Simbol-X meeting, 14-16 May 2007, Bologna, Italy

Models of Comptonization

P.O. PetrucciLAOG, Grenoble, France

Models of Comptonization

P.O. PetrucciLAOG, Grenoble, France

The Comptonization process

Astrophysical applications

The advances expected with simbol-X

Simbol-X meeting, 14-16 May 2007, Bologna, Italy

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:

Compton

Inverse Compton

For non-stationnary electron:

Simbol-X meeting, 14-16 May 2007, Bologna, Italy

Thermal Comptonization

mean relative energy gain per collision

mean number of scatterings

➨ Compton parameter

for E ≪ kT

for E ≳ kT

Tsoft

Tc, Hot phase

= coronaComptonization on a thermal plasma of electrons characterized by a temp. T and optical depth τ

Cold phase= acc. disc

Simbol-X meeting, 14-16 May 2007, Bologna, Italy

Thermal Comptonization

Spectrum

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

(Courtesy: J. Malzac)

(Beloborodov 1999, Malzac et al. 2001)

Simbol-X meeting, 14-16 May 2007, Bologna, Italy

Geometry dependence

Tsoft

Tc, (T

c,

~kTc

Corona Isotropic geomCold phaseAnisotropic geom.

« Anisotropy break »

First scatteringorder

Corona

Corona

Disc

Disc

Simbol-X meeting, 14-16 May 2007, Bologna, Italy

Geometry dependence

kT = 100 keV and τ = 0.5 kT = 100 keV and same Γ

τ = 1τ = 0.5

τ = 0.7

Slab

Sphere

Cylinder

➥ “geometrical” degeneracy

Simbol-X meeting, 14-16 May 2007, Bologna, Italy

Radiative Balance

Op

tica

l dep

th

Temperature kT/mec

Plan Hemisphere

Sphere

If the 2 phases are in radiative equilibrium, the corona temperature and optical depth follow, for a given geometry, a univocal relationship.

Theoretical predictionsfor a passive disc

«Photon fed »

Ex: intrinsic disc emission

«Photon starved »

(Haardt & Maraschi 1991; Stern et al. 1995)

Simbol-X meeting, 14-16 May 2007, Bologna, Italy

Non-thermal Comptonizaton

Comptonization by a non-thermal distribution of electrons

For electron with large Lorentz factor

➥ very efficient energy transfert

⇒

Simbol-X meeting, 14-16 May 2007, Bologna, Italy

Astrophysical ContextPresent in all SIMBOL-X science cases !

AGNs (Thermal Comp. in Seyfert galaxies, non-thermal Comp. in Blazars)

« Soft excess »

« Secondary » components- iron line- hump peaking at 30 keV

Primary continuum: cut–off power law shape

Blue bump

Madgziarz et al. (1998)

Simbol-X meeting, 14-16 May 2007, Bologna, Italy

Astrophysical ContextPresent 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)

Simbol-X meeting, 14-16 May 2007, Bologna, Italy

Astrophysical Context

X-ray background

Galaxy clusters

Supernovae remnants

GRBs

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)

Simbol-X meeting, 14-16 May 2007, Bologna, Italy

Simulation I

No spectral degeneracy any more with 50 ks 1 ks

5 ks50 ksRem:

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)

This can be complicated by complex reflection/absorption features

Simbol-X meeting, 14-16 May 2007, Bologna, Italy

Simulation I

Breaking the “geometrical” degeneracy will require long exposure…

Slab

Cylinder

Both geometries agree with the data in the Simbol X energy range with exposures of 50 ks

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.

Simbol-X meeting, 14-16 May 2007, Bologna, Italy

Spectral Variability

Temperature

Opt. depth

Temperature

Opt. depth

Corona crossing time

Corona crossing time

disc flare

coronal flareinitial

state

a few coronacrossing time

Op

t. d

ep

th

Temperature

Malzac & Jourdain (2000)

Coronal flare

Disc flare

Simbol-X meeting, 14-16 May 2007, Bologna, Italy

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)

Simbol-X meeting, 14-16 May 2007, Bologna, Italy

Simulation IIIBright blazars spectra well determined in 1 ks !

Constrains on the Synchrotron Self-Compton process from multi-λ observations (see tomorrow’s talks)

Simbol-X meeting, 14-16 May 2007, Bologna, Italy

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, ...).