Unlocking the nature of ULXs using their X-ray spectra

1. Unlocking the nature of ULXs using their X-ray spectra Jeanette Gladstone - University of Alberta Tim Roberts, Chris Done - Durham University

2. Ultraluminous X-ray Sources • Early XMM-Newton studies fit with standard disc + power-law (as used in Galactic sources) • Detection of cool disc component suggested IMBH disk power-law e.g. NGC 1313 X-1 Miller et al. (2003) kTin ~ 0.15,  ~ 1.8 ~1000M BHs Jeanette Gladstone

3. Ultraluminous X-ray Sources • Early XMM-Newton studies fit with standard disc + power-law (as used in Galactic sources) • Detection of cool disc component suggested IMBH • Resultant fits are not disc dominated - mass estimates uncertain. disk power-law e.g. NGC 1313 X-1 Miller et al. (2003) kTin ~ 0.15,  ~ 1.8 ~1000M BHs Jeanette Gladstone

4. Ultraluminous X-ray Sources • Spectral features Jeanette Gladstone

5. Ultraluminous X-ray Sources • Spectral features • Soft excess Jeanette Gladstone

6. Ultraluminous X-ray Sources • Spectral features • Soft excess • High energy break (e.g. Roberts 2007) Jeanette Gladstone

7. Explanations for spectral break Slim accretion discs (e.g. Watarai et al. 2000) Fully Comptonised VHS with spectrum modified by ionised fast outflow (Goncalves & Soria 2006). Disc plus Comptonised corona models - find fits with cool disc and cool, optically thick corona (Stobbart et al. 2006) Jeanette Gladstone

8. Understanding ULX spectra • Only the highest quality data (>10,000 counts) • Characterise the shape of the spectrum • Gain greater understanding of spectral shape by applying current physically motivated models Jeanette Gladstone

9. Understanding ULX spectra Sample of 12 sources lying within 10 Mpc, covering the range of ULX luminosities (~ 1039 - a few 1040 erg s-1) Jeanette Gladstone

10. Characterising ULX Spectra model fit disk power-law Holmberg IX X-1 Jeanette Gladstone

11. Characterising ULX Spectra • 11/12show improvement (2 > 30) with addition of disc component (soft excess) model fit disk power-law Holmberg IX X-1 Jeanette Gladstone

12. Characterising ULX Spectra • 11/12show improvement (2 > 30) with addition of disc component (soft excess) • 11/12 >98% statistical improvement for Broken power-law vs. power-law above 2 keV power-law Holmberg IX X-1 Jeanette Gladstone

13. Sample spectra Jeanette Gladstone

14. Sample spectra Jeanette Gladstone

15. Sample spectra Jeanette Gladstone

16. Sample spectra Soft excess + break not seen in any other accretion state, this is something new … Jeanette Gladstone

17. Sample spectra Soft excess + break not seen in any other accretion state, this is something new … … but what? Jeanette Gladstone

18. Physically motivated modelling Jeanette Gladstone

19. Physically motivated modelling • Slim discs? Jeanette Gladstone

20. Physically motivated modelling • Slim discs? • Comptonisation models? Jeanette Gladstone

21. Physically motivated modelling • Slim discs? • Comptonisation models? • Worked well on XRBs so why not? Jeanette Gladstone

22. Physically motivated modelling • Slim discs? • Comptonisation models? • Worked well on XRBs so why not? Holmberg IX X-1 Jeanette Gladstone

23. Physically motivated modelling • Slim discs? • Comptonisation models? • Worked well on XRBs so why not? Holmberg IX X-1 Jeanette Gladstone

24. Slim disc fits • 0.4 < p < 0.6 could imply support for slim disc diskpbb Holmberg IX X-1 Jeanette Gladstone

25. Slim disc fits • 0.4 < p < 0.6 could imply support for slim disc • Problem - 1.1 < Tin < 13 keV, higher disc temperature values are physically unrealistic diskpbb Holmberg IX X-1 Jeanette Gladstone

