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  • ASTRONOMY  (459)
  • 1980-1984
  • 1975-1979  (459)
  • 1950-1954
  • 1977  (213)
  • 1976  (246)
  • 1
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    Toward diffraction-limited seeing of dim astronomical objects from the Earth's surface using LIDAR (1977)
    In:  CASI
    Details
    Publication Date: 2005-02-28
    Keywords: ASTRONOMY
    Type: Res. in the Space Sci., Vol. 2, No. 1; 12 p
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  • 2
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    Infrared astronomy and high energy astrophysics (1977)
    In:  CASI
    Details
    Publication Date: 2006-08-09
    Description: Observations of the diffuse far-infrared flux from the galactic plane, as well as far-infrared measurements of the properties of dense molecular clouds, when combined with recent high-energy gamma-ray measurements and radio observations of carbon monoxide, yield information about the total mass of molecular clouds, the large-scale structure of the inner galaxy, and the density of cosmic rays.
    Keywords: ASTRONOMY
    Type: The Struct. and Content of the Galaxy and Galactic Gamma Rays; p 203-214
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  • 3
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    A study of the cosmic sources of hard X-rays (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: An actively-shielded, high-energy X-ray telescope was launched onboard OSO-8 on 21 June 1975. The primary objectives of this experiment are the measurements of the energy spectrum of discrete cosmic X-ray sources in the range 20 keV to 3 MeV and of the temporal variations in the intensity of each source detected with a time resolution of 0.3 msec. This detector provides the highest duty factor and the finest time resolution of any of its kind for observations over a period of up to 10 days. The background spectrum of this detector in orbit was monitored continuously since shortly after launch. The minimum detectable source strength is estimated to be between 10,000 and 100,000 photons/sq-cm-sec keV, limited primary by the effects of induced radioactivity. From 16 July through 18 July 1975, the X-ray binary, Cen X-3, was observed with the hard X-ray telescope.
    Keywords: ASTRONOMY
    Type: X-ray Binaries; p 739-746
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  • 4
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    Simultaneous X-ray and optical observations of X Persei (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Photoelectric photometry of X Persei was obtained on five out of seven consective nights in January 1975, from the Lick and Leuschner Observatories. The observations yield B = 6.848 + or - 0.002, B-V = 0.139 + or - 0.001, with no strong evidence for variability during the observing run. These are the faintest and bluest photoelectric magnitudes and colors ever reported for X Per; this change apparently occured relatively uniformly during 1973-74 and is reminiscent of behavior last observed in approximately 1900. 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. On January 21, 1975, 7 hours of data were obtained from both observatories simulataneous with OAO Copernicus X-ray observations of 3U 0352+30. The X-ray data varied during this period by a factor of two, but there is no obviously correspondent optical activity, to a level of 0.02 mag. The optical data are also used to limit to 0.01 mag variations coincident with the X-ray periodicity.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 719-726
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  • 5
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    OSO-8 GSFC results on Cen X-3 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Spectra of Cen X-3 during eclipse, in transition out of eclipse, and during several later phases of the binary orbit were obtained from quick look data of the July 16-25, 1975 observation by the Goddard X-ray spectroscopy experiment on OSO-8. In the high state there was no absorption turn over. Pulsations were present at least to 23 keV. The spectrum at the pulse minimum was flatter above 7 keV than that of the pulse peak. In transition out of eclipse Cen X-3 emerged above a small low energy flux seen during eclipse. The observations appear to indicate absorption by cold and ionized matter and the presence of iron in the companion's atmosphere. Decreased intensities were observed at late phases of some binary orbits in some cases corresponding to dips. Absorption appears although the low energy component remains. Variable features may be interpretable as absorption and emission by iron and possibly other trace elements.
    Keywords: ASTRONOMY
    Type: X-ray Binaries; p 207-218
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  • 6
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    X-ray spectroscopy with the ANS satellite (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Preliminary results from the Bragg crystal spectrometer on the ANS satellite are given. No significant Si XIII and Si XIV narrow line emission has been detected from Cygnus X-1, -2, or -3.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 49-52
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  • 7
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    OSO-8 observations of Hercules X-1 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: The X-ray binary Her X-1 was observed by the GSFC cosmic X-ray detectors aboard OSO-8 between August 26 and September 3, 1975. The results reported are based on quick look tapes which contain less than 10% of the total time spent on source. Spectra were observed during different phases of the binary period including the anomalous low state (dip) in X-ray intensity. The normal high spectra is well represented by a power law with a short cutoff above approximately 25 keV. A significant and varying enhancement in the intensity around 6.7 keV was observed, suggesting the presence of an iron line. Absorption was seen in the spectrum immediately following eclipse. The dip spectrum is found to be considerably flattened. Also spectra are presented for different phases of the pulse period.
    Keywords: ASTRONOMY
    Type: X-ray Binaries; p 161-168
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  • 8
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    Some features of the X-ray source Cyg X-3 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Data from the Copernicus satellite are presented which show that the 4.8 hour light curve of Cyg X-3 has been relatively stable in period, shape, and amplitude since the observation of the first giant radio outburst in September 1972. A pulse height spectrum of the source obtained by the Ariel 5 satellite in the 1.5 to 26 kev energy band shows convincing evidence for line emission at about 6.5 keV. The strength of this feature varies in phase with the 4.8 hour continuum modulation, but there is no simple long term relation with the mean continuum intensity per 4.8 hour cycle. Evidence is presented which indicates that the average 2-6 kev intensity of Cyg X-3 has been higher by a factor of 3 since the onset of the radio flares.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 255-265
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  • 9
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    OSO-8 observing schedule for X-ray binaries (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Six different instruments on OSO-8 have observed several binary X-ray sources between energies of 0.13 keV and 1 MeV at various times since 21 June 1975. The schedule for these observations is given, as well as the present plan for such future observations through July 1976. Included is the OSO-8 observing schedule for the transient X-ray source A0620-00.
    Keywords: ASTRONOMY
    Type: X-ray Binaries; p 729-738
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  • 10
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    X-ray observation of 3U 1700-37 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: X-ray observations with Copernicus reveal three categories of flux variability in 3U 1700-37. High amplitude hourly variations are energy independent in the 3-11 keV range while a change in the low energy absorbing column causes variations in flux level on an orbital time scale. This absorption is most severe prior to eclipse ingress, suggesting that the distribution of absorbing material around the X-ray source is asymmetrical with respect to the line of centers of the binary system. The absorbing material may be identical with a high density region inferred from optical observations of HD 153919. In the third category, the maximum source intensity per binary cycle is variable by at least a factor of two between observations. Measurement of the eclipse duration on three occasions indicate that it is significantly less than when observed by Uhuru.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 559-567
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  • 11
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    A review of 3U 1700-37 = HD 153919 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: X-ray, spectroscopic, and photometric data for the source are reviewed briefly. Some points of controversy and difficulty are discussed. The X-ray source 3U 1700-37 is moderately strong (approximately 100 Uhuru counts) and shows a long eclipse, with a period of 3.412 days. The X-rays are attenuated near 0.5 phase, and show a very wide gradual decrease on either side of the total eclipse. The low-energy cutoff is the strongest of all the X-ray binaries. These characteristics are all qualitatively compatible with the optical star's, which represent an extreme in several ways: (1) the primary is an extreme star with large mass outflow through a spherically symmetric stellar wind; (2) it is the hottest of all X-ray binary primaries (with possible exception of Cen X-3); and (3) the mass ratio is very high and the relative separation of the stars is low.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 531-535
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  • 12
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    The nature of the X-ray nova A0620-00 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: A model is presented for the X-ray nova A0620-00. Identification with a nova can be ruled out on two counts. A binary consisting of a late-type subgiant near the Roche lobe, irradiated by an accreting compact companion is shown, however, to be in agreement with all known observations. Photometry of the optical object should be pursued since variability on an approximately eight hour period is expected.
