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  • ASTRONOMY  (246)
  • 1995-1999
  • 1975-1979  (246)
  • 1965-1969
  • 1940-1944
  • 1976  (246)
  • 101
    Publication Date: 2019-06-27
    Description: Positional and color magnitude data for 5116 stars are given.
    Keywords: ASTRONOMY
    Type: NASA-CR-145823 , JPL-TM-33-758
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  • 102
    Publication Date: 2019-06-27
    Description: A FORTRAN computer program called WINDOW was written to simplify the planning of astronomical observations of a number of objects in a limited time. The program lists the azimuths at 15 minute intervals of up to 20 objects while they are in a given range of elevation angles - the window - and gives the elevation angle of each object at its time of transit. This work was motivated by the need to use observing time efficiently on flights of NASA-Ames' Lear Jet and C-141 observatories; WINDOW permits the investigator to prepare preliminary flight plans. However, the program is suited to planning ground-based observations as well. The program and a sample flight plan are described.
    Keywords: ASTRONOMY
    Type: NASA-TM-X-73156 , A-6697
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  • 103
    Publication Date: 2019-06-27
    Description: The theory required to build a numerical simulation of interacting supernova remnants is developed. The hot cavities within a population of remnants will become connected, with varying ease and speed, for a variety of assumed conditions in the outer shells of old remnants. Apparently neither radiative cooling nor thermal conduction in a large-scale galactic magnetic field can destroy hot cavity regions, if they grow, faster than they are reheated by supernova shock waves, but interstellar mass motions disrupt the contiguity of extensive cavities necessary for the dispersal of these shocks over a wide volume. Monte Carlo simulations show that a quasi-equilibrium is reached in the test space within 10 million yrs of the first supernova and is characterized by an average cavity filling fraction of the interstellar volume. Aspects of this equilibrium are discussed for a range of supernova rates. Two predictions are not confirmed within this range: critical growth of hot regions to encompass the entire medium, and the efficient quenching of a remnant's expansion by interaction with other cavities.
    Keywords: ASTRONOMY
    Type: NASA-TM-X-71148 , X-661-76-119
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  • 104
    Publication Date: 2019-06-27
    Description: Evidence for a persistent 11.17 + or - .10d period from Cyg X-2 is presented from one year of accumulated data from the Ariel-5 all-sky monitor. The effect is not a simple sidereal alias of a true source period close to one day.
    Keywords: ASTRONOMY
    Type: NASA-TM-X-71049 , X-660-76-1
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  • 105
    Publication Date: 2019-06-27
    Description: The primary objective of this review is to tabulate the basic recommendations of several solar telescope studies. A primary matrix, listing some of the basic optical parameters, was compiled and forms the basis for a table. From this table it is apparent that a strong consensus exists on the configuration of the telescope and on its fundamental dimensionless parameters. Other tables presented in this document address the basic approach of each study to the telescope design as well as to the design of critical subsystems. These subsystem problems include the material, coating, configuration, mounting, launch locks, and thermal control of the primary mirror, the structure of the main telescope and the instrument bay, the mechanisms for radiation rejection, thermal control, and meteoroid shielding, and methods of maintaining image quality by proper alignment and by image motion compensation.
    Keywords: ASTRONOMY
    Type: NASA-CR-156745
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  • 106
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    In:  CASI
    Publication Date: 2019-06-27
    Description: Analysis of the alignment and focus errors than can be tolerated, methods of sensing such errors, and mechanisms to make the necessary corrections were addressed. Alternate approaches and their relative merits were considered. The results of this study indicate that adequate alignment control can be achieved.
    Keywords: ASTRONOMY
    Type: NASA-CR-156700
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  • 107
    Publication Date: 2019-06-27
    Description: The major coordinate systems as well as the transformations and transformation angles between them, for the Space Telescope are defined. The coordinate systems were primarily developed for use in pointing and control system analysis and simulation. Additional useful information (on nomenclature, symbols, quaternion operations, etc.) is also contained.
    Keywords: ASTRONOMY
    Type: NASA-TM-X-73343
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  • 108
    Publication Date: 2019-06-27
    Description: The natural environment design requirements for the Space Telescope are presented. Because the Space Telescope is to be carried as cargo to orbital altitudes in the space shuttle bay, orbital environment impacts are the main concern.
    Keywords: ASTRONOMY
    Type: NASA-TM-X-73331
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  • 109
    Publication Date: 2019-06-27
    Description: The All-Sky Monitor on Ariel 5 has observed the Aquila-Serpens region on a quasi-continuous basis since launch in 1974 October. During this time Aql X-1 exhibited major flares in 1975 June and 1976 June, with the measured X-ray intensities increasing more than an order of magnitude to approximately that measured from the Crab nebula, and remaining above the experiment threshold (approximately 0.1 x s crab) for almost two months in both instances. These outbursts resemble the X-ray light curves of transient sources such as A0620-00 and are interpreted in terms of episodic accretion in a dwarf nova-like binary. Combination of the epoch of phase minimum for the 1.3d period (1976) with the 1975 data yields a value of P = 1.28d + or - 0.02d with a corresponding modulation of approximately 3% (3-6 keV). Modulation at this period is not apparent in the 1976 data, with an upper limit of 2% during that time.
    Keywords: ASTRONOMY
    Type: NASA-TM-X-71202 , X-661-76-218
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  • 110
    Publication Date: 2019-06-27
    Description: Over one thousand occultations of each planet in the solar system have occurred during the period from mid-1973 through mid-1976 as seen from the lunar orbiting Radio Astronomy Explorer-2 (RAE-2) spacecraft. These occultations have been examined for evidence of planetary radio emissions in the 0.025 to 13.1 MHz band. Only Jupiter and the earth have given positive results. Lack of detection of emission from the other planets can mean that either they do not emit radio noise in this band or the flux level of their emissions and/or its occurrence rate are too low to be detected by RAE-2.
    Keywords: ASTRONOMY
    Type: NASA-TM-X-71182 , X-695-76-186
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  • 111
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    In:  CASI
    Publication Date: 2019-06-27
    Description: Color and spectral data from spectrometer observations and computerized analyses of asteroid spectra are discussed. Potential occultations of bright asteroids by the moon are summarized. Analysis of anisotropic scattering within Saturn's rings indicates that mineral contamination of the 120 particles cannot exceed 5 percent by weight, and that the rings formed from particle breakup rather than from particle condensation. Raman probe applications to Jupiter and Uranus atmospheres indicate the presence of aerosol particles. A review of Mariner 9 Mars cloud topography data establishes that most blue clouds are orographic uplift clouds composed of condensates, and that sporadic red clouds are associated with blue clouds or volcanoes and thus probably do not represent dust storm phenomena.
    Keywords: ASTRONOMY
    Type: NASA-CR-148862
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  • 112
    Publication Date: 2019-06-27
    Description: Substantial X-ray emission as reported by Ariel 5 from Her X-l midway through the extended low-state portion of its 35-day cycle is examined. A similar feature during another cycle measured from UHURU satellite is also examined. It is proposed that this feature should occur regularly, consistent with some models for the mass accretion disc which have been reported in the literature. The results of the analysis of 500 days of Ariel-5 All-Sky Monitor data are reported which support the view that the feature occurs regularly in the 35-day cycle.
    Keywords: ASTRONOMY
    Type: NASA-TM-X-71174 , X-661-76-182
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  • 113
    Publication Date: 2019-06-27
    Description: Extraterrestrial particles collected during U-2 flights in the stratosphere were divided into four groups: chondritic, iron-sulfur--nickel, mafic silicates, and others. The chondritic aggregates are typically composed of Fe, Mg, Si, C, S, Ca, and Ni. Detectable levels of He-4 implanted from the solar wind occur in some. Olivine, spinel, and possibly pyrrhotite and a hydrated layered-lattice silicate were identified. The chondritic ablation particles contain no sulfur and appear to have been melted. Magnetite, olivine, and pyroxene were identified. The iron-sulfur-nickel type particles resemble meteoritic iron sulfide with a small amount of nickel, and contain magnetite and troilite. The mafic silicate type particles are iron magnesium silicate grains with clumps of chondritic aggregate particles adhering to their surfaces. Olivine and possibly pyrrhotite and pyroxene were identified. Most of the iron-nickel type particles are spherules and include taenite and wustite. The other type particles include nickel-iron mounds on spheroidal glassy-like grains having chondritic-like elemental abundances.
