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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 307 records · Page 17
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NASA NTRS1976

New observations of pulsed X-ray emission from NP 0532

Large-area proportional counters sensitive from 0.6 to 23 keV were used to observe about 3 min of pulsed X-ray emission from NP 0532 during two lunar-occultation experiments. A detailed pulse profile with 65-microsec resolution shows that the X-ray primary-pulse shape is essentially identical to its optical counterpart. Spectral data on the pulsed X-ray emission are presented. A pulse-by-pulse examination of the data shows no evidence for temporal variability.

Kestenbaum, H. L.↗
NASA NTRS1975

A large-area lithium-fluoride Bragg spectrometer for stellar X-ray astronomy

A large-area Bragg spectrometer used to search for the Fe XXV X-ray emission lines of Sco X-1 is described. The device has 3400 sq cm of LiF on nine crystal panels aligned perpendicular to the longitudinal axis of the rocket. X rays satisfying the Bragg condition reflect into an array of nine companion proportional counters. A pointing system incorporating a free gyroscope with 2 degrees of freedom assures that target X rays are reflected at the required angle and produces repeated spectral scans of the X-ray continuum, which are later superimposed to correct temporal effects. The instrument is capable of detecting a narrow line flux from Sco X-1 of about .01 photons/sq cm/sec.

Stockman, H. S., Jr.↗
NASA NTRS1976

An observation of the diffuse soft X-ray/extreme-ultraviolet background

Results are reported for observations of diffuse radiation in the spectral bands from 114 to 150 A and from 44 to 120 A, which were made with rocket-borne proportional counters in areas of the sky near galactic coordinates 150 deg longitude, -15 deg latitude and 189 deg longitude, 3 deg latitude. The observed fluxes are 0.125 photon per sq cm/s/sr/eV at 180 eV, which is consistent with previous measurements, and 3.2 photons per sq cm/s/sr/eV at 100 eV, which indicates a steeply rising spectrum. It is noted that these fluxes are significantly smaller than those detected by Yentis et al. (1972), and the differences are attributed to either a terrestrial origin of the fluxes or the direction of observation. Constraints are placed on the parameters of simple emission models of celestial origin, and a rigorous upper limit is determined for the space density of white dwarfs at a blackbody temperature of at least 100,000 K.

Cash, W.↗
NASA NTRS1975

An experiment to measure cosmic ray 2H and 3He in the 4-10 GV range

It is known that the mean matter traversed by cosmic rays, X, can be obtained from the observed ratio of the flux of daughter nuclei to that of the parent nuclei provided X is much less than the attenuation mean free of the daughter nuclei. This condition is well satisfied in the case of 2H and 3He. We propose to measure the 2H/1H and 3He/4He ratios, using a multiwire proportional counter array and a superconducting magnet to measure the rigidity, and a set of aerogel Cerenkov counters to measure the velocity, thus yielding the mass of the particle. Results of a Monte-Carlo calculation based on actual experimental conditions are presented to show the resolution of the instrument. The area solid angle of the telescope is 90 sq cm sr with an average maximum detectable momentum of 140 GV.

Badhwar, G. D.↗
NASA NTRS1976

Iron line emission from a high-temperature plasma in Cassiopeia A

The letter reports a measurement of the X-ray spectrum of Cas A with a proportional counter on board OSO-8. The high-energy data (greater than 7 keV) are found to agree equally well with a power law having a number index of about 4.5 and with a thermal spectrum having kT of about 3.9 keV. A narrow iron line predicted by the thermal model is also observed; this line is centered at about 6.67 keV and has an equivalent width of approximately 1270 eV. The low-energy data (below 6 keV) are not fully accounted for by the above thermal spectrum, but are fitted well by an additional low-temperature thermal component with kT not exceeding 0.7 keV and an atomic hydrogen column density of approximately 10 to the 22nd power per sq cm. The iron abundance in the plasma at an electron temperature of 40 keV is estimated from the observed line-to-continuum ratio, and it is shown that a normal cosmic iron abundance is adequate to explain the observation.

