A VERY REDUCED UPPER LIMIT ON THE INTERSTELLAR ABUNDANCE OF BERYLLIUM

We present the results of observations of the lambda 3130.4 Angstrom i nterstellar absorption line of Be-9 II in the direction of zeta Per. T he data were obtained at the Canada-France-Hawaii 3.6m Telescope using the Coude f/4 Gecko spectrograph at a resolving power lambda/Delta la mbda similar or equal to 1.1 x 10(5), and a signal-to-noise ratio S/N similar or equal to 2000. The Be-9 II line is not detected, and we obt ain an upper limit on the equivalent width W-3130.4 less than or equal to 30 mu Angstrom. This upper limit is 7 times below the lowest upper limit ever reported hitherto. The derived interstellar abundance is ( Be-9/H) less than or equal to 7 x 10(-13) not corrected for the deplet ion of Be-9 onto interstellar grains; it corresponds to an upper limit delta (Be) less than or equal to -1.5 dex on the depletion factor of Be-9. As such, it argues in favour of models of formation of dust grai ns in stellar atmospheres.