary restrictions on the traversable wormhole are reviewed. The suggested identification of the wormhole among other extended objects and the usages of them, under the presumption of the existence of such wormholes in our universe, are introduced. The recent works on wormhole, for example, the enlargement of them, the generalization with other fields, and the dynamics are also represented. Finally the quantum nature during the Planckian era is discussed.

Kim Yongduk

Department of Physics Sogang University Seoul 121-742, KOREA

TBA

Kotov Iouri

Director of the Astrophysical Department Moscow State Engineering Physical Institute (MEPHI)

Magnetocoulomb radiation of ultrarelativistic electrons
in matter with strong magnetic field

     Observation of absorption and emission lines in some gamma-ray bursts by Konus-Wind and Konus-A experiments have confirmed that radiation can arise in medium with strong magnetic fields (1011 - 1013 Gauss). Under such conditions the exotic mechanism of gamma-ray generation, which we referred to as magnetocoulombic process, can be important. Electron beam travelling ambient matter along the magnetic lines will be affected by a Coulomb interaction. The transverse motion of a charge particle in the magnetic field is known to be quantised. The electron subsequent transitions to lower levels are followed by the emission of photon with energy of same order as the primary electron energy. This process is 137*3.14 times more effective than the ordinary bremsstruhlung. In the talk the characteristics of magnetocoulombic radiation is discussed

Kouznetsova Inga

Moscow Institute of Physics and Technology

To structure of magnetosphere of Black hole

Ledvinka Tomas

Charles University, Prague (Inst. of Theor.Physics, Faculty of Mathematics and Physics)

Properties of disk-like sources of Kerr-Newman
and Tomimatsu-Sato spacetimes

(T. Ledvinka & J. Bicak)

     We use well-known thin shell technique to construct disk-like sources of stationary axisymmetric vacuum or electro-vacuum spacetimes. Region which contains a singularity is in this procedure removed and using appropriate identification a disk-like surface stress-energy distribution is obtained, surrounded by external part of original spacetime. We study the relation between relativistic phenomena such as existence of eroregions or closed time-like curves and the properties of the material of the disk expressed in terms of energy conditions.

Lee Bum-Hoon

Department of Physics Sogang University Seoul 121-742, KOREA

Boson stars with higher order self-interaction

     We calculate the mass of the boson star with the higher order self-interaction, ${\lamba \over 4} |\phi|^4 + {\gamma \over 6}|\phi|^6$.Even with the very small interaction of $\gamma$, the result differ significantly from the pure $\phi$-4 theory case. The maximum mass of the boson star is much larger than the pure $\phi$-4 theory case. The implication as more plausible candidates for the dark matter is discussed.

Lee Chul Hoon

Department of Physics Hanyang University Seoul 133-791, KOREA

Density perturbations with magnetic fields

     We consider the effects of primordial magnetic fields on the evolution of density perturbations and the CMB anisotropy. Assuming the random magnetic fields with a power-law spectrum, we show that the growth rate of the density perturbations is reduced compared to the case with no magnetic fileds

Lee Hyun Kyu

Department of Physics Hanyang Universi ty -Seoul 133-791, KOREA

Blandford-Znajek Process and Gamma Ray Bursts

     Two decades ago Blandford and Znajek proposed a process in which the rotational energy of a black hole can be efficiently extracted. Provided with the strong magnetic field($\sim 10^{15} gauss$) which threads the black hole, the rotating black hole can be slowed down in an appropriate time scale to power the gamma ray burst.We will discuss how the Blandford-Znajek process can be realized in nature as a central engine for the gamma ray burst.The black hole-accretion disk which is supposed to emerge eventually via binary merging sytem and the hypernovae is proposed as a relevant structure for the GRB central engine powered by the Blandford-Znajek process.The possible chracteristics of the gamma ray burst via the Blandford-Znajek process and future prospects will be discussed.

Lee Hyung Won

Department of Physics Inje University, 607 Obang-dong Kimhae, 621-749, KOREA

Chaotic structure of Einstein equations

     The time dependent behavior of full nonlinear theory of general relativity presents a challenge to physists. It is well known there will be a chaotic behavior for the nonlinearly coupled dynamical system. Einstein equations are highly nonlinear system and its solution is known only for very few cases. The exact solution for full nonlinear Einstein equation is too hard to find. Instead one can obtain some insight for understanding the universe by exploring the chaotic behavior of Einstein equations. The main purpose of this article is to get what kind of chaotic behavior will be exhibited by Einstein equations.In this article, chaotic behavior for a simple model will be studied.

