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Schnopper, H. W.

Publications and source records attributed to Schnopper, H. W..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

X-ray scattering measurements from thin foil X-ray mirrors

Thin foil X-ray mirrors are to be used as the reflecting elements in the telescopes of the X-ray satellites Spectrum-X-Gamma (SRG) and ASTRO-D. High resolution X-ray scattering measurements from the Au coated and dip-lacquered Al foils are presented. These were obtained from SRG mirrors positioned in a test quadrant of the telescope structure and from ASTRO-D foils held in a simple fixture. The X-ray data is compared with laser data and other surface structure data such as STM, atomic force microscopy (AFM), TEM, and electron micrography. The data obtained at Cu K-alpha(1), (8.05 keV) from all the mirrors produced on Al foils shows a scatter which limits the obtainable half-power width to above 1.5 arcmin. Mirrors based on electroformed Ni foils, however, show local regions with a factor of 4 better performance, and they are being developed for future applications.

Christensen, F. E.↗
NASA NTRS1986

An upper limit to X-ray emission from Saturn

X-rays are produced in auroral discharges, and their measurement can serve to characterize the interaction processes responsible for the aurora itself. The existence of auroral activity on Saturn was suggested by the observation of a magnetosphere by Pioneer 11 and confirmed by UV measurements during the Voyager encounters. The detection of X-rays from Jupiter with the Einstein Observatory (HEAO 2) satellite provided the impetus for a subsequent observation of Saturn. No emission was detected. This article presents the upper limit established by the observation and derives an expected emission level assuming X-ray production to be the result of bremsstrahlung from keV electrons precipitating into Saturn's atmosphere. The difference is a factor of 100.

Gilman, D. A.↗
NASA NTRS1984

Spectral observations of the soft X-ray background with solid-state detectors - Evidence for line emissions

The soft X-ray radiation from several regions of the sky was observed with solid-state detectors Si(Li) between 0.3 and 1.2 keV during two rocket flights. The thermal nature of the diffuse emission coming from the hot bubble surrounding the solar system is confirmed by the observation of C V-C VI and O VII lines which are typical of a temperature of about 10 to the 6th K. Evidence for the existence of a weak component at a higher temperature is given. This component, well visible in the high latitude spectra, could be produced by a hot galactic halo. In the direction of the enhancement region centered on the North Polar Spur, the radiation excess spectra are well represented by a two-temperature plasma model with rather standard abundances. The two components have temperatures of 10 to the 6th and 4.7 x 10 to the 6th K.

Rocchia, R.↗
NASA NTRS1983

The detection of X rays from Jupiter

X rays in the energy band 0.2-3.0 keV have been detected coming from both polar regions of Jupiter. The observations were made in 1979 and 1981 by using the imaging proportional counter and high resolution imaging detectors on the Einstein X-ray astronomy satellite. The measured flux density of approximately 0.0006/sq cm-sec at earth corresponds to an X ray luminosity of approximately 4 x 10 to the 9th W in the 0.2- to 3.0-keV energy band. The energy spectrum of the X rays is extremely soft and can be characterized by a power law with an exponent of approximately 2.3. Detector energy resolution is insufficient to distinguish a soft line spectrum from a continuum. However, the shape of the response and the observed X ray power indicate that the source of this auroral emission is not electron bremsstrahlung as on the earth, but is most probably line emission from O and S ions with energies between 0.03 and 4.0 MeV/nucleon precipitating from the outer boundary of the Io plasma torus at L approximately 8.

Metzger, A. E.↗
NASA NTRS1983

Spectral observation of the soft X-ray background and of the North Polar Spur with solid state spectrometers

Soft X-ray diffuse background observations in the 0.3-1.5 keV interval of two sky regions, near the north galactic pole and the North Polar Spur (NPS) are reported. Data were taken with a solid-state spectrometer carried by a rocket. The near-polar region exhibited O VII ion emissions at 530 eV. A second component was not identified but was attributed to the Galactic Halo. Fe XVIII, Ne IX, and O VIII contributions were detected in the NPS, along with an enhancement at 1.35 keV from Mg XI lines. A two-temperature contour was fit to the spectra and chi-square confidence levels of 90 and 68 percent were obtained.

