Models of Comptonization

Models of Comptonization Models of Comptonization P.O. Petrucci LAOG, Grenoble, France P.O. Petrucci LAOG, Grenoble, France • The Comptonization process • Astrophysical applications • The advances expected with simbol-X

For non-stationnary electron: Compton Inverse Compton The Comptonization Process • Discovered by A.H. Compton in 1923 • gain/loss of energy of a photon after collision with an electron If electron at rest:

Tsoft Thermal Comptonization Hot phase = corona Tc, t Comptonization on a thermal plasma of electrons characterized by a temp. T and optical depth τ Cold phase = acc. disc • mean relative energy gain per collision for E ≪ kT for E ≳ kT • mean number of scatterings ➨ Compton parameter

➥ “spectral” degeneracy, different (kT, τ) giving the same Γ Thermal Comptonization Spectrum (Beloborodov 1999, Malzac et al. 2001) (Courtesy: J. Malzac)

Corona Disc Anisotropic geom. Cold phase « Anisotropy break » Tsoft Corona Geometry dependence Isotropic geom Corona Tc, t G(Tc, t) Disc First scattering order ~kTc

Geometry dependence kT = 100 keV and τ = 0.5 kT = 100 keV and same Γ Slab Sphere τ = 0.5 τ = 1 Cylinder τ = 0.7 ➥ “geometrical” degeneracy

«Photon starved » Sphere Optical depth Plan Hemisphere «Photon fed » Theoretical predictions for a passive disc Temperature kT/mec Ex: intrinsic disc emission Radiative Balance If the 2 phases are in radiative equilibrium, the corona temperature and optical depth follow, for a given geometry, a univocal relationship. (Haardt & Maraschi 1991; Stern et al. 1995)

Non-thermal Comptonizaton • For electron with large Lorentz factor • Comptonization by a non-thermal distribution of electrons ➥ very efficient energy transfert ⇒

Primary continuum: cut–off power law shape Blue bump « Soft excess » « Secondary » components - iron line - hump peaking at 30 keV Astrophysical Context Present in all SIMBOL-X science cases ! • AGNs (Thermal Comp. in Seyfert galaxies, non-thermal Comp. in Blazars) Madgziarz et al. (1998)

Astrophysical Context Present in all SIMBOL-X science cases ! • AGNs (Thermal Comp. in Seyfert galaxies, non-thermal Comp. in Blazars) • X-ray binaries (Thermal Comp. in the hard state, non-thermal Comp. (?) in the Intermediate and Soft states) Cyg X-1 Hard State Soft State Zdziarski et al. (2002)

Astrophysical Context Present in all SIMBOL-X science cases ! • AGNs (Thermal Comp. in Seyfert galaxies, non-thermal Comp. in Blazars) • X-ray background • Galaxy clusters • Supernovae remnants • GRBs • X-ray binaries (Thermal Comp. in the hard state, non-thermal Comp. (?) in the Intermediate and Soft states)

Simulation I NGC 5548, Seyfert galaxy L2-10 keV = 10-11 erg.s-1.cm-2 kTe ≈ 250 keV, τ ≈ 0.1 and R ≈ 1. Slab geometry. (Tsoft fixed) No spectral degeneracy any more with 50 ks 1 ks 5 ks 50 ks Rem: This can be complicated by complex reflection/absorption features

Simulation I NGC 5548, Seyfert galaxy L2-10 keV = 10-11 erg.s-1.cm-2 kTe ≈ 250 keV, τ ≈ 0.1 and R ≈ 1. Slab geometry. Both geometries agree with the data in the Simbol X energy range with exposures of 50 ks Slab Cylinder Breaking the “geometrical” degeneracy will require long exposure…

Spectral Variability a few corona crossing time Coronal flare coronal flare initial state Opt. depth Corona crossing time Disc flare disc flare Temperature Corona crossing time Malzac & Jourdain (2000)

Simulation II Cyg X-1, microquasar L2-10 keV = 10-9 erg.s-1.cm-2 kTe ≈ 100 keV, τ ≈ 1.7 and R ≈ 0.3 Texp= 500 s (see Malzac’s talk)

Simulation III Bright blazars spectra well determined in 1 ks ! Constrains on the Synchrotron Self-Compton process from multi-λ observations (see tomorrow’s talks)

What can we expect with SIMBOL-X? • Strong constrains on Thermal comptonization model (on dynamical time scale for AGNs, on very short time scale in XrBs) • This picture can be complicated by the presence of complex absorption/emission features • The broadest energy range is needed, multi-wavelength observations recommended. (CTA, GLAST, HERSCHEL, ALMA, LOWFAR, WSO-UV, ...).

Models of Comptonization