Results 181 to 190 of about 63,242 (201)

Identification of the λ2, 200Å interstellar absorption feature

Nature, 1977
A BROAD absorption feature centred on λ2, 200A with a half-width of ∼ 300A appears in the spectra of reddened stars1–3. This conspicuous feature in the interstellar extinction curve, might hold an important clue to the identity of a major component of interstellar matter, but it has defied identification for over a decade. Here we identify this band as
F. Hoyle, N. C. Wickramasinghe
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Interstellar Absorption of Cosmic X Rays

Physical Review D, 1970
Improved results on the total photo-ionization cross section of atomic helium are given. The total cross section includes contributions from simultaneous ionization and excitation of ${\mathrm{He}}^{+}$ and double ionization; the combined effect of these two processes adds about 10% to the normal photo-ionization process where ${\mathrm{He}}^{+}$ is ...
Robert L. Brown, Robert J. Gould
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Interstellar Extinction and Diffuse Absorption Features

Astrophysics and Space Science, 1975
The equivalent width of the λ 2175 A band, W 2175, well known as the big bump in the interstellar extinction curves, has been found to be closely correlated with the colour excess E B-V as well as with the extinction differences E 8−6 and E 8−6 defined to characterize quantitatively the steep slopes of the extinction curves in the far ultraviolet.
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Interstellar absorption in the galactic plane

Astrophysics, 1994
UDC 524.5 We consider the distribution of interstellar absorption in the galactic plane using the classical Cepheids and main sequence stars of spectral classes B0-B3. In the method developed we use pairs of stars with the same absolute stellar magnitude, but with maximal difference of observed colors (B-V), The observed picture corresponds to the ...
R. A. Vardanyan, V. V. Ambaryan, A. V. Pogosyan   +2 more
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The 3.4-µm interstellar absorption feature

Nature, 1980
Estimation of the organic component of interstellar grains has provoked considerable interest1,2. Recently Duley and Williams2 concluded from an absence of the 3.4-µm CH absorption band in obscured IR sources that organic compounds in grains account for ⩽10% of carbon in the interstellar medium.
D. T. Wickramasinghe, D. A. Allen
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Diffuse interstellar absorption and emission bands

AIP Conference Proceedings, 1994
Unidentified astrophysical spectra are discussed including the diffuse interstellar absorption bands and visible emission bands from the Red Rectangle nebula and the R Coronae Borealis star V854 Cen. Assignments for the Red Rectangle optical emision and complementary diffuse absorption bands are not yet established, but comparison of the spectra allows
R. E. Hibbins, J. R. Miles, P. J. Sarre
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Small Scale Distribution of Interstellar Absorption

Nature, 1968
A SURVEY programme to take H α photographs of galactic emission nebulae has been in progress since October 1966 at the Tokyo Astronomical Observatory using the 50 cm Schmidt telescope at the Dodaira Station1. A combination of Eastman Kodak 103a-E plate and Hoya colour glass R64 5 mm thick are being used.
K. ISHIDA, K. AKABANE
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Distribution of stars and interstellar absorption

Vistas in Astronomy, 1962
Abstract The paper is a continuation of two earlier papers concerning the effect of interstellar absorption on the investigation of stellar distribution. It presents a considerable simplification of the formulae developed earlier, and leads not only to the tabulation of arguments but also, in turn, to the construction of tables which can be compared ...
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Investigation into broad interstellar absorption lines

Astronomical & Astrophysical Transactions, 2003
Diffuse interstellar bands (DIBs) are investigated mainly with high-resolution spectroscopy, which allows very fine structures to be detected. However, the rapidly increasing resolution of echelle spectra becomes a disadvantage when broad absorption structures are involved.
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Interstellar Emission and Absorption Lines

2012
Interstellar emission and absorption lines are discussed, including optical recombination lines, the 21cm hydrogen line, and broad lines such as the interstellar Lyman-alpha line. This chapter ends with a discussion of the curve of growth.
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