Black Hole Accretion
Theoretical Limits And Observational Implications
Black Hole Accretion
Theoretical Limits And Observational Implications
Dominikus Heinzeller
Institute for Theoretical AstrophysicsCenter for Astronomy Heidelberg
Albert-Ueberle-Str. 2, 69120 Heidelberg
Dominikus Heinzeller
Institute for Theoretical AstrophysicsCenter for Astronomy Heidelberg
Albert-Ueberle-Str. 2, 69120 Heidelberg
[email protected] Credit: Michael Owen, John Blondin
slide 2D. Heinzeller: Black Hole Accretion; IAU 2006, 08/23/2006
Outline
1. Black hole accretion and the Eddington limit
2. Spectral energy distribution of super-Eddington flows
3. Conclusions
In collaboration with W.J. Duschl, S. Mineshige, K. Ohsuga
Supported by:
Outline
Black holeaccretion
SED of super-Eddington flows
Conclusionsand outlook
slide 3D. Heinzeller: Black Hole Accretion; IAU 2006, 08/23/2006
Classical Eddington limit
• global upper limit for the luminosity of a star• spherical approximation often used in accretion discs:
rF
gF
• spherical symmetry
• homogeneous
• isotropic radiation
• no relativistic effects
• Thomson scattering
• no gas pressure
effT
r g E
4 + = 0 =
cGMF F L
38 8disc
erg1.2 10 2.6 10
s aM M
L m M m mM
Outline
Black holeaccretion
SED of super-Eddington flows
Conclusionsand outlook
slide 4D. Heinzeller: Black Hole Accretion; IAU 2006, 08/23/2006
Contradictions
• cosmology: SMBHs in the early universeaccretion scenarios require super-Eddington accretion
• observation of super-Eddington luminosities: ULXs– sub-Eddington IMBHs?
too hot accretion disc problem– super-Eddington stellar mass BHs?
Current and previous work:• modification of global classical Eddington limit• local deviations
– leaky discs (Begelman 2002)– critical accretion discs (Fukue 2000, 2004)
E10L L
Outline
Black holeaccretion
SED of super-Eddington flows
Conclusionsand outlook
slide 5D. Heinzeller: Black Hole Accretion; IAU 2006, 08/23/2006
Local Eddington limit in discs
• local Eddington limit for radial and vertical direction
• thin -discs (Shakura & Sunjaev 1973)• slim discs: advection (Abramowicz et al. 1980/1988)• Thomson scattering and interpolated opacities
(Gail, priv comm.)
• spherical symmetry
• homogeneous
• isotropic radiation
• no relativistic effects
• Thomson scattering
• no gas pressure
effT
??
rF
gF gFcF
r,oF r,iF
Outline
Black holeaccretion
SED of super-Eddington flows
Conclusionsand outlook
slide 6D. Heinzeller: Black Hole Accretion; IAU 2006, 08/23/2006
Local Eddington limit in discs
• radial upper limit on vertical upper limit• • unimportant
for high (advection),otherwise crucial
• inner boundary?(here: torque-free)
• slim disc, :
while
M
Vertical Eddington limit
BH
7i
10
8.86 10 cm
=0.1
M M
s
crit E/M M
i/s s
1 2critM s
critM
3crit E/ 1 10M M
E/ 1 20L L
/ 1h s
Outline
Black holeaccretion
SED of super-Eddington flows
Conclusionsand outlook
slide 7D. Heinzeller: Black Hole Accretion; IAU 2006, 08/23/2006
SED of super-Eddington flows
• based on 2D RHD simulations (Ohsuga et al. 2005)– high accretion rates – energy transport via radiation and advection– consideration for photon trapping
• observer at inclination • parallel line of sight calculation of radiative
transfer– relativistic
effects– electron
scattering– -dependent
ff-absorption
0 /2
3E BH( 10 , 10 )M M M M
Outline
Black holeaccretion
SED of super-Eddington flows
Conclusionsand outlook
slide 8D. Heinzeller: Black Hole Accretion; IAU 2006, 08/23/2006
SED of super-Eddington flows
[erg/s]L
[eV]E
BlackbodyBlackbodytemperaturetemperaturefit to peak:fit to peak:
6
6
5
T(0)=
1.5 10 K
T( /4)
1.2 10 K
( /2)
9.4 10 K
T
Outline
Black holeaccretion
SED of super-Eddington flows
Conclusionsand outlook
slide 9D. Heinzeller: Black Hole Accretion; IAU 2006, 08/23/2006
SED of super-Eddington flows
mild relativistic beaming mild relativistic beaming
Outline
Black holeaccretion
SED of super-Eddington flows
Conclusionsand outlook
Blackbodytemperaturefit to peak:
6
6
5
T(0)=
1.5 10 K
T( /4)
1.2 10 K
( /2)
9.4 10 K
T
slide 10D. Heinzeller: Black Hole Accretion; IAU 2006, 08/23/2006
Conclusions
Black hole accretion:• classical Eddington-limit not applicable in
discs– depends on disc model– varies with distance from central object– inner disc region/boundary decisive
• bottle-neck in inner disc region• super-Eddington accretion and luminosities
Spectral energy distribution:• modelling of disc and its environment
necessary for interpretation of spectra• mild relativistic beaming
– increased photon number for small – enhanced average photon energy– high temperatures
Influence onBH growth?
Outflows, jets?
Evidencefor IMBH?
NGC 4261Credit:R.M. Elowitz
Outline
Black holeaccretion
SED of super-Eddington flows
Conclusionsand outlook