    Keywords: ASTRONOMY
    Type: X-ray Binaries; p 361-367
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  • 13
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    New results from long-term observations of Cyg X-1 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Observations of Cyg X-1 between October 1974 and July 1975 reveal a persistent 5.6 day modulation of the 3-6 keV X-ray intensity, having a minimum in phase with superior conjunction of the HDE 226868 binary system. The modulation is found to be most pronounced just prior to the April-May 1975 increase of Cyg X-1, after which both the modulation and intensity are at their lowest values for the entire duration of the observations. These data imply that the X-ray emission from Cyg X-1 arises from the compact member of HDE 226868, and that the increase of April-May 1975 may have represented the depletion of accreting material which had not yet been mixed into a cylindrically symmetric accretion disk about the compact member.
    Keywords: ASTRONOMY
    Type: X-ray Binaries; p 391-405
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  • 14
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    The interpretation of optical light variations of Centaurus X-3 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: The interpretation of optical light variations of X-ray binaries is discussed for the case of negligible reflection effect. The limiting cases of synchronous rotation of the visible star (Roche configuration) and of no rotation (pure tidal deformation) are considered. The theoretical results are compared with the available light curves of Cen X-3. X-ray data of the Copernicus satellite are used to get an impression of the atmospheric structure of the outer layers of the visible component. It is shown, that the X-ray eclipse duration is in good agreement with the mass ration derived from the optical variations. The X-ray eclipse duration is discussed with respect to the extended low states, and a possible correlation of the extended lows with the appearance of the optical light curves is considered.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 179-185
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  • 15
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    The observation program for the GSFC cosmic X-ray spectroscopy experiment (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: The cosmic X-ray spectroscopy experiment on OSO-8 will observe seven X-ray binary sources in its first six months of operation. If possible, each of these sources will be observed for one or more binary orbits so that the X-ray spectrum of each object can be observed through all phases of its orbit. For the two pulsing binaries, Her X-1 and Cen X-3, spectral variations over the pulse period will be studied. Simultaneous radio observations of Cyg X-1 and Cyg X-3 will search for any correlation between radio and X-ray emission. During the first year of operation, the detectors will observe over 50% of the known X-ray sources.
    Keywords: ASTRONOMY
    Type: X-ray Binaries; p 737-738
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  • 16
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    Spectrophotometry of the unusual optical candidate for 3U 1728-24 (=GX 2+5 = GX 1+4) a recurrent nova? (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: The spectrum of the object suggested as a possible optical counterpart of GX 2+5, was studied, using the image tube scanner attached to the 3-m telescope of Lick Observatory. An improved X-ray error box obtained with Copernicus strongly supports this proposed identification. The candidate displays all the characteristics of the symbiotic stars and the related recurrent novae. The spectrum reveals the presence of an M star together with a blue component and a large number of emission lines displaying a wide range of ionization. There is evidence of variability of both the continuum and the line intensities. This object provides strong support for the often proposed association of some X-ray sources with nova-like systems.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 691-701
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  • 17
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    Long term X-ray studies of Sco X-1 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: No modulation of the 3-6 keV X-ray intensity of Sco X-1 at a level of excess of 1% is observed at the optical period of .787313d. Evidence is found for shot-noise character in a large fraction or the X-ray emission. Almost all of the Sco X-1 emission can be synthesized in terms of approximately 200 shots per day, each with a duration of approximately 1/3 day.
    Keywords: ASTRONOMY
    Type: X-ray Binaries; p 703-716
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  • 18
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    The X-ray binary HD 77581 + 3U 0900-40 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: The properties of the binary system in the different regions of the electromagnetic spectrum are presented from X-rays to the radio. Physical parameters and a model for the system are derived.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 575-614
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  • 19
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    The Skylab S019 ultraviolet spectra of HD 153919 (=3U 1700-37) and HDE 226868 (=Cyg X-1) (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Ultraviolet spectra of HD153919 (=3U1700-37) and HDE226868 (=Cyg X-1) were obtained with the ultraviolet objective-prism spectrograph of Skylab Experiment S019. The data consist of unwidened spectra which extend to 1,600A for HD153919 and to 2,400A for HDE226868. The wavelength resolution is about 2A to 1,400A and 12A at 2,000A. For HD153919, an unwidened spectrum of fair quality and extending to a wavelength of 1,600A was obtained at 22 sup h 08 sup m on 1 September 1973. The energy distribution in this spectrum generally resembles that of other reddened O stars. A break in continuum intensity seems to occur at a wavelength of about 1,720A. There is a suggestion of an emission line on the longward edge of the break but this could be either a chance clumping of grains or else a photographic edge-effect caused by the break.
    Keywords: ASTRONOMY
    Type: X-ray Binaries; p 551-553
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  • 20
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    High resolution measurements of Cyg X-1 from rockets (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Cyg X-1 was observed on two occasions (Oct. 4, 1973 and Oct. 3, 1974) by the Goddard X-ray rocket payload. This payload consisted of two gas proportional counters (xenon-methane with 710 sq cm and argon-methane with 610 sq cm using the same 128 channel pulse height analyzer and having 320 micro sec temporal resolution on the 1973 flight and 160 micro sec resolution on the 1974 flight. During both flights, bursts of 1 ms duration were observed with very high statistical certainty. To date all 13 of these bursts were analyzed for spectral and temporal character, and the results of this analysis are presented. The spectra of overall X-ray emission from both flights is also presented. In a source known for its variability, it is remarkable that the spectra taken one year apart are virtually identical.
    Keywords: ASTRONOMY
    Type: X-ray Binaries; p 443-451
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  • 21
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    The early light curve of A0620-00 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: The Ariel-5 All-Sky Monitor measured the 3-6 keV X-ray intensity of 0620-00 for two days shortly after peak emission in August 1975, and continuously throughout September 1975. The effective exposure each day for this source (and every other source in the 80% of the celestial sphere covered by the monitor) is approximately 250 sq cm sec. The light curve obtained through October 1 (when the spin axis was again pointed to A0620-00) is shown. The intensity difference at maximum is obviously a manifestation of the very soft spectrum of the source. Clearly, A0620-00 was approximately four times as bright as Sco X-1 at maximum in the band 3-6 keV. The decay is quite smooth, but cannot be fit with a single e-folding time. The interval between the early All-Sky Monitor points and the onset of continuous coverage has an inferred e-folding time of 22 days, but it is continually increasing throughout September. A0620-00 is apparently similar in its X-ray character to the very strong, long-lasting transient X-ray sources which presently number six. In contrast, only three can be sensibly reconciled with the lower-intensity, shorter-duration hard-spectrum transients which have been found to pulse on a time scale of minutes.