Lee Taejin

Department of Physics Kangwon National University Chuncheon 200-701, KOREA

Two Dimensional Anti-de Sitter Black Hole
and Discrete Light Cone Quantization

     We realize the two dimensional anti-de Sitter (AdS) black hole as a circle compactification of the three dimensional AdS blacl hole in the framework of DLCQ (discrete light cone quantization). This realization of the 2D AdS space illustrates how the AdS_2/CFT duality can be derived from the well-known AdS_3/CFT duality.We also evaluate the entropy for the 2D AdS black hole comparing it with the 3D AdS black hole.

LeeHyung Mok

(Seoul National University)

Tidal disruption of a star by a massive black hole and initial outburst

     A star can be tidally disrupted around a massive black hole. It has been known that the debris forms a precessing stream, which may collide with itself. The stream collision is a key process determining the subsequent evolution of the stellar debris: if the orbital energy is efficiently dissipated, the debris will eventually form a circular disk (or torus). In this paper,we have numerically studied such stream collision resulting from the encounter between a $10^6 \, \msun$ black hole and a $1 \, \msun$ normal star with a pericenter radius of 100~$\rsun$.A simple treatment for radiative cooling has been adopted for both optically thick and thin regions. We have found that approximately 10 to 15\% of the initial kinetic energy of the streams is converted into thermal energy during the collision.The spread in angular momentum of the incoming stream is increased by a factor of 2 to 3,and such increase, together with the decrease in kinetic energy,significantly helps the circularization process. Initial luminosity burst due to the collisionmay reach as high as $10^{41} \, {\rm erg \, sec^{-1}}$ in $10^4$~sec,after which the luminosity increases again (but slowly this time) to a steady value of a few $10^{40} \, {\rm erg \, sec^{-1}}$ in a few times of $10^5$~sec. The radiation from the system is expected to be close to Planckian with effective temperature of $\sim 10^5$~K.

Mastroianni Angelo

ICRA, Italy

Miniutti Giovanni

ICRA, Italy

Montani Giovanni

* International Center for Relativistic Astrophysics, Rome
&
** Dept of Theoretical Physics, Institute of Nuclear Physics, Tashkent

Gravitating macroscopic media in general relativity and macroscopic gravity

(G. Montani*, R. Ruffini* & R. Zalaletdinov**)

Narozhny Nikolai

Moscow State Engineering Physical Institute (MEPHI)

The motion of the charged dust shell

(V.Belinski, N.Narozhny & A.Fedotov)

     The analogue of the W.Israel equation of motion of the spherical dust shell obtained for the charged shell

Onikyi Boris

Oriti Daniele

Quantization of the spinor field in Rindler spacetime
and analysis of the Unruh effect

     We analyse the quantization procedure of the spinor field in the Rindler spacetime, showing the boundary conditions that should be imposed to the field, in order to have a well posed theory. We then investigate the relationship between this construction and the usual one in Minkowski spacetime. This leads to the concept of "Unruh effect", that is the thermal nature of the Minkowski vacuum state from the point of view of an accelerated observer. It is demostrated that the two constructions are qualitatively different and can not be compared and consequently the conventional interpretation of the Unruh effect is incorrect.

Preparata Giuliano

Milan University, Italy

Punsly Brian

Ragachurin R.G.

Laboratory of Nuclear Problems Institute of Nuclear Physics U07bek Tashkent UZBEKISTAN

The possible influence of Salam's effect in
unification of strong and gravitation interactions

Rosu Haret

Institute of Physics, Univ. of Guanajuato, Mexico

negative binomial radiation (provisional)

     The negative binomial features of black hole "therma" radiation are revisited

Ruffini Remo

Rome University "La Sapienza" and ICRA, Italy

Salmonson Jay

Lawrence Livermore National Laboratory, USA

Sanchez Pascual J.-Fernando

University of Valladolid Dept.Matemática Aplicada Fundamental

The choice of gauge in the gravitomagnetic equations

     We examine how the different choices of gauge can drastically change the physical contents of the linear gravitomagnetic equations.

Sigismondi Costantino

ICRA

Indications of Titan's atmosphere observed with a 4"½ telescope

     The discovery of Titan's atmosphere was proved spectroscopically with a 82" telescope in 1943 by Gerard Kuiper. Otherwise it is possible to detect evidences of the atmosphere on this satellite of Saturn comparing the observations made on different wavebands.The techniques for obtaining those data with a commercial 4"½ telescope and their didactic relevance are discussed.

