Adam Ingram Chris Done Piotr Życki P Chris Fragile Low frequency QPOs: a precession model in the context of mass accretion rate fluctuations
The truncated disc model Cool, optically Hot electrons in thick disc high scale height, thermalises to optically thin flow emit a multi Compton up-scatter coloured black disc seed photons to body spectrum give power law emission XTE 1550-564
The truncated disc model XTE 1550-564
The truncated disc model XTE 1550-564
The truncated disc model XTE 1550-564
The truncated disc model XTE 1550-564
The truncated disc model XTE 1550-564
The truncated disc model XTE 1550-564
The truncated disc model XTE 1550-564 …so what could this QPO be?
Frame dragging www.phys.ncku.edu.tw/.../ apod/ap971107.html Asymmetric potential => precession of particle orbits
Lense-Thirring precession Lense-Thirring precession Ingram, Done & Fragile 2009 Relativistic precession models: Stella & Vietri 1998
Lense-Thirring precession
Lense-Thirring precession Lense-Thirring precession Ingram, Done & Fragile 2009: show that the precession frequency can match QPO frequency
Lense-Thirring precession Lense-Thirring precession …but how does it modulate the spectrum?
Seed photon variation Less seed photons incident on the flow now
Seed photon variation …than now
Self-occultation Photons must pass through more of the flow now
Self-occultation …than now
QPO model L tot L s
QPO model r o =37
QPO model r o =21
QPO model r o =19
QPO model r o =15
QPO model r o =12
QPO model r o =10
QPO model We see: • Harmonic structure • Inclination dependence …but: • It is far too narrow • QPO width and strength are both constant • We haven’t produced the broadband noise ..or sigma - flux relation, time lags etc
Fluctuating L h • Emission from the flow not just up-scattered seed photons • Also emission from liberated gravitational potential energy • Gravitational energy emitted from an annulus of the flow: dL h M(r,t)
Fluctuating L h • Emission from the flow not just up-scattered seed photons • Also emission from liberated gravitational potential energy • Gravitational energy emitted from an annulus of the flow: dL h M(r,t) …but what is the nature of the Mdot fluctuations?
Propagating M fluctuations • Mass accretion rate fluctuations fuelled by MRI • Mdot can’t vary on shorter timescales than the local viscous timescale fP f This gives the noise spectrum GENERATED at each annulus
Propagating M fluctuations This gives the noise spectrum EMMITED at each annulus e.g. Lyubarskii 1997; Arevalo & Uttley 2006, Kotov et al 2001
Propagating M fluctuations L h Arevalo & Uttley 2006 Uttley & McHardy 2001
Propagating M fluctuations M Σ mass conservation =>
Implications for QPO So the frequency fluctuates => QPO width
Total variability model r o =37 Using approximation that under predicts the harmonics
Total variability model r o =21 Using approximation that under predicts the harmonics
Total variability model r o =19 Using approximation that under predicts the harmonics
Total variability model r o =15 Using approximation that under predicts the harmonics
Total variability model r o =9 Using approximation that under predicts the harmonics
Total variability model r o =7 Using approximation that under predicts the harmonics
Approximation The approximation honestly does under predict the harmonics!
Approximation r o =21
Approximation r o =21
Predictions, Successes and Limitations Successes: • Produce QPO and harmonic • Both evolve as observed • Reproduce the broadband noise and sigma-flux relation • This correlates with the QPO Predictions: • Iron line in QPO spectrum
Predictions, Successes and Limitations Limitations: • Not finished yet! • Currently no energy dependence • Currently no disc variability which is required in some states (Wilkinson & Uttley 2009) • BUT: – Disc variability should correlate with the flow variability – Disc variability should correlate with the QPO ...another prediction!
Registration now open at: http://astro.dur.ac.uk/xray2010/
Approximation Ω Ψ L QPO = AΩ - BΨ
Rough match to data
Photon index 1/6 7 L s 3 L h
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