INPE%20Advanced%20Course%20on%20Compact%20Objects%20Course%20IV:%20Accretion%20Processes%20in%20Neutron%20Stars%20

1
INPE Advanced Course on Compact ObjectsCourse
IV Accretion Processes in Neutron Stars Black
Holes

• Ron Remillard
• Kavli Center for Astrophysics and Space Research
• Massachusetts Institute of Technology
• http//xte.mit.edu/rr/inpe_IV.1.ppt

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Course IV Outline

• 1. Basic Elements of X-ray Binary Systems
• 2. Different States of Black-Hole Binaries
• 3. Weakly Magnetized Neutron-Star Binaries
  (Atolls and Z sources)
• 4. Periodic Variability Orbits and Pulsars
• 5. Aperiodic Variability Bursts, Flares
  Instability Cycles

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IV.1 Basic Elements of X-ray Binary Systems

• Introduction
• X-ray Astronomy window to hot and violent
  universe
• Endpoints of Stellar Evolution
• Science Goals for Observations of X-ray Binaries
• Properties of Neutron Stars and Black Holes
• Physical Properties
• Mass Determinations
• Surveys of Different Types of Compact Objects
• Fundamentals of Accretion Physics
• The Accretion Disk
• Relativistic Disk Models for Black Holes
• Non-thermal Radiation Processes
• Questions for General Relativity

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X-ray Photons

• Wiens Displacement Law (1893)
• (wavelength (l) of max. energy flux in I(n))
  --- 2 keV is hot !
• T 5 x 107 oK / lmax (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 upscatter 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 gt 1 keV

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X-ray Telescopes in Space
Chandra (NASA Great Observatory)

• Mirrors (grazing incidence) gratings?
• vs. Collimators (metal baffles)
• Coded Masks (slit plate shadows)
• Spectrometers Semiconductors (Si)
• gas (Xe) CdZnTe pixels for hard-X

Rossi X-ray Timing Explorer (NASA)
XMM-Newton (European Space Agency
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Collapsed Remnants of Old Stars

• Initial Star Compact Object Support?
  Observed?
• lt 8 Mo white dwarf degenerate
  isolated binaries (0.4-1.3 Mo
  Earth-size) gas pressure cataclysmic
  variables
• 8-25 Mo neutron star strong
  nuclear force radio pulsars hot-
• (1.4-2.0 Mo R10 km)
  isolated X-ray pulsars X-ray
  bursters
• gt 25 Mo black hole no
  classical forces accreting binaries
• (3-16 Mo event horizon) quantum gravity?
  (X-ray sources)
• Milky Way Today 108-109 BHs 109 NSs gt
  1010 WDs
• (Timmes, Woosley Weaver 1996 Adams and
  Laughlin 1996)

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Collapsed Remnants of Old Stars

• Compact Object ltMogt ltRcmgt GMmR-1 / mc2
  Boundary
• white dwarf 0.6 6x108 10-4
  crash
• neutron star 1.4 106 0.2
  crash
• black hole 10 3x106 0.5
  event horizon

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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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Measuring Masses of Compact Objects

• Dynamical study compact objectx and companion
  starc
• (for binary period, P, and inclination angle, i )
• Keplers 3rd Law 4 p2 (ax ac)3 GP2 (Mx
  Mc)
• center of mass Mx ax Mc ac
• radial velocity amplitude Kc 2 p ac sin i
  P-1
• Mass Function f(M) P K3 / 2pG Mx
  sin3(i) / (1 Mc/Mx)2 lt Mx
• Dynamical Black Hole Mx gt 3 Mo (maximum for a
  neutron star)
• BH Candidates no pulsations no X-ray bursts
  properties of BHBs

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Compact Object Mass

• Neutron Star Limit 3 Mo
• (dP/dr)0.5 lt c
• Rhoades Ruffini 1974
• Chitre Hartle 1976
• Kalogera Baym 1996
• Black Holes (BH)
• Mx 3-18 Mo
• Neutron Stars (NS)
• (X-ray radio pulsars)
• Mx 1.4 Mo

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Transients with Low-Mass Companions Best Mx
Optical images of A0620-00 BH at 0.9 kpc
quiescence
outburst 1975
P K3 / 2pG Mx sin3(i) / (1 Mc/Mx)2
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Optical Study of BH Binary in Quiescence

• A0620-00
• (X-ray Nova Mon 1975)
• f(M) 2.72 /- 0.06 Mo
• P 0.323014(1) days
• K4V companion
• i 60o
• Mx 7 /- 3 Mo

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Optical Study of BHB in Quiescence

• Optical Photometry of
• Gravity-distorted K4 star
• Model( i, fstar , Mc/Mx , Tc, klimb, kgrav)
• residual disk star spots
• Other techniques
• Rotational broadening of absorption lines
• Doppler curve of emission lines (residual disk)
• worse problems

15
Inventory of Black Hole Binaries

• BH Binary Mass from binary analyses
• BH Candidate BHB X-ray properties no
  pulsations no X-ray bursts
• Dynamical BHBs BH Candidates
• Milky Way 18 25
• LMC 2 0
• local group 1 (M33) (? many
  ULXs)
• --------------------- ---------------------
  ---------------------
• total 21 25 ?
• Transients 17 23 ?

