Decoding the time-lags in accreting black holes with XMM-

Newton

Decoding the time-lags in accreting black holes with XMM-

Newton

Phil UttleyThanks to: P. Cassatella, T. Wilkinson, J. Wilms, K.

Pottschmidt, M. Hanke, M. Böck

Phil UttleyThanks to: P. Cassatella, T. Wilkinson, J. Wilms, K.

Pottschmidt, M. Hanke, M. Böck

Background: disc variability?Background: disc variability?1974: Lightman & Eardley propose disc instability as the origin of X-

ray variability in black hole XRBsBut subsequent observations don’t seem to support this...

1974: Lightman & Eardley propose disc instability as the origin of X-ray variability in black hole XRBs

But subsequent observations don’t seem to support this...

rms

vari

abili

ty a

mplit

ud

e

spectral hardness

GX 339-4Belloni et al. 2005

Decreasing disc, increasing power-law

Done et al. (2007)

Cyg X-1

mean (time-averaged) spectrum

rms (time-varying) spectrum

Variability generated by hot flow/corona?(Churazov et al. 2001)

Hard state disc/corona interactionHard state disc/corona interaction

Several physical components: cool (kT~0.2 keV) optically thick disc, hot optically thin corona, jets

Corona and disc see each other: reflection

Can study both disc thermal and power-law spectra and variability with XMM-Newton EPIC-pn timing mode

Several physical components: cool (kT~0.2 keV) optically thick disc, hot optically thin corona, jets

Corona and disc see each other: reflection

Can study both disc thermal and power-law spectra and variability with XMM-Newton EPIC-pn timing mode

Disc X-ray reverberationDisc X-ray reverberation

~70% of incident flux ~30%

of incident flux

~1% of incident flux

X-rays from the X-rays from the continuum source continuum source (corona, jet base?) hit (corona, jet base?) hit the discthe disc Some are reflected Some are reflected (iron line and reflection (iron line and reflection continuum)continuum) The absorbed fraction The absorbed fraction is thermalised and re-is thermalised and re-emitted at the local disc emitted at the local disc temperaturetemperature

GX 339-4 2004 observation

GX 339-4 2004 observation

0.5-0.9 keV 3-10 keV

170 s of ~150 ks

Both bands (disc+pl and pl only) show large amplitude strongly correlated variability!

GX 339-4 2004 hard state: Energy-dependent PSDs and frequency-resolved

rms spectra

GX 339-4 2004 hard state: Energy-dependent PSDs and frequency-resolved

rms spectra

fast

slow

0.5-0.9 keV 3-10 keV

(Wilkinson & Uttley 2009)

Differences in PSD between hard and soft bands can be explained if variability is intrinsic to the disc and PL is correlated with it

Does the disc drive the power-law variability?

Does the disc drive the power-law variability?

Yes, at least below 1 Hz, reprocessing dominates observed disc variability > 1 Hz

(Uttley et al. 2011)

XMM-Newton TOO programmeXMM-Newton TOO programme0.12-0.49 Hz Frequency Range

Variable disc or disc/hot-flow boundary?Variable disc or disc/hot-flow boundary?

blackbody plus steep (Γ=3) power-law leads hard (Γ=1.4) power-law

blackbody leads hard (Γ=1.6) power-law

The sharpness of the change in lag below 2 keV requires that the leading component is almost a pure blackbody and not a blackbody plus a steep Comptonised component

It really looks like the ‘standard’ accretion disc! the corona does not see a lot of the disc

GX 339-4 2004: 0.034-0.12 Hz Range

Interpreting the variability: signals and amplifiers

Interpreting the variability: signals and amplifiers

Signal: mdot fluctuations in disc Amplifier: X-ray emitting regions

Delay

Em

issi

on

Time

mdo

t

*Input signal from disc is convolved with the emission vs. delay profile

The effect of the emission profileThe effect of the emission profileEmission profiles (transfer functions) and light curves for: Disc BB band Power-law band

Slow variations are strong in either band Fast variations are suppressed in the disc band

Fast variations are further reduced But reprocessing of power-law can add and dominate short-time-scale lags

A viscous propagation +

reverberation model

A viscous propagation +

reverberation model0.1 Hz

1 Hz

10 Hz

Reverberation dominates at the short time-scales where the slow viscous time-scale variations of the disc are washed out

Mapping the disc inner edge

Mapping the disc inner edge

The observed soft lags imply Rin< 50 RG in this hard stateThe observed soft lags imply Rin< 50 RG in this hard state

440 ks on Cyg X-1 coming up in October – watch this space!!!

Disk stability changesDisk stability changes Hard state disks look unstable, soft state disks look stable – where does the change occur?

Obtained 2 TOO observations of GX 339-4 at epochs where the source shows significantly low-frequency Lorentzians at significantly different frequencies than in 2004

Disk stabilises gradually through hard state? mdot connection?

0.5-0.9 keV 3-10 keV

IR vs XMM-Newton: revealing the disc-jet connection

IR vs XMM-Newton: revealing the disc-jet connection

XMM-Newton vs RXTEXMM-Newton vs IR

Covariance spectra

Covariance spectrum shows disc correlates with jet emission:Disc drives at least some jet variability!Does disc correlate better with jet than harder X-rays?

SummarySummary Disc accretion fluctuations are driving

variability in hard state BHXRBs, certainly on time-scales < 1s

Considering the interplay between the disc mdot variability and emitting regions we infer that it is likely the disc drives variability at even shorter time-scales

The disc seems to stabilise gradually towards the intermediate state

The disc is also driving the jet variations!

Disc accretion fluctuations are driving variability in hard state BHXRBs, certainly on time-scales < 1s

Considering the interplay between the disc mdot variability and emitting regions we infer that it is likely the disc drives variability at even shorter time-scales

The disc seems to stabilise gradually towards the intermediate state

The disc is also driving the jet variations!