Elemental Abundances and Ionization States within the Local Interstellar Cloud Derived fromHubble Space TelescopeandFar Ultraviolet Spectroscopic ExplorerObservations of the Capella Line of Sight

Abstract

We use ultraviolet spectra of Capella from the Hubble Space Telescope (HST) and Far Ultraviolet Spectroscopic Explorer (FUSE) satellites to study interstellar absorption lines from the Local Interstellar Cloud (LIC). Measurements of these lines are used to empirically determine the ionization states of carbon, nitrogen, and silicon in the LIC, for comparison with the predictions of theoretical photoionization models. We find that the observed ionization states are consistent with previously published photoionization predictions. Total abundances are determined for the elements mentioned above, and others, for comparison with solar abundances. Magnesium, aluminum, silicon, and iron are all depleted by at least a factor of 10 toward Capella. The abundances of carbon, nitrogen, and oxygen are essentially solar, although the error bars are large enough to also allow depletions of about a factor of 2 for these elements.

Search for indications of stellar mass ejections using FUV spectra

“…Because direct ISM measurements are not reliable owing to the low S/N ratio of the FUSE spectra (only averaging over several files reveals the ISM absorption profiles), we used the method by Guinan et al (2003). These authors made use of ISM investigations and models by together with local ISM abundances from Wood et al (2002) and Redfield & Linsky (2000). For AB Dor and AU Mic we found direct column density measurements from .…”

“…For AD Leo we used direct column density measurements from Wood et al (2005). Wood et al 2002), the column density of H i. Using the local ISM abundance log(C ii/H i) ∼ -3.66 (taken from Wood et al 2002) and the calculated column densities of H i, we can calculate the column density of C ii.…”

“…Wood et al 2002), the column density of H i. Using the local ISM abundance log(C ii/H i) ∼ -3.66 (taken from Wood et al 2002) and the calculated column densities of H i, we can calculate the column density of C ii. Now using the local ionization fraction of carbon in the ISM (Wood et al 2002, C ii/C iii ∼ 0.02) we compute the C iii column density.…”

The Structure of the Local Interstellar Medium. II. Observations of Di, Cii, Ni, Oi, Alii, and Siiitoward Stars within 100 Parsecs

“…Because the focus of this paper is the fitting of relatively broad absorption lines of low-mass ions with moderate- References.-(1) This paper; (2) Wood et al 2002. resolution data, the measurement of velocity centroids is unlikely to improve the accuracy obtained from fits to the highresolution spectra of narrow absorption lines. However, our analysis of the low-mass ion profiles provides an opportunity to measure the consistency of the observed velocity centroids for a particular absorber.…”

“…The other light ions, C ii, N i, O i, Al ii, and Si ii, have not been analyzed for the majority of sight lines with available spectra. Although a few sight line investigations have already been presented Gnaciński 2000;Wood et al 2002;Vidal-Madjar, des Etangs, & Ferlet 1998), this paper provides a valuable new database of LISM measurements of these ions, which is complete to date. By coupling the data sets presented here with those of Mg ii and Fe ii , we can investigate fundamental physical properties of the LISM, including the morphology (Redfield & Linsky 2000), small-scale structure (Redfield & Linsky 2001), ionization structure (Wood et al 2002), and the temperature and turbulent velocity structure (Redfield & Linsky 2004).…”