    Keywords: ASTRONOMY
    Type: NASA-TM-X-73152 , A-6672
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  • 114
    Publication Date: 2019-06-27
    Description: In order to understand the seemingly erratic V/R variations and radial velocity curves of emission edges and central absorption of some Be stars, a theory is advanced to explain the changes of structure of the gaseous ring around these stars. The theory is based on the interaction between the existing ring and the newly ejected matter from the star. It shows that the structural change of the ring is completely controlled by the angular momentum input factor and the dissipation factor. In light of this understanding, the observed results of beta Mon and Pi Aqr. are interpreted.
    Keywords: ASTRONOMY
    Type: NASA-CR-148563
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  • 115
    Publication Date: 2019-06-27
    Description: A program for 20-500 micron spectroscopy from the NASA flying C141 infrared observatory is being carried out with a Michelson interferometer. The parameters affecting the performance of the instrument are studied and an optimal configuration for high performance on the C-141 aircraft is recommended. As each parameter is discussed the relative merits of the two modes of mirror motion (rapid scan or step and integrate) are presented.
    Keywords: ASTRONOMY
    Type: NASA-TM-X-73159 , A-6702
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  • 116
    Publication Date: 2019-06-27
    Description: Tables of the lines found on two tracings each of the ultraviolet spectrum of Tau Her, B5 IV, and Zeta Dra, B6 III, made by the Copernicus satellite and possible identifications are given. The ranges 1025-1451A for Tau Her and 1035 to 1425A for Zeta Dra are covered by the U2 spectrometer at a resolution of 0.2A; the ranges 2028 to 2959A for Tau Her and 2000 to 3000A for Zeta Dra are covered by the V2 spectrometer at a resolution of 0.4A. The observed density of lines in the U2 region is 1.1 lines/A for Tau Her and 1.7 lines/A for Zeta Dra. In the V2 region it is 0.8 lines/A for Tau Her and 0.9 lines/A for Zeta Dra.
    Keywords: ASTRONOMY
    Type: NASA-TM-X-71167 , X-670-76-173
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  • 117
    Publication Date: 2019-06-27
    Description: Papers are presented dealing with astronomical observations of the Jupiter Red Spot, Corona Borealis Constellation, and Meteoroids. Calibration of instruments and reduction and analysis of data are discussed.
    Keywords: ASTRONOMY
    Type: NASA-CR-148486
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  • 118
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    In:  CASI
    Publication Date: 2019-06-27
    Description: Visual photometric function data for Saturn's rings were analyzed in terms of elementary anisotropic scattering radiative transfer models which involve the Henyey-Greenstein function. Limits were placed on the combinations of single scattering albedo, and backscattering directivity, which are permitted by observation. Particles with lunar-like scattering properties were excluded by the analysis. Results are consistent with the ring particles being more-or-less pure, and spherical, conglomerates of H2O frost. Multicolor (5500 A-7600 A), narrow band (100 A), area scanning photometry was used to study the wavelength variation in the optical appearance of Uranus. Limb brightening was detected in two CH4 bands, i.e. 6190A and 7300A. Spectrophotometric observations and analysis of the asteroids and Raman spectroscopy of the atmosphere of Uranus are also briefly discussed.
    Keywords: ASTRONOMY
    Type: NASA-CR-148460 , QR-2
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  • 119
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    In:  CASI
    Publication Date: 2019-06-27
    Description: Recent results in ground based very high energy gamma ray astronomy are reviewed. The various modes of the atmospheric Cerenkov technique are described, and the importance of cosmic ray rejection methods is stressed. The positive detections of the Crab pulsar that suggest a very flat spectrum and time-variable pulse phase are discussed. Observations of other pulsars (particularly Vela) suggest these features may be general. Evidence that a 4.8 hr modulated effect was detected from Cyg X-3 is strengthened in that the exact period originally proposed agrees well with a recent determination of the X-ray period. The southern sky observations are reviewed, and the significance of the detection of an active galaxy (NGC 5128) is considered for source models and future observations.
    Keywords: ASTRONOMY
    Type: CFA/HEA-76-138 , NASA. Goddard Space Flight Center The Struct. and Content of the Galaxy and Galactic Gamma Rays; p 85-107
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  • 120
    Publication Date: 2019-06-27
    Description: Spectra from observations of GX301-2 (3U1223-62) by the Goddard X-ray spectroscopy experiment on OSO-8 show an absorption edge due to cool iron with column densities of a few x 10 to the 19th power/cm squared. A decrease in intensity was associated with increased absorption and a spectrum similar to those of binary X-ray sources in absorption dips. Observed variations of the pulse period are consistent with Doppler shifts for reasonable orbit parameters.
    Keywords: ASTRONOMY
    Type: NASA-TM-X-71137 , X-661-76-117
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  • 121
    Publication Date: 2019-06-27
    Description: The All-Sky X-ray Monitor onboard Ariel 5 has observed the 3-6 keV decline of the bright transient X-ray source A0620-00 on a virtually continuous basis during the period September 1975 - March 1976. The source behavior on timescales 100 minutes is characterized by smooth, exponential decays interrupted by substantial increases in October and February. The latter increase was an order-of-magnitude rise above the extrapolated exponential fall-off, and was followed by a final rapid decline. Upper limits of 2.5% and 10% were found for any periodicities in the range 0d.2 - 10d during the early and later decay phases, respectively. A probable correlation between the optical and 3-6 keV emission from A0620-00 was noted, effectively ruling out models involving traditional optical novae in favor of Roche-lobe overflow in a binary system. The existing data on the transient X-ray sources is consistent with two distinct luminosity-lifetime classes of these objects.
    Keywords: ASTRONOMY
    Type: NASA-TM-X-71139 , X-661-76-142
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  • 122
    Publication Date: 2019-06-27
    Description: An extensive catalog of observational data is presented for stars in the region of the young stellar association Orion OB 1. In addition to new photoelectric observations obtained on the uvbyB and UBV systems, photoelectric and spectroscopic data were compiled for the stars observed and for several bright members of the association having available photometric indices. Mean weighted values were computed for the uvbyB and UBV data and are tabulated in summary tables which include all references for individual values. These tables are expected to be reasonably complete for association members earlier than spectral type A0. From an analysis of currently available proper motion, radial velocity, and photometric data, membership criteria were derived and qualitative membership probabilities for 526 stars were summarized. A set of charts is included for assistance in identification of the program stars in all regions of the association.
    Keywords: ASTRONOMY
    Type: NASA-TM-X-71151
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  • 123
    Publication Date: 2019-06-27
    Description: Digital spectra of HZ Herculis were obtained with 10 A resolution in the 3,600 - 6,000 A region, synchronously dividing the 1.24-s optical pulsation period into eight 155-ms phase bins. The optical pulses are detected in the data, but their fractional amplitude is only 0.08 percent, a factor of 4 less than typically observed. The separate spectra of each one-eighth of the pulse are identical to within the statistics of the observation. If the X-ray to optical pulse reprocessing mechanism concentrates the optical pulsations into discrete spectral line features, data require the pulses to be distributed among more than four such lines.
    Keywords: ASTRONOMY
    Type: NASA-CR-147107
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  • 124
    Publication Date: 2019-06-27
    Description: The model involves a white dwarf accreting mass from a late-type subgiant companion. The transient behavior of the X-ray source is explained by the instability to mass loss of the companion (as in Algol-type binaries). The brightening, spectrum, and decay timescale of the optical counterpart are explained in terms of re-emission of X-radiation intercepted by the subgiant. It was concluded that A0620-00 can provide an excellent test case for numerical models of stellar atmospheres irradiated by an external X-ray flux.