Rocchia, R.↗
NASA NTRS1982

X-ray spectrum of Capella and its relation to coronal structure and ultraviolet emission

The binary system Capella has been observed on 1979 March 15 and on 1980 March 15-17, with the objective grating spectrometer on board the Einstein Observatory. The spectrum measured with the 1000 1/mm grating covers the range 5-30 A with a resolution less than 1 A. The spectra show evidence for a bimodal temperature distribution of emission measure in an optically thin plasma with one component about 5,000,000 K and the other one about 10,000,000 K. Spectral features can be identified with line emissions from O VIII, Fe XVII, Fe XVIII, Fe XXIV, and Ne X ions. Good spectral fits have been obtained assuming standard cosmic abundances. The data are interpreted in terms of emission from hot static coronal loops rather similar to the magnetic arch structures found on the sun. It is shown that the conditions for such a model can exist on Capella. Typical values of loop base pressure and half-length are derived for both temperature components and discussed in relation to UV observations.

Mewe, R.↗
NASA NTRS1982

Carbon and oxygen X-ray line emission from the interstellar medium

A soft X-ray, 0.3-1.0 keV spectrum from a 1 sr region which includes a portion of the North Polar Spur, obtained by three rocketborne lithium-drifted silicon detectors, shows the C V, C VI, O VII and O VIII emission lines. The spectrum is well fitted by a two-component, modified Kato (1976) model, where the coronal emission is in collisional equilibrium, with interstellar medium and North Polar Spur temperatures of 1.1 and 3.8 million K, respectively.

Schnopper, H. W.↗
NASA NTRS1981

Cylindrical Crystal Imaging Spectrometer (CCIS) for cosmic X-ray spectroscopy

A "stigmatic" focusing, Bragg crystal spectrometer was developed and used for high spectral resolution X-ray emission line diagnostics on hot laboratory plasmas. The concept be applied at the focal plane of an orbiting X-ray telescope where it offers several advantages over conventional spectrometers, i.e., mechanical simplicity, high resolving power and sensitivity, simultaneous measurement of an extended segment of spectrum, and good imaging properties. The instrument features a simple, unambiguous, non-scanning spectrum readout that is not adversely affected by either spacecraft pointing error or source extent. The performance of the instrument is estimated in the context of the Advanced X-Ray Astrophysical Facility mission.

Schnopper, H. W.↗
NASA NTRS1981

A survey of X-ray line emission from the supernova remnant Puppis A

Initial results from the first high-resolution study of the X-ray spectrum of a supernova remnant are reported. The spectrum of Puppis A between 500 and 1100 eV has been surveyed with the Focal Plane Crystal Spectrometer on the Einstein Observatory and the flux in eight lines and three line blends from various transitions of highly ionized nitrogen, oxygen, neon, and iron has been measured. The spectrum resembles that of active regions in the solar corona, but the neon lines seem enhanced relative to the oxygen lines, and both are enhanced relative to iron. The observed line strengths serve as diagnostics of the physical conditions in the emitting material. Without a priori assumptions, the ionization temperatures of O (2.2 million K) and Ne (4 million K) and the dominant ionization stage of Fe (Fe XVII) are deduced. Isothermal equilibrium plasmas or homogeneous nonequilibrium plasmas as descriptions of the source are ruled out. It is concluded that Puppis A must contain plasma over a temperature range 2-million to 5-million K with an intervening absorption column of 4 x 10 to the 21st/sq cm.

Winkler, P. F.↗
NASA NTRS1981

First detection of line emission from the hot interstellar medium with solid state detectors

Previously reported enhanced soft X-ray emission from the North-Galactic Polar region supports the theory of a hot interstellar component. This paper reports the first detection of line emission from the hot interstellar component in the North-Galactic-Polar region. Measurements were made with solid state Si(Li) detectors aboard a spin-stabilized rocket launched from the White Sands Missile Range on March 22, 1980. Two features are clearly present in the low energy portion of the spectrum derived from the data. They correspond to emission lines from C V (300 eV) and C VI (360 eV), and from O VII (560 eV) and O VIII (650 eV). The detection of emission lines coming from these highly stripped ions is direct evidence for the thermal origin of the emission and confirms the presence of a hot (1-million K) component in the interstellar medium.

