Transient outburst mechanisms in supergiant fast X-ray transients Sidoli

1. Transient outburst mechanisms in supergiant fast X-ray transientsSidoli reporter: zhangzhen 09.11.23

2. Confirmed sources: (eight) • IGR J08408-4503 • IGR J11215-5952 • IGR J16479-4514 • XTE J1739-302 (Smith et al. 1998 arxiv:9805178v1) • IGR J17544-2619 • SAX J1818.6-1703 • IGR J18410-0535 • IGR J18483-0311

3. Sporadic outbursts lasting minutes to hours Luminosity of the peak ~ Luminosity in quiescence ~ • Spectra: HMXB A flat hard power law below 10keV a high energy cut-off at about 15-30keV • IR/optical observation: OB supergiant companion  wind accretion (Halpern et al. 2004, Pellizza et al. 2006, Masetti et al. 2006)

4. Sodoli et al. 2006 arxiv:0610890v1

5. Something extra :IGR J11215-5952 • X-ray pulsar: Ps=186.78s • Outbursts: Period ~329 days 3-4 July 2003 26-27 May 2004 (Sguera et al. arxiv:0603756) Spaced ~330 days 16-17 March 2006(smith et al. The Astronomer’s Telegram 766) 9 February 2007 (Romano et al. 2007)

6. Models • Clumpy winds • Anisotropic winds • Gated mechanisms

7. Clumpy winds

8. Outbursts from spherically symmetric clumpy winds • The mass loss rate in the form of wind clump: Walter & Zurita Heras. 2007 Arxiv:0710.2542v1 Result match Oskinova et al. 2007

9. The problem of the model • Accretion process complex: Centrifugal effect of a neutron star’s magnetic field Lx and the dense of the wind (Grebenev & Sunyaev 2007)

10. Outbursts from spherically symmetric clumpy winds Model: Oskinova et al. 2007 Negueruela et al. 2008 Arxiv: 0801.3863v1

11. Oskinova et al. 2007 arxiv:0704.2390v2

12. Anisotropic winds

13. The problem of the model (IRG J11215-5952) Sidoli et al. 2007 arxiv:0710.1175v1

14. Outbursts from anisotropic winds: a preferential plane for the outflowing wing

15. Problem of the clumpy wind model: • & • The density and/or velocity contrasts in the wind can be eased if there is a barrier that remains closed during quiescence

16. Gated mechanisms

17. Gated mechanisms • Definition of 3 radius: • Ra: the accretion radius Gravitationally focuesd • Rm: the magnetospheric radius The pressure of the magnetic field > the ram pressure of the inflowing matter • Rco: the corotation radius the angular velocity of NS = Keplerian angular velocity

18. Rm>Ra: the magnetic inhibition of accretion • Rm>Ra,Rco • The superKeplerian • magnetic inhibition regime • Rco>Rm>Ra • The subKeplerian • magneitc inhibition regime

19. Rm<Ra: propeller • Rco<Rm<Ra • The supersonic propeller regime • Rm<Ra,Rco & • Tne subsonic propeller regime

20. Rm<Ra,Rco & • The direct accretion regime

21. Transitions

23. Long spin period systems require magnetar-like B-fields • Shorter spin period systems must posses lower magnetic fields • Few or no transitions with either high magnetic fields and short spin periods, or systems with lower magnetic fields and long spin periods

24. Application to IGR J17544-2619 • Quiescent • Rise • Outburst peak • Tail

25. Ps=1300s, strong B • Quiescent superKeplerian magnetic inhibition • Rise subKeplerian magntic inhibition • Outburst peak direct accretion • Tail direct accretion Mdot decrease

26. Ps=400s, weak B • Quiescent supersonic propeller • Rise subsonic propeller • Outburst peak direct accretion • Tail direct accretion Mdot decrease

27. Problem of the model • Both explanation require B>10^15G and >10^13G, in the magnetar range

28. Thanks