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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 http://xte.mit.edu/~rr/XIVschool_III.1.ppt
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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
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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
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X-ray Photons Wien’s Displacement Law (1893) --- 10 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 0.6-12 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-)
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Window for Astrophysics from Space Photon transmission through the Galaxy X-rays: recover long-distance view at E > 1 keV
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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)
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Brightest X-ray Sources (10 to 10 -3 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
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Brightest X-ray Sources (10 to 10 -3 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
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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)
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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!
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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
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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
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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.
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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) --------------------- ----------------------------- ---------------------------- total23 27 + ? Transients 17 25 + ?
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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)
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Accretion onto Compact Objects Compact Object M o ; GMmR -1 / mc 2 Boundary Condition white dwarf 0.4-1.3 ; 6000 10 -4 crash on surface neutron star 1.4-2.0 ; ~10 0.2 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: 10 8 -10 9 BHs ; ~10 9 NSs ; > 10 10 WDs (Timmes, Woosley & Weaver 1996; Adams and Laughlin 1996)
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Black Holes: Innermost Stable Circular Orbit (ISCO) BH spin a * : 0.0 0.5 0.75 0.9 0.98 1.0 ----------------------------------------------------- ISCO (R g / GM x /c 2 ): 6.0 4.2 3.2 2.3 1.6 1.0 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
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Black Hole X-ray Transient (or ‘X-ray Nova’) GRO J1655-40 First known outbursts: 1994-95; ( ) 1996-97; 2005 Dynamical black hole binary 6.3 ( 0.5) M o Relativistic Jets in 1994 ~Radio-quiet, 1996-97, 2005
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Black Hole X-ray Transient GRO J1655-40 Different X-ray States
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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)
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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)
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Time Series of Accretion States GRO J1655-40 1996-97 outburst Thermal x Hard (jet) Steep Power Law Intermediate O
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Time Series of Accretion States XTEJ1550-564 M x = 9.6 + 1.2 M o Thermal x Hard (jet) Steep Power Law Intermediate O
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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 0.1-10 Hz): rms < 0.075 ; no quasi-periodic oscillations (QPOs): a max < 0.5%
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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
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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
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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
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Relativistic Accretion Disk: Spectral Models GR Applications for Thermal State e.g. kerrbb in xspec Li et al. 2005; Davis et al. 2005 Integrate over disk and B (T) Correct for GR effects (grav-z, Doppler, grav-focusing) Correct for radiative transfer
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Thermal state BH spin Analyses of thermal state observations with new GR-disk models quantitative measures of a * Narayan Lecture (tomorrow)
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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
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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 (0.1-50 Hz) common in some states high (50-1300 Hz) NS: var. ; BH steady harmonics very slow (10 -6 to 10 -2 Hz) some BH: disk instability cycles Appendix: Tools for X-ray Data Analysis
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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
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References: Reviews “Compact Stellar X-ray Sources”, eds. Lewin & van der Klis (2006) ; 16 chapters; some on ‘astro-ph’ preprint server: http://xxx.lanl.gov/formhttp://xxx.lanl.gov/form Overview of DiscoveryPsaltis astro-ph/0410536 Rapid X-ray Variability van der Klis astro-ph/0410551 X-ray BurstsStrohmayer & Bildsten astro-ph/0301544 Black Hole BinariesMcClintock & Remillard astro-ph/0306213 Optical ObservationsCharles & Coe astro-ph/0308020 Isolated Neutron StarsKaspi, Roberts, & Harding astro-ph/0402136 JetsFender astro-ph/0303339 Accretion TheoryKing astro-ph/0301118 MagnetarsWood & Thompson astro-ph/0406133 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
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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): http://xte.mit.edu/~rr/dwei_thesis.pdf
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