The X-ray mirrors Giovanni Miniutti Institute of Astronomy, University of Cambridge SIMBOL-X May -Bologna

Accreting BHs: main spectral components Soft excess Power law X-ray reflection e.g. Fabian & Miniutti (CUP, in press) all modified by absorption (Galactic and/or intrinsic)

The X-ray reflection spectrum PLC RDC Reynolds 96

X-ray reflection: relativistic effects Fe K intensity Doppler shifts relativistic beaming gravitational redshift gravitational light bending e.g. Fabian, Rees, Stella & White 89

X-ray reflection: two mirrors The same reflection model in the rest frame (e.g. from distant matter) and as observed if reflected from the inner accretion disc

X-ray reflection: two mirrors disc torus The observational challenge is that the two reflection spectra are ususally superimposed and it becomes difficult to disentangle

X-ray reflection: two mirrors In principle, the contribution from the distant (torus) and closeby (disc) mirrors can be disentangled via the Fe K line profile However, this is possible only in a limited number of sources mainly because the broad component is often undetected which suggests either that the broad line is absent (e.g. disc too ionized) or that the broad line it is lost into the continuum In typical exposures with limited band pass (e.g. XMM, Chandra) a typical disc reflection component and broad Fe line are indeed very easy to miss This means that we are still unable to understand the nature geometry and physical state of the inner flow in a large population via Fe line diagnostics

X-ray reflection: observational bias

A typical 40 ks XMM exposure assuming the composite model but the best-fitting model …. … does not have any disc reflection component ! … too difficult to detect.

X-ray reflection: observational bias Thus, a typical X-ray disc reflection spectrum (A fe ~1; R~1) is challenging to detect in a typical ~40ks XMM observation The best disc reflection examples are associated with peculiar conditions, in particular: Fe overabundance Higher (than expected) reflection fraction which suggests that the relatively low statistics of secure broad Fe lines and disc reflection spectra is affected by an observational bias A larger effective area at ~6keV is important (e.g. XEUS) to disentangle between narrow and broad Fe line components, but extending the band pass to higher energies is a fundamental and crucial step to have a better understanding of the inner accretion flow

The best case so far Tanaka et al 95 Fabian et al 02

The Suzaku mission Observed during the SWG phase (about 350 ks) Miniutti et al PASJ 07

The Suzaku mission Observed during the SWG phase (about 350 ks) Miniutti et al PASJ 07 (c) A. Bamba

The Suzaku mission

Prospects for SIMBOL-X Simultaneous data in the Fe K band and > 10keV have shown that sensitivity in a wide band pass is able to disentangle the models and reveal with little/no ambiguity not only the presence of disc reflection but also its strength, reflection fraction, ionization state, Fe abundance … The SIMBOL-X mission will take these studies to a new level allowing us to perform statistical studies which will not be limited to the best cases in which peculiar conditions arise (MCG has A Fe ~2-3 and R~2-3) This will open up a new parameter space to study the geometry and physical state of the inner accretion flow in AGN and X-ray binaries

Prospects for SIMBOL-X

Conclusions The simultaneous presence of (at least) 2 X-ray mirrors distant (torus) closeby (disc) Makes it difficult to interpret the spewctral shape in the Fe K band Present observatories do not have enough effective area in the Fe K band broadband sensitivity (especially > 10keV) and only reveal disc reflection in a limited number of sources ( obs bias? ) The advent of Suzaku already showed the potential of > 10keV sensitivity An advanced mission such SIMBOL-X will be able to unveil the nature of the inner accretion flow in a much large population