Transcript Models of Comptonization P.O. Petrucci LAOG, Grenoble, France The Comptonization process

Models of Comptonization
P.O. Petrucci
LAOG, 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:
For non-stationnary electron:
Compton
Inverse Compton
Simbol-X meeting, 14-16 May 2007, Bologna, Italy
Thermal Comptonization
Tc, t
Comptonization on a thermal
plasma of electrons characterized
by a temp. T and optical depth τ
Hot phase
= corona
Tsoft Cold phase
= acc. disc
mean relative energy gain per collision
for E ≪ kT
for E ≳ kT
mean number of scatterings
Compton parameter
Simbol-X meeting, 14-16 May 2007, Bologna, Italy
Thermal Comptonization
Spectrum
(Beloborodov 1999,
Malzac et al. 2001)
(Courtesy: J. Malzac)
“spectral” degeneracy, different (kT, τ) giving
the same Γ
Simbol-X meeting, 14-16 May 2007, Bologna, Italy
Geometry dependence
Corona
Disc
Tc, t
Tsoft
Corona
Anisotropic
geom.
Isotropic
geom
Cold phase G(T
, t)
c
« Anisotropy break
»
Disc
First scattering
order
Corona
Simbol-X meeting, 14-16 May 2007, Bologna, Italy
~kTc
Geometry dependence
kT = 100 keV and τ = 0.5
kT = 100 keV and same Γ
Slab
Sphere
Cylinder
τ = 0.5
τ=1
τ = 0.7
“geometrical” degeneracy
Simbol-X meeting, 14-16 May 2007, Bologna, Italy
Radiative Balance
If the 2 phases are in radiative equilibrium, the
corona temperature and optical depth follow, for a
given geometry, a univocal relationship.
«Photon starved »
Optical depth
Sphere
Plan
Hemisphere
Theoretical predictions
for a passive disc
«Photon fed »
Ex: intrinsic disc emission
Temperature kT/mec
(Haardt & Maraschi 1991; Stern et al. 1995)
Simbol-X meeting, 14-16 May 2007, Bologna, Italy
Non-thermal Comptonizaton
For electron with large Lorentz factor
very efficient energy transfert
Comptonization by a non-thermal distribution of electrons
⇒
Simbol-X meeting, 14-16 May 2007, Bologna, Italy
Astrophysical Context
Present in all SIMBOL-X science cases !
AGNs (Thermal Comp. in Seyfert galaxies, nonthermal Comp. in Blazars)
Madgziarz et al. (1998)
Blue bump
« Soft excess »
Primary continuum:
cut–off power law
shape
« Secondary » components
- iron line
- hump peaking at 30 keV
Simbol-X meeting, 14-16 May 2007, Bologna, Italy
Astrophysical Context
Present in all SIMBOL-X science cases !
AGNs (Thermal Comp. in Seyfert galaxies, nonthermal Comp. in Blazars)
X-ray binaries (Thermal Comp. in the hard state,
non-thermal Comp. (?) in the Intermediate and Soft
Cyg X-1
states)
Hard State
Soft State
Zdziarski et al. (2002)
Simbol-X meeting, 14-16 May 2007, Bologna, Italy
Astrophysical Context
Present in all SIMBOL-X science cases !
AGNs (Thermal Comp. in Seyfert galaxies, nonthermal Comp. in Blazars)
X-ray binaries (Thermal Comp. in the hard state,
non-thermal Comp. (?) in the Intermediate and Soft
states)
X-ray background
Galaxy clusters
Supernovae remnants
GRBs
Simbol-X meeting, 14-16 May 2007, Bologna, Italy
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
Rem:
1 ks
5 ks
50 ks
This
can
be
complicated
reflection/absorption features
by
Simbol-X meeting, 14-16 May 2007, Bologna, Italy
complex
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”
long exposure…
degeneracy will require
Simbol-X meeting, 14-16 May 2007, Bologna, Italy
Spectral Variability
a few corona
crossing time
Coronal flare
Opt. depth
Corona crossing time
Disc flare
Temperature
Opt. depth
Opt. depth
Temperature
coronal
flare
initial
state
disc
flare
Temperature
Corona crossing time
Malzac & Jourdain (2000)
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 III
Bright 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, multiwavelength observations recommended. (CTA,
GLAST, HERSCHEL, ALMA, LOWFAR, WSO-UV,
...).
Simbol-X meeting, 14-16 May 2007, Bologna, Italy