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Inferring Stellar Masses:

0. Inferring Stellar Masses:. More than 50 % of all stars are part of multiple systems. a) Visual Binaries:. Both components observed directly. Binary Systems. b) Astrometric Binaries:. Only brighter member can be observed; astrometric oscillations. 0. c) Eclipsing Binaries.

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Inferring Stellar Masses:

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  1. 0 Inferring Stellar Masses: More than 50 % of all stars are part of multiple systems. a) Visual Binaries: Both components observed directly. Binary Systems b) Astrometric Binaries: Only brighter member can be observed; astrometric oscillations

  2. 0 c) Eclipsing Binaries Inclination ~ 90o In addition to stellar masses,infer relative temperatures and radii

  3. 0 d) Spectrum Binaries Two superimposed, discernible spectra from the 2 stars; periodic, opposite shifts: Approaching star: blue shifted lines; Receding star: red shifted lines Doppler shift → Measurement of radial velocities → Estimate of separation a → Estimate of masses

  4. 0 Time

  5. 0 e) Spectroscopic Binaries Only one star and one absorption line system seen; Periodic Doppler shifts. { 2 Dl → Place limits on the mass of the unseen component

  6. 0 Visual Binaries Basically all parameters can be determined: observer i M1 The Ideal Case a2 a1 M2

  7. 0 Eclipsing Binaries i ≈ 90o sin i ≈ 1 f(M) ≈ M23/(M1 + M2)2

  8. Estimating Radii and Temperatures in Eclipsing Binaries 0 B0 Brightness B Bs Bp tc ta Time t tb td

  9. 0 Masses of Stars in the Hertzsprung-Russell Diagram Masses in units of solar masses 40 18 The higher a star’s mass, the more luminous (brighter) it is: High masses 6 3 L ~ M3.5 1.7 1.0 High-mass stars have much shorter lives than low-mass stars: Mass 0.8 0.5 tlife ~ M-2.5 Sun: ~ 10 billion yr. Low masses 10 Msun: ~ 30 million yr. 0.1 Msun: ~ 3 trillion yr.

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