    Keywords: ASTRONOMY
    Type: X-ray Binaries; p 311-316
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  • 22
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    Absence of iron line emission in Cyg X-3 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: An observation of Cygnus X-3 was made with soft X-ray detectors launched on an Aerobee rocket. The iron line emission observed one month later and in May 1975 was not found. A 3 sigma upper limit for this feature is 0.006 ph/2 cm/s.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 285-292
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  • 23
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    The radio sources associated with Cyg X-3 (1976)
    In:  CASI
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    Publication Date: 2006-04-18
    Description: Some of the conclusions derived from the data on the radio flaring of Cyg X-3 are summarized. In addition, recent data showing that Cyg X-3 has both active and quiet radio behavior are presented.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 233-244
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  • 24
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    Recent Uhuru results on Centaurus X-3 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: The current status of the analysis of Cen X-3 data from Uhuru concerning pulsations, orbital period and eccentricity, and extended lows, are reviewed. The pulse period decreases irregularly. The pulsed fraction (2-7 keV) is 70%-90% for single pulses but significantly less for superpositions of pulses, due to variability in shape. The pulses are narrower at higher energies with a correlated increase in fraction pulsed. The orbital period is found to both decrease and increase with p/p on the order of a few times 0.00001/year. A three sigma upper limit on the eccentricity of 0.003 is obtained; if no significant periastron motion is allowed over two years, the upper limit becomes 0.0016. The orbital period is found to be detectable during some extended lows but with a significantly decreased ratio of eclipsed to non-eclipsed intensity. Two transitions between normal high states and extended lows are studied, and a consistent model is obtained in which extended lows are caused by both burying the source in an increased stellar wind from the companion, and starving the source by decreasing the stellar wind. Changes in fraction pulsed during transitions and systematic differences in the harmonic content of the pulses are also found.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 197-206
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  • 25
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    Optical observations of HDE 226868 = Cygnus X-1: A review (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: The present state of knowledge of the binary system HDE226868 = Cygnus X-1 is summarized, including system dimensions, nature of the secondary X-ray source, and mass transfer properties. Some deficiencies in the optical observations are pointed out; these deficiencies make interpretation of the system difficult, but can be corrected.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 465-484
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  • 26
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    Intensity and spectral variations of Cyg X-1 observed from balloons (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Observations of Cyg X-1 with a 20 to 200 keV balloon carried X-ray telescope in 1969, 1970, and 1972 are presented. These results reveal the following characteristics of Cyg X-1: The steep spectrum observed at E 10 keV during the radio quiet phase can extend to 200 keV. This phase may have lasted 21 months (July 1969 to March 1971). The low flux values are factors of 3 and 8 below the normal values at 30 and 100 keV respectively, are rarely observed, and may be associated with the early phase of the 1971 April X-ray transition. During some one hour periods, the intensity remained constant to approximately 20% and during other periods it varied a factor 2 in 5 minutes and a factor 10 in 1 hour. Complex spectral variations accompanied the intensity changes.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 407-424
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  • 27
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    Introduction to Cyg X-1 X-ray panel (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: The status of X-ray observations is summarized in tabular form along with general aspects of X-ray emission. Specific questions that arise when the observed phenomena are pieced together into a coherent picture are presented. Spectral states, transitions, periodic behavior, fluctuations, and bursts are among the topics discussed.
    Keywords: ASTRONOMY
    Type: X-ray Binaries; p 369-372
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  • 28
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    The transient X-ray source A0620-00 (Nova Monocerotis 1975) (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: A0620-00 is the first of the so-called X-ray novae to be identified with an optical object. Emission in the ultraviolet, infrared, and radio wavelength regions was observed from this source. From the observed properties of the optical radiation, it is suggested that the source is a recurrent nova.
    Keywords: ASTRONOMY
    Type: X-ray Binaries; p 293-309
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  • 29
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    Pulsed X-ray observations of Cen X-3 from Ariel-5 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: The 4.8 second X-ray pulsations from Centaurus X-3 were monitored by the MSSL collimated proportional counter on board Ariel-5 between 18-27 January 1975. Analysis of the source Doppler effect shows that the pulsation period of Cen X-3 decreased by 3.70 + or - 0.04 milliseconds during the preceding 2.3 years. The Doppler analysis also yields updated values for the binary phase and period of Cen X-3. Phase zero occurred at JD 2442438.628 + or - 0.003, and the average heliocentric binary period between October 1972 and January 1975 was 2.087129 + or - 0.000007 days. Light curves of the 4.8 second pulsations in the 3-9 keV band are characterized by two pronounced peaks, in contrast with the single peak profiles observed by Uhuru.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 219-231
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  • 30
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    The interstellar matter column density to Cen X-3 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: The usual gas-to-dust ratio is shown to hold quite precisely for a sample of supernova remnants with available X-ray spectra and interstellar reddening observations. Supernova remnants are extended objects, tenuous enough to be optically thin in the X-ray range; it is shown that the X-ray observations can readily be interpreted in terms of a main source component and of an interstellar perturbation affecting the lower part of the spectrum. Cen X-3 is associated with an OB supergiant. The effect of the column density is easily detectable in the X-ray range. The spectrum exhibits a low energy cut-off, which is parameterized by a column of cold matter, NX. The cut-off is definitely observed to be variable. There is a suggestion that sometimes NX NH. It is concluded that on those occasions a spurious soft X-ray component is present in the source, bearing close similarity with Cyg X-1.
    Keywords: ASTRONOMY
    Type: X-ray Binaries; p 189-195
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  • 31
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    Radiation mechanisms and magnetospheric structure of pulsars (1976)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: A model of pulsars is outlined. Key early considerations were those which led to the identification of pulsars with neutron stars, the Goldreich-Julian model of pulsar magnetospheres, and the recognition that, in a pulsar magnetosphere, a high energy gamma ray may annihilate to produce an electron-positron pair. Arguments that suggest that pulsar magnetospheres may contain large masses of plasma, a suggestion which has important implications concerning the structure of the magnetosphere, are considered along with observational data which support a magnetosphere model based on that idea rather than the Goldreich-Julian model.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center The Struct. and Content of the Galaxy and Galactic Gamma Rays; p 108-117
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  • 32
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    Galactic distribution of pulsars (1976)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: The density distributions of pulsars in luminosity, period, Z-distance, and galactocentric distance were derived using a uniform sample of pulsars detected during a 408 MHz pulsar survey at Jodrell Bank. There are indications of a fine scale structure in the spatial distribution and evidence that there is a general correlation with other galactic populations and the overall spiral structure. The electron layer in the galaxy is shown to be wider than the pulsar layer and uniform on a large scale. The number of pulsars in the galaxy was estimated and used to derive the pulsar birthrate.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center The Struct. and Content of the Galaxy and Galactic Gamma Rays; p 299-319
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  • 33
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    Gamma ray pulsars (1976)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: Recent data from the high energy gamma ray experiment have revealed the existence of four pulsars emitting photons above 35 MeV. An attempt is made to explain the gamma ray emission from these pulsars in terms of an electron-photon cascade that develops in the magnetosphere of the pulsar. Although there is very little material above the surface of the pulsar, the very intense magnetic fields correspond to many radiation lengths which cause electrons to emit photons via magnetic bremsstrahlung and these photons to pair produce. The cascade develops until the mean photon energy drops below the pair production threshold which happens to be in the gamma ray range; at this stage the photons break out from the source.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center The Struct. and Content of the Galaxy and Galactic Gamma Rays; p 118-127
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  • 34
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    Optical observation of WRA 977 (3U 1233-62?) (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: UBV photometry of WRA 977 on 36 nights between January and July of 1974 shows that this object is active on a time scale of days at the 0.1 mag level, but that it remains quite constant during monitoring intervals lasting up to 1 hour. Periodogram analysis reveals no significant periodic variation in the brightness of this object.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 677-682
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  • 35
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    He II lambda 4686 photometry of HD 153919 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: The optical component of the binary X-ray source 3U1700-37/HD 153919 was observed with the interference filter centered on the He II lambda 4686 emission. This photometry does not reveal any dependence of lambda 4686 emission on the orbital phase thereby confirming earlier spectroscopic result that the region of formation of the ionized helium emission is confined to the envelope of the 06f primary.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 555-557
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  • 36
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    Blue band photometry of Cygnus X-1 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Results of blue band photometry of HDE 226868 in the years 1972-3-4 and provisional results for 1975 are presented. A mean light curve is obtained from the first three years observations which is based on 192 nights observations. Intercomparison of the results from the different years shows that the light curve is not constant.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 521-527
