Black holes and accretion flows Chris Done University of Durham

Aya Kubota Marek Gierlinski Nick Schurch Matt Middleton Jeanette Gladstone

Strong gravity Black holes: extreme spacetime curvature Test Einsteins GR - event horizon, last stable orbit….. The thing about a black hole, its main distinguishing feature is, its black. And the thing about space, your basic space colour is its black. So how are you supposed to see them? (Red Dwarf) RsRs

Accretion Accreting BH: huge X-ray luminosity close to event horizon R s Emission from region of strong spacetime curvature Observational constraints on strong gravity if we can understand accretion!

Appearance of BH should depend only on mass and spin (black holes have no hair!) Plus mass accretion rate, giving observed luminosity L Maximum luminosity ~L Edd where radiation pressure blows further infalling material away Get rid of most mass dependance as accretion flow should scale with L/L Edd M  : Quasars (?) M  : ULX 3-20 M  : Galactic black holes Black holes

Huge amounts of data Timescales ms – year (observable!) hours – 10 8 years in quasars Observational template of accretion flow as a function of L/L Edd onto ~10 M  BH Comparison sample of NS: 1.4 M  objects Galactic Binary systems 7 years

Einstein BH: event horizon and last stable orbit R lso ~3R s – gravity stronger than Newtonian Neutron stars. R~3R s so gravitational potential for accretion flow the same. Look at same L/L Edd for accretion flow – difference reveals presence/absence of surface ie existance of event horizon! Event horizon

Differential Keplerian rotation Viscosity B: gravity  heat Thermal emission: L = A  T 4 Temperature increases inwards GR last stable orbit gives minimum radius R lso - depends on spin 3  0.5 R s (a = 0  1) For a=0 and L~L Edd T max is 1 keV (10 7 K) for 10 M  10 eV (10 5 K) for 10 8 M  big black holes luminosity scales with mass but area scales with mass 2 so T goes down with mass! Maximum spin T max is 3x higher Spectra of accretion flow: disc Log Log f( 

Pick ONLY ones that look like a disc! L/L Edd  T 4 max (Ebisawa et al 1993; Kubota et al 1999; 2001) Constant size scale – last stable orbit!! Proportionality constant gives a measure R lso i.e. spin Consistent with low to moderate spin not extreme spin nor extreme versions of higher dimensional gravity - braneworlds (Gregory, Whisker, Beckwith & Done 2004) Gierlinski & Done 2003 Disc spectra: last stable orbit

Bewildering variety of spectra from single object Underlying pattern High L/L Edd : soft spectrum, peaks at kT max often disc- like, plus tail Lower L/L Edd : hard spectrum, peaks at high energies, not like a disc Gierlinski & Done 2003 But rest are not simple…

Disc models assumed thermal plasma – not true at low L/L Edd Instead: hot, optically thin, geometrically thick inner flow replacing the inner disc (Shapiro et al. 1976; Narayan & Yi 1995) Hot electrons Compton upscatter photons from outer cool disc Few seed photons, so spectrum is hard Jet from large scale height flow Accretion flows without discs Log Log f( 

Disc models assumed thermal plasma – not true at low L/L Edd Instead: hot, optically thin, geometrically thick inner flow replacing the inner disc (Shapiro et al. 1976; Narayan & Yi 1995) Hot electrons Compton upscatter photons from outer cool disc Few seed photons, so spectrum is hard Jet from large scale height flow Accretion flows without discs Log Log f( 

Disc models assumed thermal plasma – not true at low L/L Edd Instead: hot, optically thin, geometrically thick inner flow replacing the inner disc (Shapiro et al. 1976; Narayan & Yi 1995) Hot electrons Compton upscatter photons from outer cool disc Few seed photons, so spectrum is hard Jet from large scale height flow collapse of flow=collapse of jet Accretion flows without discs Log Log f( 

Disc models assumed thermal plasma – not true at low L/L Edd Instead: hot, optically thin, geometrically thick inner flow replacing the inner disc (Shapiro et al. 1976; Narayan & Yi 1995) Hot electrons Compton upscatter photons from outer cool disc Few seed photons, so spectrum is hard Jet from large scale height flow collapse of flow=collapse of jet Accretion flows without discs Log Log f( 

Qualitative and quantitative models: geometry Log Log f(  Log Log f(  Hard (low L/L Edd ) Soft (high L/L Edd ) Done & Gierliński 2004

Observed GBH spectra Truncated disc  R lso qualitative and quantitative RXTE archive of many GBH Same spectral evolution < L/L Edd < 1 Done & Gierliński  )  3-6.4)  )

LS VHS HS US Hard (low L/L Edd ) Soft (high L/L Edd ) Lh/LsLh/Ls 1

Scale up to AGN/QSOs Same accretion flow onto higher mass black hole (?) Spectral/jet states in AGN with L/L Edd T max  M -1/4 – disc emission in UV, not X-ray Magorrian-Gebhardt relation gives BH mass!! Black hole mass Stellar system mass

VHS HS US Hard (low L/L Edd ) Soft (high L/L Edd ) Done & Gierliński 2005 LS

Radio IR Opt UV X AGN - complex environment Log f RL QSO ’ s RQ QSO ’ s Cold absorption from torus along equatorial plane: unified schemes for AGN…BUT BHB say AGN not all the same even underneath: L/L Edd

Conclusions Test GR - X-rays from accreting black holes produced in regions of strong gravity Event horizon (compare to NS) Last stable orbit (ONLY simple disc spectra) L  T 4 max Corrections to GR from proper gravity must be smallish Accretion flow NOT always simple disc – X-ray tail! Models of accretion flow and jet changing with L/L Edd Apply to AGN – spectrum and jet and wind from disc will change with L/L Edd – feedback controls galaxy formation in Universe as a whole ASTROPHYSICS  PHYSICS