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At least 523 records · Page 29

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NASA NTRS1980

A continuum and recombination line study of the Cep IV star formation region

The Cep IV star formation region consists of the Cep IV OB association, the H II regions W 1 and NGC 7822, and an extensive fragmented dust cloud complex. Six- and nine-cm radio continuum observations and 6-cm hydrogen recombination line observations show that all of the emission nebulosity in this region, which includes a large loop-type structure suggested by Herbst and Assousa (1977) to be a supernova remnant, has a thermal spectrum. The two components of W 1 have been detected at H 110 alpha and are found to be kinematically distinct.

Rosano, G. S.↗

NASA NTRS1980

The low-frequency continuum as observed in the solar wind from ISEE 3 - Thermal electrostatic noise

The low frequency continuum (LFC) noise between 30 and 200 kHz has been investigated from the ISEE 3 spacecraft in the solar wind by means of a radio astronomy experiment more sensitive than previously available. It is demonstrated that the LFC radiation observed in the solar wind is in the form of longitudinal plasma waves rather than transverse electromagnetic waves. The observed spectral characteristics are found to be a function of antenna length. In addition, both the absence of antenna spin modulation and the fact that these plasma waves do not propagate to large distances imply a local origin for the LFC.

Hoang, S.↗

NASA NTRS1980

A continuum bright point at the penumbral edge

A small continuum bright point, observed at the outer edge of the penumbra of a small spot in a large complex spot group, is related to an occurrence beneath the suns's surface. The characteristics of the point appear to be unique, and the name 'penumbra-periphery bright point' is proposed.

Zirin, H.↗

NASA NTRS1980

A mathematical model of post-instability in continuum mechanics

The post-instability can appear in the form of failure of hyperbolicity or in the form of cascade instability (stretching of vorticity in an inviscid fluid or instability of the Navier-Stokes equations). All the cases are characterized by an unlimited decrease of the scale of the motions, in the course of which the derivatives of the corresponding functions tend to infinity, though the functions themselves remain finite. Such an instability shows that the corresponding state of a continuum cannot be properly simulated by smooth functions. Hence, the original model must be corrected by giving up the requirement about differentiability and enlarging the class of functions. Applications to a model of an inviscid fluid and to a model of turbulence are discussed.

Zak, M.↗

NASA NTRS1981

Far-infrared emission line and continuum observations of NGC 7027

The first observation of a fine-structure transition in NGC 7027 at wavelengths greater than 30 microns is reported. The flux in the 63.2-micron line is found to be approximately 10 to the -16th W/sq cm. It is noted that if NGC 7027 lies at 1 kpc, this corresponds to a luminosity, in the line, approximately 30 times greater than the solar luminosity. The flux of the 88.35-micron line is less than 10 to the -17th W/sq cm, and the upper limit to the line flux at 51.8 microns is found to be 10 to the -16th W/sq cm. These upper limits imply an electron density that is less than 1.6 x 10 to the 5th/cu cm. It is noted that the continuum measurements obtained support a dust temperature of 90 K with an emissivity approximately equal to the reciprocal of the square of the wavelength. The data exclude grain materials whose wavelength-dependent emissivity (the reciprocal of the wavelength raised to nth power) requires n to be outside the range between 1.6 and 2, unless the temperature varies drastically across the dust cloud

Melnick, G.↗

NASA NTRS1981

Infrared line and continuum views of G333.6-0.2

A 1-micron CCD picture and maps of the Ne II and Ar III fine-structure lines have been obtained in a region roughly one arcmin in size centered on the core of the compact H II region G333.6 - 0.2. The two emission-line maps show nearly identical intensity distributions, although much different fluxes. The maps are similar to the 1-micron picture smoothed to their angular resolutions. The infrared line of S IV also was detected and appears to have a spatial intensity distribution similar to that of the other fine-structure lines. The 1-micron picture reveals a small number of objects of nearly stellar appearance in the core, suggesting that G333.6 - 0.2 is powered by a compact cluster of sources. Stellar continuum radiation probably is responsible in part for the low equivalent width of the B-gamma line in the core.

