On the Binary Nature of Dust-encircled BD+20 307

Abstract

Three epochs of high resolution spectra of the star BD+20 307 show that it is a short period (~3.5 day) spectroscopic binary of two nearly identical stars. Surprisingly, the two stars, though differing in effective temperature by only ~250 K and having a mass ratio of 0.91, show very different Li line equivalent widths. A Li 6707 Angstrom line is only detected from the primary star, and it is weak. This star is therefore likely to be older than 1 Gyr. If so, the large amount of hot circumbinary dust must be from a very large and recent, but very late evolutionarily, collision of planetesimals.

Accepted to ApJ Letters, with corrected typos and added info on Li equivalent widths

References in corpus (4)

• Tertiary companions to close spectroscopic binaries
• The Chemical Compositions of Stars with Planets: A Review
• Line Strengths in Early-Type Cluster Galaxies at z=0.33: Implications for alpha/Fe, Nitrogen and the Histories of E/S0s
• Lithium abundances in the old open cluster NGC 3960 from VLT/FLAMES observations

Cited by in corpus (1)

• Planetary systems around close binary stars: the case of the very dusty, Sun-like, spectroscopic binary BD+20 307