STUDIES OF H-I AND D-I IN THE LOCAL INTERSTELLAR-MEDIUM

We present high-dispersion IUE spectra of the hydrogen Lyα chromospheric emission line of two nearby late-type stars, Capella (d = 13.2 pc, l = 163, b = 5) and λ And (d = 24, l = 110, b = -15). Both interstellar H I and D I Lyα absorption can be seen against the chromospheric line, and we have derived the density, velocity dispersion, and bulk velocity of the gas in those lines of sight. We have also placed limits on the D/H ratio. Our results are consistent with the current picture of the local interstellar medium (LISM), as we obtain a total column density of ∼1018 cm-2 toward both stars with velocity dispersions of ∼13 km s-1 (104 K). We place relatively high lower limits of 2.4 × 10-5 and 3.9 × 10-5 on the D/H ratio toward Capella and λ And, respectively, strongly indicative of variations in nD I/nH I on the small scales in the LISM.