Geballe, T. R.↗

NASA NTRS1982

Line-profile and continuum variations of the contact binary SV Centauri

A total of five high and ten low dispersion UV spectra of the interacting contact binary SV Centauri obtained between 1979 and 1982 are analyzed. The low resolution observations cover the whole phase range, while a few selected phases were observed in high dispersion. The UV data were complemented with optical photometric and spectroscopic observations, in order to determine the tructure and absolute dimensions of the system. The profiles of prominent UV resonance and metastable lines undergo drastic changes with phase angle and time. Their overall appearance indicates relatively strong mass loss from the system, exhibiting pronounced variations of the stellar wind. The far UV continuum distribution suggests the presence of a luminous hot radiation source with maximum emission in the soft X-ray range, which is most apparently seen during the first quadrature phase, while it is weakest close to primary minimum. The case exchange and mass loss process as well as the evolutionary stage of SV Centauri are discussed.

Rahe, J.↗

NASA NTRS1982

Gamma radiation and photospheric white-light flare continuum

It is noted that recent gamma-ray observations of solar flares have provided a better means for estimating the heating of the solar atmosphere by energetic protons. This type of heating has been suggested as the explanation of the continuum emission of the white-light flare. The effects on the photosphere of high-energy particles capable of producing the intense gamma-ray emission observed in the flare of July 11, 1978, are analyzed. A simple energy-balance argument is used, and hydrogen ionization is taken into account. It is found that energy deposition increases with height for the inferred proton spectra and is not strongly dependent upon the assumed angle of incidence. At the top of the photosphere, the computed energy inputs fall in the range 10-100 ergs/cu cm-s.

Hudson, H. S.↗

NASA NTRS1982

Ultraviolet continuum absorption /less than about 1000 A/ above the quiet sun transition region

Lyman continuum absorption shortward of 912 A in the quiet sun solar transition region is investigated by combining spectra obtained from the Apollo Telescope Mount experiments on Skylab. The most recent atomic data are used to compute line intensities for lines that fall on both sides of the Lyman limit. Lines of O III, O IV, O V, and S IV are considered. The computed intensity ratios of most lines from O IV, O V, and S IV agree with the experimental ratios to within a factor of 2. However, the discrepancies show no apparent wavelength dependence. From this fact, it is concluded that at least part of the discrepancy between theory and observation for lines of these ions can be accounted for by uncertainties in instrumental calibration and atomic data. However, difficulties remain in reconciling observation and theory, particularly for lines of O III, and one line of S IV. The other recent results of Schmahl and Orrall (1979) are also discussed in terms of newer atomic data.

Doschek, G. A.↗

NASA NTRS1982

A high resolution far-infrared survey of a section of the galactic plane. II - Far-infrared, CO, and radio continuum results

An area of 7.5 sq deg of the galactic plane at 70 microns have been surveyed with a 1-arcmin beam. The region lies between lII equals 10 deg and lII equals 16 deg and includes the M17 and W33 complexes. The weakest of the 42 sources detected had a flux density of 350 Jy at 70 microns. Detailed far-infrared, (C-12)O, (C-13)O, and radio continuum observations of the sources are presented. The derivation of the important physical parameters of the sources and their surrounding molecular clouds are discussed. The properties of the individual regions are also discussed and maps of selected sources are presented.

Stier, M. T.↗

NASA NTRS1982

Solar irradiance in the stratosphere - Implications for the Herzberg continuum absorption of O2

A set of solar irradiance observations is analyzed that were performed from the third Solar Absorption Balloon Experiment (SABE-3) as the payload ascended through the stratosphere from 32 to 39 km. Comparison of these data with calculations of the attenuated irradiance based on simultaneous ozone and pressure measurements made from the payload suggests a refinement of the cross section values used in photochemical models. More ultraviolet radiation in the 200-210 nm spectral region reaches the middle stratosphere than is predicted by the absorption data presently available. It is suggested that significantly smaller values for the Herzberg continuum of O2 be used in future models.

