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Absorption and Emission of EUV Radiation by the Local ISMThe Berkeley extreme ultraviolet radiation (EUV) telescope flown on the Apollo Soyuz mission in July, 1975 established the existence of a measurable flux of EUV (100 lambda or = or = 1000 A) originating from sources outside the solar system. White dwarfs, flare stars and cataclysmic variables were dicovered to be relatively intense compact sources of EUV photons. Moreover, this and other subsequent experiments have strongly suggested the presence of a truly diffuse component of the FUV radiation field possibly due to thermal emission from hot interstellar gas located in the general vicinity of the Sun. Closer to the H1, 912 A edge, the effect of a few hot O and B stars has been shown to be very important in establishing the interstellar flux density. All these results imply that the local interstellar medium (ISM) is immersed in a non-negligible EUV radiation field which, because of the strong coupling between EUV photons and matter, will play a crucial role in determining its physical structure. The available information on the local ISM derived from the limited EUV observations carried out so far is assembled and analyzed. These include measurements of the spectra of bright EUV sources that reveal clear evidence of H photo absorption at lambda 400 A and of the He ionization edge at 228 A.
Document ID
19850007254
Document Type
Conference Paper
Authors
Paresce, F.
(Space Telescope Science Inst. Baltimore, MD, United States)
Date Acquired
August 12, 2013
Publication Date
November 1, 1984
Publication Information
Publication: NASA. Goddard Space Flight Center Local Interstellar Medium, No. 81
Subject Category
Astrophysics
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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IDRelationTitle19850007230Analytic PrimaryLocal Interstellar Medium. International Astronomical Union Colloquium No. 81
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