1. Проявление магнитосферной неустойчивости в начале рентгеновских вспышек в A0535+26 К.А.Постнов (ГАИШ МГУ) In collaboration with: R.Staubert, A.Santangelo, P.Kretschmar, I.Caballero, D.Klochkov IAAT, U. of Tuebingen

2. 26.12.2007HEA-20072 Introduction

3. 26.12.2007HEA-20073

4. 26.12.2007HEA-20074

5. 26.12.2007HEA-20075

6. 26.12.2007HEA-20076

7. 26.12.2007HEA-20077

8. 26.12.2007HEA-20078

9. 26.12.2007HEA-20079

10. 26.12.2007HEA-200710

11. 26.12.2007HEA-200711

12. 26.12.2007HEA-200712

13. 26.12.2007HEA-200713

14. 26.12.2007HEA-200714 Error bars: 90% CL

15. 26.12.2007HEA-200715

16. 26.12.2007HEA-200716 outburst pre-flares

17. 26.12.2007HEA-200717 Error bars: 90% CL

18. 26.12.2007HEA-200718 Summary of the RXTE/INTEGRAL analysis

19. 26.12.2007HEA-200719 Swift BAT light curves Giant o. Apr/May 05 Look-up 1 st normal o. Aug/Sep 05 2 nd normal o. Dec 05

20. 26.12.2007HEA-200720 Rising of the Aug/Sep 2005 outburst

21. 26.12.2007HEA-200721 Disk-magnetospheric interaction Lovelace et al. 1995

22. 26.12.2007HEA-200722

23. 26.12.2007HEA-200723

24. 26.12.2007HEA-200724 Centrifug. force Bending of field lines due to instability m.f.line curvature 1 st -order correction due to current sheet

25. 26.12.2007HEA-200725

26. 26.12.2007HEA-200726 How does this explain the observed features of Aug/Sep 05 outburst? 1) X-ray luminosity of flares are due to spasmodic accretion of matter from unstable NS magnetosphere

27. 26.12.2007HEA-200727 3) Plasma entering magnetosphere through KS-instability can be frozen closer to NS and falls along different lines  difference in the CRSF in flares and the main outburst 4) Independence of E c on luminosity during the main outburst suggests the absence of radiation-dominated accretion column (like in Her X-1, Staubert et al. 2007). ΔE c /E c ~10% in the flare  ΔB/B~10%  ΔR/R~3%  ΔR~300 m! Emission during the flare comes almost from the NS surface. Explanation of the different pulse profile evolution

28. 26.12.2007HEA-200728 5) Smooth p.p. change with energy in the flare suggests pencil-beam emission diagram in the flares. In the main outburst accretion column is higher and can have additional fan-beam formed by e-photons. Fan-beam due to e-photons disappears after crossing E c Only pencil-beam ?

29. 26.12.2007HEA-200729 Pencil-beam Fan beam B Pencil-beam Flares Main outburst

30. 26.12.2007HEA-200730 6. The amplitude of X-ray flares are strongly reduced when the NS spin-up starts, because then ξ =j/j in -> 1 and the mass in the boundary layer decreases (ΔM~(1- ξ) 3/5 ). When spin-up stops, flaring activity appears again (after Sep. 14, see the BAT light curve)

31. 26.12.2007HEA-200731 Other X-ray transients: 1) 2S 1845-024 Finger et al. 1999

32. 26.12.2007HEA-200732 2) EXO 2030+375 Camero Arranz et al 2005

33. 26.12.2007HEA-200733 Conclusions X-ray flares at the beginning of X-ray outbursts in A0535+26 can be due to magnetospheric instability Spasmodic accretion on top of quasi-stationarily increasing accretion rate explains all features observed in Aug/Sep 2005 outburst of A0535+26 Such behavior is expected at some critical accretion rate and is observed in other sources (e.g. 2S 1845-024 (Finger et al. 1999), EXO 2030+375 (Camero et al. 2005)). Further studies are under way searching for cyclotron line energy in other flares of A0535+26 and in other sources