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  • 37
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    A0620-00 as a recurrent nova (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Evidence for and against the star associated with A0620-00 being a nova is presented. The conclusion is that this star closely resembles other recurrent novae with the only unusual characteristic being the apparent high temperature at maximum brightness.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 335-341
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  • 38
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    Optical identification of A0620-00 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Identification of the optical counterpart to the transient X-ray source A0620-00 was made using image tube photography. Spectra taken subsequent to the identification showed no stellar absorption or emission features. Photometric data gave a V magnitude of 11.2 + or - .1. This is about 8 magnitudes brighter than the object appears on the Palomar Sky Survey.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 327-333
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  • 39
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    Observations of Cygnus X-3 by ANS (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: The hard X-ray experiment (1 - 28 keV) on ANS observed Cygnus X-3 in November 1974, and in May 1975. The average flux intensities for these time periods were found to be 22.4 + or - 0.5 cts/sec and 12.8 + or - 0.3 cts/sec (1.3 - 7.1 keV), the former being the highest average value ever observed. The spectrum studies show an excess in the flux above the fitted continuum which can be interpreted as a line emission of FeXXIV and/or FeXXV, at approximately 6.5 keV. The strength of this feature varied in phase with the 4.8 hr X-ray modulation, and remained at a constant relative intensity. The period of the X-ray modulation is refined to 0.1996813 + or - 0.0000006 day and obtained at a 2 sigma upper limit to a continuous change in the period of 50 to the minus 13th power/sec. This new limit places serious constraints on several models for this object.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 267-275
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  • 40
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    Copernicus observations of a number of galactic X-ray sources (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: The Copernicus satellite was launched on 21 August 1972. The main experiment on board is the University of Princeton UV telescope. In addition a cosmic X-ray package of somewhat modest aperture was provided by the Mullard Space Science Laboratory (MSSL) of University College London. Following a brief description of the instrument, a list of galactic sources observed during the year is presented. Although the X-ray detection aperture is small, the ability to point the satellite for long periods of time with high accuracy makes Copernicus an ideal vehicle for the study of variable sources.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 1-25
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  • 41
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    Centaurus X-3: The observational picture (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Observations of Centaurus X-3 are briefly reviewed. The composition of the neutron star, optical light curves, and X-ray pulsations are among the topics discussed.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 173-176
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  • 42
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    Periodic flickering in the optical spectrum of HZ Herculis (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Photometric observations of HZ Herculis in the ultraviolet with a time resolution of 5 seconds are discussed. The existence of periodic flickering with a time scale of 115 to 130 seconds is observed. The amplitude modulation is about 3 to 6 percent, larger than that associated with the erratic white flickering. The flickering, either erratic or periodic, occurs, but not always, near orbital phase 0.5, irrespective of the on and off parts of the X-ray cycle.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 101-111
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  • 43
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    ANS results on X-ray binaries (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: A short description is given of the Astronomical Netherlands Satellite (ANS) and the X-ray instruments of the Space Research Laboratory in Utrecht. The ANS observed in February 1975 a soft (1/4 keV) X-ray flux in Her X-1 during the 'off'-state with an intensity of a factor 10 lower than observed in the 'on'-state. The ANS observations on Cyg X-1 are summarized. During the May 1975 flaring state a very high intensity at 0.5 keV is measured consistent with a power-law photon-spectrum with index 3.5 and an interstellar absorption of 7.10 to the 21st power atoms/sq cm, but not consistent with spectra that show an additional cut-off below 1 KeV and an absorption of 7.10 to the 21st power atoms/sq cm. Intensity changes on a time scale of minutes, as observed in Cyg X-1 low state, are not observed during the flaring state.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 27-47
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  • 44
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    The NASA-NMSU automated meteor observatory (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: A new observatory for meteor research which provides data for study of meteor heights, velocities, orbits, and meteoroid abundances is described. The observing equipment is automated to take advantage of the long periods of favorable observing weather common to the region. Four K-24 cameras, electrically operated, provide the triangulation observations, and four Maksutov f/1.3 cameras with blazed transmission grating provide spectral coverage. The patrol cameras have operated for a year and a half, and approximately 6,000 frames have been exposed by 9 March 1975. Meteor trails appear on 260 of these frames. Sixty-eight trails are of meteors photographed from two locations and thus allow trajectory and orbit determinations for 34 meteors. Photoelectric sensors initiate the 2-second spectrograph exposures, and electrical controls open and close the observatory at present times.
    Keywords: ASTRONOMY
    Type: N. Mex. State Univ. Contrib. of the Observatory of N. Mex. State Univ., Vol 1, No. 4; p 166-173
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  • 45
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    Photometry of R Coronae Borealis (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Visual and photoelectric observations of R Coronae Borealis are presented, including a number of observations surrounding the 1974 minimum. The recent visual history of the variable is examined and the discrete cloud obscuration model is considered.
    Keywords: ASTRONOMY
    Type: Contrib. of the Observatory of N. Mex. State Univ., Vol. 1, No. 4; p 134-139
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  • 46
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    Intermediate-band photometry of faint standard stars (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The David Dunlap Observatory system uses six intermediate-band filters whose central wavelengths were chosen to cover important features in the spectrum of a late-type star. Calibrations of the color indices with physical parameters, allow one to estimate T sub eff, log g, Fe/H, M sub v and reddening directly from the photometry. Although a number of standards lists exist, only a small fraction of the stars is fainter than V=6. It is desirable to add to the numbers of faint standards. Results are presented of photometry of sixteen stars obtained during a program of variable-star photometry at Blue Mesa Observatory.
    Keywords: ASTRONOMY
    Type: Contrib. of the Observatory of N. Mex. State Univ., Vol. 1, No. 4; p 140-142
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  • 47
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    Stabilization of Kepler's problem (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A regularization of Kepler's problem due to Moser (1970) is used to stabilize the equations of motion. In other words, a particular solution of Kepler's problem is imbedded in a Liapunov stable system. Perturbations can be introduced into the stabilized equations.
    Keywords: ASTRONOMY
    Type: Celestial Mechanics; 16; Sept
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  • 48
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    Aperture averaging effects in stellar scintillation (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Stellar scintillation has been measured for apertures as low as 0.012 m by using photoncounting techniques. The scintillation measurements have been made for various aperture sizes in quick succession in order to determine experimentally the effects of aperture averaging. The results of the experiment are compared with the predictions of a model proposed earlier in the literature to quantify the phenomenon.
    Keywords: ASTRONOMY
    Type: Optics Communications; 22; Sept
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  • 49
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    Far-infrared scans of the Galactic plane (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Results are reported for balloon-borne scans of the Galactic plane between longitudes of 348 and 32.5 deg, which were made in two broad spectral bands from 60 to 300 microns and from 150 to 300 microns. These results indicate that there are many bright H II regions embedded in a diffuse underlying band of emission in the examined longitude range, that the color temperatures range from 30 to 90 K, and that the width of the plane is at least 2 deg of arc in both spectral bands. A lower-limit IR luminosity of the order of 1 billion suns is computed for both the bright complex of sources at the nucleus and the underlying diffuse emission out to about + or -15 deg of arc from the nucleus. The strong relationship between far-IR emission and radio continuum expected for discrete sources is illustrated, and the results are compared with those of previous studies. It is concluded that the total far-IR luminosity of the central part of the Galaxy is understandable solely in terms of known distributions of stars and dust.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 214
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  • 50
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    90-GHz flux-density measurements of variable radio sources (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Results are presented for measurements of the flux densities of 10 variable extragalactic sources at 85.2 or 90 GHz, which were made over a period of almost seven years with the NRAO 36-ft millimeter-wave antenna. The primary flux-density calibration standards used include Jupiter, Saturn, Mars, and the small-diameter Galactic source DR 21. Measured flux densities are given as a function of time (in years) for the sources 3C 84, NRAO 150, 3C 120, OJ 287, 4C 39.25, 3C 273, 3C 279, 3C 345, BL Lac, and 3C 454.3. No statistically meaningful flux-density changes during an observing interval (1 to 3 days) are detected for any source, and a high degree of correlation between flux-density variations at 85.2 or 90 GHz and those observed at lower frequencies is found in all 10 sources. Some variations observed at different frequencies in several individual sources are briefly discussed.
    Keywords: ASTRONOMY
    Type: Astronomical Journal; 82; Apr. 197
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  • 51
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    Linearization of dynamical systems using integrals of the motion (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A method is presented which transforms certain nonlinear differential equations of dynamics into linear equations by introducing an independent variable and utilizing the integrals of motion. As examples of special interest, the linearizations of unperturbed and perturbed Keplerian motions are discussed.
