1. Extreme Gravity : Supermassive black holes & Active Galactic Nuclei
XTP-LOFT meeting
Feb 21, 2014
Extreme Gravity : Supermassive black holes & Active Galactic Nuclei
Weimin Yuan (NAOC)
contributions from
Y.F. Yuan (USTC), Y. Liu, J.M. Wang (IHEP),
X.L. Zhou, L.J. Gou, Z. Liu, H. Pan (NAOC)

2. XTP effective area
~5x XMM
~6-7x

3. Science objectives Measurement of black hole parameters (spin)
Testing GR in strong gravity & matter under extreme conditions
BH astrophysics: accretion process, jets

4. Basic paradigm of central engine of AGN
ACTIVE galactic nuclei are thought to be powered by accretion of gas onto a massive black hole at the centre of the host galaxy1, but direct evidence of the presence of a black hole is hard to obtain. As the gas moves close to the event horizon, its velocity should approach the speed of light; the resulting relativistic effects, and gravitational redshift arising from the proximity to the black hole, should be observable, allowing us to test specific predictions of the models with the observations.
Miller 2007
Relatively ‘cold’ disc illuminated by hard X-ray and produces Fe Kalpha line
Typical AGN X-ray spectra

5. Measuring BH spin from Fe K line profile
Dependence of the radius of ISCO
(innermost stable circular orbit) on BH spin
Fe Ka line profiles for a non-spinning BH and an extreme Kerr BH
Miller 2007
问题：该假设的合理性和对结果的影响程度
Assuming the disc truncates at ISCO inside which the is negligible
R(in) = R(ISCO)
The shape of the Fe line is largely determined by where the innermost disc is truncated

6. Why do we care about spins of SMBHs ?
One of the two basic parameters of BHs
Test the evolution and growth scenarios of massive BH
Test models of accretion discs & jet formation
accretion efficiency
jet powered by energy from BH spin（Blandford & Znajek 1977）
Berti & Volonteri 2008
Only about two dozen AGN with BH spins constrained so far, and …..

7. And confusing results ……
Proto-type: MCG (~1mCrab)
a ~ 0.98 (?)
XMM-Newton
A rapidly spinning BH?
Brenneman & Reynolds (2006)
Fabian et al. (2002)
However, a~0 given by Noda et al. 2010
Spectra with higher S/N are needed to draw the conclusion!

8. Simulated Observation of Broad Fe Line
MCG
XTP
MCG
XMM

9. XTP AGN sample with BH spin measurement
Broad Fe line profile can be measured for AGN with flux > E-11 erg/s/cm2 with reasonable exposure (~50ks).
Detectable in over 100 AGNs (type 1)
(Broad Fe line fraction ~ 45% (Nandra et al. 2007) )
More Considering fainter AGN with strong broad Fe lines

10. Observational test of GR in strong field
dynamics of matter close to the horizon can be used to test GR
Can be traced by variability (both energy and strength) of Fe Ka
accretion disk
Time-resolved spectroscopy can be used as a tool to probe the dynamics of matter close to the horizon
The information of the space-time geometry must be encoded in the X-rays produced in the close vicinity of BHs.
Many orders of magnitude more photons than BHXB.
Suitable for investigating sub-orbit variations of the Fe line
Bardeen et al. (1972)
Reynolds & Nowak (2003) Armitage & Reynolds (2003)
Trace the dynamics of hot spots at the inner disc close to horizon
to constrain BH mass and spin
to test GR metric
SMBH: 10^6—10^8Msun
ISCO periods= hours
Many photons for AGN in one orbit

11. Gas dynamics very close to BH:
hints from XMM data
一个有效的方法是观测铁的宽发射线在ISCO轨道周期里的变化。尽管这方面的观测很少，但有数据表明在ISCO轨道周期里铁的宽发射线有着强烈的变化（图4左； Iwasawa et al. 2004），这意味着铁线的辐射在内盘是不均匀和稳定的，极可能是受到一些辐射的亮斑的调制，因此我们有可能通过轨道周期内铁线的变化来追踪这些亮斑的轨道运动。
（Iwasawa et al. 2004）
NGC XMM-Newton data
the variability of the Fe line
--- map out energy-time of photons.
The period T match the ISCO
Constrain spin and mass by measuring T and fitting r (distance of hot spots)

12. Observational test of GR in strong field
Simulated XTP observation for
NGC3615 (1mCrab)
10mCrab
XMM
Trace the dynamics of hot spots at the inner disc close to horizon

13. X-ray timing of AGN
PSD frequency - BH mass relation
Measure characteristic break timescales of the PSD in AGN, particularly in IMBH AGN & ULX
M<~10^5 Msun, T<~10^3s
Search for QPO in AGN
Only one marginal detection in AGN (REJ1034, Gierlinski et al Nature; however see Vaughan 2010)
Search in IMBH AGN and ULX, mostly faint so large collecting area needed
Vaughan et al. 2005

14. X-ray timing of AGN: QPO simulated XTP results RE J1034+396
结论：比NGC 4395弱5-7倍的源可探测（流量 1e-12 ergs/cm^2/s量级）
Gierlinski et al. 2008
7 times weaker than J1034

15. X-ray timing of AGN: PSD IMBH NGC 4395 simulated XTP results XMM
结论：比NGC 4395弱5-7倍的源可探测（流量 1e-12 ergs/cm^2/s量级）
7 times weaker than NGC 4395
（Vaughan et al. 2005）

16. Time lag (reverberation mapping)
X-ray timing of AGN:
Time lag (reverberation mapping)
Time lag between and 1-4 keV
simulated XTP results 1H
XMM
XMM
Soft lag
(Fabian et al. 2009; Kara et al. 2013a)

17. X-ray timing of AGN: Time lag
Relationship between soft lag and BH mass
Simulated XTP results
XMM-Newton
(De Marco et al. 2013a)

18. Conclusion
XTP’s large photon collecting area improves significantly up on XMM-Newton on spectroscopic, timing, and time resolved spectroscopic studies
Render a powerful tool for study the effects of extreme gravity near BHs in AGN
Spin measurements for a large sample
Start to trace GR dynamics near the BH horizon
Timing diagnostic give new insight into the structure and dynamics of accretion flows