Extreme ultraviolet observations of G191-B2B and the local interstellar medium with the Hopkins Ultraviolet Telescope
Extreme ultraviolet observations of G191-B2B and the local interstellar medium with the Hopkins Ultraviolet Telescope
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霍普金斯紫外线望远镜对 G191-B2B 和当地星际介质的极紫外线观测
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发表时间：
1993
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通讯作者：
G. Kriss
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作者：
R. Kimble;A. Davidsen;W. Blair;C. Bowers;W. Dixon;S. Durrance;P. Feldman;H. Ferguson;R. Henry;G. Kriss
在1990年12月的Astro-1使命中，霍普金斯紫外望远镜（HUT）被用来观测热DA白色矮星GI 91-B2 B的极紫外光谱（415-912 A）。在原始光谱中清楚地检测到504 A He I吸收边的中性氦短路吸收。模型与观测光谱的拟合要求星际中性氦和中性氢柱密度分别为1.45 +/- 0.065 x 10 exp 17/sq cm和1.69 +/- 0.12 x 10 exp 18/sq cm。中性柱的比较产生了对太阳周围的局部星际云的电离状态的直接评估。HUT观测到的中性氢氦比为11.6 +/- 1.0，这与普遍认为的在局部星际介质中氢比氦更电离的观点强烈矛盾，这种观点激发了一些对假设的高电离的奇异理论解释。
During the Astro-l mission in 1990 December, the Hopkins Ultraviolet Telescope (HUT) was used to observe the extreme ultraviolet spectrum (415-912 A) of the hot DA white dwarf GI91-B2B. Absorption by neutral helium shortward of the 504 A He I absorption edge is clearly detected in the raw spectrum. Model fits to the observed spectrum require interstellar neutral helium and neutral hydrogen column densities of 1.45 +/- 0.065 x 10 exp 17/sq cm and 1.69 +/- 0.12 x 10 exp 18/sq cm, respectively. Comparison of the neutral columns yields a direct assessment of the ionization state of the local interstellar cloud surrounding the Sun. The neutral hydrogen to helium ratio of 11.6 +/- 1.0 observed by HUT strongly contradicts the widespread view that hydrogen is much more ionized than helium in the local interstellar medium, a view which has motivated some exotic theoretical explanations for the supposed high ionization.