XIV Advanced School on Astrophysics Topic III: Observations of the Accretion Disks of Black Holes and Neutron Stars Ron Remillard Kavli Institute for Astrophysics and Space Research Massachusetts Institute of Technology

Topic III: General Outline III.1 Accretion States of Black Hole Binaries (I)  X-ray Astronomy and Identification of Accreting Binaries  Properties of Compact Objects and Accretion Disks  Different X-ray States in Black Hole Binaries  Thermal State: Thermal Radiation from the Accretion Disk III.2 Accretion States of Black Hole Binaries (II)  Observations of the Black Hole Hard State  Observations of the Steep Power Law State  Transients in Quiescence  X-ray Quasi-Periodic Oscillations in Black Hole Binaries III.3 Accretion Disks around Neutron Stars  Timing Properties of Accreting Neutron Stars  Observations of Atoll Type Sources  New Interpretations for Z Type Sources

III.1 Accretion States of Black Hole Binaries (I)  Introduction to X-ray Binary Systems Context for X-ray Astronomy Classifications of X-ray Binaries  Black Holes, Neutron Stars, & Accretion Disks Physical Properties Measurement Techniques  X-ray States of Black Hole Binaries Spectral/Timing Evolution of Accreting Black Holes Illustrations of Black Hole X-ray States  Thermal State: Hot Accretion Disk Expectations and Definition of the Thermal State Building the Paradigm for the Thermal State

X-ray Photons Wien’s Displacement Law (1893) Angstroms (wavelength ( ) of max. energy flux in  ( )) is very hot ! T = 5 x 10 7 o K / max (Angstroms) Wilhelm Carl Werner Otto Fritz Franz Wien X-rays: Photons Angstroms  Energies 20-1 keV  Thermal Equivalent kT = 4 to 80 million o K  Heating mechanisms  non-thermal processes synchrotron radiation (high energy e- in B field) inverse Compton (photon upscattered by high energy e-)

Window for Astrophysics from Space Photon transmission through the Galaxy X-rays: recover long-distance view at E > 1 keV

X-ray Telescopes in Space Chandra (NASA Great Observatory) Rossi X-ray Timing Explorer (NASA) XMM-Newton (European Space Agency) MIRAX (small mission planned by Brazil)

Brightest X-ray Sources (10 to Crab) Milky Way Sources primary X-spectrum Accreting Neutron Stars Atoll- and Z-sources thermal ; non-thermal hard state Accretion-powered Pulsarsnon-thermal Isolated Pulsars mixed types Accreting Black Holes thermal + non-thermal states Supernova Remnants thermal (shocks) Stellar Coronae thermal (B instability) Accreting White Dwarfs thermal Extragalactic Active Galactic Nuclei non-thermal (hard state) Blazars non-thermal (jets) Clusters of Galaxies thermal (bremsstrahlung) _____________ 1.0 Crab ~ 2.4x10 -8 erg cm -2 s -1 at 2-10 keV

Brightest X-ray Sources (10 to Crab) Milky Way Sources primary X-spectrumaccretion disk Accreting Neutron Stars Atoll- and Z-sources thermal ; non-thermal hard state yes Accretion-powered Pulsarsnon-thermal Isolated pulsars mixed types Accreting Black Holes thermal + non-thermal states yes Supernova Remnants thermal (shocks) Stellar Coronae thermal (B instability) Accreting White Dwarfs thermal yes Extragalactic Active Galactic Nuclei non-thermal (hard state) yes Blazars non-thermal (jets) yes Clusters of Galaxies thermal (bremsstrahlung) _____________ 1.0 Crab ~ 2.4x10 -8 erg cm -2 s -1 at 2-10 keV

Binary Evolution for Accreting Compact Objects Scenario 1: Roche Lobe overflow More massive star dies first Binary separation can shrink (magnetic braking and/or grav. radiation) Companion may evolve and grow Common for Low-Mass (Companion) X-ray Binaries (LMXB) Scenario 2: Stellar Wind Accretion More massive star dies first Stellar wind captured (with possible inner accretion disk) Common for High-Mass (Companion) X-ray Binaries (HMXB)

Properties of Black Holes mass: M x Spin parameter: a * = cJ / GM x 2 (J = angular momentum ; dimensionless 0 < a * < 1 ; E rot < 0.29 M) charge: assume Q x = 0 (local plasma prevents charge buildup) event horizon ! (math. surface of ‘no escape’) (see Shapiro & Teukolsky 1983; Narayan 2004) Can spin be measured? Will quantitative, GR-based astrophysics be successful? Accretion disk observations / accretion theory are the primary tools!

