Discordant Estimates of Mass-Loss Rates for O-Type Stars

1. Discordant Estimates of Mass-Loss Rates for O-Type Stars Alex Fullerton STScI /HIA Derck Massa (STScI/SGT) & Raman Prinja (UCL)

2. Mass-Loss Diagnostics H emission: recombination  2 Thermal radio emission: free-free  2 UV resonance lines: scattering   O5 If+ 10.0 × 10-6 Msun/yr 7.5 5.0 Kudritzki & Puls 2000, ARAA, 38, 613

3. Mass-Loss Diagnostics H emission: recombination  2 Thermal radio emission: free-free  2 UV resonance lines: scattering  

4. Mass-Loss Diagnostics H emission: recombination  2 Thermal radio emission: free-free  2 UV resonance lines: scattering  

5. Mass-Loss Diagnostics Thermal radio emission: free-free  2 H emission: recombination  2 UV resonance lines: scattering   Constants, Parameters Velocity Law Optical Depth Ionization Fraction: 0  qi  1 Usually Don’t Know Usually Can’t Estimate

6. UV Resonance Lines in Hot-Star Winds P V λλ 1117.977, 1128.008 fblue, fred = 0.473, 0.234 Δv = 2690 km/s (P/H)solar = 2.8 × 10-7 (P/C)solar = 8.5 × 10-4

7. P V Morphology O2 O4 O6 O9.7 Walborn et al., 2002 , ApJS, 141, 443

8. Wind Profile Fits to P V 1118, 1128 O4 O5 O6 O7.5 O8 O9.5 Fullerton, Massa, & Prinja 2006, ApJ, 637, 1025

9. A Mass Loss Discrepancy Fullerton, Massa, & Prinja 2006, ApJ, 637, 1025

10. Empirical Ionization Fraction of P4+ Fullerton, Massa, & Prinja 2006, ApJ, 637, 1025

11. Similarly for the LMC Massa, Fullerton, Sonneborn, & Hutchings 2003, ApJ, 586, 996

12. Critique

13. Critique

14. Critique O8 I O7 I Collisional Equilibria q O6 I O5 I q v / v∞ v / v∞ Puls et al. 2008, ASPC, 388, 101 Sutherland & Dopita 1993, ApJS, 88, 253

15. Critique

16. Critique

17. Consequences of Clumping (1) “Direct”: Mass-loss rates determined from ρ2 diagnostics are over-estimated. “Indirect”: The ionization stratification of the wind is altered by enhanced recombination in the clumps. q(P4+) clumped wind f∞ = 0.04 If all the P V - ρ2discrepancy is assigned to the ρ2 diagnostics, then The ρ2mass-loss rates must be reduced by factor of at least 10; and Volume filling factors of << 0.01 are implied. CMFGEN Model of HD 190429A (O4 If+) Bouret, Lanz, & Hillier 2005, A&A, 438, 301 q(P4+) smooth wind

18. Consequences of Clumping (2) ζ Puppis O4 I(n)f Spatial Porosity: When clumps become optically thick, the effective opacity of the wind decreases because star light can find an unattenuated channel through the wind. Material can be hidden in the clumps. “Macroclumping”: Not all transitions have the same optical depth, so porosity affects some lines more than others. “Velocity Porosity”: For line transfer, gaps in the velocity profile (“vorosity”) permit star light to leak through the wind, irrespective of the spatial porosity. This effect also weakens an absorption trough. Oskinova, Hamann, & Feldmeier 2007, A&A, 476, 1331

19. Consequences of Clumping (2) Spatial Porosity: When clumps become optically thick, the effective opacity of the wind decreases because star light can find an unattenuated channel through the wind. Material can be hidden in the clumps. “Macroclumping”: Not all transitions have the same optical depth, so porosity affects some lines more than others. “Velocity Porosity”: For line transfer, gaps in the velocity profile (“vorosity”) permit star light to leak through the wind, irrespective of the spatial porosity. This effect also weakens an absorption trough. Owocki 2007 “Clumping in Hot-Star Winds” (Potsdam)

20. Summary • The discrepancy between mass-loss rates estimated from P V and 2 diagnostics is very important. • The paradigm is evolving: winds are significantly structured. • But on what scale[s]? By what process[es]? • Consequently: • Mass-loss rates derived from 2 diagnostics are biased: too large. • Mass-loss estimates from P V are biased if the “clumps” are optically thick: too small(?) • We don’t know what the mass-loss rates are to within ??? • Concordance will likely require inclusion of several effects. • We need to use all available diagnostics to break multiple degeneracies.

21. Good Science Opens Doors “…the reasonable assumption that the mass loss rate for any star should be the same irrespective of which line is used …” Conti & Garmany (1980, ApJ, 238, 190) Questions!

22. Back-Up Slides

23. Why Was Clumping Ignored? Lamers & Leitherer (1993, ApJ, 412, 771): ζ Puppis O4 I(n)f Absence of variability on flow time scale. Mass fluxes determined at different radio wavelengths (i.e., radial distances) agreed. The mass fluxes obtained from H (formed near the star) and the radio free-free continuum (formed far from the star) agree. Since it is unlikely that the clumping factor would be the same at both radii, it must be unity; i.e., no clumping. He II 4686 Eversberg, Lépine, & Moffat 1998, ApJ, 494, 799 Lépine & Moffat 2008, AJ, 136, 548

24. Why Was Clumping Ignored? Lamers & Leitherer (1993, ApJ, 412, 771): Absence of variability on flow time scale. Mass fluxes determined at different radio wavelengths (i.e., radial distances) agreed. The mass fluxes obtained from H (formed near the star) and the radio free-free continuum (formed far from the star) agree. Since it is unlikely that the clumping factor would be the same at both radii, it must be unity; i.e., no clumping. ζ Puppis O4 I(n)f Blomme et al. 2003, A&A, 408, 715

25. Why Was Clumping Ignored? Lamers & Leitherer (1993, ApJ, 412, 771): Absence of variability on flow time scale. Mass fluxes determined at different radio wavelengths (i.e., radial distances) agreed. The mass fluxes obtained from H (formed near the star) and the radio free-free continuum (formed far from the star) agree. Since it is unlikely that the clumping factor would be the same at both radii, it must be unity; i.e., no clumping. ζ Puppis O4 I(n)f Puls et al. 2006, A&A, 454, 625

26. Summary: Effects of Clumping

27. Sk -67°166 O4 If+

28. Wind Profile Fits to P V 1118, 1128 O7 II(f) O7 Ib(f) O7.5 III O7 V ((f)) Fullerton, Massa, & Prinja 2006, ApJ, 637, 1025