Understanding Strong Gravity Effects in AGN X-ray Spectra and Variability

1. Strong Gravity Effects:X-ray spectra, timing and polarimetry AC Fabian IoA Cambridge UK With help from Giovanni Miniutti, Josefin Larsson, Jamie Crummy, Gabriele Ponti, Randy Ross and the MCG6 Suzaku team

2. Rapid variability in AGN MCG-6-30-15

3. Emission dominated by innermost regions Orbital frequency at 10rs Vaughan+

4. Accretion makes massive black holes Soltan 82 Radiative efficiency η Mean redshift The comparison of Є from AGN light and the local BH mass density reqired that the efficiency be at least 0.1

5. REAFs DominateRadiatively efficient accretion flows • Dominant mode of SMBH in terms of GROWTH (Soltan-type arguments) • Inner radius of rad efficient disc is few Rg • Much of the radiation emerges within 6Rg

6. Clues from spectra and variability • X-ray ‘reflection’ gives important clues in the spectrum • Variability timescales and spectral changes show different spectral components

7. Components of an AGN (with Galactic absorption)

8. Reflection from photoionized matter (Ross & Fabian 93, 05) Also see Young+, Nayakshin+, Ballantyne+, Rozanska+, Dumont+

9. Schwarzschild Kerr Fabian+89, Laor 90… Dovciak+04; Beckwith+Done05

10. Vary spectral index Add relativistic blurring Soft excess – broad iron line – Compton hump

11. Very Broad Line  Spinning BH Tanaka+ Iwasawa+ Wilms+ Fabian+

12. Galactic Black Hole GX339-4 Very Broad Line  spinning BH Miller+

13. Soft Excesses Crummy+05 22 PG QSO +12 Seyf1

14. The soft X-ray excess the soft excess in AGNs seems to have a “universal” temperature despite large differences in BH mass, hard spectral shape, accretion rates … (Czerny+03; Gierlinski & Done 04) it could indicate that the process involved is not thermal as usually assumed but rather linked to atomic processes Can be EXPLAINED by REFLECTION (Ross & Fabian 05; Crummy+05)

15. XMM pn + BeppoSAX PDS MCG-6

16. XTE J1650-500 from BeppoSAX (G. Miniutti)

17. SPIN

18. Assumption: measurements of rms determine (or constrain) a

19. ISCO conjecture • Measure Rin from spectra  RISCO  spin? • Maybe not, due to B decreasing Rin (Begelman & Reynolds, Gammie, Krolik, Hawley…)?? • BUT low ionization thin, slowly accretion disc, which is not plunging, so Rin = RISCO We conjecture that Rin measured from iron line is within 1rg of Risco

20. NO Broad Line (apparently) Ark 120 Vaughan+ 04

21. Cautionary remarks • Narrow 6.4~keV components are expected from distant matter • Iron line and reflection continuum need to be self-consistent and blurred together • Warm, partial, outflow and other absorption components need to be considered • Iron abundance could be a factor (high in MCG-6 and some NLS1, low in other objects) • Going within 6GM/c2 = 3Rs can make a large difference in increasing the blurring and so making features less obvious, particularly if abundances only less than solar

22. MCG-5-23-16 Suzaku: Reeves+06

23. Cautionary remarks • Narrow 6.4~keV components are expected from distant matter • Iron line and reflection continuum need to be self-consistent and blurred together • Warm, partial, outflow and other absorption components need to be considered • Iron abundance could be a factor (high in MCG-6 and some NLS1, low in other objects) • Going within 6GM/c2 = 3Rs can make a large difference in increasing the blurring and so making features less obvious, particularly if abundances only less than solar

24. Complex absorption • Spectral models can be made for many sources by using complex absorption (partial covering etc) • These can be tested/rejected by: higher spectral resolution broader bandwidth variability

25. Young+05 Chandra HETG Constrains absorption by highly ionized species Implies that simple absorption models for red wing do NOT work

26. Armitage & Reynolds

27. How does it vary? Iwasawa+ Shih+ Fabian+ Vaughan+ McHardy+ Uttley+ Reynolds+

28. MCG-6-30-15 Spectral changes seen in 10 flux slices

29. Difference spectrum: (High flux)-(Low flux) is a power-law modified by absorption Ratio to power-law 1 keV 10 keV So we know which large scale features are due to absorption

30. Flux-flux variability Vaughan+Fabian 04

31. Schematic picture of the two-component model Variable power-law Quasi-constant reflection-dominated component

32. Light bending model in Kerr spacetime Miniutti et al 03; Miniutti & Fabian 04; earlier work by Matt et al see also Tsuebsuwong,Malzac+06

34. A source of constant intrinsic luminosity will appear to vary if it changes position within the strong gravity regime close to the black hole

35. PLC and Fe line variability induced by light bending when an intrinsically constant source changes height Small h = low PLC flux Large h = high PLC flux PLC Fe line hs The Fe line varies with much smaller amplitude

36. Reflection – Power-law relation

37. MCG-6-30-15 Suzaku Miniutti+06

40. Hard X-ray variability measured for the first time Suzaku

41. Suzaku difference spectrum MCG-6-30-15

42. XTE J1650-500 during outburst Rossi +05

43. Is it absorption or a line? Fabian+02,04 1H0707

45. NGC4051 (Ponti+06)

46. Rapid spectral variability of NLS1explained by GR light bending effects if source within 6m 1H0707

47. Conclusions on broad Fe line • A consistent model for the broad iron lines seen in some Seyferts and GBH • involves both • strong gravitational redshift • and light bending • indicating that much of the reflection and thus primary emission is occurring within a few gravitational radii of the event horizon • Good evidence from several objects that BH is spinning (Kerr solution necessary)

48. X-ray Polarization

49. Clear broad iron line may need • accretion at high Eddington fraction • high iron abundance • little complex absorption