Measuring Masses of Compact Objects Dynamical study: compact object x and companion star c (for binary period, P, and inclination angle, i ) Kepler’s 3 rd Law: 4  2 (a x + a c ) 3 = GP 2 (M x + M c ) center of mass:M x a x = M c a c radial velocity amplitude K c = 2  a c sin i P -1 “Mass Function”: f(M) = P K 3 / 2  G = M x sin 3 (i) / (1 + M c / M x ) 2 < M x Techniques to infer i and estimate M c /M x (see references)  M x

Compact Object Mass Neutron Star Limit: 3 M o (dP/d  ) 0.5 < c Rhoades & Ruffini 1974 Chitre & Hartle 1976 Kalogera & Baym 1996 Black Holes (BH) M x = 4-20 M o Neutron Stars (NS) (X-ray & radio pulsars) M x ~ 1.4 M o

Black Holes in the Milky Way 18 BHBs in Milky Way 16 fairly well constrained  (Jerry Orosz) Scaled, tilted, and colored for surface temp. of companion star.

Identifications of X-ray Binaries NS Binary: X-ray Bursts or Coherent X-ray Pulsations NS Candidates: resemble NSBs in spectral & timing properties (limited info.) BH Binary: Mass > 3 M o from binary analyses ; no NS properties BH Candidate: BHB X-ray properties + no pulsations + no X-ray bursts Dynamical BHBs BH Candidates Milky Way18 27 LMC 2 0 nearby galaxies 3 (e.g., M33-X7) (? many ULXs) total ? Transients ?

Accretion Disks and the Inner Disk Boundary Keplerian orbits for accreting m E(r)= U+K = 0.5 U(r) = -0.5 G M x m r -1 Particle dE/dr = 0.5 G M x m r -2  L(r) ~ d (dE/dr) = 0.5  G M x m r -2 dt L(r)  2  r dr  T 4  T(r)  r -3/4 Real physical model (and MHD simulations): transport & conserve angular momentum; outflow?, rad. efficiency (  ) 3-D geometry (disk thickness, hydrostatic eq., radiative transfer) B-fields and instabilities GR effects (Innermost Stable Circular Orbit, grav. redshift, beaming)

Accretion onto Compact Objects Compact Object M o ; GMmR -1 / mc 2 Boundary Condition white dwarf ; crash on surface neutron star ; ~ crash on surface black hole 4-20 ; ~30 a ~0.5 event horizon BH accretion disk ~60 a ~0.2 innermost stable ( a for 10M o, a* = 0.5) circular orbit (ISCO) Milky Way Today: BHs ; ~10 9 NSs ; > WDs (Timmes, Woosley & Weaver 1996; Adams and Laughlin 1996)

Black Holes: Innermost Stable Circular Orbit (ISCO) BH spin a * : ISCO (R g / GM x /c 2 ): Neutron Stars Inner Accretion Disk (? R NS < R ISCO ?) NS Surface  Boundary Layer (2 nd heat source) NS Spin (can influence bounday layer physics) Magnetic Field Affects (Alfven Radius; control of inner accretion flow ; accretion focus at polar cap  pulsars) Inner Disk Boundary for Accretion Disks

Black Hole X-ray Transient (or ‘X-ray Nova’) GRO J First known outbursts: ; (  ) ; 2005 Dynamical black hole binary 6.3 (   0.5) M o Relativistic Jets in 1994 ~Radio-quiet, , 2005

Black Hole X-ray Transient GRO J  Different X-ray States

Illustrating 3 BH States of Active Accretion Energy spectra Power density spectra State physical picture  steep power law Disk + ??  thermal  hard state Energy (keV) Frequency (Hz)

Illustrating 3 BH States of Active Accretion Energy spectra Power density spectra State physical picture  steep power law Disk + ??  thermal  hard state Energy (keV) Frequency (Hz)

Time Series of Accretion States GRO J outburst Thermal x Hard (jet)  Steep Power Law  Intermediate O

Time Series of Accretion States XTEJ M x = M o Thermal x Hard (jet)   Steep Power Law  Intermediate O

Thermal State of Black Hole Binaries 1.Thermal State: radiant heat of the inner accretion disk disk fraction (2-20 keV) in energy spectrum: f disk > 75% ; power continuum (integrated Hz): rms < ; no quasi-periodic oscillations (QPOs): a max < 0.5%

