Engineering Papers⌕ Search

Engineering topics

Henry, R. C.

Publications and source records attributed to Henry, R. C..

At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Far-ultraviolet studies. VII - The spectrum and latitude dependence of the local interstellar radiation field

A direct measurement has been made of the spectrum (1180-1680 A) and Gould-latitude dependence of the local interstellar radiation field, over about one-third of the sky. The result is corrected to give expected values for the entire sky. The average local 1180-1680 A energy density is 5.8 x 10 to the -17th ergs/cu cm A. The surface brightness falls off toward high latitudes much more steeply than published models predict.

Henry, R. C.↗
NASA NTRS1980

Far-ultraviolet studies. VIII - Apollo 17 search for zodiacal light

The analysis in a previous paper of a large quantity of far-ultraviolet spectrometer data from the Apollo 17 mission is reexamined with the intent of searching for zodiacal light. An upper limit at somewhat longer wavelengths than before is set. Spectrometer scannings were made from 1180 to 1680 A every 12 sec. Little evidence for a dependence of the residuals (calculated by subtracting the star catalog integration from the observed signal at 1558 to 1669 A for two portions of the sky) on an ecliptic parameter is shown. The present data do not show any detection of far ultraviolet zodiacal light or indeed of any light at all, but merely reflect the limitations of the star catalog integration.

Henry, R. C.↗
NASA NTRS1979

Far-ultraviolet studies. V - Rocket observation of the diffuse cosmic background

A far-ultraviolet spectrometer and several far-ultraviolet photometers have been carried to an altitude of 347 km to measure the spectrum of three regions at high galactic latitudes. After correction for O I airglow and for stars in the field of view, a nearly uniform residual intensity of 285 plus or minus 32 photons per (sq cm s sr A) is found over the spectral range 1230-1680 A, along with some evidence for a sharp rise in intensity longward of 1680 A. It is argued that the signal is not likely to be due to light scattering from interstellar dust. The flat spectrum could represent the integrated light of distance galaxies. The sharp rise must be due to some other phenomenon.

Anderson, R. C.↗
NASA NTRS1979

The spectrum of the diffuse cosmic ultraviolet background

A far-ultraviolet spectrometer and several far-ultraviolet photometers were carried to an altitude of 347 km and used to measure the spectrum of three regions at high galactic latitudes. After correction for O I airglow and for stars in the field of view, a nearly uniform residual intensity of 285 + or - 32 photons (per sq cm s sr A) over the spectral range 1230-1680 A is found, along with some evidence for a sharp rise in intensity longward of 1680 A. It is believed that the signal is not likely to be due to light scattering from interstellar dust. The flat spectrum is perhaps the integrated light of distant galaxies. The sharp rise must be due to some other phenomenon.

Anderson, R. C.↗
NASA NTRS1978

Ultraviolet observations of cool stars. VIII - Interstellar matter toward Procyon

The profile of the chromospheric L-alpha emission line of the F5 IV-V star Procyon (Alpha CMi, d = 3.5 pc) has been measured using the high-resolution Princeton spectrometer aboard NASA's Copernicus satellite. L-alpha absorption lines of interstellar deuterium and hydrogen are distinctly present. The average number density of interstellar hydrogen along the line of sight is found to be 0.11 + or - 0.02 per cu cm, similar to the densities that have been found in the directions of the stars Epsilon Eri, Epsilon Ind, and Alpha Cen A. These stars are all within 3.5 pc of the earth. The ratio of deuterium to hydrogen in the direction of Procyon is found to be 1.3 (+1.2, -0.5) x 10 to the -5th.

