measuring the spin of black holes
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Measuring the SPIN of Black Holes. Andy Fabian Institute of Astronomy University of Cambridge. Astrophysical Black Holes have only MASS and SPIN (like elementary particles, except BH can have any mass ). BLACK HOLES. Karl Schwarzschild. Roy Kerr. - PowerPoint PPT PresentationTRANSCRIPT
Measuring the SPIN of Black Holes
Andy FabianInstitute of Astronomy
University of Cambridge
Astrophysical Black Holes have only MASS and SPIN (like elementary particles, except BH
can have any mass )
BLACK HOLES
Karl Schwarzschild Roy Kerr
MASS can be measured over wide range of radii
but SPIN requires measuring properties at small radii
What effects are characteristic of small radii around a Black Hole?
Strong Gravity Effects
• Gravitational redshift
• Gravitational light bending
• Dragging of inertial frames in Kerr metric (ISCO depends on BH spin)
GPS GR=45microsec/day(or ~10km/day)
GRAVITATIONAL LIGHT BENDING
Information from spectra and variability
• X-ray ‘reflection’ gives important clues in the spectrum
• Variability timescales and spectral changes show different spectral components
Reflection from photoionized matter(Ross & Fabian 93, 05)
Also see Young+, Nayakshin+, Ballantyne+, Rozanska+, Dumont+
Schwarzschild
Kerr
Fabian+89, Laor 90… Dovciak+04;
Beckwith+Done05
Suzaku
Strength and behaviour of line implies GRAVITATIONAL LIGHT BENDING
MCG-6-30-15
Red wing due to large gravitational redshiftimplying BH rapidly
spinning
Lockman Hole800 ks XMM-Newton observation
Hasinger
Lockman Hole800 ks XMM-Newton observation
Hasinger
Streblyanskaya et al 2004
Assumption: measurements of rISCO determine (or constrain) a
Radius of innermost stable circular orbit-ISCO
Probing Black Hole Spin
Light bending model in Kerr spacetime
Miniutti et al 03; Miniutti & Fabian 04; earlier work by Martocchia, Matt+
see also Tsuebsuwong, Malzac+06
Armitage & Reynolds
SPIN also affects radiative efficiency of accretion, η
2
2
cML
McE
2
2
2
42.0
057.0
005.0
McE
McE
McE
Nuclear fusion
Black Hole Accretion
211105 McE TNT
Max spin BH accretion
Accretion makes massive black holes
2
1)1( cz
Soltan 82
Mean redshift Radiative efficiency
Light Mass density in BH
η > 0.1Observations
Much of the radiation originates within 6Rg
Accretion makes massive black holes
2
1)1( cz
Soltan 82
Mean redshift Radiative efficiency
Light Mass density in BH
η > 0.1Observations
Most Massive BH are rapidly spinning