26. Slim disc fits • 0.4 < p < 0.6 could imply support for slim disc • Problem - 1.1 < Tin < 13 keV, higher disc temperature values are physically unrealistic diskpbb Holmberg IX X-1 Jeanette Gladstone

27. Slim disc fits • 0.4 < p < 0.6 could imply support for slim disc • Problem - 1.1 < Tin < 13 keV, higher disc temperature values are physically unrealistic diskpbb Holmberg IX X-1 Jeanette Gladstone

28. Comptonisation models • Two different Comptonisation models applied • COMPTT • EQPAIR model fit disk comptt DISKPN + COMPTT Jeanette Gladstone

29. Comptonisation models • Two different Comptonisation models applied • COMPTT • EQPAIR • Fit with cool disc + cool optically thick corona ( > 6) model fit disk comptt DISKPN + COMPTT Jeanette Gladstone

30. Comptonisation models • Galactic sources? All thin ( < 1-2) except in VHS ( ~3, kT ~20 keV) model fit disk eqpair DISKPN + EQPAIR Jeanette Gladstone

31. Comptonisation models • Galactic sources? All thin ( < 1-2) except in VHS ( ~3, kT ~20 keV) • More extreme - super-Eddington? model fit disk eqpair DISKPN + EQPAIR Jeanette Gladstone

32. Implications of Corona? model fit disk comptt model fit disk eqpair Jeanette Gladstone

33. Implications of Corona? • Masking of innermost regions of the accretion disc • Material and power may be drawn from the disc to feed the corona model fit disk comptt model fit disk eqpair Jeanette Gladstone

34. As accretion rate increases, material & energy fed into corona Energetic disc-corona coupling Jeanette Gladstone

35. As accretion rate increases, material & energy fed into corona Observe Outer disc Corona Energetic disc-corona coupling model fit disk corona Jeanette Gladstone

36. Energetically coupled inner disc cannot be seen Neither feature can give direct information on temperature of inner accretion disc Energetic disc-corona coupling model fit disk corona Jeanette Gladstone

37. Spectra of ULXs Jeanette Gladstone

38. Spectra of ULXs Jeanette Gladstone

39. Disc- like spectra? • Looks disc-like • Recovered disc similar to actual data Jeanette Gladstone

40. Disc- like spectra? • Looks disc-like • Recovered disc similar to actual data • Disc + power-law reveals warm disc fit Jeanette Gladstone

41. Disc- like spectra? • Looks disc-like • Recovered disc similar to actual data • Disc + power-law reveals warm disc fit • Physical meaning? • Broadening to create more realistic disc in this energy band (e.g. Done & Davis 2008) Jeanette Gladstone

42. Ultraluminous state spectra • Double hump feature • First modelled by cool disc • Second modelled by break, or by Comptonising corona when applying more physical models Jeanette Gladstone

43. Ultraluminous state spectra • Double hump feature • First modelled by cool disc • Second modelled by break, or by Comptonising corona when applying more physical models • Both features, new state? Jeanette Gladstone

44. IMBH? Low temperature discs? Jeanette Gladstone

45. IMBH? Something else? So far we have tracked increasing mass accretion rate Low temperature discs? Jeanette Gladstone

46. IMBH? Something else? So far we have tracked increasing mass accretion rate Theory predicts that a photosphere + wind are key components of super-Eddington accretion First observational evidence of photosphere? Low temperature discs? Jeanette Gladstone

47. IMBH? Something else? So far we have tracked increasing mass accretion rate Theory predicts that a photosphere + wind are key components of super-Eddington accretion First observational evidence of photosphere? If this is the case we are looking at stellar-mass black hole in an extreme accretion state Low temperature discs? Jeanette Gladstone

48. Extreme accretion? Jeanette Gladstone

49. Extreme accretion? Jeanette Gladstone

50. Extreme accretion? Jeanette Gladstone