1. LINE SHIFT IN ACCRETION DISKS - THE CASE OF Fe Kα
P. Jovanović1, V. Borka Jovanović2,
D. Borka2 and L. Č. Popović1
1Astronomical Observatory, Belgrade, Serbia
2Lab. 040, Vinča Institute of Nuclear Sciences, Belgrade, Serbia

2. Outline The broad Fe Kα spectral line
Influence of the following shift types on the line profile:
classical Doppler shift
special relativistic transverse Doppler shift and Doppler beaming
general relativistic gravitational redshift
Our results - simulations of the Fe Kα line emitted from:
a relativistic accretion disk around a single supermassive black hole (SMBH)
two accretion disks around both components of a SMBH binary
Conclusions

3. The broad Fe Kα spectral line from AGN
The Fe Kα line profile from Seyfert I galaxy MCG observed by the ASCA (Tanaka, Y. et al, 1995, Nature, 375, 659) and the modeled profile expected from an accretion disk around a Schwarzschild BH.
broad emission spectral line at 6.4 keV
asymetric profile with narrow bright blue
peak and wide faint red peak
Line width corresponds to high velocity:
v ~ km/s (MCG )
v ~ km/s (MCG )
v ~ – km/s (many other)

4. Production of Fe Kα: thin disk + hot corona
Comptonized photons irradiate accretion disk with power law spectrum
Compton reflection hump at 30 keV
Flourescent emission line at 6.4 keV
Fabian, A. C. 2006, AN, 327, 943
Wilms et al. 2004, MemSAI, 75, 519 4

5. Classical and relativistic shifts in the case of the Fe Kα line
Classical Doppler shift: symmetric, double-peaked profile
Special relativistic transverse Doppler shift and relativistic beaming: enhance blue peak relative to red peak
General relativistic gravitational redshift: smearing blue emission into red:
Fabian, A. C. 2006, AN, 327, 943 5

6. Observed variability of the Fe Kα line from MCG-6-30-15 due to gravitational redshift
1994
1997
Both peculiar line shapes can be explained by large gravitational redshift in small radii on the accretion disk
Reynolds, C. S., Nowak, M. A. 2003, Physics Reports, 377, 389
Time-avg
Peculiar 6

7. Our results: model of a relativistic accretion disk based on ray-tracing in Kerr metric
Surface emissivity of the disk:
Armitage & Reynolds, 2003, MNRAS, 341, 1041
Total observed flux:
Energy shift:

8. Simulations of a highly inclined accretion disk around a Kerr SMBH with different spins (left), and the corresponding simulated Fe Kα line profiles (right)
Jovanović & Popović, 2008, Fortschr. Phys.
56, 456
Simulations of a disk with different inclinations around a Schwarzschild SMBH (left), and the corresponding simulated Fe Kα line profiles (right)

9. Profiles of the Fe Kα line emitted from narrow rings in accretion disk

10. Modeled Fe Kα spectral line profiles for several values of SMBH spin a, and for inclination angles i = 20º (left) and i = 40º (right)
Chandra observations of the Fe Kα line emitted from the nucleus of Cygnus A (3C 405) (black crosses with error bars), and the corresponding simulated profiles for 4 different values of black hole spin (solid color lines).
Jovanović, Borka Jovanović, Borka, 2011, Baltic Astronomy, 20, 468

11. Variability of the Fe Kα line due to a bright spot in accretion disk
Perturbed disk emissivity:
Simulated emissivity perturbations along the receding (left) and approaching (right) side of a disk in Schwarzschild metric, and the corresponding variability of the Fe Kα line profile
Jovanović, P., Popović, L. Č., Stalevski, M., Shapovalova, A. I ApJ, 718, 168

12. Variability of the Hβ line in the case of quasar 3C390.3
Jovanović, P., Popović, L. Č., Stalevski, M., Shapovalova, A. I ApJ, 718, 168

13. Fragments of spiral arms in accretion disk of 3C390.3
Jovanović, P., Popović, L. Č., Stalevski, M., Shapovalova, A. I ApJ, 718, 168

14. Doppler shifts due to orbital motion of SMBH binaries
Composite line profiles:
Keplerian radial velocity curves:
Semiamplitudes:

15. Doppler shifts due to the radial velocities of the primary and secondary SMBHs and variability of the composite Fe Kα line
Example I: q = 0.5, a = 0.01 pc, i = 30o, e = 0, ω = 90o
Example II: q = 1.0, a = 0.01 pc, i = 60o, e = 0.75, ω = 90o

16. Shape of the Fe Kα line in the case when secondary SMBH is embedded in the accretion disk around the primary
Two examples of accretion disk with an empty gap caused by the secondary SMBH, and the corresponding Fe Kα line profiles

17. Left: decomposition of the observed Hα line of NGC 4151 into three Gaussian components
Top: Keplerian radial velocity curves of the sub-parsec SMBH binary in the core of Seyfert galaxy NGC 4151

18. Conclusions
We developed and performed simulations of the X-ray radiation from relativistic accretion disks around single and binary SMBHs, based on ray-tracing method in Kerr metric
The shape of the emitted broad Fe Kα line is strongly affected by three types of shifts:
classical Doppler shift - causing double-peaked profile
special relativistic transverse Doppler shift and relativistic beaming - enhancing blue peak relative to red one
general relativistic gravitational redshift - smearing blue emission into red one
The obtained simulated Fe Kα line profiles enabled us to study space-time geometry, accretion physics and strong gravity effects in vicinity of SMBHs
Shifted, complex Fe Kα line profiles with ripple variability could represent observational signatures of the binary SMBHs

19. Thank you for attention!