Pravdo, S. H.↗
NASA NTRS1976

Simultaneous photometry of X Persei and 3U 0352+30

The suggested association of X Persei with the weak X-ray source 3U 0352+30 raises the possibility of detection of X-ray/optical covariability. The paper reports a successfully conducted simultaneous optical/X-ray observation utilizing ground-based photometry and a satellite-borne proportional counter. Photoelectric photometry of X Persei was obtained on five out of seven consecutive nights in January 1975. The observations yield the faintest and bluest photoelectric magnitudes and colors ever reported for X Per; this change apparently occurred relatively uniformly during 1973-74 and is reminiscent of behavior last observed in about 1900. On January 21, 7 hr of data were obtained simultaneously with OAO Copernicus X-ray observations of 3U 0352+30. The X-ray flux varied during this period by a factor of 2, but there is no obviously correspondent optical activity, to a level of 0.02 mag. The optical data are also used to limit the 0.01-mag variations coincident with the X-ray periodicity reported by White et al. (1976).

Margon, B.↗
NASA NTRS1976

An X-ray survey of BL Lacertae objects

Results are reported for X-ray observations and nearly simultaneous photographic photometry of four BL Lacertae objects (BL Lac, W Com, ON 325, and AP Lib). The X-ray data were obtained in the band from 2.5 to 7.5 keV using a collimated proportional counter aboard OAO-C. Although none of the sources was detected above background at a statistically significant level, two-sigma upper limits on the X-ray flux incident at earth are given for each object. The photometric data indicate that all four objects were near the faint end of their visibility ranges during the time of the X-ray observations. The X-ray upper limits and B magnitudes are employed to calculate upper limits on the brightness temperatures and angular sizes of the radio synchrotron sources; upper limits on the distances to the objects are obtained from limits on the physical source sizes deduced from the radio variabilities. The strictest distance limit is 240 Mpc for BL Lac. Substantial evidence is noted for variability of ON 325 on a timescale of hours.

Margon, B.↗
NASA NTRS1976

An X-ray redshift measure for clusters of galaxies up to z not less than 1

Correlated measurements of redshifted iron line emission and apparent surface brightness are suggested for unambiguously defining intrinsic X-ray characteristics for clusters of galaxies up to z not less than 1. If some of the weak unidentified high-galactic-latitude X-ray sources are clusters at z roughly equal to 1-3, then such correlated measurements should be feasible within the complement of instruments aboard the HEAO-B orbiting X-ray telescope observatory. In addition, those clusters at z less than 1 would require spectral data from broader bandwidth experiments, such as the all-sky survey to be provided by the proportional counters aboard the first mission of the High Energy Astronomy Observatory (HEAO-A).

Boldt, E.↗
NASA NTRS1976

X-ray observations of the Vela pulsar - Statistics and spectrum

The Vela pulsar (3U 0833-45) was observed in the range 2-60 keV by a proportional-counter experiment on board OSO-8 with temporal resolution sufficient to make possible a sensitive search for pulsed X-rays at the radio pulsar period. A statistical analysis yielded 8 percent as the 3-sigma upper limit on the pulsed fraction. The energy spectrum is fitted well by a structureless power law with number index 2.2 (+ or - 0.2) and absorption by a hydrogen column density of 2.9(+ or - 2.0) by 10 to the 22nd power per sq cm.

Pravdo, S. H.↗
NASA NTRS1977

Large-area soft X-ray imaging system

System consists of large-area focusing collector and position sensitive proportional counter. Device can be used to study plasmas, with X-ray imaging in biological sciences, and crystallography.

Gorenstein, P.↗
NASA NTRS1977

Skylab ATM/S-056 X-ray event analyzer observations versus solar flare activity: An event compilation

An event compilation is presented which correlates ATM/S-056 X-ray event analyzer solar observations with solar flare activity. Approximately 1,070 h of pulse height analyzed X-ray proportional counter data were obtained with the X-ray event analyzer during Skylab. During its operation, 449 flares (including 343 flare peaks) were observed. Seventy events of peak X-ray emission or = Cl were simultaneously observed by ground based telescopes, SOLRAD 9 and/or Vela, and the X-ray event analyzer. These events were observed from preflare through flare rise to peak and through flare decline.

