A very reduced upper limit on the interstellar abundance of beryllium

Abstract

We present the results of observations of the $\lambda 3130.4$ Åinterstellar absorption line of Be II in the direction of zeta Per. The data were obtained at the Canada-France-Hawaii 3.6m Telescope using the Coudé f/4 Gecko spectrograph at a resolving power $\simeq 1.1\times 10^5$, and a signal-to-noise ratio S/N $\simeq$ 2000. The Be II line is not detected, and we obtain an upper limit on the equivalent width $W_{3130.4}\le 30$ $\mu$Å. This upper limit is 7 times below the lowest upper limit ever reported hitherto. The derived interstellar abundance is (${}^9$Be/H) $\le 7\times 10^{-13}$, not corrected for the depletion of Be onto interstellar grains; it corresponds to an upper limit ${\delta }_{Be}\le -1.5$ dex on the depletion factor of Be. As such, it argues in favour of models of formation of dust grains in stellar atmospheres.

arXiv comment5 pages, latex, 2 figures, accepted for publication in Astronomy and Astrophysics, Main Journal