Schnopper, H. W.↗
NASA NTRS1980

Radio and X-ray observations of Abell 754

The cluster of galaxies Abell 754 has been observed at 610 MHz with the Westerbork Synthesis Radio Telescope at 1420 MHz with the synthesis telescope of the Dominion Radio Astrophysical Observatory and in the interval 2-10 keV with the rotating modulation collimators on SAS-3. A complete source list for the field is given together with radio contour diagrams of extended sources associated with cluster galaxies. No X-rays were detected and a diameter of greater than 6 arcmin may be assigned to the associated source 4U 0900-09 (2A 0906-095) if a constant intensity is assumed for a single source. Upper limits to the luminosity of the cD galaxy are 2 x 10 to the 44th erg/sec in the X-ray and 5 x 10 to the 39th erg/sec in the radio.

Harris, D. E.↗
NASA NTRS1980

Simultaneous X-ray and optical observations of rapid variability in Scorpius X-1

Copernicus and SAS-3 observations of Sco X-1 during very active states show strong and rapid X-ray flickering with time scales as short as 20 sec. Simultaneous optical photometry reveals similar and remarkably well correlated flickering of lower amplitude. The level of correlation decreases when the X-ray source becomes fainter, but optical and X-ray fluxes, averaged over 1 min, are usually well correlated for B magnitudes less than 12.9. Cross-correlation analysis of the data during periods of high activity shows no really significant time delay between X-ray and optical features, although the cross-correlation function peaks systematically for positive lag values (optical following X-rays). The amplitude of the X-ray flickering exhibits a strong energy-dependence consistent with the well-known intensity versus spectral-hardness relation derived from previous observations. The highly correlated optical activity is interpreted as due to reprocessing of X-ray photons in the binary system.

Ilovaisky, S. A.↗
NASA NTRS1980

SAS 3 and related observations of Abell 2029

X-ray and radio observations of the cluster of galaxies show that the central cD galaxy dominates the emissions. Resolution of the X-ray source shows that its extent is significantly greater than that of the profile of surface brightness of the cD galaxy. Dressler's model of most of the cluster mass with very high M/L(v) is similarly extended. The optically dark mass may provide low-energy X-ray emission of the coronae of 5 x 10 to the 16th stars with very high M/L(v), but in the 2-10 keV range the data are consistent with current theoretical predictions for hot intracluster gas.

Johnson, H. M.↗
NASA NTRS1979

The MIT/OSO 7 catalog of X-ray sources - Intensities, spectra, and long-term variability

This paper is a summary of the observations of the cosmic X-ray sky performed by the MIT 1-40-keV X-ray detectors on OSO 7 between October 1971 and May 1973. Specifically, mean intensities or upper limits of all third Uhuru or OSO 7 cataloged sources (185 sources) in the 3-10-keV range are computed. For those sources for which a statistically significant (greater than 20) intensity was found in the 3-10-keV band (138 sources), further intensity determinations were made in the 1-15-keV, 1-6-keV, and 15-40-keV energy bands. Graphs and other simple techniques are provided to aid the user in converting the observed counting rates to convenient units and in determining spectral parameters. Long-term light curves (counting rates in one or more energy bands as a function of time) are plotted for 86 of the brighter sources.

Markert, T. H.↗
NASA NTRS1978

Si XIII and Si XIV line emission search with the ANS crystal spectrometer

The final results of the search for Si XIII and Si XIV line emission, using the ANS Bragg crystal spectrometer, are presented. No positive line detection was achieved in any of the measurements made on several types of cosmic object; i.e., a transient X-ray source, close binary systems, supernova remnants, GX sources, and clusters of galaxies. Three-sigma upper limits for discrete line emission from these objects are reported and compared with line strengths inferred from other proportional-counter and Bragg spectrometer data. The present upper limit of 1.0 eV for the equivalent width of a narrow Si XIV line emission from the X-ray nova A0620-00 is an order of magnitude lower than previous limits set by other experiments.

Parsignault, D. R.↗
NASA NTRS1978

X-ray observation of IC 4329 A

X-rays from the extreme type 1 Seyfert galaxy IC 4329 A have been observed with the rotating modulation collimator on board SAS 3. In addition to establishing IC 4329 A as an X-ray source, the SAS 3 data require that the source be extended, that there be at least one other nearby source, or both.

Delvaille, J. P.↗