    Keywords: ASTRONOMY
    Type: NASA-TM-X-71074 , X-671-76-42
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  • 125
    Publication Date: 2019-06-27
    Description: The X-ray spectrum of Cassiopeia A was observed for several days by the proportional counter experiment on board OSO-8. The high energy ( 5 keV) data are fit well by a thermal spectrum. A narrow iron line which is predicted by the thermal model is also observed. The low energy (2-5 keV) data show an excess over the high temperature component which is consistent with the presence of an additional low temperature thermal component. Iron abundance in the source relative to normal cosmic abundance is discussed, as in the relation of this observation to shock wave and multi-component thermal models for supernova remnants.
    Keywords: ASTRONOMY
    Type: NASA-TM-X-71064 , X-661-76-8
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  • 126
    Publication Date: 2019-06-27
    Description: Analysis of All-Sky Monitor observations of Cir X-1 (3U1516-56) over the period October 1975 - April 1976 revealed a well-defined modulation of the 3-6 keV flux at a period of 16.585 + or - 0.01. The light-curve is characterized by an abrupt drop in emission occurring on a timescale of 0.07, with epoch JD 2,442,877.181 + or - 0.07. No clear correspondingly sharp increase in emission is observed during the cycle, so that a noneclipse origin for this effect cannot be ruled out.
    Keywords: ASTRONOMY
    Type: NASA-TM-X-71114 , X-661-76-96
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  • 127
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    In:  CASI
    Publication Date: 2019-06-27
    Description: The UV spectra of the sun, as well as the differences and ratios of planetary and solar spectra, are presented. The results indicate that SO, SO2 and ClO2 may be present in Venus' atmosphere, and Formaldehyde CH2O and ClO2 on Jupiter. The solar UV measurements were analyzed to deduce ozone concentration in the earth's atmosphere.
    Keywords: ASTRONOMY
    Type: NASA-CR-147233
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  • 128
    Publication Date: 2019-06-27
    Description: Line profiles of 36 multiplets of silicon (Si) II, III, and IV were computed for a grid of model atmospheres covering the range from 15,000 to 35,000 K in effective temperature and 2.5 to 4.5 in log (gravity). The computations involved simultaneous solution of the steady-state statistical equilibrium equations for the populations and of the equation of radiative transfer in the lines. The variables were linearized, and successive corrections were computed until a minimal accuracy of 1/1000 in the line intensities was reached. The common assumption of local thermodynamic equilibrium (LTE) was dropped. The model atmospheres used also were computed by non-LTE methods. Some effects that were incorporated into the calculations were the depression of the continuum by free electrons, hydrogen and ionized helium line blocking, and auto-ionization and dielectronic recombination, which later were found to be insignificant. Use of radiation damping and detailed electron (quadratic Stark) damping constants had small but significant effects on the strong resonance lines of Si III and IV. For weak and intermediate-strength lines, large differences with respect to LTE computations, the results of which are also presented, were found in line shapes and strengths. For the strong lines the differences are generally small, except for the models at the hot, low-gravity extreme of our range. These computations should be useful in the interpretation of the spectra of stars in the spectral range B0-B5, luminosity classes III, IV, and V.
    Keywords: ASTRONOMY
    Type: NASA-TR-R-455 , G-7569
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  • 129
    Publication Date: 2019-06-27
    Keywords: ASTRONOMY
    Type: Astronomical Journal; 81; Dec. 197
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  • 130
    Publication Date: 2019-06-27
    Description: The 3700 square degrees around the South Equatorial Pole have been surveyed using a broad-band photometer with peak response at 90 A. One source was detected at about the same intensity as HZ 43. An extrapolation of the results implies that there are about 10 extreme-ultraviolet objects over the whole sky which are as bright as HZ 43. Implications of these results for theories of white dwarf evolution are briefly discussed.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 209; Oct. 1
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  • 131
    Publication Date: 2019-06-27
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 209; Oct. 1
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  • 132
    Publication Date: 2019-06-27
    Description: Accurate positions of compact radio sources have been determined from very-long-baseline interferometry (VLBI) observations based on the bandwidth-synthesis technique. The coordinates for 18 extragalactic sources were obtained from sets of observations spread over the period from April 1972 to January 1975; the scatter among the independent determinations of the source coordinates from the separate sets of observations is about 0.05 arcsec, except for the declinations of near-equatorial sources, where the scatter is about 0.15 arcsec. Comparison of these positions with those determined with the Cambridge 5-km radio interferometer shows the rms scatter about the mean difference to be about 0.04 arcsec in each coordinate (no sources of low declination were in common). A similar comparison of the present results with those obtained by the Jet Propulsion Laboratory from separate VLBI observations yields a slightly larger rms scatter, after exlusion of the declinations of the near-equatorial sources. A position is also obtained for the galactic object Beta Persei (Algol), which agrees well with the position given in the FK 4 catalogue.
    Keywords: ASTRONOMY
    Type: Astronomical Journal; 81; Aug. 197
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  • 133
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    Publication Date: 2019-06-27
    Description: The paper presents results of a search for optical counterparts of confirmed AFCRL infrared sources using the Palomar Sky Survey and direct photography with the Carnegie image tube camera. Positions and identification charts for possible counterparts to 26 AFCRL sources are presented. A list of AFCRL sources for which no optical counterparts were found is given, and some arguments to explain why the results of this search were negative are presented.
    Keywords: ASTRONOMY
    Type: Astronomical Journal; 81; July 197
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  • 134
    Publication Date: 2019-06-27
    Description: A far-infrared map of M20 shows a total flux of 26 kJy at an effective wavelength of 69 microns and a size of 8 arcmin FWHM. In the region near M20, two compact far-infrared sources were also detected; one source coincides with W28 C, and the other is not identified with any radio source.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 208; Sept. 1
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  • 135
    Publication Date: 2019-06-27
    Description: Broadband photometric observations of IRC + 10216 in five wavelength intervals from 50 to 1000 microns are reported. The observed radiation is interpreted as thermal emission from dust in the extended molecular cloud heated by the compact 2-20-micron source at the cloud core. The shape of the 50-1000-micron spectrum suggests that the emissivity of the dust particles varies approximately as the inverse wavelength over this spectral interval. The mass of dust inferred from the far-infrared emission is comparable with the mass of heavy molecules in the cloud.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 208; Sept. 1
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  • 136
    Publication Date: 2019-06-27
    Description: A cluster of compact infrared sources plus extended emission has been found at the peak of the molecular cloud in Mon R2. The extended emission is probably due to heated dust associated with PKS 0605-06, a compact H II region embedded in the molecular cloud. Several of the compact infrared sources have properties indicative of protostars. For one of these, the associated dust is apparently seen in projection against the H II region.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 208; Sept. 1
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  • 137
    Publication Date: 2019-06-27
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 208; Aug. 15
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  • 138
    Publication Date: 2019-06-27
    Description: A fundamental problem is the determination of the orientation of the earth in the celestial coordinate system. Classical reductions for precession and nutation can be expected to be consistent with the present-day observations, however, corrections to the classical theory are difficult to model because of the large number of coefficients involved. Consequently, a portion of the research has been devoted to numerically integrating the Eulerian equations of motion for a rigid earth and considering the six initial conditions of the integration as unknowns. Comparison of the three adjusted Eulerian angles from the numerical integration over 1000 days indicates agreement with classical theory to within 0.003 seconds of arc.
