QuasiPeriodic Oscillations in accretion onto compact objects

1
Quasi-Periodic Oscillationsin accretion onto
compact objects

• Niayesh Afshordi
• Princeton University
• 16 April, 2003

2
References

• van der Klis, M. 2000, ARAA, 38717-60 (review)
• Belloni, T., Psaltis, D., van der Klis, M.
  2002, ApJ, 572392-406 (frequency correlation at
  100 Hz sources)
• Psaltis, D., Belloni, T., van der Klis 1999,
  ApJ 520, 262 (frequency correlation for kHz
  sources)
• Mauche, C.W. 2002, ApJ 580423-428 (dwarf novae
  may fit the same correlation)
• Titarchuk, L. G., Wood, K. S. 2002, ApJ, 577,
  L23-26 (a sample theoretical model for the freq.
  correlation)

3
This Talk

• Variability Analysis and the Usual Suspects
• What are QPOs?
• Dwarf Nova QPOs
• kHz QPOs Black Holes Neutron Stars
• Correlations among QPO frequencies
• QPO models
• The Moral

4
Variability Analysis and the Usual Suspects

• Variability Power Spectrum (Take Fourier
  Transform)
• Lorentzian Profile (Damped Harmonic Oscillator)
• 1/f noise (Any scale-free random process)

5
What Are QPOs?
Belloni, Psaltis and van der Klis 2002

• Different Variability Peaks in the Power Spectrum
• Each Peak should have Qgt2

Ptolemy 200
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Dwarf Novae QPOs

• In the high state of the dwarf novae

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Low magnetic field Neutron Stars

• The QPO is undetectable at highest M_dot level
• Frequency correlates with the position in the
• color-color diagram, not flux or M_dot
• The larger QPO frequency (those that have one)
• has a maximum in the range 1000-1400 Hz for
• almost all the sources
• Frequency at the Marginally Stable Orbit ?
• The amplitude of oscillation increases with
• photon energy

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kHz QPOs Neutron Star Candidates

• Z-sources
• L L_Edd
• Move on Z-tracks in color-color diagrams in hours
• Atoll Sources
• L (0.02-0.1) L_Edd
• Move on C or U tracks in color-color diagrams in
  hours to days

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Black Hole vs. Neutron Star

• Typically you need five Lorentzian profiles to
  fit the data but not
• always
• Belloni, Psaltis and van der Klis 2002 claims
  that there is no need
• For a 1/f noise

Black Hole Neutron Star
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Neutron Star vs. Black Hole
atoll source
milisecond pulsar
Z source
black hole candidate
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kHz QPOs Black Hole Candidates

• Frequencies are typically less than 200 kHz
• Highest QPO frequency is not as high, relative to
  other frequencies
• The power is roughly similar to power law, though
  not as steep as 1/f

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Are Frequencies Correlated?
Black Hole Candidate X-ray burster Luminous
Neutron Star Z-source Shifted Frequencies
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Correlation among different QPO frequencies
Now lets include some white dwarfs

• Various peak frequencies seem to be correlated
  with each other

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QPO Models

• Upper Frequency Orbital freq. close to compact
  object
• Lower Frequency(ies)
• Beat with NS rotation, NS rotation (coincidence
  with the burst frequency)
• Relativistic nodal and periastron precession
  (correct correlation among frequencies, works for
  Black Holes)
• Magnetosonic oscillations ( (H/r) F_u)

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The Moral

• QPOs are signatures of accretion onto compact
  objects
• Their power spectra can be fit by a handful of
  Lorentzian profiles
• Various QPO frequencies vary with time, but are
  correlated with each other
• At least the highest QPO frequencies map gravity
  close to the compact object
• There is NO model that can explain all the
  apparent features/correlations in the QPO
  phenomenology