    Keywords: ASTRONOMY
    Type: Celestial Mechanics; 14; Dec. 197
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    On the stability of the solutions of the general problem of three bodies (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The extent through which the initial conditions of a given three-body system may be varied without completely changing the qualitative nature of the subsequent system evolution is investigated. It is assumed that the three masses are equal, all initial velocities are zero, the first two bodies initially lie on the x-axis, and the position of the third body is confined to a specific region of space. Analysis of the system evolution for different initial positions of the third body shows that there is a whole area or 'island' in the x-y plane throughout which the initial position of the third body may be moved in a continuous fashion to produce an evolution which also changes in a continuous manner. A Monte Carlo approach is adopted to determine the full extent of this island in the general problem. It is concluded that the stability of a full solution may be directly related to the size of its island in phase space.
    Keywords: ASTRONOMY
    Type: Celestial Mechanics; 14; Dec. 197
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  • 53
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    Copernicus observations of the Ap star Epsilon Ursae Majoris (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Spectral scans of the Ap star Epsilon UMa made with the Copernicus satellite show strong line blanketing from profuse Cr II and Fe II lines. In the spectral region covering 1900 to 3000 A, about 500 lines are present which suppress the apparent continuum by at least 15-30%. An accurate line-identification list is compiled showing Eu II present in addition to Mn II and Ni II. The identification of Eu II, however, rests on very stringent identification limits for Fe II. If these are relaxed, the existence of Eu II is dubious. There are no broad features in this spectral region which would suggest strong photoionization discontinuities by metals, but one feature near 2137 A might contain the photoionization edge due to Cr I 5S lying 0.94 eV above the ground level. However, a significant correlation between the line-blanketing strength and the amplitude of the OAO-2 ultraviolet light curves was found such that both monotonically increase in the same proportion toward shorter wavelengths. This gives additional strength to the suggestion that variations in the metal line-blanketing cause the observed photometric variations.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal Supplement Series; 33; Jan. 197
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  • 54
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    5 GHz observations of galactic supernova remnants (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Brightness and polarization distributions over several galactic supernova remnants have been observed at a wavelength of 6 cm. These observations have confirmed the nonthermal nature of most of the observed sources. It is suggested, however, that the objects G33.1-0.1 (KES 78), G35.6-0.0, G37.6-0.1, G37.7+0.1, and G37.9-0.4 are thermal. The results of these observations are presented in the form of total intensity contour maps with superimposed polarization vectors.
    Keywords: ASTRONOMY
    Type: Astronomy and Astrophysics; 55; 1, Fe; Feb. 197
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  • 55
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    Far-ultraviolet imagery of the Barnard Loop Nebula (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: An electrographic Schmidt camera carried on a sounding rocket has yielded far-ultraviolet (1050-2000 A and 1230-2000 A) images of the Barnard Loop Nebula and of the general background in the Orion region due to scattering of ultraviolet starlight by interstellar dust particles. The total intensity in the Barnard Loop region agrees well with OAO-2 measurements, but the discrete Loop structure contributes only some 15% of the total. The measurements are consistent with a relatively high albedo for the dust grains in the far-ultraviolet.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 212
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  • 56
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    Apollo-16 far-ultraviolet spectra in the Large Magellanic Cloud (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Spectra in the wavelength ranges from 900 to 1600 A and 1050 to 1600 A of some OB associations in the Large Magellanic Cloud were obtained from the lunar surface by the Apollo-16 far-ultraviolet camera/spectrograph on April 22, 1972. The observed spectral distributions appear consistent with a stellar model having an effective temperature of 30,000 K, reddened by E(B-V) = 0.3, and characterized by the average far-ultraviolet extinction curve of Bless and Savage (1972). However, the absolute intensity of the far-ultraviolet spectrum of the associations NGC 2050 and 2055 seems somewhat too bright in comparison with ground-based photometry.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 211
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  • 57
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    Far infrared observations of IRC + 10216 (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Results are reported for measurements of IRC + 10216 at 100 microns made with the 91-cm telescope of NASA's Kuiper Airborne Infrared Observatory. The IR photometer employed consisted of a gallium-doped germanium photoconductive detector with a MOSFET preamplifier and load resistor. Signals obtained from the source at modulation frequencies of 30 and 100 Hz are plotted, and the 100-micron flux measurements are shown to be in agreement with previous bolometric measurements. It is noted that the sensitivity of the photoconductive detection system is comparable to that of the conventional bolometers that have been used in airborne IR observations.
    Keywords: ASTRONOMY
    Type: Nature; 265; Feb. 10
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  • 58
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    The elimination of short and intermediate period terms from the problem of a high altitude earth satellite (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The Delaunay-Similar elements of Scheifele (1976) are applied to the problem of an earth satellite that is perturbed by the sun, moon, and J2. All three effects are assumed to be the same order of magnitude. Since the external body terms depend explicitly on time, the time element appears as an additional angle variable. Also, the eccentric anomaly is used as a noncanonical auxiliary variable. A solution to the first Von Zeipel equation allows simultaneous elimination of short- and intermediate-period terms. The canonical transformation to mean elements is defined by a generating function that is a series involving Bessel coefficients.
    Keywords: ASTRONOMY
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  • 59
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    Comet West and the scattering function of cometary dust (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Observations of Comet West (1975n) at wavelengths from 0.5 to 18 microns and at a variety of scattering angles are used to infer the scattering phase function for the cometary dust. This function is strongly peaked in the forward direction. The form of the function indicates that the particles are dielectric grains with radii of approximately 1 micron. Abrupt increases in the intrinsic brightness of the coma (both in scattered sunlight and in thermal emission) are consistent with the projected times of comet fragmentation.
    Keywords: ASTRONOMY
    Type: Science; 194; Dec. 3
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  • 60
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    Interference in astronomical speckle patterns (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Astronomical speckle patterns are examined in an atmospheric-optics context in order to determine what kind of image quality is to be expected from several different imaging techniques. The model used to describe the instantaneous complex field distribution across the pupil of a large telescope regards the pupil as a deep phase grating with a periodicity given by the size of the cell of uniform phase or the refractive index structure function. This model is used along with an empirical formula derived purely from the physical appearance of the speckle patterns to discuss the orders of interference in astronomical speckle patterns.