    Keywords: ASTRONOMY
    Type: Bulletin Geodesique; 50; 2, 19; 1976
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  • 139
    Publication Date: 2019-06-27
    Keywords: ASTRONOMY
    Type: Journal of Applied Meteorology; 15; July 197
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  • 140
    Publication Date: 2019-06-27
    Description: An X-ray burst from a 0.5 x 10 deg region centered near NGC 1851 (MX 0513-40) was detected in observations made with the Uhuru X-ray observatory on September 19, 1972. The source was observed for 15 seconds with a peak rate of 0.5 that of the Crab (2-6 keV) and was not detected above 0.01 of the Crab in observations 4.5 minutes before or after this event. During the observation, the spectrum developed a low-energy cutoff. NGC 1851 is the second globular cluster identified as a source of X-ray bursts, which suggests that all X-ray bursts may originate in globular clusters, some of which may be optically obscured.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 207; Aug. 1
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  • 141
    Publication Date: 2019-06-27
    Description: Spectral and photometric observations of ADS 2859 B, the faint companion to X Per, show it to be a normal M giant rather than a T Tauri star as previously reported in the literature. Consequently, there is no substantive reason to associate it with the X-ray source 3U 0352 + 30. A search for rapid light variations of X Per itself proved negative.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 207; Aug. 1
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  • 142
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    In:  Other Sources
    Publication Date: 2019-06-27
    Description: 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.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 207; Aug. 1
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  • 143
    Publication Date: 2019-06-27
    Description: Observations of pulsars, especially the Crab Nebula pulsar, made in very long baseline interferometry (VLBI) experiments are discussed. Based on a crude 144 MHz visibility curve which is consistent with a Gaussian brightness distribution, the measured visibilities at 196, 111, and 74 MHz were interpreted to yield apparent angular diameters (at half-power) of about 0.03 sec, 0.07 sec, and 0.18 sec, respectively. These sizes scale approximately as wavelength-squared, and the 74 MHz size agrees with recent observations using interplanetary scintillation techniques. The total flux densities lie on the extrapolation from higher frequencies of the pulsing flux densities. Variations in the total flux density up to 25 per cent were observed. A lack of fine structure other than the pulsar in the nebula is indicated by the simple visibility curves. The pulse shapes are similar to single-dish measurements at 196 MHz but reveal a steady, nonpulsing component at 111 MHz. The ratio of pulsing to total power was approximately equal to one-half but varied with time. It was found that four strong, low-dispersion pulsars were only slightly resolved.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 207; Aug. 1
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  • 144
    Publication Date: 2019-06-27
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 207; Aug. 1
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  • 145
    Publication Date: 2019-06-27
    Description: Accurate spectrophotometric observations of the nebulae Sh 156 and Sh 162 and of their exciting stars, combined with high-resolution radio maps by Israel (1976), enable the derivation of the total visual extinction towards 15 points in these nebulae. These values are compared with other values of the total visual extinction for the entire nebulae and their exciting stars.
    Keywords: ASTRONOMY
    Type: Royal Astronomical Society; vol. 176
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  • 146
    Publication Date: 2019-06-27
    Description: From a comparison of the 2:1 and 3:2 resonances (in the asteroidal belt) two possible explanations to the absence of 3:2 apocentric librators are suggested. The first one is that such 3:2 resonant motion is dynamically unstable. The second interpretation requires the absence of near-circular orbits originally at 4 AU. The latter view, if correct, is inconsistent with cosmogonic models which predict the original orbits of the asteroids to be nearly circular.
    Keywords: ASTRONOMY
    Type: Astrophysics and Space Science; 42; June 197
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  • 147
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    In:  Other Sources
    Publication Date: 2019-06-27
    Description: A variety of transient X-ray phenomena have been studied. Data from the OSO-7 satellite reveal both long and short time-scale transients. Extensive observations have been made of the Lupus X-ray Nova (3U1543-47) and GX339-4(MX 1658-48) which may represent a very different type of transient source. A unique, intense X-ray flare lasting ten minutes was also recorded, and the X-ray emission from the active galaxy Cen A was found to vary significantly over a period of several days. In a recent balloon flight the Crab pulsar, NP0532, was observed to exhibit a transient pulsed component distinct from the usual main pulse and interpulse. A sounding-rocket experiment detected an ultrasoft transient X-ray source tentatively associated with SS Cygni, and preliminary results from SAS-3 show a very hard spectrum for the new source A0535 + 26. On the other hand, extensive OSO-7 null observations of both Type I and II supernovae and of the flaring radio star Algol make it unlikely that these types of objects are potent transient X-ray emitters.
    Keywords: ASTRONOMY
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  • 148
    Publication Date: 2019-06-27
    Description: An extremely short-lived transient X-ray source has been detected with the SAS-3 satellite at a high galactic latitude (about -51 deg). The source, designated MX 2346-65, had a duration of between 45 s and 2200 s as well as a very hard spectrum. This source had not been detected in previous sky surveys and was not seen again by SAS-3 in 7 days of further periodic observations. Possible explanations of this type of event are discussed.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 206; June 15
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  • 149
    Publication Date: 2019-06-27
    Description: An extensive area of the Ophiuchus dark cloud has been mapped at far-infrared (40-50 microns) wavelengths with high angular resolution (1 arcmin) using a 102-cm balloon-borne telescope. Three sources were detected and resolved. Two of the sources were identified with strong 2-micron sources that were also associated with radio continuum emission. The far-infrared flux is consistent with radiation from dust heated by an early B star. Previous 2-micron observations have indicated the presence of a large number of early B stars embedded in the dark cloud; the far-infrared observations indicate, however, that although some early B stars are in the dark cloud, most of the 2-micron sources are either behind the cloud or are stars not on the main sequence.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 206; June 15
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  • 150
    Publication Date: 2019-06-27
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 206; June 15
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  • 151
    Publication Date: 2019-06-27
    Keywords: ASTRONOMY
    Type: Astronomy and Astrophysics; 48; 3, Ma; May 1976
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  • 152
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    In:  Other Sources
    Publication Date: 2019-06-27
    Description: The occultation of 3rd magnitude Epsilon Geminorum by Mars was observed using a 36-inch telescope equipped with a photoelectric photometer at the bent Cassegrain focus, carried aboard the Kuiper Airborne Observatory at altitudes up to 45,000 feet. Scintillation from the earth's atmosphere was greatly reduced in comparison with ground observations. The observations clearly show the central flash, caused by the symmetrical refraction of light by the atmosphere of Mars. The data are being analyzed to obtain temperature profiles and to assess the relative abundance of argon and carbon dioxide in the atmosphere of the planet.
