3-D R adiative Transfer in Clumped Hot Star Winds

1. 3-D Radiative Transfer in Clumped Hot Star Winds Surlan et al. 1202.4787 Surlan et al. 1202.4494 Reporter: Wei Sun Mar. 5th, 2012

2. Why hot star winds? • Mass loss plays an important role in • the stellar evolution (Meynet et al. 1994), • the affection to the interstellar environment: chemical, momentum, and mechanical feedback; • Typical values • mass-loss rate ; • terminal velocity ; • mechanical energy ; • β-velocity law:

3. Mass-loss rate, mass-loss rate, mass-loss rate! • diagnostics: fitting the spectroscopic observations via line-blanketed, non-LTE atmosphere models (e.g., CMFGEN Hillier & Miller 1998, PoWRGräfener et al. 2002, FASTWIND Puls et al. 2005), “density squared” vs. “radial optical depth” • recombination lines (e.g., Hα line, Puls et al, 1996); • free-free continuum emission in radio band; • UV resonance-line absorption (e.g., C IV λλ1548, 1551, P V λλ1118, 1128) • influence from X-rays: changes of the ionization/excitation balance by Auger effect

4. Why clumping winds? • the intrinsic instability of the line-driven winds (Lucy & White, 1980); • stochastic variability (Eversberg et al., 1998); • the X-ray line formation favors the inhomogeneities of the stellar winds (Oskinova et al., 2006); • a combine optical/IR/radio analysis derived a lower mass-loss rate comparing to Hα’s result (Puls et al., 2006): • the P V problem (Fullerton, Massa, & Prinja, 2006); O VIII line in ζOri (Oskinova et al., 2006) Fullerton, Massa, & Prinja, 2006 ζ Pup, Lépine & Moffat, 2008

5. Why macro-clumping winds? • The mass-loss rate derived from the P-Cygni P V resonance line is extremely low; • macro- vs. micro-: • optical thick vs. thin = porosity vs. clumped; • optically thin emission: not influenced vs. enhanced; • optically thick emission: reduced vs. not influenced; • mass-loss rate: seemly not reduced vs. reduced;

6. Previous Work • first attempt: Oskinova et al., 2006; • non-monotonic velocity field: Owocki 2008; • non-void inter-clump medium: Zsargó et al., 2008; • 2-D stochastic wind model: Sundqvist et al., 2010; • extended to pseudo-3D: Sundqvist et al., 2011.

7. Model Description • basic assumptions: • core-halo model: only counts in the line opacity; • spherical clumps (radius neither split nor merge ; • free parameters: • the average clump separation • the clump condensation factor • the ICM dilution factor • derived parameter: • total mass • filling factor

8. Radiative Transfer • Calculate τ • random scattering

9. Results: clumping separation

10. Results: on-set radius

11. Results: non-void ICM

12. Results: velocity dispersion inside clumps

13. Results: a doublet

14. Summary • larger separation: reducing the line strength; • The photons can also be scattered in the density “holes” due to ICM; The strong lines are saturated more; • clumping starts higher in the wind, the absorption near the line center is broader; • The velocity dispersion inside clumps broadens the line widths; • the clumping effects are analogues in the case of resonance doublets. • Clumping lowers the effective opacity.

15. Thanks!