The relxill model, which employs general relativistic ray-tracing methods, is used to predict the reflection. Results are compared with previous models and a Monte Carlo simulation. While for the reflection fraction the normalization parameter does not change with the inclination to the system, the reflection strength shows a clear dependence. The strongest reflection is created for large spin and low source height in every case. A slowly rotating black hole is not capable of producing an enhanced relativistic reflection, i.e. a reflection stronger than the direct continuum. Using the definition of the intrinsic reflection fraction in the relxill model, allows us to draw conclusions about the geometry of the system when fitting measured data. It is also shown that such a definition yields a reflection fraction parameter, which is not correlated directly with the relativistic parameters. As of v0.4a of the relxill model, this parameter is now implemented with the name refl_frac in all flavors of the model, including the non-relativistic reflection model xillver.

The only relativistic reflection model that implements a parameter relating the intensity incident on an accretion disk to the observed intensity is relxill. The parameter used in earlier versions of this model, referred to as the reflection strength, is unsatisfactory, and it has been superseded by a parameter that provides insight into the accretion geometry, namely the reflection fraction. The reflection fraction is defined as the ratio of the coronal intensity illuminating the disk to the coronal intensity that reaches the observer. The relxill model combines a general relativistic ray-tracing code and a photoionization code to compute the component of radiation reflected from an accretion that is illuminated by an internal source. The reflection fraction is a particularly important parameter for relativistic models with well-defined geometry, such as the lamppost model, which is a focus of this paper. Relativistic spectra are compared for three inclinations and for four values of the key parameter of the lamppost model, namely the height above the black hole of the illuminating, on-axis point source. In all cases, the strongest reflection is produced for low source heights and high spin. A low-spin black hole is shown to be incapable of producing enhanced relativistic reflection. Results for the relxill model are compared to those obtained with other models and a Monte Carlo simulation. Fitting data using the relxill model and the recently implemented parameter the reflection fraction, one can constrain the geometry of a system, under the assumption of a lamppost-like accretion geometry. The reflection fraction is independent of such system parameters as inclination and black hole spin. The reflection fraction parameter was implemented with the name refl_frac in all flavors of the relxill model, and the nonrelativistic reflection model xillver, in v0.4a (18 January 2016).

The only relativistic reflection model that implements a parameter relating the intensity incident on an accretion disk to the observed intensity is relxill. The parameter used in earlier versions of this model, referred to as the reflection strength, is unsatisfactory, and it has been superseded by a parameter that provides insight into the accretion geometry, namely the reflection fraction. The reflection fraction is defined as the ratio of the coronal intensity illuminating the disk to the coronal intensity that reaches the observer. The relxill model combines a general relativistic ray-tracing code and a photoionization code to compute the component of radiation reflected from an accretion that is illuminated by an internal source. The reflection fraction is a particularly important parameter for relativistic models with well-defined geometry, such as the lamppost model, which is a focus of this paper. Relativistic spectra are compared for three inclinations and for four values of the key parameter of the lamppost model, namely the height above the black hole of the illuminating, on-axis point source. In all cases, the strongest reflection is produced for low source heights and high spin. A low-spin black hole is shown to be incapable of producing enhanced relativistic reflection. Results for the relxill model are compared to those obtained with other models and a Monte Carlo simulation. Fitting data using the relxill model and the recently implemented parameter the reflection fraction, one can constrain the geometry of a system, under the assumption of a lamppost-like accretion geometry. The reflection fraction is independent of such system parameters as inclination and black hole spin. The reflection fraction parameter was implemented with the name refl_frac in all flavors of the relxill model, and the nonrelativistic reflection model xillver, in v0.4a (18 January 2016).

In the framework of radio monitoring of NS/BH Galactic Binaries with Sardinia Radio Telescope (www.srt.inaf.it) during SRT Early Science Program S0013 (PI Egron), we detected Cyg X-1 in C-band through on-the-fly mapping centered on the source position (see also Atels #8921, #8849, #8821).

We present a comprehensive analysis of the whole sample of available XMM-Newton observations of high-mass X-ray binaries (HMXBs) until August 2013, focusing on the FeK alpha emission line. This line is key to better understanding the physical properties of the material surrounding the X-ray source within a few stellar radii (the circumstellar medium). We collected observations from 46 HMXBs and detected FeK alpha in 21 of them. We used the standard classification of HMXBs to divide the sample into different groups. We find that (1) different classes of HMXBs display different qualitative behaviours in the FeK alpha spectral region. This is visible especially in SGXBs (showing ubiquitous Fe fluorescence but not recombination Fe lines) and in gamma Cass analogues (showing both fluorescent and recombination Fe lines). (2) FeK alpha is centred at a mean value of 6.42 keV. Considering the instrumental and fits uncertainties, this value is compatible with ionization states that are lower than Fe xviii. (3) The flux of the continuum is well correlated with the flux of the line, as expected. Eclipse observations show that the Fe fluorescence emission comes from an extended region surrounding the X-ray source. (4) We observe an inverse correlation between the X-ray luminosity and the equivalent width of FeK alpha (EW). This phenomenon is known as the X-ray Baldwin effect. (5) FeK alpha is narrow (sigma(line) < 0.15 keV), reflecting that the reprocessing material does not move at high speeds. We attempt to explain the broadness of the line in terms of three possible broadening phenomena: line blending, Compton scattering, and Doppler shifts (with velocities of the reprocessing material V similar to 1000 km s(-1)). (6) The equivalent hydrogen column (N-H) directly correlates to the EW of FeK alpha, displaying clear similarities to numerical simulations. It highlights the strong link between the absorbing and the fluorescent matter. (7) The observed NH in supergiant X-ray binaries (SGXBs) is in general higher than in supergiant fast X-ray transients (SFXTs). We suggest two possible explanations: different orbital configurations or a different interaction compact object - wind. (8) Finally, we analysed the sources IGR J16320-4751 and 4U 1700-37 in more detail, covering several orbital phases. The observed variation in NH between phases is compatible with the absorption produced by the wind of their optical companions. The results clearly point to a very important contribution of the donor's wind in the FeK alpha emission and the absorption when the donor is a supergiant massive star.

