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Modeling Clumped Stellar Winds in Supergiant HMXBs: A CAK Approach

This study explores clumpy stellar winds in supergiant High-Mass X-ray Binaries (HMXBs) using the CAK model. It bridges detailed theoretical models of inhomogeneous stellar winds in single stars with observational data on donor winds in HMXBs. The CAK model focuses on line radiation scattering and key stellar envelope equations like mass conservation and momentum balance. Results from simulations and modifications show how microclumping affects mass loss rates. The study offers insights into the complex wind structures of supergiant HMXBs like 4U1700-37 and Vela X-1.

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Modeling Clumped Stellar Winds in Supergiant HMXBs: A CAK Approach

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  1. Clumped stellar winds in supergiant HMXBs ArXiv: 1201.1951v1 Oskinova et. al. Reporter: Zhang Zhen 2012.3.13

  2. Outlines • Introduction • The CAK model • Bondi-Hoyle-Lyttleton accretion • Simulations and paradox • Modification and results • Conclusion

  3. Introduction • Theories about clumpy wind • CAK: line scattering 2500km/s • Owocki et al. 1988: numerical simulation Small-amplitude perturbation  Highly structured wind • Runacres & Owocki 2002 Evolution of wind structures  Inhomogeneous

  4. Introduction • Observations about clumpy wind • Prinja & Massa (2010)

  5. Introduction • Clumpy wind in supergiant HMXBs • van der Meer et al. (2005): 4U1700-37 • SFXT • Furst et al. (2010): Vela X-1

  6. Purpose • Bridge the gap between detailed models of inhomogeneous stellar winds in single stars and the phenomenological description of donor winds in supergiant high-mass X-ray binaries (HMXBs).

  7. CAK model

  8. CAK • Main idea: scattering of line radiation • Basic equations for the stellar envelope • Mass conservation: • Momentum balance: • Equation of state

  9. About • Castor, 1974, MNRAS, 169, 279

  10. CAK result

  11. Results • For a class O5

  12. Bondi accretion

  13. BHL accretion • Reviewed by Edgar (2004) & Negueruela (2009) • Bondi radius: • Accretion rate

  14. Simulations and paradox

  15. HYDRODYNAMICAL SIMULATIONS • Feldmeier et al. (1997a,b): hydrodynamical simulations of the line driven stellar wind

  16. L_x: a change up to eight orders of magnitude

  17. Modification and results

  18. Background • Microclumping: optically thin Leads to smaller mass-loss rate Hillier 1991; Hamann & Koesterke 1998 Bouret et al. (2005) and Fullerton et al. (2006) • Modification: Photo-ionization Absorption

  19. Photo-ionization • Neglecting absorption, the mean primary photon intensity at frequency v at a distance r: •  • Photo-ionization parameter:

  20. Absorption

  21. Calculation • 2_D stochastic wind model: Oskinova et al. (2004) Feldmeier et al. (1997a,b) + Absorption • Notation: 1. spherically symmetric 2. solid angle 3. “balls” & “pancakes” 4. no self-absorption & no re-emission. 5. edge on system

  22. Results

  23. Thanks

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