One loop light-cone QCD, effective action for reggeized gluons and QCD RFT calculus

The effective action for reggeized gluons is based on the gluodynamic Yang-Mills Lagrangian with external current for longitudinal gluons added, see [1]. On the base of classical solutions, obtained in [2], the one-loop corrections to this effective action in light-cone gauge are calculated. The RFT calculus for reggeized gluons similarly to the RFT introduced in [3] is proposed and discussed. The correctness of the results is verified by calculation of the propagator of $A_{+}$ and $A_{-}$ reggeized gluons fields and application of the obtained results is discussed as well.Comment: 24 page

Timing and Spectral Properties of X-ray Emission from the Converging Flows onto Black hole: Monte-Carlo Simulations

We demonstrate that a X-ray spectrum of a converging inflow (CI) onto a black hole is the sum of a thermal (disk) component and the convolution of some fraction of this component with the Comptonization spread (Green's) function. The latter component is seen as an extended power law at energies much higher than the characteristic energy of the soft photons. We show that the high energy photon production (source function) in the CI atmosphere is distributed with the characteristic maximum at about the photon bending radius, 1.5r_S, independently of the seed (soft) photon distribution. We show that high frequency oscillations of the soft photon source in this region lead to the oscillations of the high energy part of the spectrum but not of the thermal component. The high frequency oscillations of the inner region are not significant in the thermal component of the spectrum. We further demonstrate that Doppler and recoil effects (which are responsible for the formation of the CI spectrum) are related to the hard (positive) and soft (negative) time lags between the soft and hard photon energy channels respectively.Comment: 9 pages and 4 figures, to be published in the Astrophysical Journal Letter

Comptomization and radiation spectra of X-ray sources. Calculation of the Monte Carlo method

The results of computations of the Comptomization of low frequency radiation in weakly relativistic plasma are presented. The influence of photoabsorption by iron ions on a hard X-ray spectrum is considered

X-ray Polarization Signatures of Compton Scattering in Magnetic Cataclysmic Variables

Compton scattering within the accretion column of magnetic cataclysmic variables (mCVs) can induce a net polarization in the X-ray emission. We investigate this process using Monte Carlo simulations and find that significant polarization can arise as a result of the stratified flow structure in the shock-ionized column. We find that the degree of linear polarization can reach levels up to ~8% for systems with high accretion rates and low white-dwarf masses, when viewed at large inclination angles with respect to the accretion column axis. These levels are substantially higher than previously predicted estimates using an accretion column model with uniform density and temperature. We also find that for systems with a relatively low-mass white dwarf accreting at a high accretion rate, the polarization properties may be insensitive to the magnetic field, since most of the scattering occurs at the base of the accretion column where the density structure is determined mainly by bremsstrahlung cooling instead of cyclotron cooling.Comment: 7 pages, 8 figures, accepted by MNRA

Inverse Compton scattering in mildly relativistic plasma

We investigated the effect of inverse Compton scattering in mildly relativistic static and moving plasmas with low optical depth using Monte Carlo simulations, and calculated the Sunyaev-Zel'dovich effect in the cosmic background radiation. Our semi-analytic method is based on a separation of photon diffusion in frequency and real space. We use Monte Carlo simulation to derive the intensity and frequency of the scattered photons for a monochromatic incoming radiation. The outgoing spectrum is determined by integrating over the spectrum of the incoming radiation using the intensity to determine the correct weight. This method makes it possible to study the emerging radiation as a function of frequency and direction. As a first application we have studied the effects of finite optical depth and gas infall on the Sunyaev-Zel'dovich effect (not possible with the extended Kompaneets equation) and discuss the parameter range in which the Boltzmann equation and its expansions can be used. For high temperature clusters ($k_B T_e \gtrsim 15$ keV) relativistic corrections based on a fifth order expansion of the extended Kompaneets equation seriously underestimate the Sunyaev-Zel'dovich effect at high frequencies. The contribution from plasma infall is less important for reasonable velocities. We give a convenient analytical expression for the dependence of the cross-over frequency on temperature, optical depth, and gas infall speed. Optical depth effects are often more important than relativistic corrections, and should be taken into account for high-precision work, but are smaller than the typical kinematic effect from cluster radial velocities.Comment: LateX, 30 pages and 11 figures. Accepted for publication in the Astrophysical Journa

