Detection of interstellar carbonyl sulfide
Interstellar carbonyl sulfide transition at 109.5 GHz, noting column density
Jefferts, K. B.↗
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A closer look at interstellar Lyman-alpha absorption
Interstellar Lyman alpha absorption equivalent widths in hot stars spectra, examining rocket and satellite observations
Jenkins, E. B.↗
Search for interstellar silicate absorption in spectrum of VI Cyg No. 12
Interstellar silicate absorption search using VI Cyg No 12 spectrum observations
Gillett, F. C.↗
Interaction between interstellar helium and the solar wind
Interstellar He photoionization effect on solar wind abundance
Axford, W. I.↗
Low intensity H-beta emission from the interstellar medium
A search for diffuse galactic H beta emission not associated with any known H II regions was conducted using a 2-inch-diamenter pressure-scanned Fabry-Perot spectrometer at the Coude focus of a 36-inch telescope. Observations were made near the directions of four pulsars. Emissions with intensities from 40,000 to 400,000 photons/sq cm sec ster (corresponding to emission measures of approximately 10 - 100) were detected in three of the directions. The data indicate an average ionization rate (assuming steady state) of approximately 10 to the minus 14th power/H-atom sec for the interstellar hydrogen in these directions and temperatures between 1000 and 10,000 K for the emitting regions. Plans were made to continue the investigation of these very faint hydrogen emission sources using a 6-inch-diameter Fabry-Perot spectrometer.
Reynolds, R. J.↗
Interaction of cosmic rays with interstellar matter and possible excitation of X-ray lines
It is proposed that the excess diffuse cosmic X-rays in the fractional keV energy band are produced as a result of excitation of neutral carbon, sulphur, and argon atoms by cosmic rays, with subsequent emission of the K X-rays of carbon and the L X-rays of sulphur and argon. It is suggested that if the intensities of low energy cosmic rays, and the cross sections for the production of X-ray lines were known, the observations of X-ray lines could provide k direct information concerning abundances of elements in the interstellar regions.
Verma, S. D.↗
Photochemistry and lifetimes of interstellar molecules
A quantitative discussion is presented of the lifetime against photodecomposition, or the probability of photodecomposition, of interstellar molecules. In addition to photodissociation, molecules can also be destroyed by interaction with high energy radiation and energetic particles. These processes are much less effective than destruction by ultraviolet radiation. However, when the ultraviolet is highly attenuated in clouds, the energetic radiation and particles will persist and will become relatively more important and the ultimate lifetimes in clouds may depend upon these processes.
Stief, L. J.↗
Optical depths in the interstellar and intergalactic media
Optical depths of the interstellar and intergalactic media for supernova remnants, stars, and galaxies are presented in tabular form.
Schocken, K.↗
Stellar ultraviolet colors and interstellar extinction
A sample of celescope results is studied. Most of the sample stars belong to the Orion and Vela regions. Stars with visual excess E(B-V) less than 0.05 are selected in order to derive relationships of intrinsic color index versus spectral type. The resulting intrinsic color-color relations are compared with existing blanketed and unblanketed model calculations. Finally, the preceding intrinsic relations are utilized to derive some results on interstellar extinction. Owing to the rather large scatter in the celescope data, the Vela stars give the more significant results because their visible excess E(B-V) is, in general, larger than that for the Orion stars.
Peytremann, E.↗
Interstellar extinction in the ultraviolet
Interstellar extinction curves over the region 3600-1100 A for 17 stars are presented. The observations were made by the two Wisconsin spectrometers onboard the OAO-2 with spectral resolutions of 10 A and 20 A. The extinction curves generally show a pronounced maximum at 2175 plus or minus 25 A, a broad minimum in the region 1800-1350 A, and finally a rapid rise to the far ultraviolet. Large extinction variations from star to star are found, especially in the far ultraviolet; however, with only two possible exceptions in this sample, the wavelength at the maximum of the extinction bump is essentially constant. These data are combined with visual and infrared observations to display the extinction behavior over a range in wavelength of about a factor of 20.