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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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Inventory of Neutron-Star X-ray Sources

• Subtype Typical Characteristics Number
  Transients
• Atoll Sources Low-B LMXBs X-ray bursts like
  BHBs 100 60
• Msec X-ray Pulsars 182-599 Hz atoll-like
  X-spectra 8 8
• Z-sources high- Lx LMXBs unique
  spectral/timing var. 9 1
• HMXB or Pulsars hard spectrum cutoff most are
  X-pulsars 90 50
• Magnetars Soft Gama Repeaters (4 1 cand.)
  14 7
• Anomalous X-ray Pulsars (8 1 cand.)
• Other Isolated Pulsars young SNRs X-detect
  radio pulsars 70? 0?
• ---------- ---------
  
• Total 291 126
• Cataloged radio pulsars number
  approaching 2000?

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X-ray Transients in the Milky Way

• RXTE ASM
• 47 Persistent Sources gt 20 mCrab (1.5 ASM c/s)
• 80 Galactic Transients
• (1996-2007 some recurrent)
• Transients timeline of science opportunities.

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Science Goals for Observing X-ray Binaries

• Locate stellar black holes and neutron stars100
  of BHs from X-ray sources special applications
  for X-selected NSs
• Measure Physical Properties of Compact Objects
• Mass (Mx)
• Spin NS pulsations BH infer a cJ /
  GMx2
• BH event horizon compare NS accretion (hard
  surface) vs. BH (none?)
• NS surface B field (lt108 to gt1015 G)
• NS Interior (Eq. of state burst models
  oscillation modes)
• Understand Accretion Physics
• origin of different X-ray states accretion
  disk and Rin transient jets
• hard X-rays (hot Comptonizing corona)
  quasi-periodic oscillations
• primary variables Mx , dM/dt , spin
• other variables i, qspin, surface B (NS),
  global B, plasma b ?

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Accretion Disks and the Inner Disk Boundary
Keplerian Orbits for sample m E(r) UK 0.5
U(r) -0.5 G Mx m r -1 Particle dE/dr 0.5 G
Mx m r -2

dL(r) d
(dE/dr) 0.5 e G Mx m r -2 dt dL(r) 2p
r dr sT4 ? T(r) r -3/4

• Real physical model
• conserve angular momentum (viscosity)
  outflow?, rad. efficiency (e)
• 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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Toward a Complete Model of Accretion Disks

• Shakura Sunyaev a-disk (1973)
• viscosity scales with total pressure
• shear stress trf a P (P Pgas Prad)
• thin disk h ltlt R
• high radiative efficiency (local L release)
• Makishima et al. 1986 apply to obs.
• T(r) r -3/4 L 4p Rin2 s T4

problem no independent measure of mass
accretion rate

• MRI Magneto-Rotational Instability (Balbus
  Hawley 1991)
• MHD simulations plasma eddies with local B, are
  sheared in a rotating disk
• this process transports angular momentum outward.
• Continued MHD accretion simulations in General
  Relativity
• (e.g. Hawley Balbus 2002 DeVilliers, Hawley,
  Krolik 2003 McKinney Gammie 2004)
• no dissipation (radiation) included in GR MHD
  simulations, thus far

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Inner Disk Boundary for Accretion Disks

• 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
• Surface (and ? RNS lt RISCO ?) ? Boundary Layer
  (2nd heat source)
• Magnetic Field Affects (Alfven Radius control
  of inner accretion flow
• accretion focus at polar cap ? pulsars)

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GR Applications for Thermal State

• Emissivity vs. Radius in the Accretion Disk

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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GR Applications for Thermal State

• Relativistic Accretion Disk Spectral Models

• e.g. kerrbb in xspec
• Li et al. 2005 Davis et al. 2005
• Integrate over disk and Bn(T)
• Correct for GR effects
• (grav-z, Doppler, grav-focusing)
• Correct for radiative transfer

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Tools for X-ray Data Analysis

• 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-a (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

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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 n (0.1-50 Hz) common in some
  states
• high n (50-1300 Hz) NS var. n BH
  steady harmonics
• very slow (10-6 to 10-2 Hz) some BH
  disk instability cycles

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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

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Defining X-ray States in BHB?

• Thermal State
• inner accretion disk

X-ray states ? Lecture IV.2
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Searches for the Event Horizon

• Game model infall to hard surface (NS) vs. none
  (BH)
• Topic Black Hole Neutron Star Model
• Quiescent X-ray State
• Measure Lx (erg s-1) 1031 few
  1032 advection
• Thermonuclear Bursts
• Measure rate (at 0.1 LEdd) none 5x10-5
  burst model
• Thermal X-ray State
• X-ray Spectrum max. fdisk gt 90
  80 boundary layer
• (Narayan 2004 Narayan Heyl 2002 Remillard
  et al. 2006 Done Gierlinski 2003)

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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/fo
  rm
• 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
• Fast Transients, Flashes Heise in t Zand
  ---
• 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

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References Reviews

• Other Reviews
• 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,
  AA Reviews, in press, astro-ph/07080148
• X-ray Binary Catalogs
• (HMXB) Liu, van Paradijs, van den Heuvel
  2006, AA, 455, 1165
• (LMXB) Liu, van Paradijs, van den Heuvel
  2007, AA, 469, 807