Anderson, R. C.↗
NASA NTRS1978

Ultraviolet observations of cool stars. VII - Local interstellar hydrogen and deuterium Lyman-alpha

High-resolution Copernicus spectra of Epsilon Eri and Epsilon Ind containing interstellar hydrogen and deuterium L-alpha absorption lines are presented, reduced, and analyzed. Parameters of the interstellar hydrogen and deuterium toward these two stars are derived independently, without any assumptions concerning the D/H ratio. Copernicus spectra of Alpha Aur and Alpha Cen A are reanalyzed, and limits on the D/H number-density ratio consistent with the data for all four stars are considered. A comparison of the present estimates for the parameters of the local interstellar medium with those obtained by other techniques shows that there is no compelling evidence for significant variations in the hydrogen density and D/H ratio in the local interstellar medium. On this basis the hypothesis of an approaching local interstellar cloud proposed by Vidal-Madjar et al. (1978) is rejected

Mcclintock, W.↗
NASA NTRS1978

Far-ultraviolet studies. III - A search for light scattered at large angles by dust

The Apollo 17 far-ultraviolet spectrometer was used during trans-earth coast to measure the brightness of two regions at moderate galactic latitudes. The signal obtained can be entirely accounted for by light from stars in the field of view, with no contribution from galactic-plane starlight scattered off interstellar dust. It is concluded that the interstellar grains are extremely poor large-angle scatterers in the far-ultraviolet.

Henry, R. C.↗
NASA NTRS1978

Ultraviolet observations of cool stars. VI - L alpha and Mg II emission line profiles /and a search for flux variability/ in Arcturus

High-precision, high-resolution profiles of the L alpha and Mg II k chromospheric emission lines from Arcturus (alpha Boo) obtained with the Princeton Experimental Package aboard the Copernicus satellite are presented. Asymmetries seen in the profiles of these lines are probably intrinsic to the star, rather than the result of interstellar absorption. In contrast to previous observations of the Ca II K emission line, no evidence is found during a three-year period for variability in the profiles or in the total fluxes from these lines on time scales ranging from hours to months. Also presented is a flux profile of the O I 1302 line and flux upper limits for L beta, O VI 1032, Si III 1206, and O V 1218.

Mcclintock, W.↗
NASA NTRS1978

Midlatitude oxygen ultraviolet nightglow

A rocket-borne spectrometer measured the weak UV nightglow from 1240 to 1670 A in the altitude range 180-345 km above White Sands, New Mexico. Detection of nightglow emissions at the atomic oxygen lines (1304 and 1356 A) confirmed the existence of a weak midlatitude oxygen nightglow similar to the tropical airglow. Radiative recombination appeared to be the principal cause of the peak observed intensities of the atomic oxygen line emissions, though a maximum 25% contribution from mutual neutralization of O(+) and O(-) could also be contemplated. Partial radiative recombination coefficients are derived from the data.

Brune, W. H.↗
NASA NTRS1977

High-resolution optical observations of Ca II K in Deneb and Aldebaran

High-spectral-resolution echellograms confirm the existence of an asymmetric emission core in the K line of Deneb that may be due to chromospheric emission from this A-type supergiant or that may be due to scattering from a circumstellar shell. If the core is due to chromospheric emission, its width does not agree with what is predicted using the Wilson-Bappu relation for late-type stars. This would indicate that the chromospheres of hotter stars are qualitatively different from those of cooler stars. A K-emission-core profile for Aldebaran is also presented.

Mcclintock, W.↗
NASA NTRS1977

Soft X-ray sources and supernova remnants in Cygnus - Rocket and Apollo-Soyuz results

Soft X-ray observations of the Cygnus region obtained from proportional counters aboard a rocket and also on the Apollo-Soyuz mission are reported. It is found that Cyg X-6, a source whose flux in confined to the 0.5-2.0-keV band, is a long narrow filament oriented nearly perpendicular to the galactic plane. This feature has a linear dimension greater than or of the order of 150 parsecs, and its spectrum is adequately described by an exponential. Another intense soft source whose flux is also confined to the 0.5-2.0-keV band has been discovered near Gamma Cygni. This source, designed Cyg X-7, has a spectrum characterized by a temperature of 1.5 to 5 million K and a hydrogen column density of at least 10 to the 21st power per sq cm. The possible association of Cyg X-7 with the supernova remnant DR 4 is discussed. An interpretation of this object in terms of the standard adiabatic spherical-shock-wave model yields plausible values for the free paramenters. HB 21, another old supernova remnant, has not been detected as a soft X-ray source.