    Keywords: ASTRONOMY
    Type: Sky and Telescope; 52; July 197
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  • 153
    Publication Date: 2019-06-27
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 206; June 1
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  • 154
    Publication Date: 2019-06-27
    Description: Uhuru observations of the galactic plane in 1970, 1971, and 1972 are analyzed. The great majority of the galactic X-ray sources are not 'transient'. Some of the so-called transient sources persist for long periods of time at an intensity of a few percent of their peak values. The data suggest that the transient sources may be quite similar to the other galactic sources with outbursts caused by changes in the accretion rate.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 206; May 15
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  • 155
    Publication Date: 2019-06-27
    Description: Results are reported for four X-ray scans of the region containing Cen A. It is found that the X-ray source had a hard number spectrum (spectral index of -1.2) during these observations and that the intensity in the range from 10 to 100 keV apparently increased by 230% with no detectable change in spectral shape between two observations 210 days apart. Either a Compton-synchrotron mechanism or thermal bremsstrahlung at any temperature greater than 200 keV is suggested as the source of the X-rays. It is noted that the present observations, together with a similar detection of another galaxy, may establish a distinct class of extragalactic X-ray objects with flat and highly absorbed spectra.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 206; May 15
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  • 156
    Publication Date: 2019-06-27
    Description: Six hundred days of observations by the X-ray detectors aboard OSO-7 have been analyzed. All-sky maps of X-ray intensity have been constructed from these data. A sample map is displayed. Seven sources with galactic latitude greater than 10 deg, discovered during the mapping process, are reported, and upper limits are set on other high-latitude sources. The OSO-7 results are compared with those of Uhuru, and an implication of this comparison, that many of the high-latitude sources may be variable, is discussed.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 206; May 15
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  • 157
    Publication Date: 2019-06-27
    Description: Results are reported for coarse-resolution far-IR spectral observations of the H II regions M17 and M41 in the wavelength range from 42 to 115 microns. The observations were made at an altitude of 13.7 km with the 30-cm telescope of the NASA Lear jet. The spectrum of M42 is shown to be quite smooth and to fit a diluted 100-K blackbody very well. It is found that the emission from M17 falls steeply from 40 to 63 microns, then rises again to 80 microns before falling off once more toward longer wavelengths. The best fit of this spectrum for an inverse-square-wavelength emissivity law is found to require a two-temperature model with temperatures below 30 K for the cold dust component. It is concluded that the spectrum of M17 seems to require the presence of a material with a better far-IR emissivity than those for which detailed laboratory measurements have been made.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 205; Apr. 15
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  • 158
    Publication Date: 2019-06-27
    Description: Two stars behind the Vela supernova remnant and two stars offset from the remnant have been observed with the UV spectrometer aboard the Copernicus satellite. Over 200 interstellar atomic and molecular absorption features between 1000 and 1400 A have been identified and measured for radial velocity and equivalent width. In many cases, additional information was obtained by studying the detailed shapes of the recorded profiles. Most of the stars show several absorption components, with clouds of the highest radial velocity appearing in the spectra of stars behind the remnant. For each component, column densities were derived using velocity dispersion parameters which yielded the most self-consistent results. Qualitatively, the gas toward the remnant exhibits a number of unusual properties, when compared with normal interstellar material. First, abnormally high radial velocities were evident. Second, the degree of ionization of some elements suggested the existence of ionizing processes significantly more potent than those found in general regions of space. Finally, an investigation of electron densities shows that much of the gas, especially that at high velocity, must exist in the form of relatively thin sheets or filaments. If cosmic abundances prevail, the column densities of high-velocity excited material suggest that H-alpha emission measures could be as large as 100 sq cm/cu pc.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal Supplement Series; 32; Dec. 197
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  • 159
    Publication Date: 2019-06-27
    Description: Data are presented for the X-ray source 4U 1608-52, summarizing its light curve, location, and spectral parameters. Evidence is presented showing that this source is the 'steady' X-ray counterpart of the X-ray burst source in Norma. The spectrum of the 'steady' source is compared with the spectrum observed during two bursts, and it is noted that there is substantially more low-energy absorption during the bursts. The 'steady' source spectral data are used to examine the optical data, and it is concluded that if the X-ray spectrum is thermal, then a globular-cluster counterpart probably would have been detected (whereas none has been). Further X-ray and optical observations are suggested for this source, since an optical identification may be central in determining whether all X-ray bursts have a common origin and if this origin requires a globular-cluster environment.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 209; Nov. 1
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  • 160
    Publication Date: 2019-06-27
    Description: A simplified analytical technique is presented for modeling the interplanetary scintillation of radio sources of finite angular size with a power-law electron-density-fluctuation power spectrum. The simplification results from the representation of the scintillation spectrum in confluent hypergeometric functions. The approximations presented allow fast numerical evaluation of a spectrum for a weakly scattering but extended medium with less than 10% error over the entire spectrum. Parameters describing anisotropic electron irregularities as well as anisotropic source structure are included, and the dependence of the spectrum normalization on the scales of the medium is derived explicitly. The parametric description of the domains of convergence of the approximate expansions also provides a simple conceptualization of the relative contributions of the scattered radiation along the line of sight to the observed spectrum. This is particularly useful for sources of finite angular size. This technique is applied to previously published observations.
    Keywords: ASTRONOMY
    Type: Journal of Geophysical Research; 81; Oct. 1
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  • 161
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    In:  CASI
    Publication Date: 2019-06-27
    Description: The implications of the 10 micron polarization of the Orion Nebula were re-examined. The polarization was produced by preferential extinction in one of the well studied regions of the Kleinman-Low Nebula and/or its surroundings. In particular, the need for abnormally low temperatures in the polarizing medium was obviated. The most likely candidate for the polarizing medium was the extended region surrounding the Kleinman-Low Nebula. The degree of polarization produced by emission in the far infrared was estimated to be as large as 8 percent, although other factors could reduce the observable value.
    Keywords: ASTRONOMY
    Type: NASA-CR-149366
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  • 162
    Publication Date: 2019-06-27
    Description: A cosmic X-ray spectroscopy experiment onboard the Orbiting Solar Observatory 8 (OSO-8), observed Her x-1 continuously for approximately 8 days. Spectral-temporal correlations of the X-ray emission were obtained. The major results concern observations of: (1) iron band emission, (2) spectral hardening (increase in effective x-ray temperature) within the X-ray pulse, and (3) a transition from an X-ray low state to a high state. The spectrum obtained prior to the high state can be interpreted as reflected emission from a hot coronal gas surrounding an accretion disk, which itself shields the primary X-ray source from the line of sight during the low state. The spectral hardening within the X-ray pulse was indicative of the beaming mechanism at the neutron star surface. The hardest spectrum by pulse phase was identified with the line of sight close to the Her x-1 magnetic dipole axis, and the X-ray pencil beam become harder with decreasing angle between the line of sight and the dipole axis.
    Keywords: ASTRONOMY
    Type: NASA-TM-X-71247 , X-661-76-280
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  • 163
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    In:  CASI
    Publication Date: 2019-06-27
    Description: Seven epochs of very long baseline radio interferometric observations of the Seyfert galaxies 3C 120 and 3C 84, at 3.8-cm wave length using stations at Westford, Massachusetts, Goldstone, California, Green Bank, West Virginia, and Onsala, Sweden, have been analyzed for source structure. An algorithm for reconstructing the brightness distribution of a spatially confined source from fringe amplitude and so called closure phase data has been developed and successfully applied to artificially generated test data and to data on the above mentioned sources. Over the two year time period of observation, 3C 120 was observed to consist of a double source showing apparent super relativistic expansion and separation velocities. The total flux changes comprising one outburst can be attributed to one of these components. 3C 84 showed much slower changes, evidently involving flux density changes in individual stationary components rather than relative motion.
    Keywords: ASTRONOMY
    Type: NASA-TM-X-71239 , X-693-76-268
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  • 164
    Publication Date: 2019-06-27
    Description: A far-ultraviolet spectral survey of Capella (Alpha Aur, G5 III + G0 III) has been obtained using a highly sensitive rocketborne spectrograph with a microchannel plate detector. The spectral distribution is very similar to that of the sun; however, if the line surface fluxes are due to the primary (G5 III), then, except for Ly-alpha, they are about an order of magnitude greater than those of the quiet sun
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 205; Apr. 1
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  • 165
    Publication Date: 2019-06-27
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 204; Mar. 15
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  • 166
    Publication Date: 2019-06-27
    Description: Physical and electrical parameters for the 34.3-MHz Cocoa Cross radio telescope are given. The telescope is dedicated to the determination of solar-wind characteristics in and out of the ecliptic plane through measurement of electron-density irregularity structure as determined from IPS (interplanetary scintillation) of natural radio sources. The collecting area (72,000 sq m), angular resolution (0.4 deg EW by 0.6 deg NS), and spatial extent (1.3 km EW by 0.8 km NS) make the telescope well suited for measurements of IPS index and frequency scale for hundreds of weak radio sources without serious confusion effects.
