On the Binary Nature of Dust - Encircled Bd + 20 307
نویسنده
چکیده
Three epochs of high resolution spectra of the star BD+20 307 show that it is a short period (∼3.4 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 6707Å 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. Subject headings: stars: individual (BD+20 307) — binaries: spectroscopic — circumstellar matter
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