Uv spectra of nearby white dwarfs and the nature of the local interstellar medium
We have investigated the local interstellar medium in the directions of four white dwarfs, G191-B2B, W1346, HD 149499B, and Sirius B. All the observational data were obtained at the high-resolution mode (lambda/..delta..lambdaroughly-equal10/sup 4/) in the spectral range from about 1150 to 3200 A with the International Ultraviolet Explorer (IUE). Interstellar absorption lines of several elements in various stages of ionization are seen against the continuum of the white dwarfs. Low average hydrogen number densities (n-bar/sub HtsI/) are found. They range from n-bar/sub HtsI/ = 0.08 cm/sup -3/ for Sirius B, the nearest white dwarf (2.7 pc), to n-bar/sub HtsI/ = 0.006 cm/sup -3/ for G191-B2B, the most distant white dwarf (48 pc) studied. The results show, when combined with other recent ultraviolet, EUV, and diffuse X-ray observations, that: (a) the Sun is located inside a low-density (n-bar/sub HtsI/roughly-equal0.1 cm/sup -3/) cloud; (b) beyond 2--3 pc from the Sun, this cloud is surrounded, at least in most directions, by an extended region of hot (Troughly-equal10/sup 5en-dash6/ K) thin (nroughly-equal10/sup -2/ to 10/sup -3/ cm/sup -3/) interstellar plasma with no evidence for additional clouds in the lines of sight studied; (c) the elemental depletions of C, N, O, Si, Mg, and possibly Fe are low in the solar vicinity as previously found toward ..cap alpha.. Vir, (d) the Sun is moving through this cloud at a relative velocity of about 20 km s/sup -1/; and (e) the current results, which are quite consistent with previous ultraviolet, EUV, and diffuse X-ray observations, have significant bearings on the theoretical modeling of the interstellar medium. Subject headings: interstellar: abundances: interstellar: matter: stars: white dwarfs: ultraviolet: spectra
- Research Organization:
- Astronomy Department, Computer Sciences Corporation
- OSTI ID:
- 6807285
- Journal Information:
- Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 259:1; ISSN ASJOA
- Country of Publication:
- United States
- Language:
- English
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Radio & X-Ray Sources
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABUNDANCE
CHARGED PARTICLES
CHEMICAL COMPOSITION
COSMIC DUST
COSMIC GASES
DIAGRAMS
DUSTS
DWARF STARS
FLUIDS
GASES
INTERSTELLAR GRAINS
IONS
OPTICAL DEPTH CURVE
PARTICLES
SPECTRA
SPECTROSCOPIC CURVE OF GROWTH
STARS
ULTRAVIOLET SPECTRA
WHITE DWARF STARS