    Keywords: ASTRONOMY
    Type: Journal of Geophysical Research; 81; Feb. 1
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  • 167
    Publication Date: 2019-06-27
    Description: 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.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 203; Jan. 15
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  • 168
    Publication Date: 2019-06-27
    Description: Results are reported for observations of EUV emission from an extrasolar object which were made with a grazing-incidence telescope during the Apollo-Soyuz mission. The total energy flux in the spectral band between 170 and 620 A is estimated to be approximately 4 by 10 to the -9th power erg/sq cm per sec. It is shown that the data support the identification of the EUV object with the ultrasoft X-ray source in Coma Berenices. The source of both emissions is suggested to be the hot white dwarf HZ 43, located at right ascension 13 hr 43 min and declination +29 deg 22 min (1950). The temperature of HZ 43 is estimated as 110,000 K, giving it the highest temperature of any known white dwarf.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 203; Jan. 15
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  • 169
    Publication Date: 2019-06-27
    Description: The detection of far-IR emission from the galaxy NGC 1068 in four passbands spanning the spectral range from 28 to 320 microns is reported. The observations were made with a 61-cm airborne IR telescope and a liquid-helium-cooled multifilter radiometer. It is found that the flux density between 38 and 100 microns increases with increasing wavelength to a maximum value of 454 (plus or minus 94) Jy, but decreases rapidly for wavelengths greater than 100 microns. The total flux is estimated to be about 3 by 10 to the -11th power W/sq m, which corresponds to a bolometric luminosity of 3.7 by 10 to 11th power times the solar luminosity at a distance of 20 Mpc. The nuclear M/L ratio is shown to be no greater than about 0.003, indicating that the scale, optical depth, or both, of a thermal far-IR source in NGC 1068 would have to be larger than those of the extended IR sources around the nuclei of our Galaxy, NGC 253, or M82.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 203; Jan. 15
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  • 170
    Publication Date: 2019-06-27
    Description: The UV Ceti-type stars, YZ Canis Minoris, AD Leonis, and Wolf 424 AB, were monitored for 57.8 hours from January 15 to February 22, 1974, using the 1000-foot (305-m) radio telescope at Arecibo, Puerto Rico, and the 91-cm or 76-cm reflector at McDonald Observatory. Radio observations were made at frequencies of 430, 318, and 196 MHz, and optical monitoring was done in the Johnson U or B band, the Stromgren u band, or white light. During the period of simultaneous observations, 62 optical flares were detected. A total of 13 RF flares were independently identified, of which 10 reached maximum flux within 10 min of the peak time of an optical flare. Using times of optical-flare events as reference data, an additional 15 cases of radio enhancements associated with optical flares are identified. The most probable delay interval between the optical-flare maximum and 318-MHz radio peak was found to be 0 to 5 min, with the optical flare occurring first. Aside from this statistical delay of peak occurrence and a general tendency for radio and optical flares to be associated, no systematic correlations of optical and radio amplitudes or morphology were found. The possible consequences of the radio emission's being due to a coherent process are discussed.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 203; Jan. 15
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  • 171
    Publication Date: 2019-06-27
    Description: Results of a photographic and spectrophotometric search to a limiting B magnitude of approximately 18.5 for the optical counterparts of nine galactic X-ray sources with good positions are reported. The sources included in this survey are 3U 1709-23, 1728-16, 1728-24, 1758-20, 1758-25, 1811-17, 1813-14, 1837+04, 1908+00. Optical candidates for six of these sources are discussed, including blue objects which may be the optical counterparts of 1709-23 and 1728-16, a distant B star near 1908+00, and a very unusual strong-emission-line object which is probably associated with 1728-24 (GX 2+5). Coordinates, magnitudes, colors, spectral data, and finding charts are presented.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 203; Jan. 15
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  • 172
    Publication Date: 2019-06-27
    Description: An intense soft X-ray source with an extraordinary spectrum has been observed in Coma Berenices, 4 deg northeast of and not associated with the Coma cluster of galaxies. Two spectra, obtained at different times in a sounding-rocket flight, indicate that the source temperature in thermal models is less than 1 million K; a power-law model requires photon power-law indices steeper than n = -3. The intensity in the 44-165 A band is of the order of 5 by 10 to the -10th power erg/sq cm/sec, but no flux is present at energies 0.3-2.1 keV to a limit of 1 by 10 to the -10th power erg/sq cm/sec. The lack of bright stars or a supernova remnant in the error box implies that this may be a new class of soft X-ray sources.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 203; Jan. 1
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  • 173
    Publication Date: 2019-06-27
    Description: The optical object corresponding to the transient X-ray source A0620-00 is identified. The position (1950) of this object is given to a precision of 2 sec as: right ascension 6 hr 20 min 11.2 sec, declination -0 deg 19 min 10 sec. It is noted that the object has undergone a substantial change in brightness since the X-ray source was first detected and that three low-dispersion spectra of it show no emission or absorption features. Similarities between the present object and Sco X-1 are discussed.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 203; Jan. 1
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  • 174
    Publication Date: 2019-06-27
    Description: A compact X-ray source near the North Galactic Pole has been detected with the low-energy X-ray telescope aboard the SAS-3 satellite. The spectral temperature of the source is less than 1 million K, and the energy flux at the earth is 3 by 10 to the -10th power erg/sq cm/sec above 0.1 keV. The flux appeared to be constant both on short time scales (10-1000 s), and over the interval from the first SAS-3 observation (June 12, 1975) to the latest (July 15, 1975). The possible identification of this source with the hot white dwarf HZ 43 is discussed.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 203; Jan. 1
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  • 175
    Publication Date: 2019-06-27
    Description: Results are reported for digicon spectrophotometric observations of the radio source 0938+119, which was originally classified as a faint red galaxy. A prism spectrum of the source is presented along with the corresponding sky measurement, and several features of the spectrum are described. It is shown that this source is a QSO with a magnitude of 20.1, a redshift z = 3.19, and a spectrum similar to that of OH 471 or 4C 05.34. The question of whether other faint high-redshift QSOs have been misclassified as galaxies is considered.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 203; Jan. 1
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  • 176
    Publication Date: 2019-06-27
    Description: The X-ray nova A0620-00 (Nova Monocerotis 1975) has been observed with the SAS-3 satellite. The 1-10 keV intensity was observed to increase by a factor of 2.3 from August 8 to August 11, 1975. It reached and maintained a constant intensity of 1.7 by 10 to the -6 power erg/sq cm/sec from August 11 to August 13. Limits on periodicities of not more than 2 per cent of the power were obtained for periods from 0.2 ms to 435 s. A precise position was obtained with the SAS-3 modulation collimators on August 15. This led directly to optical and radio identifications. Observations with the SAS-3 low-energy concentrator system on August 27 showed an intense 0.4-0.8 keV flux emanating from the nova. A hydrogen column density of 3.5 (plus or minus 0.3) by 10 to the 21st power per sq cm was inferred from these data.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 203; Jan. 1
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  • 177
    Publication Date: 2019-06-27
    Description: The intensity and spectrum of the transient X-ray source 3U 1543-47 were measured by X-ray detectors on the OSO-7 satellite on 13 occasions between November 1971 and December 1972. The results, together with observations of the same object by the Vela and Uhuru satellites, can be described in terms of four qualitatively distinct phases in the X-ray light curve: (1) outburst; (2) relatively steady intensity and spectrum; (3) rapid decrease in intensity and decrease in apparent temperature; and (4) irregular intensity fluctuations with complex spectra. The term 'X-ray nova' is proposed to characterize this and similar transient sources, and a new model for such X-ray novae is proposed.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 203; Jan. 1
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  • 178
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    In:  Other Sources
    Publication Date: 2019-06-27
    Description: Scans have been made of H-alpha, 6584-A forbidden N II, 5007-A forbidden O III, and 5876-A He I emissions in selected directions in the Gum Nebula. Analyses of the line profiles and line intensities indicate that much of the emitting gas in the Gum Nebula is confined to an expanding shell which has a radius of about 125 pc, an expansion velocity of approximately 20 km/s, an emission measure which ranges from about 15 units to about 500 units, and a temperature near 11,000 K. The ultraviolet flux from zeta Pup and gamma-2 Vel appears to be capable of producing most of the observed ionization, although the origin of the shell structure and high expansion velocity is not certain.-
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 203; Jan. 1
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  • 179
    Publication Date: 2019-06-27
    Description: Isophotes have been determined from 10 narrow-band filter photographs of Comet Tago-Sato-Kosaka 1969g (1969IX) taken between Feb. 11 and 14, 1970. The five interference filters used were centered on the CN band sequence at 3383A, the C2 band sequence at 4737A and 5165A, the C3 sequence at 4050A, and the continuum at 5300A. Gradients of intensity in various directions from the nucleus have been derived from the isophotes.