Thermal State Paradigm Theory: Hot gas in thin disk + viscous dissipation Rel. MHD: Plasma + Magneto-Rotational Instability  Thermal radiation ; weakly magnetized disk T(r)  r -p ; p ~ 0.7 (Kubota et al 2005) (GR tweak of p=0.75) Disk blackbody shape? Disk blackbody energetics? Kubota & Done 2004; Gierlinski & Done 2004

Other Measures of Disk Structure Disk Structure Changes in Other States? GX339-4 Relativistic Fe line e.g. Miller et al. 2004; but see Merloni & Fabian 2003

Emissivity vs. Radius in the Accretion Disk GR Applications for Thermal State Shakura & Sunyaev 1973; Makishima et al. 1986;Page & Thorne 1974; Zhang, Cui, & Chen 1997 Gierlinski et al. 2001; Li et al. 2005

Relativistic Accretion Disk: Spectral Models GR Applications for Thermal State e.g. kerrbb in xspec Li et al. 2005; Davis et al Integrate over disk and B (T) Correct for GR effects (grav-z, Doppler, grav-focusing) Correct for radiative transfer

Thermal state  BH spin Analyses of thermal state observations with new GR-disk models  quantitative measures of a *  Narayan Lecture (tomorrow)

Method Application Comments Images impulsive BJB jets two cases (Chandra) Spectrum Model Continuum accretion disk BH: infer a * if known M x ; d Model Hard X-rays hot corona / Comptonization two types: (1) jet ; (2) ??? Spectral Lines BH: broad Fe K-  (6.4 keV) corona fluoresces inner disk emission profile  M x ; a * ‘’ high-ioniz. absorption lines seen in a few BHs variable, magnetized disk? ‘’ redshifted absorption line 1 NS?: surface grav. redshift Appendix: Tools for X-ray Data Analysis

Method Application Comments Timing Period Search NS: X-ray Pulsars several types; measure dP/dt and pulse-profiles(E) ‘’ NS or BH binary orbits wind-caused for HMXB some LMXB eclipsers, dippers ‘’ Long-term Periods precessing disks ; ? slow waves in dM/dt ? Quasi-Period Oscillations BH and NS rich in detail low ( Hz) common in some states high ( Hz) NS: var. ; BH steady harmonics very slow (10 -6 to Hz) some BH: disk instability cycles Appendix: Tools for X-ray Data Analysis

MethodApplication Comments Timing Aperiodic Phenoma ‘’Type I X-ray Bursts in NS thermonucl. explosions on surface ID as NS ; oscillations  spin ; infer distance ; physical models improving ‘’Type II X-ray Bursts two NS cases ; cause ?? ‘’Superbursts (many hours) C detonation in subsurface ? Probe NS interiors ‘’Giant flares in Magnetars ? crust shifts + B reconnection Progress?: coordinated timing / spectral analyses Appendix: Tools for X-ray Data Analysis

References: Reviews “Compact Stellar X-ray Sources”, eds. Lewin & van der Klis (2006) ; 16 chapters; some on ‘astro-ph’ preprint server: Overview of DiscoveryPsaltis astro-ph/ Rapid X-ray Variability van der Klis astro-ph/ X-ray BurstsStrohmayer & Bildsten astro-ph/ Black Hole BinariesMcClintock & Remillard astro-ph/ Optical ObservationsCharles & Coe astro-ph/ Isolated Neutron StarsKaspi, Roberts, & Harding astro-ph/ JetsFender astro-ph/ Accretion TheoryKing astro-ph/ MagnetarsWood & Thompson astro-ph/ Other Reviews: Narayan 2004, “Black Hole Event Horizon”, PThPS, 155, 263 Remillard & McClintock 2006, "X-Ray Properties of Black-Hole Binaries", ARAA, 44, 49 Done. Gierlinski, & Kubota 2007, “Modelling the behaviour of accretion flows in X-ray binaries”, A&A Reviews, 15, 1

References Other references.: Most are in ARAA, 44, 49 or in McClintock & Remillard 2006 (previous slide) Additional References: Adams and Laughlin 1996, ApJ, 468, 576 Done & Gierlinski 2003, MNRAS, 342, 1041 Gierlinski & Done 2004, MNRAS, 347, 885 Kubota & Done 2004, MNRAS, 353, 980 Timmes, Woosley, & Weaver 1996, ApJ, 457, 834 Power Density Spectra and deadtime corrections: Leahy et al. 1983, ApJ, 266, 160 Zhang et al. 1995, ApJ, 449, 930 Dennis Wei undergrad thesis (MIT; 2006):