Stellar Winds Jorick Vink (Keele University)

Transcription

1 Stellar Winds Jorick Vink (Keele University)

2 Outline Why predict Mass-loss rates? (as a function of Z) Monte Carlo Method Results O & B, LBV, B[e] & WR winds Cosmological implications?

3 Why predict Mdot? Energy & Momentum input into ISM

4 Massive star feedback NGC 3603 (Credit: Brandner & NASA)

5 Why predict Mdot? Energy & Momentum input into ISM Direct chemical enrichment

6 Why predict Mdot? Energy & Momentum input into ISM Direct chemical enrichment Stellar Evolution

7 Evolution of a Massive Star O B[e]

8 Why predict Mdot? Energy & Momentum input into ISM Direct chemical enrichment Stellar Evolution - Explosions: SNe, GRBs

9 Why predict Mdot? Energy & Momentum input into ISM Direct chemical enrichment Stellar Evolution - Explosions: SNe, GRBs - Final products: neutron star, black hole?

10 The Final products of Pop III stars (Heger et al. 2003)

11 Why predict Mdot? Energy & Momentum input into ISM Direct chemical enrichment Stellar Evolution Indirect chemical enrichment

12 Why predict Mdot? Energy & Momentum input into ISM Direct chemical enrichment Stellar Evolution Indirect chemical enrichment Stellar spectra

13 Why predict Mdot? Energy & Momentum input into ISM Direct chemical enrichment Stellar Evolution Indirect chemical enrichment Stellar spectra Stellar cosmology

14 From Scientific American (V. Bromm)

15 Goal: quantifying mass loss a function of Z (and z)

16 Observations of the first stars

17 Goal: quantifying mass loss a function of Z (and z) What do we know at solar Z?

18 Radiation-driven wind by Lines Lucy & Solomon (1970); Castor, Abbott & Klein (1975) = CAK STAR WIND Fe Outward Force Mass Loss dm/dt = f (Z) dm/dt = f (Z,L,M,Teff) with Z = (C,N,O,.,Fe)

19 Monte Carlo approach (Abbott & Lucy 1985)

20 Approach: Assume velocity law Compute model atmosphere, ionization stratification, level populations Monte Carlo to compute radiative force

21 OB Mass loss parameter study

22 Wind momenta for O stars Models Vink, de Koter & Lamers (2000)

23 Lamers et al. (1995), Crowther et al. (2006) Vink et al. (1999): Fe IV III

24 Monte Carlo Mass-loss rates dm/dt increases by factor 5 (Vink et al. 1999

25 The Bi-stability Jump HOT COOL Fe IV Fe III low dm/dt high V(inf) dm/dt = 5 dm/dt HOT V(inf) = ½ vinf HOT Low density High density = 10 HOT

26 Stars should pass the Bistable limit During evolution from O B LBVs on timescales of years

27 LBVs in the HRD Smith, Vink & de Koter (2004)

28 The mass loss of LBVs Models Data Stahl et al. (2001) Vink & de Koter (2002)

29 Implications for circumstellar medium (CSM) - Mass-loss rate up - Wind velocity down CSM density variations!

30 The Radio SN 2001ig Ryder et al. (2004) An LBV progenitor? Kotak & Vink (2006)

31 Rotating stars near Bistable Limit - Hot pole: low density - Cool equator: high density (Lamers & Pauldrach 1991)

32 Rotating star hotter at pole Von Zeipel (1924): Equatorial gravity darkening Polar brightening

33 Bistable Equatorial outflow Density (eq) = 10 Density (pole) B[e] supergiants Vink, de Koter & Lamers (1999) Pelupessy, Lamers & Vink (2000) Angular momentum evolution in stellar models

34 Monte Carlo successes at solar Z O-star Mass loss rates Prediction of the Bistability jump Mass loss behaviour of LBVs like AG Car Monte Carlo mass-loss used in stellar models in Galaxy

35 O star mass-loss Z-dependence (Vink et al. 2001)

36 O star mass-loss Z-dependence Kudritzki (2002) -- Vink et al. (2001) see Vink astro-ph/

37 O star mass-loss Z-dependence

38 Which metals are important? Vink et al. (2001) solar Z Fe CNO H,He low Z At lower Z : Fe CNO

39 WR stars produce Carbon! Geneva models (Maeder & Meynet 1987)

40 WR stars produce Carbon! Geneva models (Maeder & Meynet 1987)

41 Which element drives WR winds? - C WR mass loss not Z(Fe)-dependent - Fe WR mass loss depends on Z host

42 Z-dependence of WR winds WN WC Vink & de Koter (2005, A&A 442, 587)

43 Corollary of lower WR mass loss: less angular momentum loss may favour the collapse of WR stars to produce GRBs (Yoon & Langer - Woosley & Heger) Long-duration GRBs favoured at low Z

44 Z-dependence of WR winds WN WC Vink & de Koter (2005, A&A 442, 587)

45 Mass loss & Eddington Limit ~ Gamma^5 Vink ( astro-ph/ )

46 Summary Successful MC Models at solar Z O star winds are Z-dependent (Fe) WR winds are Z-dependent (Fe) GRBs Low-Z WC models: flattening of this dependence Below log(z/zsun) = -3 Plateau

47 Implications for First stars Self-enrichment (WC-type enrichment) Proximity to Eddington Limit Rotational mixing & self-enrichment Stellar Winds may be relevant for the evolution of the Early Universe