    Keywords: ASTRONOMY
    Type: Astronomy and Astrophysics Supplement Series; 23; Jan. 197
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  • 180
    Publication Date: 2019-06-27
    Description: Reflection and transmission of electromagnetic waves at an interface between two homogeneous materials is modified when a transition zone of linearly increasing permittivity is inserted between the half spaces. Mathematical expressions for reflection and transmission coefficients are derived for waves at arbitrary incidence angles and polarized either in or perpendicular to the plane of incidence. Discontinuities in permittivity at the transition-zone boundaries are allowed. There is efficient transmission between the two half-spaces for transition-zone thicknesses of a wavelength or greater. For sharper changes, the matching layer has diminishing effect and the wave-interface interaction is characterized by the difference in properties between the two half-spaces. Examples applicable to lunar radar astronomy and airborne terrestrial remote sensing are used to illustrate the relationship between wavelength and thickness of the transition layer.
    Keywords: ASTRONOMY
    Type: IEEE Transactions on Antennas and Propagation; AP-24; Jan. 197
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  • 181
    Publication Date: 2019-06-27
    Description: Results of ultraviolet spectrophotometric observations with the satellite Copernicus (OAO-3) are summarized, and are intended to be completely covered through January 1, 1976. Interstellar research recently reviewed elsewhere is not included, although some newer interstellar results are described. A large fraction of the research covered in this review has been carried out by Guest Investigators with Copernicus. A brief description of the spacecraft and its operation is included.
    Keywords: ASTRONOMY
    Type: Earth and Extraterrestrial Sciences; 3; 1-2,; 1976
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  • 182
    Publication Date: 2019-07-13
    Description: A 15-cm aperture f/3 Ritchey-Chretien telescope equipped with a 4 deg calcium fluoride prism was employed in taking objective prism spectra from 1300 to 5000 A in 188 stars, in the three Skylab missions. Spectra of 2 A resolution at 1400 A and 10 A at 2000 A, extending to B0 stars such that V equals 6.5, were taken of 400 stars in the neighborhood of 1500 A. Stellar temperature and luminosity variations are revealed in resonance lines of C IV and Si IV. Profiles of P Cygni type show up in the spectra of all stars with absolute bolometric magnitudes brighter than minus 8.4, implying appreciable outflow of mass. Spectra with emission lines shortward of 2000 A were obtained for 12 WR stars, and spectra of some companion stars dominating the UV spectra are reported.
    Keywords: ASTRONOMY
    Type: Open Meetings of Working Groups on Physical Sciences; May 29, 1975 - Jun 07, 1975; Varna; Bulgaria|Symposium and Workshop on Results from Coordinated Upper Atmosphere Measurement Programs; May 29, 1975 - May 31, 1975
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  • 183
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    Publication Date: 2019-07-13
    Description: In the last decade twelve major space experiments have observed Be stars in the UV region of the spectrum. The characteristics of the experiments are listed in a table. The studies were conducted with the aid of two rockets, five astronomical satellites, three manned satellites, and one planetary probe. Another table shows the name and the spectral type of the bright Be stars observed in the UV. Approaches concerning a system for ultraviolet spectral classification are discussed. Attention is also given to aspects of mass loss, the effects of rapid rotation, and the properties of the shell.
    Keywords: ASTRONOMY
    Type: Merrill-McLaughlin Memorial Symposium; Sep 15, 1975 - Sep 18, 1975; Bass River, MA
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  • 184
    Publication Date: 2019-07-13
    Description: The Ap variable star iota Cas was observed with the photometers on OAO-2 covering the spectral range 1430-4250 A. The ultraviolet light curves show a double wave with primary minimum and maximum at phase ? 0.00 and 0.35, respectively. Secondary minimum light is at phase ? 0.65 with secondary maximum at phase ? 0.85. The light curves longward of 3150 A vary in opposition to those shortward of this 'null region'. Ground-based coude spectra show that the Fe II and Cr II line strengths have a double-wave variation such that maximum strength occurs at minimum ultraviolet light. We suggest that the strong ultraviolet opacities due to photoionization and line blanketing by these metals may cause the observed photometric variations. We have also constructed an oblique-rotator model which shows iron and chromium lying in a great circle band rather than in circular spots.
    Keywords: ASTRONOMY
    Type: Colloquium on Physics of Ap-stars; Sep 08, 1975 - Sep 11, 1975; Vienna; Austria
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  • 185
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    Publication Date: 2019-07-13
    Description: Non-LTE strengths of Si II lines were computed in an effort to reproduce the observed strengths of Si II lines in the shell spectrum of Zeta Tau. This effort was unsuccessful, probably because it assumed that the shell could be represented by a finite, plane-parallel slab. The main conclusion of this study, then, is that in order to understand the shell spectra of Be stars, a more realistic geometry must be assumed, in which the shell is represented by a thick disk.
    Keywords: ASTRONOMY
    Type: Merrill-McLaughlin Memorial Symposium; Sep 15, 1975 - Sep 18, 1975; Bass River, MA
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  • 186
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    Publication Date: 2019-07-13
    Description: The feasibility of the design concept for a 1-m-aperture, cryogenically cooled telescope for Spacelab is assessed. The device makes use of double-folded Gregorian reflective optics. The planned cryogen is helium, and beryllium will be used for the 1.2 m primary mirror. Results of studies based on smaller instruments indicate that no new technology will be required to construct a Shuttle Infrared Telescope Facility which will offer improvement over the sensitivity of conventional telescopes by a factor of 1000 at 10 micrometers.
    Keywords: ASTRONOMY
    Type: International Meeting on Utilization of Space Shuttle and Spacelab; Jun 02, 1976 - Jun 04, 1976; Bonn
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  • 187
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    Publication Date: 2019-07-13
    Description: The advantages of an orbiting astronomical observatory are discussed. The principal consequence of having the telescope in space is that more light will be concentrated in the images, which has two effects: (1) the ability to view more accurately complex sources, and (2) the ability to detect and measure extremely faint point sources. The fact that higher resolution will reveal complex and unexpected detail is demonstrated by comparing a well-known astronomical scene with an image artifically degraded. Five scientific functions are envisaged for the Space Telescope. The first flight will feature performance of four of these functions with these four pieces of equipment: the f24 field camera, the faint object spectrograph, the infrared photometer, and the faint object camera. Astrometry will be done not by any specialized scientific instrument but with the fine guidance and pointing system.
    Keywords: ASTRONOMY
    Type: International Meeting on Utilization of Space Shuttle and Spacelab; Jun 02, 1976 - Jun 04, 1976; Bonn
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  • 188
    Publication Date: 2019-07-13
    Description: A program is discussed which involved monitoring the photometric activity of 18 bright variable IR stars at 2.7 microns with satellite- and rocket-borne instrumentation in the period from 1971 to 1975. The stellar sample includes 3 Lb variables, 8 semiregular variables, 5 Mira-type variables, and 2 previously unknown and unclassified IR variables. Detailed light curves of many of these stars were determined for intervals of 3 yr or more; spectra from 2.7 to 20 microns were constructed for nine of them using data obtained entirely with instruments above the atmosphere. Photometric IR light curves and other data are presented for SW Virginis, R Aquilae, S Scuti, IRC 00265, RT Hydrae, S Orionis, S Canis Minoris, Omicron Ceti, and R Leonis. Several hypotheses concerning the interpretation of the IR data are examined.
    Keywords: ASTRONOMY
    Type: COSPAR, Plenary Meeting; Jun 08, 1976 - Jun 19, 1976; Philadelphia, PA
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  • 189
    Publication Date: 2019-07-13
    Description: Technology was developed for production of doped-germanium detectors which have optimized performance in the 30- to 120-micrometer wavelength range and are capable of achieving the objectives of the Infrared Astronomy Satellite space mission. The work of this phase was divided into the following major tasks: (1) growth of Ge:Ga crystals from high-purity starting material with Ga concentrations different from that previously produced, and development of a zone leveling method to produce a uniform Ga doping concentration; (2) growth of uncompensated Ge:Be crystals from high-purity starting material with a range of Be concentrations between 10 to the 14th power and 10 to the 16th power atoms/cubic cm; (3) evaluation of crystals by means of Hall effect and resistance measurements as a function of temperature; (4) fabrication and test of detectors made from both Ge:Be and Ge:Ga crystals to determine the relative performance between different crystals. Correlation of detector test data with material evaluation data and analysis of how to further optimize detector performance.
