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Monte-Carlo experiments on NS Spin Evolution of BeXBs

Monte-Carlo experiments on NS Spin Evolution of BeXBs. arXiv:1111.2051v1 (Christian Knigge,etal) arXiv:1101.5036v1 (Pablo Reig)

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Monte-Carlo experiments on NS Spin Evolution of BeXBs

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  1. Monte-Carlo experiments on NS Spin Evolution of BeXBs arXiv:1111.2051v1 (Christian Knigge,etal) arXiv:1101.5036v1 (Pablo Reig) Reporter: Zhongqun Cheng 2012-12-03

  2. Outlines • Background and motivation • Spin evolution of neutron stars • Two accretion modes for BeXBs • Monte carlo results • Disccusion

  3. Background and motivation

  4. Galactic BeXBS(Pablo Reig 2011)

  5. Bimodal distribution of Be/X-ray binaries in Corbet diagram(Christian Knigge,etal 2011)

  6. Interpretion of the bimodal distribution • two distinct neutron star spin equilibria accessible at all orbital periods • two distinct long-lived evolution stages depend on orbital period evolution • two distinct BeXB formation channels,that is two type of supernovae creats the bimodal distribution

  7. Interpretion of the bimodal distribution • electron-capture supernova • iron-core collapse supernova

  8. Spin down of neutron star(Davis&Pringle1981) • pulsar phase or ejector (a) • propeller phase (1)very rapid rotator (b) (2)supersonic propeller (c) (3)subsonic propeller (d) • equilibrium accretion phase

  9. pulsar phase • very rapid rotator

  10. supersonic propeller • subsonic propeller • equilibrium accretion

  11. Accretion rate of BeXBs • spherical wind • disk wind

  12. Accretion modes of BeXBs(Water&Kerkwijk,1989) • spherical wind accretion • disk wind accretion

  13. Angular momentum in two accretion modes • spherical wind accretion • disk wind accretion

  14. The dominant mode of BeXBs accretion • precondition of accretion disk formed around neutron star(X.-D.Li,1996) • for a BeXB system with disk wind, calculate its magnetic radius and circulation radius

  15. Monte Carlo parameters:

  16. spin evolution of NS

  17. Discussion • the bimodal distribution of BeXBs on Corbet diagram may ascribe to the spin down evolutionary process, two different wind accretion modes may take place in one BeXBs,but which one dominate remain to be determined. • accretion disk formed around the NS or not is the final decisive factor to the spin evolution equilibrium period. system with accretion disk formed may stay on a lower equilibrium period otherwise the NS may reach a higher equilibrium period.

  18. Thanks!

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