An XSPEC model to explore spectral features from black-hole sources - II. The relativistic iron line in the lamp-post geometry
arXiv:1412.8627
Abstract
In X-ray spectra of several active galactic nuclei and Galactic black hole binaries a broad relativistically smeared iron line is observed. This feature arises by fluorescence when the accretion disc is illuminated by hot corona above it. Due to central location of the corona the illumination and thus also the line emission decrease with radius. It was reported in the literature that this decrease is very steep in some of the sources, suggesting a highly compact corona. We revisit the lamp-post setup in which the corona is positioned on the axis above the rotating black hole and investigate to what extent the steep emissivity can be explained by this scenario. We show the contributions of the relativistic effects to the disc illumination by the primary source - energy shift, light bending and aberration. The lamp-post radial illumination pattern is compared to the widely used radial broken power-law emissivity profile. We find that very steep emissivities require the primary illuminating source to be positioned very near the black hole horizon and/or the spectral power-law index of the primary emission to be very high. The broken power-law approximation of the illumination can be safely used when the primary source is located at larger heights. However, for low heights the lamp-post illumination considerably differs from this approximation. We also show the variations of the iron line local flux over the disc due to the flux dependence on incident and emission angles. The former depends mainly on the height of the primary source while the latter depends on the inclination angle of the observer. Thus the strength of the line varies substantially across the disc. This effect may contribute to the observed steeper emissivity.
arXiv comment34 pages, 17 figures, RAGtime 12 - workshop on black holes and neutron stars, 15-17 September 2010, Opava, Czech Republic
References in corpus (16)
- A light bending model for the X-ray temporal and spectral properties of accreting black holes
- Irradiation of an Accretion Disc by a Jet: General Properties and Implications for Spin Measurements of Black Holes
- A long hard look at MCG-6-30-15 with XMM-Newton
- XMM-EPIC observation of MCG-6-30-15: Direct evidence for the extraction of energy from aspinning black hole?
- A rapidly spinning supermassive black hole at the centre of NGC 1365
- An extended scheme for fitting X-ray data with accretion disk spectra in the strong gravity regime
- Aborted jets and the X-ray emission of radio-quiet AGNs
- 1H0707-495 in 2011: An X-ray source within a gravitational radius of the event horizon
- General relativistic modelling of the negative reverberation X-ray time delays in AGN
- Long XMM observation of the Narrow-Line Seyfert 1 galaxy IRAS13224-3809: rapid variability, high spin and a soft lag
- On the determination of the spin and disc truncation of accreting black holes using X-ray reflection
- A two-component ionized reflection model of MCG--6-30-15
- Role of emission angular directionality in spin determination of accreting black holes with broad iron line
- The hard X-ray spectrum of NGC 1365: scattered light, not black hole spin
- Broad iron lines in neutrons stars: dynamical broadening or wind scattering?
- A code for optically thick and hot photoionized media