Bless, R. C.↗
A survey of local interstellar hydrogen from OAO-2 observations of Lyman alpha absorption
The Wisconsin far ultraviolet spectrometer aboard OAO-2 observed the wavelength region near 1216 A for 69 stars of spectral type B2 or earlier. From the strength of the observed interstellar L sub alpha absorption, atomic hydrogen column densities were derived over distances averaging 300 pc away from the sun. The OAO data were compared to synthetic ultraviolet spectra, originally derived from earlier higher resolution rocket observations, which were computer processed to simulate the effects of absorption by different amounts of hydrogen followed by the instrumental blending.
Savage, B. D.↗
The formation of interstellar diatomic molecules
Reactions between atoms and ions of the interstellar medium and vibrationally excited molecular hydrogen are shown to produce a specific set of molecules. Molecules such as CO and CN can readily be produced in abundances greater than those of corresponding hydrides. When quantified in a simple manner the equilibrium density of molecules compares well with the observed values for the star Oph.
Stecher, T. P.↗
The interstellar redding law in the ultraviolet deduced from filter photometry obtained by the OAO-2 satellite
Filter photometry has been obtained of 16 BO stars at ten effective wavelengths in the range 4250-1430 A. The wavelength dependence of the interstellar reddening law, deduced from a least squares fit of the observed values to the reddening line at each band, is found in satisfactory agreement with that derived by Bless and Savage (1972). Toward the shorter wavelengths the increase of the computed probable error of the slope of the mean reddening line suggests that large fluctuations in the law may occur from star to star. Similar computations, separating main-sequence stars and supergiants, indicate that the large fluctuations of the law appear to be well related to the luminosity of the stars; the supergiants show systematically less extinction, this deficiency becoming large toward the far UV. The small number in the sample however, does not allow a general conclusion to be drawn.
Laget, M.↗
The shape of the interstellar reddening law
The spectral distribution of pairs of stars within the same spectral type and luminosity class, one of which is reddened and the other unreddened is compared. It is assumed that the observed difference between two stars is only attributed to the interstellar medium. Their physical properties, size distribution of particles, geometrical shape, and their location in space are considered.
Laget, M.↗
Interstellar CO in the ultraviolet spectrum of zeta Ophiuchi
Optical methods in the vacuum ultraviolet were used to detect interstellar H2 in the spectrum of epsilon Persei; CO in the spectrum of zeta Ophiuchi was also observed. By contrast with radio results, the regions sampled are small, being one or a few clouds in the line of sight, and isotopic effects are detected in the spectrum.
Smith, A. M.↗
Low intensity H-beta emission from the interstellar medium
Pulsar pulse dispersions and low-frequency absorption of galactic and extragalactic radio sources strongly suggest that the interstellar medium is much more ionized than previously assumed. The search was confined to directions near pulsars because of the additional information provided by the dispersion measure which gives the total number of electrons along the line of sight to the pulsar. Of the four directions in which observations were made, an emission line appears to be present in at least two and possibly three directions. The data are shown from a low galactic latitude direction near the Crab Nebula pulsar. The observing direction was about 9 arcmin off the Crab with the field of view of about 1.5 arcmin. The number of counts was plotted versus the local standard of rest velocity and local standard wavelength of H-beta.
Reynolds, R. J.↗
Lower limit to the interstellar C 12/C 13 ratio in the direction of 20 Tauri.
Results of photoelectric scanning of the spectrum of 20 Tau in the vicinity of 4232 A of interstellar CH(+). From the observed absence of the isotopically shifted line of super 13CH(+) it is deduced that the C 12/C 13 isotopic abundance ratio in this direction is greater than 33, and hence consistent with the terrestrial value.
Vanden Bout, P.↗
Interstellar sodium lines and the two-component model of galactic H I regions.
The intensities and widths of the interstellar sodium lines are considered as possible discriminants between two different two-component models recently proposed for galactic H I regions. Depending on the model, the observed sodium lines are either formed entirely in the clouds or, alternatively, in both the clouds and the intercloud medium. Present observational evidence is insufficient to distinguish between these two possibilities.
Hobbs, L. M.↗