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Catura, R. C.

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

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

X-ray spectra of solar flares obtained with a high-resolution bent crystal spectrometer

Preliminary results obtained for three solar flares with the bent crystal spectrometer on the SMM are presented. Resonance and satellite lines of Ca XIX and XVIII and Fe XXV and XXIV are observed together with the Fe XXVI Lyman-alpha line. Plasma properties are deduced from line ratios and evidence is presented for changes of line widths coincident with the occurrence of a hard X-ray impulsive burst. Fe K-alpha spectra from a disk center and a limb flare agree with the predictions of a fluorescence excitation model. However, a transient Fe K-alpha burst observed in a third flare may be explained by the collisional ionization of cool iron by energetic electrons.

Culhane, J. L.↗
NASA NTRS1979

Cosmic X-ray telescope for ARIES rocket observations

A rocket-borne Wolter Type I X-ray telescope having a focal length of 2.3m, an entrance aperture of 66cm and a geometrical area of 380cm2 is nearing completion. The telescope mirrors are formed by diamond turning their figures into forged aluminum substrates of 5083 alloy. These diamond-turned substrates are subsequently plated with a thin coating of electroless nickel and polished to obtain the final X-ray reflecting surfaces. Details of the rocket payload, the X-ray telescope, its calculated response and the experience gained in selecting the mirror substrate alloy are discussed and the current status of the telescope is reviewed.

Catura, R. C.↗
NASA NTRS1978

Searches for correlated X-ray and radio emission from X-ray burst sources

The NRAO Green Bank interferometer has been used to monitor MXB 1730-335 and MXB 1837+05 during periods when 68 X-ray bursts were detected by X-ray observations. No significant radio emission was detected from these objects, or from MXB 1820-30 and MXB 1906+00, which emitted no bursts throughout the simultaneous observations. The data place upper limits on radio emission from these objects in the 2695 and 8085 MHz bands.

Johnson, H. M.↗
NASA NTRS1978

X-ray and radio observations of GX 17+2 and GX 13+1

X-ray data on the sources 3U 1813-14 (GX 17+2) and 3U 1811-17 (GX 13+1), obtained by Copernicus between 1975 and 1977, are examined. These reveal correlated intensity and spectral-slope variations in GX 17+2 similar to those seen in Sco X-1 and four other galactic sources, 3U 0614+09, 3U 1702-36, 3U 1728-16, and 3U 1758-25. The data on GX 17+2 have been unsuccessfully searched for further evidence of a shallow 31.9-minute modulation. In the case of GX 13+1 no significant variability was seen in either intensity or spectrum. A simultaneous search made from the NRAO simultaneously with some of the X-ray observations revealed no significant radio emission from either source.

White, N. E.↗
NASA NTRS1977

Demand-type gas supply system for rocket borne thin-window proportional counters

A simple closed loop control system has been developed to maintain the gas pressure in thin-window proportional counters during rocket flights. This system permits convenient external control of detector pressure and system flushing rate. The control system is activated at launch with the sealing of a reference volume at the existing system pressure. Inflight control to plus or minus 2 torr at a working pressure of 760 torr has been achieved on six rocket flights.

Acton, L. W.↗
NASA NTRS1977

Bent crystal spectrometer for solar X-ray spectroscopy

A bent crystal spectrometer employs a collimated beam of X-rays incident on the crystal over a range of Bragg angles determined by the orientation and curvature of the crystal surface. It provides continuous and simultaneous coverage of all X-ray wavelengths within its spectral range. In-flight testing for solar X-ray spectroscopy was performed using a small instrument to supplement the wavelength coverage of several scanning spectrometers used to study solar active regions in the 9-24 A range. Later testing included modifications to alleviate problems caused by ultraviolet radiation. Future usage of the device will include studies of time variable emission from solar flares or discrete galactic X-ray sources, and the first major experiment to utilize bent crystal spectrometers will be the Solar Maximum Mission satellite in 1979.

Rapley, C. G.↗
NASA NTRS1977

A focussing iron line crystal spectrometer for Spacelab

A crystal spectrometer system is described which employs conical focusing of 12 curved LiF crystal panels to minimize the detector size and reduce the background counting rate. The wavelength range from 1.70 to 1.98 A is covered, including the resonance lines of Fe XXV and Fe XXVI as well as the Fe I K-alpha line and absorption edge. Operation of the spectrometer is discussed, noting that diffracted X-rays are registered in one-dimensional position-sensitive detectors and that the arrival position of a photon in a detector is related to its wavelength due to the fixed curvature of the crystal panels in the dispersion plane. Some characteristics of the multianode position-sensitive detectors are reviewed along with the crystal arrangement and mounting. The instrument sensitivity is evaluated in relation to the strengths of 6.7-keV emission features detected by the Ariel 5 and OSO 8 proportional-counter spectrometers.

Catura, R. C.↗
NASA NTRS1977

Solar X-ray spectroscopy with a Bent Crystal Spectrometer /BCS/

A high-resolution Bent Crystal Spectrometer (BCS) which provides simultaneous and continuous time coverage of a range of wavelengths is described; its application to spectral studies of solar X-ray emission is discussed. Design of the BCS and its accompanying position-sensitive detector is considered. Calibrations of the crystal curvature, the angle between a crystal reference plane and the collimator axis, and the position response of the position-sensitive proportional counter in determining absolute wavelengths are also mentioned. An active solar region spectrum obtained during an airborne BCS test is compared to wavelength data derived from theory or previous experiments, and excellent agreement is found. Specifications for a BCS system to be used in the Solar Maximum Mission satellite of 1979 are given.

