A Census of Stars: the Hertzsprung-Russell Diagram

• Gaia: 4+ million star HR diagram study (Gaia Collaboration 2018)
  • HR diagrams within 25, 50, and 100 pc
  • for 4.2+ million stars
  • illustrating the binary sequence
  • video and visualization
  • Gaia data archive
• deluxe labelled HR diagram
• size comparisons: universe, stars

Stellar Masses an Binary Stars

• stars are social -- most are multiples! (Raghavan+ 2010)
• types of binaries:
  • visual/resolved, e.g. Castor, movies
  • astrometric
  • spectroscopic
  • eclipsing
    light curve examples here (Zasche 2009) here (source: TT Aur), and here
• simulations: center of mass, eclipsing binary light curves, orbits, more orbits
• binary stars as gravitational laboratories: stellar masses

The Main-Sequence Mass-Luminosity Relation

• relation plotted here (Eker+ 2018) and here
• implications for nature of Main Sequence

Decoding the H-R Diagram: Star Clusters

• open clusters Plieades, Hyades, Praesepe/Beehive
• globular clusters: 47 Tuc, M15
• Gaia DR2 HR diagrams:
  • open clusters: Hyades and Praesepe, 32 clusters
  • globular clusters: 47 Tuc, 14 clusters