Broad iron lines from accretion disks

1. Broad iron lines from accretion disks K. Iwasawa University of Cambridge

2. Accreting black hole systems Most energy dissipates at inner radii of the accretion disk

3. In the accretion disk + corona model An X-ray source illuminates the disk to give rise reflection The most prominent spectral feature is Fe Ka line

4. Effects of strong gravity Because of the proximity to a black hole, relativistic effects are important Doppler shift Gravitational redshift

5. ASCA observation of MCG-6-30-15 Tanaka et al 1995

6. Other examples of broad iron emission Seyfert nucleus IRAS 18325-5926 Iwasawa et al 2003 Galactic black hole binary XTE J1650-500 Miniutti et al 2003

7. XMM-Newton observations of MCG-6-30-15 Vaughan & Fabian 2003 MNRAS submitted See also Wilms et al 2002; Fabian et al 2002; Vaughan et al 2002; Fabian & Vaughan 2002; Ballantyne et al 2003; Reynolds et al 2003

8. Overall spectral shape of MCG-6-30-15 MCG-6-30-15 / 3C273 Fluxed spectrum

9. Fe K line profile after correcting for warm absorption (modelled by Turner et al 2003 based on RGS data analysis)

10. RMS variability spectra for the 2001 data Whole observation Neighbouring bins (See also Matsumoto et al 2003)

11. Spectral changes seen in 10 flux slices

12. Spectrum of the variable component Difference spectrum: (High flux)-(Low flux)

13. Presence of a stable component In MCG-6-30-15 Offset

14. Spectrum of the constant component fraction

15. Schematic picture of the two-component model Variable power-law Stable reflection-dominated component

16. Variability of Fe K line in MCG-6-30-15 ASCA 1994 ASCA 1997 Iwasawa et al 1996 Iwasawa et al 1999

17. Excess emission above a fitted absorbed power-law continuum

18. Line-Flux correlations from the 2000 + 2001 observations

19. Line-Flux correlations from a simulation for the 2000+2001 data

20. Comparison between real-data and simulations

21. Simulation for the 2000 observation

22. Line-Flux correlations from the 2000 observation

23. Simulation-Realdata comparison for the 2000 observation

24. Rapid variation of the line core during the 2000 observation See also M Cappi’s poster

25. Simulation-Realdata comparison for the 2nd orbit of the 2001 observation (high-flux state)

26. Summary of the Fe K line properties in MCG-6-30-15 • Presence of red wing appears to be robust • Spectral variability can be explained by the two-component model:variable power-law + (semi)-stable reflection dominated emission. • There are occasional variability. • The line emission is most likely to originate from the relativistic region close to a black hole.

27. Broad Fe lines from Accretion Disks Giovanni Miniutti Institute of Astronomy - Cambridge In collaboration withAndy Fabianand with Russell Goyder,andAnthony Lasenby

28. Summary of MCG-6-30-15 observations: • The broad Fe line • A broad Fe line is present in all flux states Tanaka et al ’95 – Iwasawa et al ’96 - Guainazzi et al ’99 – Wilms et al 01 – Fabian et al 02 … • Fe line red wing suggests a rotating Kerr black hole Fabian et al 02

29. Summary of MCG-6-30-15 observations: • The broad Fe line • A broad Fe line is present in all flux states Tanaka et al ’95 – Iwasawa et al ’96 - Guainazzi et al ’99 – Wilms et al 01 – Fabian et al 02 … • Fe line red wing suggests a rotating Kerr black hole • A steep emissivity profile is implied ( b > 3 ) possibly in the form of a broken power-law • The emissivity suggests the presence of a centrally concentrated primary source of hard X-rays

30. Summary of MCG-6-30-15 observations: • The variability properties (> 10ks) • The Fe line generally appears to be broader in low flux states narrower in high flux states Iwasawa et al ’96 – Iwasawa et al ’99 – Wilms et al 01 – Lee at al 02... • The Feline-continuum correlation is puzzling • Fe line almostconstantin “normal” flux states while the continuum varies by a factor 3-4 Shih et al 02 - Fabian & Vaughan 03 – Vaughan & Fabian 03 (submitted) • Fe line is correlatedwith continuum in low flux states Reynolds et al 03 (submitted)

31. A light bending model in the Kerr BH spacetime • Primary source of X-rays • isotropic emission • position specified by h • Photons lost into the BH • RDC reaches the disc and • then the observer • PLC reaches the observer GM et al 03, MNRAS, 344, L22 – GM & Fabian 03, astro-ph/0309064 (submitted) The variability of the PLC is induced by light bending The source is linked to the disc corotating The orbital timescale << 10ks ring-like source

32. The variability is due to changes in the height of the primary source at constant intrinsic luminosity (i.e. at constant mass accretion rate) • If the height of the source is small most of the emitted photons are bent towards the disc and only a small fraction can escape at infinit so that the observed PLC is small (low flux states) • if the height is increased light bending is less effective and more photons are able to reach infinity so that the observed PLC increases The main idea is thus that changes in the height of the source induce the observed variability via gravitational light bending

33. Primary source emission: where do photons land ? Disk + lost photons Disk PLC the PLC drops as the source height (x-axis) gets smaller

34. Disk emissivity averaged (ring-like) non averaged (point-like) present X-ray missions future X-ray missions We present results for averaged emissivity

35. Emissivity dependence on the primary source height (decreasing clockwise)

38. b=6 hs = 1 rg hs = 20 rg b=3 Flat profile at large heights and steep at low heights The emissivity has the form of a broken power law steeper in the inner disk region and flatter in the outer

39. PLC and Fe line variability induced by light bending Small h = low PLC flux Large h = high PLC flux PLC Fe line hs The Fe line varies with much smaller amplitude

40. The Fe line EW is anti-correlated with the PLC Fe line EW PLC Fe line hs The Fe line EW tends to constant at very low PLC flux

41. Fe line – PLC correlation I II III Regime III: large source height and anti-correlation Regime II: intermediate source height and constant Fe line Regime I: small source height and correlation

42. III

43. II III

44. I II III

45. Variability timescales Assuming the primary source is moving with v = 0.1 c and that the BH has a mass of 10 solar masses 7 • the PLC can vary by a factor 4 in about 2ks • (or by a factor 20 in 10ks) • this may help to explain the extreme variability • in some systems (such as e.g IRAS 13224-3809) most extreme variation is a factor 3-4 in 10ks

46. XTE J1650-500 during outburst Rossi et al 03 I/II Fe line flux ? III I II III 9-100 keV PLC flux GM & Fabian 03

47. Conclusions Some predictions of the light bending model The Fe line fluxiscorrelated with the continuum during low flux states andanti-correlated during high flux states The Fe line fluxisconstant during intermediate flux states while the continuum varies by a factor 4 constant anti-correlated correlated

48. Conclusions Some predictions of the light bending model The Fe line fluxiscorrelated with the continuum during low flux states andanti-correlated during high flux states The Fe line fluxisconstant during intermediate flux states while the continuum varies by a factor 4 The Fe line EWisgenerallyanti-correlatedwith the continuum and almost constant only during very low flux states The hard spectrum is more and more reflection dominatedas the PLC flux drops Thank you