X-ray reflection models are used to constrain the properties of the accretion disk, such as the degree of ionization of the gas and the elemental abundances. In combination with general relativistic ray tracing codes, additional parameters like the spin of the black hole and the inclination to the system can be determined. However, current reflection models used for such studies only provide angle-averaged solutions for the flux reflected at the surface of the disk. Moreover, the emission angle of the photons changes over the disk due to relativistic light bending. To overcome this simplification, we have constructed the new angle-dependent reflection model RELXILL, by self-consistently connecting the XILLVER reflection models with the relativistic blurring code RELLINE.

The spectral shape of an X-ray source strongly depends on the amount and distribution of the surrounding material. The spectrum of a primary source which is located in an optically thin medium with respect to Compton scattering is mainly modified by photo absorption in the lower energy range and is almost unaltered above ~ 10 keV. This picture changes when the source is obscured by gas exceeding hydrogen column densities of ~ 10 24 cm −2 . At this degree of absorption it is likely that photons are scattered at least twice before leaving the medium. The multiple scatterings lead to a lack of photons in the high energy range of the resulting spectrum as well as to an accumulation of photons at moderate energies forming the so-called Compton-bump. The shape of the fluorescent lines also changes since scattered line photons form several Compton-shoulders which are very prominent especially for Compton-thick sources. Using a Monte Carlo method, we demonstrate the importance of Compton scattering for high column densities. For that purpose, we compare our results with existing absorption models that do not consider Compton scattering. These calculations will be implemented in a prospective version of the tbabs absorption model including an analytic evaluation of the strength of the fluorescent lines.

The shape and intensity of fluorescence lines is an important diagnostic tool to explore the characteristics of the material along the line of sight from an X-ray source.We present a Monte Carlo simulation of radiative transfer through a neutral gas, including photo absorption, fluorescent line emission, and Compton (down-)scattering.The primary spectrum is emitted by a source which is located either in the center of a spherical cloud or above a semi-infinite slab.In the former case, a pure transmitted spectrum is obtained while in the later case the reflected component is of interest.We present the dependence of intensity of the Fe K α and K β line and the centroid energy of the Compton shoulder as a function of N H .These calculations will be implemented in a revised version of the absorption model tbabs which includes lines emission and effective Compton down-scattering from the high energy range.This model is appropriate for column densities in excess of 10 24 cm -2 .

We present a new and complete library of synthetic spectra for modeling the component of emission that is reflected from an illuminated accretion disk. The spectra were computed using an updated version of our code XILLVER that incorporates new routines and a richer atomic database. We offer in the form of a table model an extensive grid of reflection models that cover a wide range of parameters. Each individual model is characterized by the photon index G of the illuminating radiation, the ionization parameter xi at the surface of the disk (i.e., the ratio of the X-ray flux to the gas density), and the iron abundance A(Fe) relative to the solar value. The ranges of the parameters covered are 1.2 <= Gamma <= 3.4, 1 <= xi <= 10(4), and 0.5 <= A(Fe) <= 10. These ranges capture the physical conditions typically inferred from observations of active galactic nuclei, and also stellar-mass black holes in the hard state. This library is intended for use when the thermal disk flux is faint compared to the incident power-law flux. The models are expected to provide an accurate description of the Fe K emission line, which is the crucial spectral feature used to measure black hole spin. A total of 720 reflection spectra are provided in a single FITS file (http://hea-www.cfa.harvard.edu/similar to javier/xillver/) suitable for the analysis of X-ray observations via the atable model in XSPEC. Detailed comparisons with previous reflection models illustrate the improvements incorporated in this version of XILLVER.

The eROSITA instrument on board the Russian Spectrum Roentgen Gamma spacecraft, which will be launched in 2013,will conduct an all sky survey in X-rays. A main objective of the survey is to observe galaxy clusters in order to constrain cosmological parameters and to obtain further knowledge about dark matter and dark energy. For the simulation of the eROSITA survey we present a Monte-Carlo code generating a mock catalogue of galaxy clusters distributed accordingto the mass function of [1]. The simulation generates the celestial coordinates as well as the cluster mass and redshift. From these parameters, the observed intensity and angular diameter are derived. These are used to scale Chandra cluster images as input for the survey-simulation.