1. Strong gravity with Athena Jiří Svoboda Czech Academy of Sciences using simulations and figures done by the Athena Science working group “The Close Environments of Super- massive Black Holes”, chaired by G.Matt and M.Dovčiak AXRO, Prague, 9th Dec 2014

2. Outline Introduction –Exploring strong gravity via X-ray spectroscopy –Current X-ray measurements Strong gravity with Athena –Brief description of the mission concept –Main expectations with Athena regarding the strong gravity exploration Conclusions

3. Active Galactic Nuclei central super- massive black hole M ~ 10 5 -10 10 M ʘ

4. Why to study black holes? test of the Einstein’s theory of relativity in the extreme conditions of strong gravity and very high velocities Credit: M. Bursa

5. Why to study black holes? black hole growth & galaxy formation –how were galaxies formed? –how did black holes evolve? Current spin measurements (based on data from Reynolds, 2013) (based on Berti & Volonteri, 2008)

6. How to measure the BH spin? ISCO (innermost stable circular orbit) –the accretion disc is not stable below it –represents the innermost edge of the accretion disc

7. A schematic view of an accreting black hole accretion disc - is heated up by gravitational forces and viscous friction corona -thermal photons are up-scattered in a hot atmosphere (corona) and get energy due to the inverse Compton effect -its exact geometry is not yet known reflection - some of the scattered radiation is reflected off the accretion disc the light rays are curved due to the strong gravitational light bending

8. A schematic view of an X-ray spectrum Credit: J. Miller Active Galaxy X-ray Binary

9. A schematic view of an X-ray spectrum Credit: J. Miller Active Galaxy X-ray Binary its origin is not known yet

10. Reflection spectrum continuum + fluorescent lines iron line iron edge Compton hump

11. Relativistic effects effects of strong gravity and high velocities: –gravitational redshift –Doppler effect –aberration –light bending –gravitational lensing frequency shift Sketch of the line-profile distortion:

12. Relativistic iron line iron line from an accretion disc around a black hole Credit: M. Dovčiak

13. Relativistic reflection used models: * reflection, model Xillver (García et al. 2013) * relativistic smearing, KY (Dovčiak et al. 2004) Compton hump iron line broad red wing soft excess ─ reflection model ─ relativistic smearing

14. Parameters of the relativistic reflection models reflection: –ionization –abundances (iron) relativistic smearing –spin of the black hole –inner and outer edge of the disc –inclination angle –radial and angular emissivity

15. Parameters of the relativistic reflection models reflection: –ionization –abundances (iron) relativistic smearing –spin of the black hole –inner and outer edge of the disc –inclination angle –radial and angular emissivity related by ISCO

16. Parameters of the relativistic reflection models reflection: –ionization –abundances (iron) relativistic smearing –spin of the black hole –inner and outer edge of the disc –inclination angle –radial and angular emissivity physical state geometry related by ISCO

17. Geometry of the corona

18. Lamp-post geometry approximation for a compact centrally localized corona

19. Lamp-post geometry approximation for a compact centrally localized corona steep radial emissivity

20. Observations currently best X-ray observatory for strong gravity is the combination of XMM-Newton and Nustar

21. NGC 1365 Risaliti et al., 2013

22. Mrk 335 Parker et al., 2014

23. Caveats with observations relativistic reflection is not evident in all sources –e.g. IRAS 05078+1626 accretion rate estimated as Ṁ ~ 0.1 Ṁ Edd –a standard thin accretion disc should be present missing relativistic reflection due to an over-ionization of the innermost disc? Svoboda et al., 2010

24. Caveats with observations when relativistic reflection is “evident”... –MCG -6-30-15 Miniutti et al., 2007

25. Caveats with observations... it’s not the only model that can describe the data... → scenario with partially covering absorbers Miller et al., 2008

26. X-ray timing timing studies may help to distinguish between two different scenarios... –X-ray reverberation method comparing light curves of different energy bands calculate the Fourier transforms and compare their phases –measure a delay (time lag) between the phases dependent on the frequency and the energy need for high-quality light curves –need for long exposure with the most sensitive detectors

27. X-ray timing timing studies may help to distinguish between two different scenarios...

28. X-ray timing timing studies may help to distinguish between two different scenarios... reflection dominated power-law dominated compare light curves of the different bands

29. X-ray timing timing studies may help to distinguish between two different scenarios... soft lag of 30s

30. Time lag spectra dependendence on –Fourier frequency –spectral energy: low frequency high frequency

31. Credit: M. Dovčiak

32. Time lags in Compton humps new observations with NUSTAR allow to measure the time lags also for the Comtpon hump in hard X-rays:

33. Athena X-ray Observatory brief history: –November 2013: ESA selected the topic of the next large mission “Hot and Energetic Universe” –June 2014: ESA selected Athena mission as L2 mission aims to answer two key questions in astrophysics: 1.How does ordinary matter assemble into large scale structures that we see today? 2.How do black holes grow and shape the Universe?

34. Caveats with X-ray timing what do we measure? –the measured time lag is not exactly the light-travel-time lag between two components, although it’s related very high-quality data are needed to apply physical models (relativistic reflection, absorption) –need for long uninterrupted lightcurves best are laboratories at high orbital orbits, like XMM-Newton –need for very good time resolution to reach the highest frequencies

35. Athena X-ray Observatory brief history: –November 2013: ESA selected the topic of the next large mission “Hot and Energetic Universe” –June 2014: ESA selected Athena mission as L2 mission the expected launch is in 2028 aims to answer two key questions in astrophysics: 1.How does ordinary matter assemble into large scale structures that we see today? 2.How do black holes grow and shape the Universe?

36. The Athena Observatory L2 orbit Ariane V Mass < 5100 kg Power 2500 W 5 year mission X-ray Integral Field Unit:  E: 2.5 eV Field of View: 5 arcmin Operating temp: 50 mk Wide Field Imager:  E: 125 eV Field of View: 40 arcmin High countrate capability Silicon Pore Optics: 2 m 2 at 1 keV 5 arcsec HEW Focal length: 12 m Sensitivity: 3 10 -17 erg cm -2 s -1 Rau et al. 2013 arXiv1307.1709 Barret et al., 2013 arXiv:1308.6784 Willingale et al, 2013 arXiv1308.6785

37. Athena X-ray Observatory Willingale et al., 2013

38. Iron Line

39. X-ray timing 500ks simulated observation of 1H 0707-495 with Athena: 1 σ XMM XMM Athena

40. X-ray timing

41. a

42. Orbiting spots

43. X-ray soft-excess

44. Mapping the circum-nuclear matter narrow iron line almost invariably present in AGN –Athena will allow to locate its origin and to constrain relative fractions from different regions

45. Conclusions X-ray spectroscopy and timing provides a very useful tool to investigate the innermost regions around black holes Athena represents a next step in our research thanks to its high spectral and timing resolution –it will allow to measure BH spin in much more sources and up to larger cosmological redshifts –it will allow to model X-ray reverberation in many new sources, up to higher frequencies and with reasonable exposure times –it will allow to study in detail the circumnuclear matter

46. Thank you for your attention!!!