Frederick, J. E.↗

NASA NTRS1983

Parameter identification in continuum models

Approximation techniques for use in numerical schemes for estimating spatially varying coefficients in continuum models such as those for Euler-Bernoulli beams are discussed. The techniques are based on quintic spline state approximations and cubic spline parameter approximations. Both theoretical and numerical results are presented.

Banks, H. T.↗

NASA NTRS1983

The line continuum luminosity ratio in AGN: Or on the Baldwin Effect

The luminosity dependence of the equivalent width of CIV in active galaxies, the "Baldwin" effect, is shown to be a consequence of a luminosity dependent ionization parameter. This law also agrees with the lack of a "Baldwin" effect in Ly alpha or other hydrogen lines. A fit to the available data gives a weak indication that the mean covering factor decreases with increasing luminosity, consistent with the inference from X-ray observations. The effects of continuum shape and density on various line ratios of interest are discussed.

Mushotzky, R.↗

NASA NTRS1983

Introduction and survey on continuum models for repetitive lattice structures

A brief introduction and survey to aid and familiarize researchers interested in the use of continuum modeling procedures applied towards large space structure technology are presented. The use of such structural models for the distributed control of large flexible lattice structures offers a significant advantage over a numerical approach.

Weisstein, L. S.↗

NASA NTRS1982

Post-instability in continuous systems. I - Failure of differentiability of solutions in continuum mechanics

It is pointed out that mathematical models of continua are based on certain assumptions regarding functions which must be at least piece-wise differentiable. The assumption about smoothness of the functions makes it possible to use the mathematical technique of differentiable equations. However, this artificial mathematical limitation follows neither from the principles of mechanics nor from the definition of a continuum. The price paid for such a mathematical convenience is instability (in the class of smooth functions) of the solutions to the corresponding governing equations in some regions of the parameters. A new mathematical technique should, therefore, be developed to describe the solutions which are not necessarily differentiable. The present investigation is concerned with the criteria of applicability of the classical models of continua from the view point of stability of the corresponding solutions, postinstability models derived by reformulation of the original models, and postinstability models in enlarged classes of functions.

Zak, M.↗

NASA NTRS1983

System identification of large flexible structures by using simple continuum models

Simple continuum models for the representation of large truss beams and truss platforms are constructed and employed in the solution of system identification problems permitting the significant reduction of the number of structural parameters. Two simple and easily computer-implemented algorithms are presented for the estimation of a simple model's equivalent structural parameters, and analytical and numerical solutions are given for the truss beam and truss platform cases in order to illustrate the basic concepts. It is found that model simplicity, in conjunction with the principle of least square erors, yields a feasible integration of structural and identification problems.

Juang, J. N.↗

NASA NTRS1983

Ultraviolet continuum and H2 fluorescent emission in Herbig-Haro objects 43 and 47

IUE short wavelength spectra are presented for the low excitation Herbig-Haro objects HH 43 and HH 47. In the former, several emission lines in the Lyman band of H2 from an excited state are observed which are due to fluorescence from the H Ly-alpha line pumping a lower state (that is in turn excited by a low-velocity shock wave). No evidence of highly ionized gas emission is found in the UV spectra, and both objects exhibit a UV continuum which peaks in the vicinity of 1500 A and is probably caused by H two-photon emission enhanced by low velocity shock collisional excitation.

Schwartz, R. D.↗

NASA NTRS1983

A helium-3 cooled bolometer system for one millimeter continuum observations

A new, 1-mm-continuum, bolometer detector system has been constructed employing internal adsorption pumping of He-3 to reach an operating temperature close to 0.4 K. The system spectral bandwidth is 800 to 1200 microns. Although the system was originally designed to be used on the 5-m Hale telescope, it has also been successfully used on the 4-m Anglo-Australian telescope and on the 10-m dish at Owens Valley, California. At the 5-m Hale telescope, the system has a full width-half maximum (FWHM) beam size of 55 sec and an instantaneous noise-equivalent flux density of 6 Jy/square root of (Hz)/ in good weather.

Roellig, T. P. L.↗