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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Broad-line variability in NGC 3783

New intermediate-resolution optical spectrophotometry of the nucleus of the southern Seyfert 1 galaxy NGC 3783 is presented. These data demonstrate that the nucleus was in a very luminous state in May, 1983 manifested through considerably enhanced broad-line and optical continuum emission compared to the quiescent state evident in the data of Evans (1988) obtained in March, 1984. The two data sets are compared to derive the relative strengths of the continuum and broad-line intensities, and profile ratios are constructed for the H-alpha and H-beta Balmer lines to detect differences in the line profiles between the two epochs.

Evans, I. N.↗
NASA NTRS1994

X-ray spectroscopy of SNR E0102-72 with the ASCA satellite

The Advanced Satellite for Cosmology and Astrophysics (ASCA) satellite has obtained a moderate-resolution energy spectrum of E0102-72, the brightest Supernova Remnant (SNR) in the Small Magellanic Cloud (SMC). This paper reports on the first results of the analysis of the high quality spectrum of E0102-72. The spectrum shows resolved emission lines of He-like K alpha, H-like K alpha and K beta from oxygen, neon, and magnesium. The intensity ratios of these lines cannot be explained by a multi-component plasma model with uniform abundances, but requires abundance inhomogeneity in the plasma. We demonstrate how the spectral capabilities of the ASCA SIS make available new diagnostics of X-ray plasmas in a state of non-equilibrium ionization. Some interpretation based on the spectral analysis is also given.

Hayashi, Ichizo↗
NASA NTRS1999

Line Ratio Imaging of a Gas Discharge

The intensity ratio of two atomic or ionic spectral lines in a plasma is a function of electron temperature. By imaging two spectral lines, and computing the line ratio, pixel by pixel, an image of the electron temperature is produced. This is demonstrated using a dusty plasma consisting of submicron particles suspended in an argon RF glow discharge.

Samsonov, D.↗
NASA NTRS1983

Profiles and intensity ratios of the C IV lambda 1548, 1550 emission lines in planetary nebulae

The C IV resonance doublet at lambda 1548, 1550 is an important diagnostic tool in the study of planetary nebulae. The predicted theoretical intensity ratio of 2:1 is, however, rarely observed in the high dispersion IUE spectrograms. Values of 0.8-2.0 are observed for a sampling of 11 planetary nebulae of various excitation classes and for three proto-planetary nebulae. A diversity of line profiles is observed. In addition to the C IV doublet, weak subsidiary lines are seen. The spacing between these pseudo-lines happens to correspond to the separation of the C IV lines but are believed to be due to hot pixels and do not conform to the radial velocity displacement of the C IV lines.

Feibelman, W. A.↗
NASA NTRS1994

Observation of EX Hydrae with ASCA

We have observed the intermediate polar EX Hya with Advanced Satellite for Cosmology and Astrophysics (ASCA), and have clearly detected He-like and H-like K alpha emission lines from Mg to Fe. The intensity ratios of these pairs of lines are not compatible with an isothermal plasma, and a temperature distribution can no longer be parameterized by the conventional two emission component model. We have successfully decomposed iron line emission into thermal plasma component and flourescent component. The equivalent width of the flourescent component is approximately 80 eV.

Ishida, Manabu↗
NASA NTRS1991

Continuous wave laser absorption techniques for gasdynamic measurements in supersonic flows

Line-of-sight measurements of velocity, temperature, pressure, density, and mass flux were performed in a transient shock tube flow using three laser absorption schemes. All methods employed an intracavity-doubled ring dye laser tuned to an OH transition at 306 nm. In the first scheme, the gas was labeled by 193.3-nm excimer photolysis of H2O, and the passage of the generated OH was detected downstream. In the second method, the laser was tuned at a rate of 3 kHz over the R1(7) and R1(11) line pair, and absorption was simultaneously monitored at 90 and 60 deg with respect to the flow. Velocity was determined from the Doppler shift of the profiles and the temperature from the intensity ratio of the lines. Pressure was determined from both the magnitude of absorption and the collisional broadening. In the third method, the laser wavelength was fixed at a single frequency, and a continuous measurement of velocity and pressure was obtained using the signals from the two beam paths. All methods gave results which compare favorably to calculated values.

Davidson, David F.↗
NASA NTRS1985

The excitation of helium resonance lines in solar flares

Helium resonance line intensities are calculated for a set of six flare models corresponding to two rates of heating and three widely varying incident fluxes of soft X-rays. The differing ionization and excitation equilibria produced by these models, the processes which dominate the various cases, and the predicted helium line spectra are examined. The line intensities and their ratios are compared with values derived from Skylab NRL spectroheliograms for a class M flare, thus determining which of these models most nearly represents the density vs temperature structure and soft X-ray flux in the flaring solar transition region, and the temperature and dominant mechanaism of formation of the helium line spectrum during a flare.

Porter, J. G.↗
NASA NTRS1977

On the problem of density diagnostics for the EUV spectrum of the solar transition zone

Spectral-line ratios that may be used to determine the electron temperature and density in the solar transition zone and corona are identified. The problem of interpreting the intensity ratios of C III lines observed in Skylab EUV limb spectra is considered. It is shown that the intensity distribution with height above the solar limb of the 1176-A C III lines is different from that of the 1909-A C III lines in the Skylab spectra, suggesting that model atmospheres must be folded into the C III calculations for proper interpretation of the data. Possible reasons for the differences in the intensity distributions and widths of the 1176-A and 1909-A lines are discussed along with an application to the analogous lines of Si III.