Rapley, C. G.↗
NASA NTRS1977

Radio and X-ray observations of NGC 1851 and NGC 1904

The globular clusters NGC 1851 and NGC 1904, have been observed simultaneously at radio and X-ray wavelengths with the aid of the Green Bank interferometer and the proportional counter on OAO Copernicus. The combined radio and X-ray observations provided simultaneous coverage of each subject for a total of about one hour. Data concerning the radio frequency observations of the two globular clusters are presented in a table. The X-ray counts per frame are shown in a graph as a function of time, taking into account a five day interval in December 1975.

Johnson, H. M.↗
NASA NTRS1976

Instrumentation for solar and cosmic X-ray spectroscopy

Five flight instruments for high resolution X-ray spectroscopy are described. They include one- and two-dimensionally collimated solar rocket X-ray spectrometers, a 1-23 A X-ray polychromator for the Solar Maximum Mission, a collimated crystal spectrometer for cosmic X-ray studies, and a grating spectrometer/spectrograph with paraboloidal telescope for 10 to 50 A solar X-ray research. The discussion includes factors motivating design and use, examples of results for those already flown, and potential for future studies.

Acton, L. W.↗
NASA NTRS1976

X-ray structure of the Puppis supernova remnant

The angular distribution of X-ray emission from the Puppis supernova remnant was investigated with a focusing X-ray collector during a rocket observation. Extent of the X-ray emitting region along the direction of scan is 42 (+ or - 4) arcmin and is well correlated with the size of the Puppis A radioshell. The existence of a feature within the remnant is confirmed whose X-ray emission is strongly localized, and its spectrum is observed to be softer than the rest of the remnant.

Catura, R. C.↗
NASA NTRS1976

Spectroscopic studies of the solar corona at X-ray wavelengths

The spatial distribution of emission in several X-ray lines is discussed with emphasis on temperature dependence and association with active regions. Results are presented for the trio of helium-like O VII lines which demonstrate (1) a spatial variation in the density-dependent forbidden-to-intersystem line ratio, and (2) a strong spatial variation in the intensity of the O VII resonance line relative to the optically forbidden transitions. The second effect appears to be caused by resonance scattering by material in the line of sight.

Acton, L. W.↗
NASA NTRS1976

Intense soft X-ray flux from Her-1

An intense flux of soft X-rays extending up to at least 1 keV has been observed from Her X-1. If the soft X-ray intensity is corrected for interstellar absorption the luminosity between 0.16 and 1 keV is comparable to that from 2-10 keV. The soft X-rays are modulated with the 1.24 sec period observed at higher energies but are approximately 180 deg out of phase with the high energy flux. These results extend the detection of this flux to higher energy, a different binary phase, and to a time 19 periods (of the 35 day cycle) later. These observations suggest that this soft emission is a stable feature in the spectrum of this source during its X-ray on state and that this emission is local to Her X-1.

Catura, R. C.↗
NASA NTRS1975

Intense soft X-ray flux from Hercules X-1

An intense flux of soft X-rays extending up to at least 1 keV has been observed from Her X-1. If the soft X-ray intensity is corrected for interstellar absorption, the luminosity in the 0.16-0.28 keV band is comparable to that from 2 to 10 keV. This confirms the conclusion of Shulman et al. (1975) but extends the detection of this flux to higher energy, a different binary phase, and to a time 19 periods later in the 35-day cycle. These observations suggest that this soft emission may be a stable feature in the spectrum of Her X-1 during its X-ray on state. It appears difficult to account for the high soft X-ray luminosity by current simple models of the X-ray source.

Catura, R. C.↗
NASA NTRS1975

Analysis of Aerobee 17.012 data

The results are summarized of reduction and analysis of data acquired during the flight of NASA-Aerobee 17.012CG. This rocket was launched from White Sands Missile Range on 6 April 1974 at 0410 U.T. The primary instrument in the experiment payload was a singly focussing x-ray reflector system sensitive in the range from 0.18 to 3 keV. X-ray detectors for this system consisted of two gas flow proportional counters with fields of view defined by apertures of 0.1 deg and 0.3 deg at the reflector focus. A Bragg spectrometer utilizing KAP crystals was included in the payload with the objective of detecting the Lyman alpha line of 0 VIII at 18.97A in the Puppis supernova remanant. A 35 mm camera photographed the star field every 1.6 sec throughout the flight to provide aspect information.

Catura, R. C.↗
NASA NTRS1975

A focussing X-ray collector and its response in flight

A singly focussing X-ray reflector system designed for rocket observation of cosmic X-ray sources is described. The reflector has an angular resolution of one arc minute in X-rays. Focussing properties of this reflector as measured in the laboratory with X-rays and visible light are discussed and the response observed as the flight instrument was scanned over the galactic X-ray source, Sco X-1, is presented.

Catura, R. C.↗
NASA NTRS1975

Observation of soft X-rays from cosmic sources

A binary X-ray source, an extended extragalactic X-ray source and several nearby stars were surveyed for X-ray emission. The energy spectrum and time structure of X-ray flux from the binary source, Her X-l, was investigated in the range from 0.15 to 6 KeV. This source was observed at a binary phase of 0.18 with the system near elongation normal to the line of sight. Intense pulsations were observed in optical emission lines near this binary phase. The spectrum and angular distribution of X-ray emission from the X-ray source in the Virgo Cluster of Galaxies, near M 87, was also observed. In addition, the stars Alpha Leo, Zeta Her, and Epsilon Vir were investigated. Epsilon Aur and Alpha Aur were also scanned. These stars were studied since there is increasing evidence that such objects may be transient sources of soft X-rays.

Catura, R. C.↗