Transient outburst mechanisms in supergiant fast X-ray transients
Sidoli
reporter: zhangzhen 09.11.23
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
• 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)
36 3710 1031 3310 10
• Sodoli et al. 2006 arxiv:0610890v1
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)
Models
• Clumpy winds
• Anisotropic winds
• Gated mechanisms
Clumpy winds
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
• 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)
Outbursts from spherically symmetric clumpy winds
Model: Oskinova et al. 2007
Negueruela et al. 2008Arxiv: 0801.3863v1
Oskinova et al. 2007 arxiv:0704.2390v2
Anisotropic winds
• The problem of the model (IRG J11215-5952)
Sidoli et al. 2007 arxiv:0710.1175v1
Outbursts from anisotropic winds: a preferential plane for the outflowing wing
• 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
MrelV
Gated mechanisms
Gated mechanisms• Definition of 3 radius:• Ra: the accretion radius Gravitationally focuesd• Rm: the magnetospheric radius The pressure of the magnetic field > the ram pr
essure of the inflowing matter• Rco: the corotation radius the angular velocity of NS = Keplerian angular ve
locity
Rm>Ra: the magnetic inhibition of accretion
• Rm>Ra,Rco• The superKeplerian • magnetic inhibition regime
• Rco>Rm>Ra• The subKeplerian • magneitc inhibition regime
Rm<Ra: propeller
• Rco<Rm<Ra• The supersonic propeller
regime
• Rm<Ra,Rco & • Tne subsonic propeller re
gime
limwM M
• Rm<Ra,Rco &
• The direct accretion regime
limwM M& &
Transitions
• 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
Application to IGR J17544-2619
• Quiescent
• Rise
• Outburst peak
• Tail
32 12 10xL ergs
34 11.5 10xL ergs
37 14 10xL ergs
36 12 10xL ergs
Ps=1300s, strong B• Quiescent superKeplerian magnetic inhibition• Rise subKeplerian magntic inhibition• Outburst peak direct accretion • Tail direct accretion Mdot decrease
Ps=400s, weak B
• Quiescent supersonic propeller• Rise subsonic propeller• Outburst peak direct accretion • Tail direct accretion Mdot decrease
• Problem of the model
• Both explanation require B>10^15G and >10^13G, in the magnetar range
Thanks