    Keywords: ASTRONOMY
    Type: Optical Society of America; vol. 66
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  • 61
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    Direct photography of the Gum Nebula (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The paper discusses a series of wide-angle photographs taken of the Gum Nebula in the traditional region including H-alpha with the aid of a 40-cm and an 80-cm lens in both the red and the green. The photographs support the large dimensions (75 deg in galactic longitude by 40 deg in galactic latitude) of the Gum Nebula suggested earlier, and the appearance is consistent with an origin due to photons from a supernova outburst. The relatively high-density gas has cooled and is visible on the red plates. The low-density gas has remained at a high temperature and may be visible as diffuse emission on the green plates.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 208; Aug. 15
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  • 62
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    Far-ultraviolet imagery of the Orion Nebula (1977)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Two electrographic cameras carried on a sounding rocket have yielded useful-resolution far-ultraviolet (1000-2000 A) imagery of the Orion Nebula. The brightness distribution in the images is consistent with a primary source which is due to scattering of starlight by dust grains, although an emission-line contribution, particularly in the fainter outer regions, is not ruled out. The results are consistent with an albedo of the dust grains that is high in the far-ultraviolet and which increases toward shorter wavelengths below 1230 A.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 217
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    OSO-8 X-ray observations of AM Herculis (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Results are reported for hard X-ray observations of the binary system AM Her, which were coincident with soft X-ray and ground-based optical measurements. In the 2-60-keV band, variability was detected with an eclipse during phases 0.5 to 0.7 with respect to the 0.12892-day optical minima, synchronous with the known soft X-ray eclipse. The 2-60-keV uneclipsed flux was 9.5 by 10 to the -10th power erg/sq cm per sec, of which 86% lies above 10 keV. Thus, AM Her contains a hard source located near the similarly eclipsed soft X-ray source. The X-ray data are interpreted in terms of thermal bremsstrahlung from accretion onto a white dwarf.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 216
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  • 64
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    The far-infrared spectrum of the core of Sagittarius B2 (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A Michelson interferometer aboard NASA's Kuiper Airborne Observatory has been used to measure the spectrum of Sgr B2 from 40 to 200 kaysers with 5-kayser resolution in a 1.4-arcmin beam. The measured spectrum is smooth and featureless with a broad maximum at about 85 kaysers. The data can be fitted analytically with a model corresponding to thermal emission by a uniform sla of dust filling the beam, with an average temperature of approximately 32 K, an optical depth at 100 microns of about 1.6, and a spectral index of the dust emissivity about 1.5. The absence of features implies either that the source is optically thick or that the emission spectrum of the individual grains is smooth in the passband. The possible physical significance of this model is discussed.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 216
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  • 65
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    X-ray spectra of Hercules X-1. II - The pulse (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 216
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  • 66
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    A1540-53, an eclipsing X-ray binary pulsator (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: An eclipsing X-ray binary pulsator consistent with the location of A1540-53 has been observed. The source pulse period was 528.93 + or - 0.10 s. The binary nature is confirmed by a Doppler curve for the pulsation period. The eclipse angle of 30.5 + or - 3 deg and the 4-hour transition to and from eclipse suggest an early-type giant or supergiant primary star.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 216
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  • 67
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    The spectral development of Nova Cygni 1975 (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Optical and near-infrared (0.3-2.5 microns) observations of Nova Cygni 1975 made during the period from August 30 to December 11, 1975, are reported. The persistent strength of O I at 8446 and 11,287 A is shown to be due to L-beta fluorescence in clouds with high (greater than 1000) H-alpha optical depth. A simple model of the nova ejecta is presented and shown to be consistent with the observed evolution of the nova spectrum.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 216
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  • 68
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    Radar detectability of asteroids - A survey of opportunities for 1977 through 1987 (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The study of asteroids by earth-based radar during the period 1977 to 1987 is discussed. Detection modeling, including backscattering laws, limits of detectability, and in particular, measurement of center frequency, center-to-limb bandwidth, and areal spectral density, is reviewed. The number of detectable objects and detectable events falling into various 5-decibel radar target loss slots is estimated; a total of 60 different asteroids should be observable on about 130 occasions by either the Goldstone or Arecibo radar systems during the decade considered. Furthermore, the detectability margins for many objects should be large enough to permit more refined analysis of the radar spectrograms. Data acquired during the ten-year period may be used to find the radius, average surface roughness, rotation rate, direction of polar axis, and estimates of the Doppler frequency offsets for many of the asteroids. Also, information about radar albedos and orbital parameters may be obtainable in a number of cases.
    Keywords: ASTRONOMY
    Type: Icarus; 31; Aug. 197
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  • 69
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    UBV photometry of small and distant asteroids (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Photoelectric magnitudes and colors on the ultraviolet (UBV) system are presented for 65 minor planets, including four Mars crossers, six Trojans, and main-belt objects down to 6 km in diameter. The Trojans all have very similar colors not characteristic of the main-belt population. A paucity of S-type asteroids at the smallest diameters, predicted from trends seen at larger sizes, is not observed. The newly available color data for small objects ranging from 1.0 to 5.2 astronomic units in heliocentric distance show the main belt to be a transition zone between predominantly silicate and carbonaceous compositions.
    Keywords: ASTRONOMY
    Type: Icarus; 31; Aug. 197
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  • 70
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    Effect of the Shuttle contaminant environment on a sensitive infrared telescope (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A sensitive IR telescope on the Space Shuttle Orbiter will be limited in its performance by fluctuations in the IR radiation from the natural environment and the contaminant atmosphere. Models of the Orbiter's contaminant atmosphere were used to predict its spectral radiance from 3 to 300 microns. At 350 km, statistical fluctuations in the radiation from a water vapor column, and a noise equivalent power were measured. This noise is somewhat smaller than the expected contribution from zodiacal light from 5 to 30 microns. The column density of all IR emitting molecules can be kept low only if restrictions on rocket firings and liquid vents are maintained. The relatively low frequency of particle sightings from Skylab, coupled with improvements in Orbiter venting techniques, indicate that sightings of particles 2 microns and larger in radius will not seriously hamper telescope performance provided that liquid vents and rocket firings are properly restricted.
    Keywords: ASTRONOMY
    Type: Applied Optics; 16; Aug. 197
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  • 71
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    A new optical supernova remnant in Cygnus (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The letter reports the discovery of a filamentary emission-line structure at right ascension 19 hr 31 min and declination +31 deg 10 min (1950) during an emission-line survey of the Milky Way. This structure is classified as a supernova remnant on the basis of its similarity to several other SNRs, but is shown not to be part of the Gamma Cygni complex. A physical diameter of about 70 pc is obtained for this SNR along with a distance of approximately 1200 pc, a shock velocity of at least 50 km/s, an initial density of about 0.5 per cu cm, and an age of approximately 300,000 yr.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 215
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  • 72
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    The ultraviolet spectra of four binaries observed with the S59 spectrometer (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Ultraviolet spectra of Omicron And, Alpha CrB, Eta Ori A, and Alpha Vir, which were obtained with the S59 spectrometer at a resolution of 1.7 A in three 100-A-wide regions centered at 2110, 2454, and 2825 A, have been studied for the presence or absence of effects due to their binary nature. As may have been anticipated from their orbital and other characteristics, no indication of strong binary interactions were seen in these observations. However, there are certain spectral peculiarities suggesting the possibility of modifications of spectral classifications for some of these objects. A rather unusual spectral behavior in Alpha Vir is also noted. In addition, based primarily on a review of available literature, attention is drawn to a remarkable property of the third component in Eta Ori A.
    Keywords: ASTRONOMY
    Type: Astrophysics and Space Science; 46; Feb. 197
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  • 73
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    Spectroscopic studies of very old hot stars. II - Spectral classification, absolute magnitudes, and distances of O-type planetary nuclei (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 215
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  • 74
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    Orbital evolution (1977)
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    Publication Date: 2011-08-17
    Description: The orbital evolution of a large satellite is governed primarily by tidal interactions between the satellite and the planet it orbits. Tides raised on a planet by a satellite transfer energy and angular momentum to the satellite orbit; this changes the semimajor axes of satellite orbits, increasing the size of those orbits where the satellite mean motion is smaller than the planetary angular velocity, and decreasing those where the opposite is true. Substantial changes caused by such tides for satellites of the terrestrial planets may explain the absence of satellites about Mercury and Venus. For Jovian and Saturnian satellites, such tides probably are only important in bringing about some of the observed orbital resonances. Tides raised on satellites generally cause decreasing orbital eccentricities, indicating why close satellites always have nearly circular orbits. Different processes of orbital evolution dominate for small bodies; their effects probably are critical in positioning material in the primordial dust cloud so that satellite coagulation may occur. A qualitative description is given of the orbital results of gas drag, radiation pressure, Poynting-Robertson drag and electromagnetic forces.
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  • 75
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    K/S two-point-boundary-value problems (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A method for developing the missing general K/S (Kustaanheimo/Stiefel) boundary conditions is presented, with use of the formalism of optimal control theory. As an illustrative example, the method is applied to the K/S Lambert problem to derive the missing terminal condition. The necessary equations are developed for a solution to this problem with the generalized eccentric anomaly, E, as the independent variable. This formulation, requiring the solution of only one nonlinear, well-behaved equation in one unknown, E, results in considerable simplification of the problem.
    Keywords: ASTRONOMY
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  • 76
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    Trajectories and orbits from the NASA-NMSU meteor observatory. I (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Reduced trajectory data and orbital elements are reported for 20 double-station meteors photographed at the NASA-NMSU meteor observatory during the winter of 1974/75. The objects photographed include 10 sporadic meteors and 10 members of the Geminid shower. The data for the sporadic meteors indicate that their magnitudes range from 0 to -4, all have eccentricities greater than 0.4, all but three are in direct orbits, and one is probably a member of the Coma Berenicid shower. The elements for the Geminids are obtained using times of appearance chosen by adopting 34.6 km/s as the heliocentric velocity of the shower. The results are compared with previous orbital determinations, and it is concluded that there is no evidence for significant evolution of the Geminid-stream orbit over a period of several decades.
