Observations of Massive Stars

Transcript

1. Observations of Massive Stars and the Atmospheric Eddington Limit Kolby Weisenburger 23 May 2016 ASTR 531
2. Eddington Limit log L/L☉ log Teff 5 4 6 5 4 3 LE MS L E = 4πGM κ
3. Atmospheric Eddington Limit
4. Atmospheric Eddington Limit We are used to dealing with high temperatures, high densities, and opacities due to electron scattering
5. Atmospheric Eddington Limit But now, in the atmospheres of cool stars, the opacity due to H- is much greater and implies a drop in the Eddington limit
6. Eddington Limit log L/L☉ log Teff 5 4 6 5 4 3 LE MS L E = 4πGM κ
7. log L/L☉ log Teff 5 4 6 5 4 3 LE MS LE ATM Atmospheric Eddington Limit L E = 4πGM κ
8. log L/L☉ log Teff 5 4 6 5 4 3 LE MS Atmospheric Eddington Limit Higher metallicity (due to increase)
9. log L/L☉ log Teff 5 4 6 5 4 3 LE MS Atmospheric Eddington Limit
10. log L/L☉ log Teff 5 4 6 5 4 3 LE Atmospheric Eddington Limit RSG 20 M 25 M
11. log L/L☉ log Teff 5 4 6 5 4 3 LE Atmospheric Eddington Limit RSG YSG 50 M 20 M 25 M
12. Supergiants YSG • 5000 - 10,000 K; F or G spectral type • Highly variable and unstable • Often observed as Cepheid Variables RSG • > 4000 K; K or M spectral type • Less massive than YSGs • Most massive will end as supernovae
13. log L/L☉ log Teff 5 4 6 5 4 3 LE Atmospheric Eddington Limit RSG YSG 50 M 20 M 25 M
14. log L/L☉ log Teff 5 4 6 5 4 3 LE Atmospheric Eddington Limit RSG YSG LBV 20 M 25 M 50 M 100 M
15. Luminous Blue Variables • Mass loss rates > 10-5 M☉ /yr • Eruptions every 100 to 1000 years • Large and irregular variations in V magnitude, but luminosity remains constant… • Leads to huge radius fluctuations: 20-30 R☉ → 100-200 R☉ • Only ~tens known so must be a short-lived phase NASA
16. log L/L☉ log Teff 5 4 6 5 4 3 LE Atmospheric Eddington Limit RSG YSG LBV 20 M 25 M 50 M 100 M
17. Atmospheric Eddington Limit log L/L☉ log Teff 5 4 6 5 4 3 LE RSG YSG LBV WR 50 M 20 M 25 M
18. Hubble Legacy Archive Wolf-Rayet Stars • 30,000 to 100,000 K • Broad emission lines indicate strong stellar winds with a mass loss rate of 4 x 10-5 M☉ /yr • Atmospheres strongly enriched by fusion products WNL: N and He-rich, C and O-poor, some H (CNO) WNE: N and He-rich, C-poor, no H (CNO) WC: C and He-rich, no N or H (3α)
19. Atmospheric Eddington Limit log L/L☉ log Teff 5 4 6 5 4 3 LE RSG YSG LBV WR 50 M 20 M 25 M
20. NASA