Davidsen, A. F.↗
NASA NTRS1977

Metal abundance in the Praesepe and Hyades clusters

Calcium K-line photometry is reported for 27 A-type stars in the Praesepe cluster, and the data obtained are compared with previous K-line observations of Hyades stars. It is found that calcium and other metals are generally overabundant in Praesepe relative to field stars and that there is a considerable scatter in metal-abundance indices. Comparison with the Hyades results indicates that the Praesepe stars are as metal-enriched as the Hyades stars. These results are taken as evidence favoring Eggen's (1960) proposal that the Hyades and Praesepe clusters should be regarded as a single group having, on the average, about a factor-of-two higher metal abundance than solar-neighborhood field stars as well as a high internal dispersion in metal-line strengths. The questions of where and how the Praesepe-Hyades stars acquired their high average metal abundances, K-line strengths, and associated dispersions are briefly considered.

Henry, R. C.↗
NASA NTRS1977

Scanner K-line photometry of Orion stars

Results are presented for two-channel scanner measurements of calcium K-line strengths in 39 Orion sword and belt stars. Values of the calcium k index and its associated standard error are given for each observed star, and the K-line strengths are compared with those of K-line standard stars and Hyades stars. Plots of k index against reddening-corrected color and of k-index deviation against metal-strength index deviation are provided which show that the Orion sword and belt stars do not differ significantly in their calcium and metal abundances from general field stars.

Hesser, J. E.↗
NASA NTRS1977

Far-ultraviolet studies. II - Galactic-latitude dependence of the 1530 A interstellar radiation field

A 0.62-sq cm Geiger counter, sensitive between 1425 and 1640 A, was used to map the far-ultraviolet brightness of about half the sky, providing an experimental measurement of the far-ultraviolet interstellar radiation field. At 1530 A, the energy density is approximately 7.4 by 10 to the -17th power erg/cu cm per A. Comparison with integrations of star catalogs calibrated to the ultraviolet shows, as expected, that the bulk of the radiation comes directly from B- and A-type stars. The galactic-latitude dependence of the radiation is analyzed in an unsuccessful attempt to set limits on the absorbing and scattering properties of the interstellar grains in the far-ultraviolet. Excess radiation observed at the galactic pole is probably residual airglow from above the rocket altitude.

Henry, R. C.↗
NASA NTRS1977

Copernicus observations of Nova Cygni 1975

Near-ultraviolet radiation from Nova Cygni 1975 was detected by the Copernicus satellite on five occasions from 1975 September 1 to 1975 September 9. The nova was not seen in the UV after this date. The principal result was the observation of a broad emission feature from the Mg II doublet at 2800 A. The absence of strong UV radiation at shorter wavelengths suggests that these lines are produced by collisional excitation in the outer layers of an expanding shell with electron temperature of approximately 4000 K. The absence of observed emission lines from highly ionized species indicates that the amount of material with log T between 4.4 and 5.7 is less than 0.001 times that which produces the Mg II emission. The continuum flux in the near-UV decreased as the nova evolved, showing that the total luminosity decreased as the nova faded in the visible.

Jenkins, E. B.↗
NASA NTRS1976

Apollo 17 far-ultraviolet spectra in the Large Magellanic Cloud

During the Apollo 17 mission, low-resolution far-ultraviolet spectra were obtained for two parts of the Large Magellanic Cloud. The spectra are reasonably well fit by a model of a 30,000-K star reddened by a (B-V) color excess of 0.3 magnitude, but other combinations of temperature and reddening provide equally good fits.

Henry, R. C.↗