Low frequency QPOs: a precession model in the context of mass - - PowerPoint PPT Presentation

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Low frequency QPOs: a precession model in the context of mass - - PowerPoint PPT Presentation

Dec 24, 2022 34 likes •516 views

Adam Ingram Chris Done Piotr ycki 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,

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Low frequency QPOs: a precession model in the context of mass accretion rate fluctuations

Adam Ingram Chris Done Piotr Życki P Chris Fragile

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Cool, optically thick disc thermalises to emit a multi coloured black body spectrum Hot electrons in high scale height,

  • ptically thin flow

Compton up-scatter disc seed photons to give power law emission

XTE 1550-564

The truncated disc model

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XTE 1550-564

The truncated disc model

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XTE 1550-564

The truncated disc model

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XTE 1550-564

The truncated disc model

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XTE 1550-564

The truncated disc model

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XTE 1550-564

The truncated disc model

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XTE 1550-564

The truncated disc model

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XTE 1550-564

The truncated disc model

…so what could this QPO be?

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Frame dragging

Asymmetric potential => precession of particle

  • rbits

www.phys.ncku.edu.tw/.../ apod/ap971107.html

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Lense-Thirring precession Lense-Thirring precession

Ingram, Done & Fragile 2009 Relativistic precession models: Stella & Vietri 1998

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Lense-Thirring precession

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Lense-Thirring precession Lense-Thirring precession

Ingram, Done & Fragile 2009: show that the precession frequency can match QPO frequency

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Lense-Thirring precession Lense-Thirring precession

…but how does it modulate the spectrum?

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Seed photon variation

Less seed photons incident on the flow now

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Seed photon variation

…than now

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Self-occultation

Photons must pass through more of the flow now

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Self-occultation

…than now

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QPO model

Ls Ltot

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QPO model

ro=37

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QPO model

ro=21

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QPO model

ro=19

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QPO model

ro=15

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QPO model

ro=12

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QPO model

ro=10

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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

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Fluctuating Lh

dLh M(r,t)

฀  

  • 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:

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Fluctuating Lh

…but what is the nature of the Mdot fluctuations?

  • 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:

dLh M(r,t)

฀  

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  • Mass accretion rate fluctuations fuelled by

MRI

  • Mdot can’t vary on shorter timescales than

the local viscous timescale

This gives the noise spectrum GENERATED at each annulus

fPf

Propagating M fluctuations

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This gives the noise spectrum EMMITED at each annulus

e.g. Lyubarskii 1997; Arevalo & Uttley 2006, Kotov et al 2001

Propagating M fluctuations

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Propagating M fluctuations

Lh

Arevalo & Uttley 2006 Uttley & McHardy 2001

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Propagating M fluctuations

mass conservation =>

M Σ

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Implications for QPO

So the frequency fluctuates => QPO width

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Total variability model

ro=37

Using approximation that under predicts the harmonics

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Total variability model

ro=21

Using approximation that under predicts the harmonics

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Total variability model

ro=19

Using approximation that under predicts the harmonics

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Total variability model

ro=15

Using approximation that under predicts the harmonics

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Total variability model

ro=9

Using approximation that under predicts the harmonics

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Total variability model

ro=7

Using approximation that under predicts the harmonics

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Approximation

The approximation honestly does under predict the harmonics!

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Approximation

ro=21

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Approximation

ro=21

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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
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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!

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Registration now open at: http://astro.dur.ac.uk/xray2010/

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Approximation

Ω Ψ

LQPO = AΩ - BΨ

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Rough match to data

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Photon index

฀    7 3 Ls Lh      

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