Sohrab Rahvar Nemat Abad

IPM(Institue for Studies in Theoretical Physics and Mathematices), IRAN

Song Doo Jong

Korea Astronomy Observatory 36-1 Wham-dong, Yousung-ku Taejeon 305-348, KOREA

The Cosmological Lens Equation in the Perturbed Bianchi Type Universe:
Formalism and Application

     We have formulate the cosmological lens equation in the perturbed Bianchi type I spacetime by solving the null geodesic equation. The formula is expressed in terms of gauge invariants combinations for scalar, vector and tensor type perturbations. The results are generalizations of those of a perturbed flat Friedmann spacetime and their cosmological applications are considered.

Sonnino Giorgio

"European Commission DG XII" and "Insituts Internationaux de Physique et de Chimie" , Belgium

Thermodynamic Field theory

The objective of the Thermodynamic Field Theory is to evaluate the relationship between the generalised thermodynamic fluxes and forces for thermodynamic systems even in strong non-equilibrium conditions.
     Thanks to general balance equations, we can describe the evolution of some arbitrary extensive quantity "a" in the course of time. Examples of balance equations of fundamental importance in the field theory are the mass, charge, impulse and angular momentum balances. However, as known, when we wish to obtain a general set of transport equations describing the state of the system (for example the equation for the local temperature "T", the local pressure "p" or the equation of the concentration "c" of a given chemical species) we need to combine the related balance equation with "phenomenological laws". When a system is close to equilibrium, a general theory based on linear relations between forces and flows can be formulated (Onsager theory). Examples of phenomenological laws described in the Onsager theory are the well-known Fourier's law of heat conduction, the Fick's law of diffusion or the Ohm's law of electrical conduction.
     However, when the thermodynamic system is far from equilibrium it might happen that the generalised thermodynamic forces and fluxes are no longer related by a linear law and the phenomenological coefficients no longer satisfy the Onsager's relations. An extreme case, which is interesting to consider, is the case in which the matrix formed by the phenomenological coefficients is purely anti-symmetric. This occurs in chemical systems where the steady state (chemical "oscillations") is far from equilibrium.
     In the present paper, I will show that it is possible to formulate a (covariant) thermodynamic field theory and to find a field equation whose solutions give the generalised relation between fluxes and thermodynamic flows. It can be shown that thermodynamic systems can be described with spaces with symmetric connection. When the system is in equilibrium or in non-equilibrium condition (but far from critical points), the thermodynamic space can be described by a Riemannian space. When the system is far from equilibrium (i.e. the control parameter is greater than its critical value) the related thermodynamic space is described by a Weyl space. I will prove that the solutions of the field equation reduce to the Onsager's relations when the system approaches equilibrium. Moreover, the solutions of the field equation satisfy the "General Criterion of Evolution" for thermodynamic systems even in strong non-equilibrium conditions. As known, Glansdorff and Prigogine obtained this result in 1954 trough a purely thermodynamic approach. The inequality expressed by the "Universal Criterion of Evolution" is the most general result obtained up to now in thermodynamics of irreversible processes. The Prigogine's theorem of "Minimum Production of Entropy" is also satisfied by the solutions of the field equation when the system is near the equilibrium. Subsequently, I will show that the "dynamic" equations can be derived from a "principle of least action". Finally, an application of the field equation to the Fourier's law for systems (very) far from equilibrium and to a simple chemical reaction will be presented. In the case of the Fourier's law, the theoretical results are in perfect agreement with experimental data. The analysis of a simple chemical reaction will lead us to the re-obtain the De Donder law through the field equation in the weak-field approximation.

Spallicci Alessandro D.A.

Università del Sannio at Benevento

On the radiation reaction via perturbations equations of black holes

Takahashi Masaaki

Department of Physics and Astronomy, Aichi University of Education, Japan

The conditions for MHD Accretion onto a Kerr Black Hole

     We present the critical conditions of trans-fast magnetohydrodynamical (MHD) accretions in a stationary and axisymmetric black-hole magnetosphere. We assume that the black-hole magnetosphere is composed of a massive black hole with surrounding plasma and magnetic field; the magnetic field is originated from an accretion disk rotating around the black hole, and the black hole is immersed in this magnetic field; the accreting plasma is provided from the disk surface and falls into the black hole along the magnetic field line.The MHD accretion injected from the plasma source with low-velocity must pass through the slow magnetosonic point, the Alfv\'en point and the fast magnetosonic point in order. To pass through smoothly these points, the five parameters of MHD flows are restricted by the regularity conditions at these points. The main result is the discovery of two separate regimes: "magnetic-like'' MHD accretion and "fluid-like'' MHD accretion. For a weak magnetic field limit, the former has no solution, while the latter coincides with the hydrodynamical case. Transition between these two regimes is discontinuous. We also present a standing shock formation.

