XIV Advanced School on Astrophysics

Topic III: Observations of the Accretion Disks of Black Holes and Neutron Stars

Ron RemillardKavli Institute for Astrophysics and Space ResearchMassachusetts Institute of Technology

http://xte.mit.edu/~rr/XIVschool_III.1.ppt

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) --- 10 Angstroms

(wavelength () of max. energy flux in ()) is very hot !

T = 5 x 107 oK / 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 oK 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 10-3 Crab)

Milky Way Sources primary X-spectrum

Accreting Neutron Stars Atoll- and Z-sources thermal ; non-thermal hard state Accretion-powered Pulsars non-thermalIsolated Pulsars mixed typesAccreting Black Holes thermal + non-thermal statesSupernova 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 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 Pulsars non-thermalIsolated pulsars mixed typesAccreting Black Holes thermal + non-thermal states yesSupernova Remnants thermal (shocks)

Stellar Coronae thermal (B instability)Accreting White Dwarfs thermal yes Extragalactic

Active Galactic Nuclei non-thermal (hard state) yesBlazars non-thermal (jets) yesClusters 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: Mx

Spin parameter: a* = cJ / GMx2

(J = angular momentum ; dimensionless 0 < a* < 1 ; Erot < 0.29 M)

charge: assume Qx = 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 objectx and companion starc

(for binary period, P, and inclination angle, i )

Kepler’s 3rd Law: 4 2 (ax + ac)3 = GP2 (Mx + Mc)

center of mass: Mx ax = Mc ac

radial velocity amplitude Kc = 2 ac sin i P-1

“Mass Function”: f(M) = P K3 / 2G = Mx sin3(i) / (1 + Mc/Mx)2 < Mx

Techniques to infer i and estimate Mc/Mx (see references) Mx

Compact Object Mass

Neutron Star Limit: 3 Mo

(dP/d)0.5 < cRhoades & Ruffini 1974

Chitre & Hartle 1976

Kalogera & Baym 1996

Black Holes (BH)

Mx = 4-20 Mo

Neutron Stars (NS)

(X-ray & radio pulsars)

Mx ~ 1.4 Mo

Black Holes in the Milky Way

18 BHBs in Milky Way

16 fairly well constrained

(Jerry Orosz)

Scaled, tilted, andcolored 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 Mo from binary analyses ; no NS properties

BH Candidate: BHB X-ray properties + no pulsations + no X-ray bursts

Dynamical BHBs BH Candidates

Milky Way 18 27

LMC 2 0

nearby galaxies 3 (e.g., M33-X7) (? many ULXs)--------------------- ----------------------------- ----------------------------

total 23 27 + ?

Transients 17 25 + ?

Accretion Disks and the Inner Disk Boundary

Keplerian orbits for accreting m

E(r)= U+K = 0.5 U(r) = -0.5 G Mx m r -1

Particle dE/dr = 0.5 G Mx m r -2

L(r) ~ d (dE/dr) = 0.5 G Mx m r -2

dt

L(r) 2r dr T4 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 Mo ; <Rkm> GMmR-1 / mc2 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 ; ~30a ~0.5 event horizon

BH accretion disk ~60a ~0.2 innermost stable(a for 10Mo, a* = 0.5) circular orbit (ISCO)

Milky Way Today: 108-109 BHs ; ~109 NSs ; > 1010 WDs (Timmes, Woosley & Weaver 1996; Adams and Laughlin 1996)

Black Holes: Innermost Stable Circular Orbit (ISCO)

BH spin a*: 0.0 0.5 0.75 0.9 0.98 1.0

-----------------------------------------------------

ISCO (Rg / GMx/c2): 6.0 4.2 3.2 2.3 1.6 1.0

Neutron Stars

Inner Accretion Disk (? RNS < RISCO ?)

NS Surface Boundary Layer (2nd 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 J1655-40

First known outbursts: 1994-95;() 1996-97; 2005

Dynamical black hole binary6.3 (0.5) Mo

Relativistic Jets in 1994~Radio-quiet, 1996-97, 2005

Black Hole X-ray Transient

GRO J1655-40

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 J1655-40

1996-97 outburst

Thermal x

Hard (jet)

Steep Power Law

Intermediate O

Time Series of Accretion States

XTEJ1550-564

Mx = 9.6 + 1.2 Mo

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: fdisk > 75% ;power continuum (integrated 0.1-10 Hz): rms < 0.075 ; no quasi-periodic oscillations (QPOs): amax < 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 1997Gierlinski et al. 2001; Li et al. 2005

Relativistic Accretion Disk: Spectral Models

GR Applications for Thermal State

e.g. kerrbb in xspecLi 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

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 Mx ; 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 Mx ; 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 (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

Method Application 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: http://xxx.lanl.gov/form

Overview of Discovery Psaltis astro-ph/0410536

Rapid X-ray Variability van der Klis astro-ph/0410551

X-ray Bursts Strohmayer & Bildsten astro-ph/0301544

Black Hole Binaries McClintock & Remillard astro-ph/0306213

Optical Observations Charles & Coe astro-ph/0308020

Isolated Neutron Stars Kaspi, Roberts, & Harding astro-ph/0402136

Jets Fender astro-ph/0303339

Accretion Theory King astro-ph/0301118

Magnetars Wood & 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

ReferencesOther 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