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Decoding the time-lags in accreting black holes with XMM-Newton Phil Uttley Thanks to: P. Cassatella, T. Wilkinson, J. Wilms, K. Pottschmidt, M. Hanke,

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Presentation on theme: "Decoding the time-lags in accreting black holes with XMM-Newton Phil Uttley Thanks to: P. Cassatella, T. Wilkinson, J. Wilms, K. Pottschmidt, M. Hanke,"— Presentation transcript:

1 Decoding the time-lags in accreting black holes with XMM-Newton Phil Uttley Thanks to: P. Cassatella, T. Wilkinson, J. Wilms, K. Pottschmidt, M. Hanke, M. Böck Phil Uttley Thanks to: P. Cassatella, T. Wilkinson, J. Wilms, K. Pottschmidt, M. Hanke, M. Böck

2 Background: disc variability? 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... 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 variability amplitude spectral hardness GX 339-4 Belloni 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)

3 Hard state disc/corona interaction G Several physical components: cool (kT~0.2 keV) optically thick disc, hot optically thin corona, jets G Corona and disc see each other: reflection G Can study both disc thermal and power-law spectra and variability with XMM-Newton EPIC-pn timing mode G Several physical components: cool (kT~0.2 keV) optically thick disc, hot optically thin corona, jets G Corona and disc see each other: reflection G Can study both disc thermal and power-law spectra and variability with XMM-Newton EPIC-pn timing mode

4 Disc X-ray reverberation ~70% of incident flux ~30% of incident flux ~1% of incident flux  X-rays from the continuum source (corona, jet base?) hit the disc  Some are reflected (iron line and reflection continuum)  The absorbed fraction is thermalised and re-emitted at the local disc temperature

5 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!

6 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

7 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)

8 XMM-Newton TOO programme 0.12-0.49 Hz Frequency Range

9 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

10 Interpreting the variability: signals and amplifiers Signal: mdot fluctuations in discAmplifier: X-ray emitting regions Delay Emission Time mdot * Input signal from disc is convolved with the emission vs. delay profile

11 The effect of the emission profile Emission 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

12 A viscous propagation + reverberation model 0.1 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

13 Mapping the disc inner edge The observed soft lags imply R in < 50 R G in this hard state 440 ks on Cyg X-1 coming up in October – watch this space!!!

14 Disk 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

15 IR vs XMM-Newton: revealing the disc-jet connection XMM-Newton vs RXTE XMM-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?

16 Summary G Disc accretion fluctuations are driving variability in hard state BHXRBs, certainly on time-scales < 1s G 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 G The disc seems to stabilise gradually towards the intermediate state G The disc is also driving the jet variations! G Disc accretion fluctuations are driving variability in hard state BHXRBs, certainly on time-scales < 1s G 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 G The disc seems to stabilise gradually towards the intermediate state G The disc is also driving the jet variations!


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