Doschek, G. A.↗
NASA NTRS1980

Anomalous /C-13/H4:/C-12/H4 line strengths in 2 nu 3

Anomalous intensity ratios between 2 nu 3 singlet lines of C-13 methane and C-12 methane are reported. Absolute strengths of the Q1, R0 and R1 singlets were measured for essentially pure samples of (C-13)H4 and (C-12)H4 at a resolution of 0.035 kaysers at pressures of 10 and 20 Torr, using a computer controlled grating spectrometer. Line strength ratios between the isotopic species are presented which demonstrate a dramatic effect of isotopic substitution on line strengths. If this effect can be observed in the 3 nu 3 vibration-rotation band of methane, which is widely used in planetary atmosphere studies, revision of the (C-12)H4/(C-13)H4 abundance ratios of the outer planets will be necessary.

Fox, K.↗
NASA NTRS1982

X-ray, optical, and radio properties of quasars

A sample of 26 low-redshift quasars was examined for relationships between X-ray luminosity and optical spectroscopic features; all quasars were observed with the Einstein Observatory and with the IDS on the Lick 3 meter telescope. Evidence is found for correlations between quasar X-ray luminosity and both optical continuum luminosity and H-beta luminosity. In the latter case, there is a smooth relationship connecting quasars, Seyfert 1, and Seyfert 2 galaxies. For the quasars in this sample, there is also a strong correlation between optical continuum luminosity and both the H-beta luminosity and equivalent width. Evidence is also found for a weak correlation between alpha-prime (ox), the mean continuum spectral index between 5000 A and 2 keV, and Fe II equivalent width, H-beta equivalent width, H-beta line width at zero intensity, and the ratio of H-beta equivalent width to its line width at zero intensity.

Blumenthal, G. R.↗
NASA NTRS1972

On the minimum intensity of the Na D2-5890 A line in sunspot umbra /Research note/.

The largest spot in the group Rome 5847 was observed on two successive days (July 6 and 7, 1970), and the data were reduced separately. Taking the instrumental parasitic light contamination (Wyller and Fay, 1972) into account, the value of the line-to-continuum intensity ratio is found to be 0.033 plus or minus 0.05 by two methods.

Fay, T.↗
NASA NTRS1973

Selective reabsorption leading to multiple oscillations in the 8446-A atomic-oxygen laser.

Laser oscillation of atomic oxygen at 8446 A occurs in four closely spaced lines with peculiar intensity ratios, all detuned from the atomic center frequencies of the three fine-structure transitions. These anomalies are caused by the selective reabsorption of resonance radiation from the lower laser level by ground-state oxygen atoms. The selectivity results from the fact that the velocity distribution of the laser levels is considerably wider than that of the ground state, because of the dissociative mode of production of excited oxygen atoms. Possible extension of this mechanism to the atomic-hydrogen system is discussed.

Feld, M. S.↗
NASA NTRS1974

Spectroscopic results in helium from the NASA Lewis Bumpy Torus plasma

Spectroscopic measurements were carried out on the NASA Lewis Bumpy Torus experiment in which a steady state ion heating method based on the modified Penning discharge is applied in a bumpy torus confinement geometry. Electron temperatures in pure helium are measured from the ratio of spectral line intensities. Measured electron temperatures range from 10 to 100 eV. Relative electron densities are also measured over the range of operating conditions. Radial profiles of temperature and relative density are measured in the two basic modes of operation of the device called the low and high pressure modes. The electron temperatures are used to estimate particle confinement times based on a steady state particle balance.

Richardson, R. W.↗
NASA NTRS1974

Spectroscopic results in helium from the NASA Lewis Bumpy Torus plasma

Spectroscopic measurements have been carried out on the NASA Lewis Bumpy Torus experiment in which a steady state ion heating method based on the modified Penning discharge is applied in a bumpy torus confinement geometry. Electron temperatures in pure helium are measured from the ratio of spectral line intensities. Measured electron temperatures range from 10 to 100 eV. Relative electron densities are also measured over the range of operating conditions. Radial profiles of temperature and relative density are measured in the two basic modes of operation of the device called the low and high pressure modes. The electron temperatures are used to estimate particle confinement times based on a steady state particle balance.

Richardson, R. W.↗
NASA NTRS1987

Infrared investigation of water in Comet P/Halley

The results of the investigation of gaseous water, detected in the IR spectra of the Comet Halley's coma taken by the NASA's Kuiper Airborne Observatory, are summarized. High-resolution spectra revealed, near the wavelength of 2.65 microns, solar-pumped fluorescent emission in the (001-000) band of H2O and three lines of the (011-010) 'hot' band. The absolute production rate of H2O and its spatial distribution, temporal variability, and outflow velocity were measured along with the H2O ortho/para ratio. The measured line intensities indicate that water in the coma is rotationally relaxed. The aperture-averaged excitation temperatures for the low-lying rotational transitions were about 40 K, indicating that the coma kinetic temperature is extremely cold. Significant short-term temporal variations in the H2O line intensities were detected together with a strong pre- to postperihelion asymmetry (a factor of about 7) in the water production rate at a heliocentric distance of about 1 AU.

Weaver, H. A.↗