The Local Interstellar Medium. VII. The Local Interstellar Wind and Interstellar Material in Front of the Nearby Star alpha Ophiuchi

Abstract

IUE observations of Mg I λ2852.127 are used to search for warm interstellar gas in the direction of α Oph. Mg I should be a sensitive tracer of warm gas because of dielectronic recombination. However, the authors show that the observed Mg I absorption feature is dominated by material associated with a wisp of relatively cool H I found at the position of α Oph. This H I wisp is also the site of the observed Ca II, Na I, and Ti II absorption lines. If it is assumed that two absorbing regions are present in front of α Oph, one cool (T ≡ 500K) and one warm (T ≡ 10,000K), then together these regions fill half or less of the space in front of α Oph. Any gas filling the remaining space must be either hot (T very large10⁴K) or low density (n ⪉ 10^-3cm^-3).