    Keywords: ASTRONOMY
    Type: Astronomical Journal; 81; Nov. 197
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  • 77
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    Emission nebulae in the Magellanic Clouds. I - The H II regions (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A review of optical and radio studies of the H II regions in the Magellanic Clouds is presented. Recent studies are emphasized, particularly optical studies of the kinematics, spectra, and chemical composition. The implications of the studies for the understanding of the evolution of stars and galaxies in general, and the Magellanic Clouds in particular, are noted. Suggestions for future work are also given.
    Keywords: ASTRONOMY
    Type: Earth and Extraterrestrial Sciences; 2; June 197
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  • 78
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    Minor planets and related objects. XXI - Photometry of eight asteroids (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Light curves, UBV colors, rotational periods, phase coefficients, and absolute magnitudes are presented. The asteroids studied are (1) Ceres, (4) Vesta, (16) Psyche, (78) Diana, (281) Lucretia, (451) Patientia, (1212) Francette, and (1362) Griqua. The rotation axis of Lucretia is nearly perpendicular to the plane of the ecliptic. Ceres appears to be nearly spherical with an absolute magnitude of B(1,0)=4.42, which is 0.3 mag fainter than previously reported. The determination of the absolute magnitude for an asteroid depends on its aspect, and for each opposition there is, therefore, a different absolute magnitude.
    Keywords: ASTRONOMY
    Type: Astronomical Journal; 81; Sept
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  • 79
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    NASA's 91-cm. airborne telescope (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The Gerard P. Kuiper Airborne Observatory (KAO), commissioned in May 1975, is the result of the multi-year NASA program of infrared observations from high-flying aircraft. The KAO is a highly modified Lockheed C-141 jet transport, equipped with a 91-cm bent-Cassegrain telescope, as an international facility for research in infrared astronomy. To minimize the effects of aircraft vibration, the telescope is mounted on four pneumatic shock absorbers, and the entire assembly is balanced on the side of a spherical compressed-air bearing, containing a 0.018 mm-thick air film under a pressure of 19 atmospheres. The use of the KAO is not limited to infrared research, its total observable wavelength band extending from the near UV (3000 A) to the millimeter region. Design and technical characteristics of the telescope are discussed, including the image stabilization and target acquisition systems, as well as observational results obtained during the first year of the KAO operation.
    Keywords: ASTRONOMY
    Type: Sky and Telescope; 52; Nov. 197
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  • 80
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    Black holes and relativitic gravity theories (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: All presently known relativistic gravitation theories were considered which have a Riemannian background geometry and possess exact static, spherically symmetric solutions which are asymptotically flat. Each theory predicts the existence of trapped surfaces (black holes). For a general static isotropic metric, MACSYMA was used to compute the Newman-Penrose equations, the black hole radius, the impact parameter, and capture radius for photon accretion. These results were then applied to several of the better known gravitation theories.
    Keywords: ASTRONOMY
    Type: NASA. Langley Res. Center Proc. of the 1977 MACSYMA Users' Conf. (NASA); p 97-107
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  • 81
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    Calculation of the twilight visibility function of near-sun objects (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The visibility function, defined here as the magnitude difference between the excess brightness of a given object and that of the background sky, of near-sun objects during twilight is obtained from a general calculation which considers the twilight sky background, atmospheric extinction, and night glow. Visibility curves are computed for a number of cases in which observations have been recorded, particularly that of comet Kohoutek. For this object, the computed visibility maxima agree well in time with the reported times of observation.
    Keywords: ASTRONOMY
    Type: Royal Astronomical Society of Canada; vol. 70
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  • 82
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    Emissivities and detectability of the pure rotational transitions of molecular hydrogen (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The emissivities of the infrared rotational transitions of H2 are calculated for temperatures from 10 K to 6000 K. The calculations are made for several ratios, R, of Para (J=0) to Ortho (J=1)H2. The possibility of detecting these transitions in interstellar molecular clouds is discussed.
    Keywords: ASTRONOMY
    Type: Contrib. of the Observatory of N. Mex. State Univ., Vol. 1, No. 4; p 123-133
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  • 83
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    A method for developing K/S boundary conditions (1976)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: A method for developing the missing general K/S (Kustaanheimo/Stiefel) boundary conditions is presented, with use of the formalism of optimal control theory. As illustrative examples, the method is applied to the transfer between two position and velocity vectors and to the K/S Lambert problem to derive the missing terminal conditions. The necessary equations for a solution are then developed to the K/S Lambert problem with both the fictitious time, s, and the generalized eccentric anomaly, E, as the independent variables. The latter formulation, requiring the solution of only one nonlinear, well-behaved equation in one unknown, E, results in considerable simplification of the problem. This simplification is possible because the energy equation, in the E-formulation, is separable.
    Keywords: ASTRONOMY
    Type: Journal of the Astronautical Sciences; 24; Jan
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  • 84
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    Evidence for an 11.2 day periodicity from Cygnus X-2 (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Evidence is reported for a periodicity of 11.17 (+ or - 0.10) days in the emission from Cygnus X-2. The data were obtained quasi-continuously over a period of more than one year with the Ariel-5 All-Sky Monitor. It is noted that this period is more than an order of magnitude larger than the 0.787-day binary period of Sco X-1 and is not a simple alias of a similarly short period. It is suggested that the 11.17-day modulation might be precessionally induced; otherwise, it would be rather unusual since the Cyg X-2 candidate is assumed to have a low-mass primary and periods in excess of about 2 days are usually associated with high-mass primaries.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 205; May 1
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  • 85
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    Far-ultraviolet brightness of nebulae in Cygnus (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: A far-ultraviolet electrographic Schmidt camera was operated on the lunar surface during the Apollo 16 mission. Among the results obtained were imagery in the 1050-1600-A and 1250-1600-A wavelength ranges of a 20-deg-diameter field in Cygnus containing the Cygnus Loop nebula, the North America nebula (NGC 7000), and the H II region of the O8 star 68 Cygni. The maximum intensity in the Cygnus Loop was 100 R in the 1250-1600-A range and 130 R in the 1050-1600-A range. The maximum brightnesses in the 1250-1600-A range of the 68 Cyg H II region and of NGC 7000 were about 60 and more than 80 R, respectively, but require relatively large corrections for interstellar extinction.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 205; Apr. 15
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  • 86
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    Gamma-ray astronomy in the medium energy (10-50 MeV) range (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: To observe the medium energy component of the intense galactic center gamma-ray emission, two balloon flights of a medium energy gamma-ray spark chamber telescope were flown in Brazil in 1975. The results indicate the emission is higher than previously thought and above the predictions of a theoretical model proposed.
    Keywords: ASTRONOMY
    Type: ESA Recent Advan. in Gamma-Ray Astronomy; p 117-124
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  • 87
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    Long-term X-ray studies of Scorpius X-1. I - Search for binary periodicity (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: No evidence for modulation of the Sco X-1 intensity between 3 and 6 keV at the optical period of 0.787313 day is found during one year of quasi-continuous observation. Any persistent X-ray modulation at this period must be less than one percent.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 205; Apr. 1
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  • 88
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    Survey of the BY Draconis syndrome among dMe stars (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Results are reported for a BVr photometric survey of 22 dK, dKe, dM, and dMe stars conducted to search for slow quasi-sinusoidal fluctuations in V (the BY Draconis syndrome). The (B-V) and (V-r) color indices are determined in an attempt to detect wavelength-dependent color changes produced by starspots and to infer starspot temperatures. It is found that nine of the stars exhibit variations in V of the order of 0.05 to 0.10 magnitude on a time scale of days or weeks, that at least three more display changes in mean light level over a period of years, that the stars generally tend to become redder at minimum light, and that some of the stars show no detectable color changes over their photometric cycle. The color data are taken to suggest a probable temperature difference of about 200 to 500 K between the stellar photospheres and starspots if the V variations are attributed to dark spots. It is concluded that the BY Draconis syndrome is clearly a very common occurrence among dMe stars.
