X-Ray Reflected Spectra From Accretion Disk Models. Iii. A Complete Grid of Ionized Reflection Calculations

Abstract

We present a new and complete library of synthetic spectra for modeling the component of emission that is reflected from an illuminated accretion disk.The spectra were computed using an updated version of our code xillver that incorporates new routines and a richer atomic data base. We offer in the form of a table model an extensive grid of reflection models that cover a wide range of parameters. Each individual model is characterized by the photon index Γ of the illuminating radiation, the ionization parameter ξ 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 ≤ Γ ≤ 3.4, 1 ≤ ξ ≤ 10 4 , and 0.5 ≤ A Fe ≤ 10. These ranges capture the physical conditions typically inferred from observations of active galactic nuclei, and also stellarmass 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 1 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. 1997; Dauser et al. 2013). The presence of this dense (n H 10 12 cm −3 ), warm (T ∼ 10 5 − 10 7 K), and optically-thick (τ T 1) medium is also supported by the detection of atomic features from several ions. These and other features constitute an important component of the X-ray -5spectrum observed from accreting sources, resulting from the reprocessing of radiation by the material in the disk. This component is commonly referred to as reflection, in the sense that it is the result of radiation that is returned from the accretion disk by fluorescence or electron scattering. The current paradigm is that the original power-law radiation irradiates the surface of the accretion disk. The X-ray photons then interact with the material producing diverse atomic features. These can be produced both via absorption (mostly in form of edges), and emission (in form of fluorescence lines and radiative recombination continua, RRC). Therefore, the reflection component provides direct information about structure, temperature, ionization stage, and composition of the gas in the accretion disk.The presence of the Fe K-shell fluorescence emission and the absorption K-edge observed in the 6 − 8 keV energy range are recognized as strong evidence for reflection.X-ray photons that are photoelectrically absorbed have enough energy to remove a 1s electron from its K-shell, leaving it in a quasi-bound state above the continuum (autoionizing state). The K-hole is then filled by an electron, and the energy difference can be released by emitting a second electron (Auger process), or by the emission of a K-shell photon....

Detection of a second high-velocity component in the highly ionized wind from PG 1211+143

“…In particular, scattering from optically thick matter (or so-called 'reflection' found to be common in AGN spectra (Nandra and Pounds 1994)) may impose a step change near the Fe K absorption edge (∼6.5 keV in observer space), and an indication of such an effect can be seen in Figure 3 (top panel). To quantify that 'reflection' we added a Xillver component (Garcia et al 2013) to the power law continuum model in XSPEC, simultaneously matching the fluorescent Fe K emission line and continuum reflection from optically thick ionized matter. When previously modelled with a Gaussian, the Fe K line energy of ∼5.96 keV (∼6.44 keV at the AGN redshift), and EW of 73 eV yielded a 2-10 keV spectral fit statistic of (χ 2 ν of 1513/1364).…”

Complex narrow-line Seyfert 1s: high spin or high inclination?

“…Thermalization is more important for discs in hydrostatic equilibrium (Nayakshin & Kallman 2001) but current reflection models are calculated for constant density discs (e.g. Ross & Fabian 2005;García et al 2013). The high disc temperatures expected in NLS1s means that this component must be important at some level in contributing to the soft X-ray excess in these objects, and since it is predominantly thermal then it has no strong soft X-rays lines which require high spin to smear them into the observed smooth continuum.…”

THENuSTAREXTRAGALACTIC SURVEY: FIRST DIRECT MEASUREMENTS OF THE ≳10 keV X-RAY LUMINOSITY FUNCTION FOR ACTIVE GALACTIC NUCLEI ATz> 0.1

“…Our measurements of the 10-40 keV XLF indicate that moderate-to-strong reflection (R ∼ 1−2) is required to describe the average spectral characteristics of L 10 10 40 keV 43 46 --erg s −1 AGNs at z ∼ 0.1-3. The extent, strength, and spectral characteristics of reflection provide insights into the physical nature of the obscuring material and the accretion disk (e.g., García et al 2013;Falocco et al 2014;Brightman et al 2015). Strong reflection could also indicate a substantial population of rapidly spinning black holes in the detected sample; however, a relatively small intrinsic fraction of high-spin sources (∼7%) can potentially dominate the observed number counts at a given flux limit (Brenneman et al 2011;Vasudevan et al 2015).…”