The rotation rates of massive stars: the role of binary interaction

Transcript

1. Anna Ho Journal Club 12 January 2018 de Mink et al. 2013 The rotation rates of massive stars: the role of binary interaction
2. We want to know the initial spin distribution of a population of massive stars (constraints on theories of massive star formation, input for models of stellar populations in local Universe and at high-z…)
3. We want to know the initial spin distribution of a population of massive stars We can’t observe the initial distribution We can observe the current distribution
4. We want to know the initial spin distribution of a population of massive stars We can’t observe the initial distribution We can observe the current distribution ?
5. Hunter et al. (2008) 270 stars in the LMC Rotational Velocity Distribution
6. Spin: a matter of life and death On the whole, this review points out that stellar evolution is not only a function of mass M and metallicity Z, but of angular velocity Ω as well. (Maeder & Meynet 2000)
7. Spin: a matter of life and death On the whole, this review points out that stellar evolution is not only a function of mass M and metallicity Z, but of angular velocity Ω as well. (Maeder & Meynet 2000) from Heger & Langer (2000) M = 20 M̥
8. Spin: a matter of life and death Widens MS Increases core H-burning lifetime Increases size of core —> nucleosynthetic yield, luminosity Changes surface abundances (“rotational mixing”) Determines SN progenitor
9. Initial spin distribution Final spin distribution Spin of molecular cloud
10. Initial spin distribution Final spin distribution Somehow lose angular momentum in star formation Spin of molecular cloud
11. Initial spin distribution Final spin distribution Somehow lose angular momentum in star formation Expansion during core hydrogen burning Spin of molecular cloud
12. Initial spin distribution Final spin distribution Somehow lose angular momentum in star formation Expansion during core hydrogen burning Stellar winds Spin of molecular cloud
13. Initial spin distribution Final spin distribution Somehow lose angular momentum in star formation Expansion during core hydrogen burning Close binary interactions Stellar winds Spin of molecular cloud
14. de Mink et al. 2013: modeling the effects of binarity Conclusions: 1. 20% of massive MS stars rotate rapidly (vrot > 200 km/s) 2. Most are products of close binary evolution Procedure 1. Construct population of massive stars 2. Evolve stars with inertia, winds, binary interaction (tides, mass transfer, mergers) 3. Measure evolution of vrot 4. Compare vrot with observations
15. Evolution of Keplerian rotational velocity for individual systems de Mink+ 2013
16. Evolution of vrot for main-sequence stars in binary de Mink+ 2013
17. Equatorial vrot Keplerian vrot Expansion accelerates Evolution of vrot for main-sequence stars in binary de Mink+ 2013
18. Equatorial vrot Keplerian vrot Evolution of vrot for main-sequence stars in binary de Mink+ 2013
19. Evolution of vrot for main-sequence stars in binary de Mink+ 2013
20. Increase due to tides Evolution of vrot for main-sequence stars in binary de Mink+ 2013
21. Evolution of vrot for main-sequence stars in binary de Mink+ 2013
22. Binary evolution: implications for rotational mixing Brott et al. (2011)
23. Langer (2012) Binary evolution: implications for rotational mixing
24. Binary evolution: implications for Be stars (20-30% of early B-stars) Transfer of mass and angular momentum Supernova System remains bound System disrupted
25. Comparison with observed populations % with vsini > 200 km/s % with vsini > 300 km/s % with vsini > 400 km/s Predicted Observed (VFTS; 30 Dor) 19% 30-50% 11% 15-16% 2% 3-5% MORE BINARIES
26. We want to know the initial spin distribution of a population of massive stars We can’t observe the initial distribution We can observe the current distribution ?
27. Heger & Langer 2000