Tchetchetkin Valery  M.

Keldysh Institute of Applied Mathematics-Moscow

Magnetohydrodynamics around compact stars

     Magnetohydrodynamic outflow from a rotating accretion disk are investigated numerically by time-dependent simulation.Defferent outer boundary conditions on magnetic field were investigated.It was shown that simulation results may depends on the shape of the simulation region.

Titarchuk Lev

NASA/GSFC/GMU

Spectral and Timing Properties of Black Hole and Neutron Star Systems.
Theory and Observations.

     An accreting black hole is, by definition, characterized by the drain.Namely, the matter falls into a black hole much the same way as water disappears down a drain - matter goes in and nothing comes out.
     As this can only happen in a black hole, it provides a way to see "a black hole", an unique observational signature of black holes.The accretion proceeds almost in a free-fall manner close to the black hole horizon, where the strong gravitational field dominates the pressure forces. In this talk I present analyzing the exact general relativistic integrodifferential equation of radiative transfer and using Monte-Carlo simulations the specific features of X-ray spectra formed as a result of upscattering of the soft (disk) photons in the converging inflow (CI) within about 3 Schwarzschild radii of the black hole. I will show that spectra in the soft state of black hole systems (BHS) can be described as the sum of a thermal (disk) component and the convolution of some fraction of this component with the CI upscattering spread (Green's) function. The latter boosted photon component is seen as an extended power-law at energies much higher than the characteristic energy of the soft photons. I will demonstrate the stability of the power spectral index ( 1.8+/- 0.1) over a wide range of the plasma temperature 0-10 keV and mass accretion rates (higher than 2 in Eddington units). We also demonstrate that the sharp high energy cutoff occurs at energies of 200-400 keV which are related to the average energy of electrons mc^2 impinging upon the event horizon. The spectrum is practically identical to the standard thermal Comptonization spectrum (Hua & Titarchuk 1995) when the CI plasma temperature is getting of order of 50 keV (the typical ones for the hard state of BHS). In this case one can see the effect of the bulk motion only at high energies where there is an excess in the CI spectrum with respect to the pure thermal one. Furthermore we demonstrate that the change of spectral shapes from the soft X--ray state to the hard X--ray state is clearly to be related with the temperature of the bulk flow. In other words the effect of the bulk Comptonization compared to the thermal one is getting stronger when the plasma temperature drops below 10 keV.These CI spectra are a inevitable stamp of the BHS where the strong gravitational field dominates the pressure forces.I will also present our analysis of the high-energy radiation from black hole (BH) transients, using archival data obtained primarily with the Rossi X-ray Timing Explorer (RXTE), and a comprehensive test of the converging inflow (CI) model for the high-soft state continuum. The emergent spectra of over 30 separate measurements of GRO J1655-40, GRS 1915+105, GRS 1739-278, 4U 1630-47 XTE J1755-32, and EXO~1846-031 X-ray sources are successfully fitted by the CI model. Using our inferred model parameters: color temperature, spectral index and an absolute normalization I will present new, independently derived, constraints on the black hole mass, mass accretion rate and the distance for the aforementioned sources. Also notable is the relationship between the color temperature and flux, which for GRO~J1655-40 is entirely distinct from a simple T^4 dependence, and strikingly consistent with the disk model we have invoked - standard Shakura-Sunyaev's disk with the modification to the electron scattering.
     This provides insight into the origin of the seed soft photons, and allows us to impose an important estimation of the hardness parameter, T_h, which is the ratio of the color temperature to the effective temperature - we find $T_{h}\simeq2.6$, higher than previous estimates used in the literature.I will also present the theory of the unification of the quasiperiodic oscillations (QPO) observed in the neutron star systems.

Treves Aldo

Como University, Italy

Valbonesi Enrico

student of Rome III

Vella Massimiliano

ICRA, Italy

Xue She-Sheng

ICRA, Italy

On the Pair Electromagnetic Pulse of a Black Hole with Electromagnetic Structure

(R. Ruffini, J.D. Salmonson, J.R. Wilson, S.S. Xue)

Zerilli Frank J.

NSWC Indian Head Division