    Keywords: ASTRONOMY
    Type: Astronomical Journal; 82; Nov. 197
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  • 89
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    Antenna concepts for interstellar search systems (1977)
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    Publication Date: 2011-08-17
    Description: An evaluation is made of microwave receiving systems designed to search for signals from extraterrestrial intelligence. Specific design concepts are analyzed parametrically to determine whether the optimum antenna system location is on earth, in space, or on the moon. Parameters considered include the hypothesized number of transmitting civilizations, the number of stars that must be searched to give any desired probability of receiving a signal, the antenna collecting area, the search time, the search range, and the cost. This analysis suggests that (1) search systems based on the moon are not cost-competitive, (2) if the search is extended only a few hundred light years from the earth, a Cyclops-type array on earth may be the most cost-effective system, (3) for a search extending to 500 light years or more, a substantial cost and search-time advantage can be achieved with a large spherical reflector in space with multiple feeds, (4) radio frequency interference shields can be provided for space systems, and (5) cost can range from a few hundred million to tens of billions of dollars, depending on the parameter values assumed.
    Keywords: ASTRONOMY
    Type: Radio Science; 12; Sept
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  • 90
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    Temporal X-ray astronomy with a pinhole camera (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Preliminary results from the Ariel-5 All-Sky X-Ray Monitor are presented, along with sufficient experiment details to define the experiment sensitivity. Periodic modulation of the X-ray emission is investigated from three sources with which specific periods have been associated, with the results that the 4.8 h variation from Cyg X-3 is confirmed, a long-term average 5.6 day variation from Cyg X-1 is discovered, and no detectable 0.787 day modulation of Sco X-1 is observed. Consistency of the long-term Sco X-1 emission with a 'shot-noise' model is discussed, wherein the source behavior is shown to be interpretable as about 100 'flares' per day, each with a duration of several hours. A sudden increase in the Cyg X-1 intensity by almost a factor of three on 22 April 1975 is reported, after 5 months of relative source constancy. The light curve of a bright nova-like transient source in Triangulum is presented, and compared with previously observed transient sources. Preliminary evidence for the existence of X-ray 'bursts' with duration less than 1 h is offered, with the caveat that there is not yet any supporting evidence to guarantee that the effect is truly astronomical.
    Keywords: ASTRONOMY
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  • 91
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    Search for X-ray emission from Nova Cygni 1975 (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: A search for X-rays from Nova Cygni 1975 was carried out before, during, and after the time of optical maximum. No X-rays were detected over the spectral range 0.1-50 keV. On the basis of these results a strong upper limit of .0001 has been placed on the ratio of X-ray to optical luminosity for this nova, consistent with effective temperatures of about 10,000 K. If Nova Cygni 1975 is a virgin nova, its low mass exchange rate would imply that any associated X-ray emission would not be detectable by present techniques.
    Keywords: ASTRONOMY
    Type: Nature; 261; May 20
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  • 92
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    Evaluation of a large radio-telescope array on the lunar farside (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Keywords: ASTRONOMY
    Type: Lunar Science Inst., Abstracts of Papers Presented at a Special Session of the Seventh Annual Lunar Science Conference on Utilization of Lunar Materials and Expertise for Large Scale Operations in Space; p 39-41
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  • 93
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    Positions of three X-ray burst sources (1977)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Precise (20-30 arcsec) positions are reported for three steady X-ray sources that have been identified recently as X-ray burst sources: 4U (MXB) 1636-53, 4U 1728-33 (MXB 1728-34), and 4U (MXB) 1735-44. The positions were derived from data obtained with the SAS 3 rotating modulation collimators during a survey of the galactic plane. Possible optical counterparts are noted.
    Keywords: ASTRONOMY
    Type: Nature; 270; Nov. 24
    Format: text
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  • 94
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    High-resolution rocket spectra of the 1920-A and 1720-A features in the spectrum of Zeta Tauri (1977)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: High-resolution ultraviolet spectrograms of the B-shell star Zeta Tau reveal two features characteristic of B supergiants, one at 1720 A and the other at 1920 A. The presence of these features in the spectrum of this object shows that they are indicative of an extended atmosphere - either the tenuous atmosphere of a supergiant or the envelope surrounding a rapidly rotating main-sequence star - and are therefore not purely luminosity criteria. The high spectral resolution allows an identification of the contributors to these features. The dominant contributor to the 1920-A feature is Fe III, while the primary contributor to the 1720-A feature is Al II.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 217
    Format: text
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  • 95
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    Trajectories and orbits from the NASA-NMSU Meteor Observatory. II (1977)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Trajectory data and orbital elements for 12 double-station meteors photographed by the NASA-NMSU Meteor Observatory during the winter of 1975-1976 are presented. Three of these are members of the Quadrantid stream. Photoelectric timing of meteors, uncertainties in the derived orbital elements, and monitoring of the night sky with a two-channel photometer are discussed.
    Keywords: ASTRONOMY
    Type: Astronomical Journal; 82; June 197
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  • 96
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    Optical contamination - Its prevention in the XUV spectrographs flown by the U.S. Naval Research Laboratory in the Apollo Telescope Mount (1977)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: During construction and testing of the XUV spectrographs flown in the ATM by the Naval Research Laboratory, many problems associated with optical contamination were encountered. Solving these problems required setting up a contamination prevention program to select the materials used in constructing the instruments and to delineate procedures in assembling, testing, and storing the instruments. A brief description is given of methods of assessing the effects of contamination and of the procedures used to prevent contamination.
    Keywords: ASTRONOMY
    Type: Applied Optics; 16; Apr. 197
    Format: text
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  • 97
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    Cooled infrared telescope development (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Because infrared astronomy will be significantly advanced by use of cooled telescopes in space, a study has been made of the design characteristics of a 1-m-aperture, cryogenically-cooled telescope for Spacelab. Feasibility of the concept has been assessed from the standpoint of the technology required for its fabrication and operation. The telescope's compatibility with the physical and operational characteristics of Spacelab and Shuttle has also been evaluated. The result is a satisfactory preliminary definition of payload and mission characteristics.
    Keywords: ASTRONOMY
    Type: Raumfahrtforschung; 20; Nov
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  • 98
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    Optical polarization of Nova Monocerotis 1975 /= A0620-00/ (1976)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: The linear polarization of the optical counterpart of the transient X-ray source A0620-00 is interstellar in magnitude, position angle, and wavelength dependence. The magnitude of the polarization is consistent with a distance greater than 1 kpc.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 210; Dec. 15
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  • 99
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    Evidence for a 16.6 day period from Circinus X-1 (1976)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: Analysis of All-Sky Monitor observations of Cir X-1 (3U 1516-56) over the period from October 1975 to April 1976 has revealed a well-defined modulation of the 3-6-keV flux at a period of 16.585(+ or - 0.01) days. The light-curve is characterized by an abrupt drop in emission occurring on a time scale of no more than about 0.07 day, with epoch JD 2,442,877.181(+ or - 0.07). No clear correspondingly sharp increase in emission is observed during the cycle, so a noneclipse origin for this effect cannot be ruled out.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 208; Sept. 1
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  • 100
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    Optical, infrared and radio studies of compact H II regions. I - The complex in S 106 (1976)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: The paper reports on combined optical, infrared, and radio observations of the compact complex S 106. The source could be resolved into ten components, three of which are compact components of size approximately 0.2 pc and were detected at 12.6 microns and 2.7 GHz. Two of the components are point-like sources detected at 8000 A. One of the components detected at 8000 A is spatially coincident with a strong 3.5 micron source and is suggested as a possible exciting star for the complex.
    Keywords: ASTRONOMY
    Type: Astronomy and Astrophysics; 51; 2, Se; Sept
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