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.
@article{arxiv.0804.1799,
title = {On the Binary Nature of Dust-encircled BD+20 307},
author = {A. J. Weinberger},
journal= {arXiv preprint arXiv:0804.1799},
year = {2009}
}
Comments
Accepted to ApJ Letters, with corrected typos and added info on Li equivalent widths