Evolution of the Low-Energy Photon Spectra in Gamma-Ray Bursts

We report evidence that the asymptotic low-energy power law slope alpha (below the spectral break) of BATSE gamma-ray burst photon spectra evolves with time rather than remaining constant. We find a high degree of positive correlation exists between the time-resolved spectral break energy E_pk and alpha. In samples of 18 "hard-to-soft" and 12 "tracking" pulses, evolution of alpha was found to correlate with that of the spectral break energy E_pk at the 99.7% and 98% confidence levels respectively. We also find that in the flux rise phase of "hard-to-soft" pulses, the mean value of alpha is often positive and in some bursts the maximum value of alpha is consistent with a value > +1. BATSE burst 3B 910927, for example, has a alpha_max equal to 1.6 +/- 0.3. These findings challenge GRB spectral models in which alpha must be negative of remain constant.Comment: 12 pages (including 6 figures), accepted to Ap

X-ray Spectral Signatures of the Photon Bubble Model for Ultraluminous X-ray Sources

The nature of ultraluminous X-ray sources in nearby galaxies is one of the major open questions in modern X-ray astrophysics. One possible explanation for these objects is an inhomogeneous, radiation dominated accretion disk around a $\sim 10 M_{\odot}$ black hole -- the so-called ``photon bubble'' model. While previous studies of this model have focused primarily on its radiation-hydrodynamics aspects, in this paper, we provide an analysis of its X-ray spectral (continuum and possible edge and line) characteristics. Compton reflection between high and low density regions in the disk may provide the key to distinguishing this model from others, such as accretion onto an intermediate mass black hole. We couple a Monte Carlo/Fokker-Planck radiation transport code with the XSTAR code for reflection to simulate the photon spectra produced in a photon bubble model for ULXs. We find that reflection components tend to be very weak and in most cases not observable, and make predictions for the shape of the high-energy Comptonizing spectra. In many cases the Comptonization dominates the spectra even down to $\sim$ a few keV. In one simulation, a \sim 9 \kev feature was found, which may be considered a signature of photon bubbles in ULXs; furthermore, we make predictions of high energy power-laws which may be observed by future instruments.Comment: Accepted for publication in the Astrophysical Journa

Wien Fireball Model of Relativistic Outflows in Active Galactic Nuclei

We study steady and spherically symmetric outflows of pure electron-positron pair plasma as a possible acceleration mechanism of relativistic jets up to the bulk Lorentz factor of greater than 10. These outflows are initiated by the ``Wien fireball'', which is optically thick to Compton scattering but thin to absorption and in a Wien equilibrium state between pairs and photons at a relativistic temperature.Comment: 16 pages, 13 figures, 1 table, ApJ in pres

Low frequency radio and X-ray properties of core-collapse supernovae

Radio and X-ray studies of young supernovae probe the interaction between the supernova shock waves and the surrounding medium and give clues to the nature and past of the progenitor star. Here we discuss the early emission from type Ic SN 2002ap and argue that repeated Compton boosting of optical photons by hot electrons presents the most natural explanation of the prompt X-ray emission. We describe the radio spectrum of another type Ic SN 2003dh (GRB030329) obtained with combined GMRT and VLA data. We report on the low frequency radio monitoring of SN 1995N and our objectives of distinguishing between competing models of X-ray emission from this SN and the nature of its progenitor by X-ray spectroscopy. Radio studies on SN 2001gd, SN 2001ig and SN 2002hh are mentioned.Comment: 5 pages, 4 figures. Uses svmult.cls. To appear in proceedings of IAU Colloquium 192 "Supernovae (10 years of SN 1993J)", April 2003, Valencia, Spain, eds. J. M. Marcaide and K. W. Weile

Quasi-thermal Comptonization and gamma-ray bursts

Quasi-thermal Comptonization in internal shocks formed between relativistic shells can account for the high energy emission of gamma-ray bursts. This is in fact the dominant cooling mechanism if the typical energy of the emitting particles is achieved either through the balance between heating and cooling or as a result of electron-positron pair production. Both processes yield sub or mildly relativistic energies. In this case the synchrotron spectrum is self-absorbed, providing the seed soft photons for the Comptonization process, whose spectrum is flat [F(v) ~ const], ending either in an exponential cutoff or a Wien peak, depending on the scattering optical depth of the emitting particles. Self-consistent particle energy and optical depth are estimated and found in agreement with the observed spectra.Comment: 10 pages, ApJ Letters, accepted for publicatio