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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

(abstract) Circumstellar Molecular Gas of the HH 1-2 and HH 24 Exciting Stars

13 CO and C 18 O observations of HH 1-2 VLA and SSV 63, the exciting stars of the HH 1-2 and HH 24 outflows, have been obtained with the Owens Valley Millimeter Array. The HH 1-2 source has been detected in both lines and in the 2.7 mm continuum. In the continuum, the central source appears unresolved in the 5" beam with a flux density of 20 mJy. A secondary peak of 8 mJy appears 12" SE of VLA 1. A strong peak of molecular line emission appears at the position of VLA 1. Molecular gas associated with SSV 63 has also been detected. Maps of circumstellar material of both sources will be presented.

circumstellar↗
NASA NTRS1969

On the composition of circumstellar grains.

Circumstellar grain compositions of stars with various O to C abundance ratios, calculating molecular equilibrium of condensates and gaseous compounds in stellar atmospheres

Gilman, R. C.↗
NASA NTRS1971

Variability of radiation from circumstellar grains surrounding R Coronae Borealis.

Radiation at IR wavelengths from circumstellar grains surrounding R CrB has been observed for approximately three years. Variations of flux with time have been larger at a wavelength of 3.5 microns than at 11 microns. Observations at IR and visual wavelengths of R CrB are presented in a graph. Another graph shows the change in the shape of the excess radiaton between two observations spaced by a period of about one year.

Forrest, W. J.↗
NASA NTRS1972

Circumstellar shells in the young cluster NGC 2264. II - Infrared and further optical observations.

Flux measurements at 1.6, 2.2, and 3.4 microns for 42 stars in the young cluster NGC 2264 suggest that a significant number of these stars are surrounded by circumstellar material which produces observable infrared excesses. Hydrogen line profiles are used to estimate surface gravities and thereby to predict visual luminosities for a number of pre-main-sequence A stars. Those stars which appear faintest as compared with their predicted luminosities all have infrared excesses.

Strom, S. E.↗
NASA NTRS1972

On circumstellar molecules in the Pleiades.

Consideration of both old and new observations of the interstellar 4232-A line of CH(+) for the brightest members of the Pleiades. These observations suggest that the molecules are circumstellar in some sense, perhaps resembling in this respect the micron-sized grains inferred to be present in this region.

Hobbs, L. M.↗
NASA NTRS1973

Optical transmission in a circumstellar dust cloud

It is shown from the equation of radiative transfer that the visual attenuation of an optically thick, spherically symmetric circumstellar cloud of dust can be small compared to that produced by an equal optical depth of interstellar dust. The reasons for this are the moderately large albedos of the grains and their tendency to emphasize forward scattering.

Jones, T. W.↗
NASA NTRS1976

Radiative transfer in circumstellar dust shells

An iterative numerical procedure is developed to calculate the radiation field as a function of position, direction, and wavelength within a spherically symmetric circumstellar dust shell. The dust shell is assumed to consist of gray, isotropically scattering dust particles in thermal equilibrium with the radiation field and to be characterized by seven parameters: radius of the central star, inner radius of the shell, outer radius of the shell, total optical depth of the shell, an index which specifies the density distribution, albedo of the dust particles, and temperature of the central star. When the shell is close to the star, the angular distribution of the stellar component of the radiation field is determined by direct integration along lines of sight to the stellar surface, and the back-warming effect of the shell is included in the calculations to determine the net stellar flux. Using this procedure, the temperature distributions and radiation fields within several model dust shells are determined and used to calculate for each shell the spectral-energy and spatial-energy distributions of the radiation emitted at 11 wavelengths from 0.4 to 20 microns. For shells of moderate optical depth, it is found that the radiation field is quite anisotropic, especially at shorter wavelengths, and that the shape of the spectral-energy distribution is strongly dependent on all seven model parameters. The Eddington factor as a function of wavelength and optical depth is calculated for each model.

Harvel, C. A.↗