Interstellar Matter Near the Pleiades. V. Observations of Na i toward 36 Stars

Abstract

This paper reports high-resolution, moderate to high signal-to-noise ratio observations of 23 certain Pleiades members, four possible members, and nine nonmembers in the Na I D lines, as well as observations of 12 of the stars in the Na I ultraviolet doublet. In spite of the relative proximity of the stars to the sun (even most of the nonmembers lie within 200 pc), the line profiles exhibit remarkable complexity, with up to five absorption components and equally remarkable star-to-star variation. The velocity range, 2-20 km s-1, conforms well to the range expected for gas deflected by the passage of the cluster. The paper includes a careful discussion of uncertainties in the data, the most important conclusions of which are that the velocity scatter is consistent with that expected from random errors in the wavelength calibration and that systematic errors probably are 0.1 km s-1. Appendices detail the choice of stellar data and the procedure adopted for removing telluric absorption lines. Analysis follows in a separate paper.