Far-ultraviolet Space Telescope Imaging Spectrometer spectra of the white dwarf REJ 1032+532. I. Interstellar line of sight

An 1150-1725 Angstrom echelle spectrum of the hot DA white dwarf REJ 1032 532, recently obtained with the Space Telescope Imaging Spectrometer E140M grating, reveals numerous stellar and interstellar lines. The interstellar column densities and abundances of C, N, O, Si, and S relative to the dire ctly measured H column are determined for this particular line of sight thr ough the local interstellar medium (ISM). An estimate of the electron densi ty, n(e) = 0.11(-0.06)(+0.07), is obtained from the population ratio of the excited to ground state fine-structure levels in C II. This electron volum e density is compared with an independent Extreme Ultraviolet Explorer meas urement of the total line-of-sight electron column density derived from the ionization state of H and He. A path length of similar to 10 pc is estimat ed for the region responsible for the bulk of the ISM absorption. From the observed ISM velocity components, we identify this absorbing component as t he local interstellar cloud (LIC) surrounding the solar system. For the LIC we find the abundances of nitrogen, oxygen, and silicon relative to hydrog en to be significantly less than those characteristic of much longer lines of sight through the local ISM. The LIC abundances of these elements are ve ry consistent with the recent determinations of Vidal-Madjar and coworkers for the LIC.