Models of Comptonization
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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.

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Models of Comptonization

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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


The comptonization process

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:


Thermal comptonization

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


Thermal comptonization spectrum

➥ “spectral” degeneracy, different (kT, τ) giving the same Γ

Thermal Comptonization Spectrum

(Beloborodov 1999, Malzac et al. 2001)

(Courtesy: J. Malzac)


Geometry dependence

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 dependence1

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


Radiative balance

«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

Non-thermal Comptonizaton

  • For electron with large Lorentz factor

  • Comptonization by a non-thermal distribution of electrons

➥ very efficient energy transfert


Astrophysical context

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 context1

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 context2

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

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 i1

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

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

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

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

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, ...).


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