Wilson, R. M.↗
NASA NTRS1976

User's guide to the data obtained by the Skylab/ATM NASA-Marshall Space Flight Center/The Aerospace Corporation S-056 X-ray experiment

The S-056 observations consist of 27,000 photographs (filterheliograms) obtained by the X-ray telescope and 1,100 h of proportional counter data obtained by the X-ray event analyzer in the soft X-ray region of the solar spectrum. A description of the S-056 data together with additional relevant information that may be needed by users of the data is given.

Source record↗
NASA NTRS1977

The COS-B experiment and mission

The COS-B satellite carries a single experiment, capable of detecting gamma rays with energies greater than 30 MeV to study the spatial, energy, and time characteristics of high-energy radiation of galactic and extragalactic origin. The capability to search for gamma ray pulsations is enhanced by the inclusion in the payload of a proportional counter sensitive of X-rays of 2 to 12 keV. The experiment was calibrated using particle accelerators. The results of these measurements are presented, and the performance of the system in orbit is discussed.

Source record↗
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 NTRS1977

The HEAO-A Scanning Modulation Collimator instrument

The Scanning Modulation Collimator X-ray instrument for the HEAO-A satellite was designed to measure celestial radiation in the range between 1 and 15 KeV and to resolve, and correlate, the position of X-ray sources with visible light sources on the celestial sphere to within 5 arc seconds. The positional accuracy is made possible by mechanical collimation of the X-ray sources viewed by the instrument. High sensitivity is provided from two systems each containing four gas filled proportional counters followed by preamplification, signal summing, pulse height analysis, pulse shape discrimination, X-ray event accumulators and telemetry processing electronics.

Roy, A.↗
NASA NTRS1977

Direct delivery of automated spacecraft using the Shuttle - Thoughts for the designer

Following an outline of the main functions of the Tracking and Data Relay Satellite System (TDRSS) and the Astrophysics Transient Explorer (ATREX), the design options of the delivery into orbit of automated spacecraft, ATREX in particular, on board the Shuttle are discussed. The proportional counters used as detectors in ATREX need protection from humidity, so the spacecraft will be shipped in a sealed container filled with dry nitrogen and not opened until it is safely in the clean room at the launch site. The spacecraft and its booster will be loaded into a canister maintaining low humidity, to protect them all the way through the payload changeout room and into the Shuttle itself. After launching the Shuttle into orbit, the spacecraft will be tested on board the Shuttle just before releasing it. The future applications of this technique in Extravehicular Activity (EVA) and Gamma Ray Astronomy Observatories are discussed.

Townsend, M. R.↗
NASA NTRS1977

Soft X-ray sources and supernova remnants in Cygnus - Rocket and Apollo-Soyuz results

Soft X-ray observations of the Cygnus region obtained from proportional counters aboard a rocket and also on the Apollo-Soyuz mission are reported. It is found that Cyg X-6, a source whose flux in confined to the 0.5-2.0-keV band, is a long narrow filament oriented nearly perpendicular to the galactic plane. This feature has a linear dimension greater than or of the order of 150 parsecs, and its spectrum is adequately described by an exponential. Another intense soft source whose flux is also confined to the 0.5-2.0-keV band has been discovered near Gamma Cygni. This source, designed Cyg X-7, has a spectrum characterized by a temperature of 1.5 to 5 million K and a hydrogen column density of at least 10 to the 21st power per sq cm. The possible association of Cyg X-7 with the supernova remnant DR 4 is discussed. An interpretation of this object in terms of the standard adiabatic spherical-shock-wave model yields plausible values for the free paramenters. HB 21, another old supernova remnant, has not been detected as a soft X-ray source.

Davidsen, A. F.↗
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.↗