    Keywords: ASTRONOMY
    Type: NASA-CR-152046
    Format: application/pdf
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  • 190
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    Publication Date: 2019-07-13
    Description: The Infrared Astronomical Satellite (IRAS) will be used to survey the 8 to 120 micron spectrum of the entire sky to the faintest flux levels possible by using state-of-the-art detectors and preamplifiers. As a result of a recently completed study of the telescope and focal plane, a concept has been devised that demonstrates the feasibility of using stored cryogen to cool the telescope for one year of operation in a polar twilight orbit at an altitude of 900 km. Predictions regarding noise equivalent flux density, cryogenic lifetime, and the number of noise spikes caused by Van Allen belt radiation are presented. The telescope is cooled both by supercritical and by superfluid helium. The on-board signal processing includes provisions for suppressing noise spikes.
    Keywords: ASTRONOMY
    Type: Seminar on Modern utilization of infrared technology II: Civilian and military; Aug 26, 1976 - Aug 27, 1976; San Diego, CA
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  • 191
    Publication Date: 2019-07-13
    Description: A selection of infrared variable stars was studied at wavelength 2.7 microns during 1971-1975 with data from U.S. Air Force satellites. Stars observed in this program are classified as long-period variable stars, semiregular variables, and irregular variables and are among the strongest stellar sources at this wavelength. In addition, a few new, as yet unclassified variable stars were identified during the course of the investigation. Time scales of reproducible variations range from a few weeks to a few years, and amplitudes of variation are as large as a factor of three for stars with periods of order one year. The minimum infrared flux density of a long-period star repeats accurately from one cycle to the next, whereas the maximum flux density was found to be unstable. The correlation of 2.7 micron and radio emission line data from one, well-studied long-period variable is consistent with the hypothesis that the H2O and OH circumstellar masers are saturated, if pumped by the stellar infrared flux near 2.7 microns.
    Keywords: ASTRONOMY
    Type: Seminar on Modern utilization of infrared technology II: Civilian and military; Aug 26, 1976 - Aug 27, 1976; San Diego, CA
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  • 192
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    Publication Date: 2019-07-13
    Description: The Shuttle Infrared Telescope Facility (SIRTF) will combine high sensitivity with the flexibility offered by the Space Transportation System. A recently completed study has generated a preliminary design which demonstrates the feasibility of SIRTF. The 1.0 to 1.5 meter aperture, f/8 Gregorian telescope will be cooled to 20 K by a stored supercritical helium system. The telescope will be pointed and stabilized at two levels: the European-developed Instrument Pointing System provides primary pointing and stabilization; and an internal star tracker senses residual errors and drives a folding mirror inside the telescope to null the errors. The folding mirror can also be driven by square or triangular waves to provide space chopping or small-area scanning.
    Keywords: ASTRONOMY
    Type: Seminar on Modern utilization of infrared technology II: Civilian and military; Aug 26, 1976 - Aug 27, 1976; San Diego, CA
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  • 193
    Publication Date: 2019-07-13
    Description: The 30 by 5 cm aperture telescope described uses six moveable mirrors to compensate for phase distortions induced by the atmosphere. A feedback system is used to adjust the mirrors in real time to maximize the intensity of light passing through a narrow slit in the image plane. Using the telescope, diffraction-limited images of objects were obtained, using both laser and white light, through 250 meters of turbulent atmosphere.
    Keywords: ASTRONOMY
    Type: Seminar on Imaging through the atmosphere; Mar 22, 1976 - Mar 23, 1976; Reston, VA
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  • 194
    Publication Date: 2019-06-27
    Description: Properties of a balloon-borne inertially guided telescope designed to perform high-resolution mapping of far-IR sources are reviewed. Scientific results obtained to date are presented in terms of the sensitivity and angular resolution achieved. The objects observed and mapped include Orion A, W3, M43, OMC-2, NGC 7538, the infrared star IRC+10216, Uranus, and M82. Several modifications of the telescope are described which have markedly increased its IR sensitivity and its efficiency in acquiring sources.
    Keywords: ASTRONOMY
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  • 195
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    Publication Date: 2019-06-27
    Description: The design and construction of a high-resolution far-infrared Fourier-transform spectrometer for use on the Smithsonian balloon-borne one-meter telescope is described. The instrument will operate at a resolution of about 0.1 kayser in the region from 25 to 150 microns. It will be used to obtain spectra of Jupiter, Venus, Orion, and other H II and molecular cloud regions, as well as the terrestrial stratosphere.
    Keywords: ASTRONOMY
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  • 196
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    Publication Date: 2019-06-27
    Description: This monograph reviews the major theoretical and experimental efforts made during the past 12 years in gamma-ray astronomy over the energy range from 10 keV to about 100 MeV, where nuclear-transition lines are expected. Early attempts to detect celestial gamma rays are recounted, mechanisms of gamma-ray line and continuum production are examined, and formulas giving the various possible differential gamma-ray spectral shapes are provided. Predicted fluxes are discussed for solar gamma rays as well as for gamma emission from supernova remnants, supernovae, neutron stars, flare stars, the galactic core and disk, black holes, and diffuse sources. Gamma-ray interactions with matter are analyzed, particularly the photoelectric effect, Compton scattering from free electrons, and pair production in nuclear fields. Significant results are summarized for observations of gamma rays from the sun as well as from point and extended sources within and beyond the Galaxy, including diffuse fluxes and transient gamma-ray bursts. Factors pertaining to the design of gamma-ray astronomy experiments are considered, especially detector background limitations, gamma-ray production within instruments, and present-day detection methods.
    Keywords: ASTRONOMY
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  • 197
    Publication Date: 2019-06-27
    Description: Diffuse-band data have been collected from the literature and reduced statistically to a common measurement system, enabling correlation analyses to be made with a larger quantity of data than previously possible. A full listing of the catalogued data is presented, along with some discussion of the correlations. One important application of such studies is the identification of cases of peculiar diffuse-band behavior, and a table is given showing all cases of band strengths deviating by more than twice the mean dispersion from the best-fit correlations. This table may be useful in planning further observations.
    Keywords: ASTRONOMY
    Type: Astronomical Journal; 82; Feb. 197
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  • 198
    Publication Date: 2019-06-27
    Description: This paper describes the S056 X-ray instrument which was carried aboard the Skylab Apollo Telescope Mount as part of the solar instrument cluster. The instrument, which was built at the NASA Marshall Space Flight Center, consisted of a glancing incidence X-ray telescope to record solar images in the 6-40-A region, together with an X-ray event analyzer to monitor the total solar soft X-ray flux in several wavelength bands. The X-ray telescope used film as a recording medium and thin foil filters to isolate specific wavelength bands. The instrument subsystems are described in detail and typical results presented.
    Keywords: ASTRONOMY
    Type: Applied Optics; 16; Apr. 197
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  • 199
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    Publication Date: 2019-06-27
    Description: The paper describes a computer-operated image-scanning and data-collection system for the magnetograph at the Mt. Wilson 150-foot Tower telescope. The system is based on a minicomputer with a 32K word core memory and a generalized interface unit for controlling image motion, a keyboard, and an associated television screen. Operation of the solar image guider and the data-collection assembly is outlined along with the observation and data-reduction procedures. Advantages of the system include the ability to move the image in almost any conceivable fashion, a wide choice of integration times, and increased accuracy in magnetic and Doppler calibrations as well as in setting of the magnetic zero level.
    Keywords: ASTRONOMY
    Type: Solar Physics; 48; June 197
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  • 200
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    Publication Date: 2019-06-27
    Description: Several arguments based on the orbital dynamics of the asteroids are used to support the idea that the original solar nebula might not necessarily be the Laplacian type of thin disk-like structure. The orbital distribution of the large asteroids is suggested to be a direct result of their accretions of condensed grains in eccentric orbits via the jet stream process.
    Keywords: ASTRONOMY
    Type: Astrophysics and Space Science; 45; Nov. 197
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