Highlights - Volume 499-3 (June I 2009)
- Published on 02 June 2009
|HIGHLIGHTS: this week in A&A
Volume 499-3 (June I 2009)
|In section 5. Galactic structure, stellar clusters and populations
“Lucky Imaging of M subdwarfs”, by N. Lodieu, M. R. Zapatero Osorio, and E. L. Martin, A&A 499, p. 729
The fraction of multiple stars, as a function of major stellar mass and of the initial conditions of stellar formation, is a major constraint on star formation theories. This paper presents significant, new results on the binary fraction of very-low-mass stars of the Galactic halo. The authors' new high-resolution imaging has identified a new “extreme M subdwarf” binary system and confirmed or rejected other authors' candidate pairs. The most significant result is that the derived binary fraction (3%) of M subdwarfs proves that the halo binary fraction for VLM stars is substantially different than in Galactic disk, solar-metallicity M dwarfs. This is an important data point for future theoretical work.
© Astronomy & Astrophysics 2009