Models of Comptonization
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This overview by P.O. Petrucci from LAOG, Grenoble, focuses on the Comptonization process, critical for understanding the interactions between photons and electrons in astrophysical contexts, such as AGNs, X-ray binaries, and supernova remnants. The presentation discusses thermal and non-thermal Comptonization, highlighting advances expected with SIMBOL-X. It examines the intricacies of photon energy gain, the influence of electron distributions, and various geometrical configurations. The insights gained will inform future observational strategies and theoretical frameworks in astrophysics.
Models of Comptonization
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Presentation Transcript
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, ...).
