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  • ASTROPHYSICS  (459)
  • 1995-1999
  • 1980-1984
  • 1975-1979  (459)
  • 1976  (459)
  • 101
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    Physical properties of interplanetary grains (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Morphological analyses of micrometeorite craters found on lunar rocks and laboratory simulation experiments are used to formulate a meteoritic interplanetary dust particle for optical scattering calculations that is roughly spherical and has a density of 2g cm/3. The model particle has chondritic elemental abundances and also contains a high content of finely dispersed carbon.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Study of Comets, Part 2; p 962-982
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  • 102
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    Orbital error analysis for comet Encke, 1980 (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Before a particular comet is selected as a flyby target, the following criteria should be considered in determining its ephemeris uncertainty: (1) A target comet should have good observability during the apparition of the proposed intercept; and (2) A target comet should have a good observational history. Several well observed and consecutive apparitions allow an accurate determination of a comet's mean motion and nongravitational parameters. Using these criteria, along with statistical and empirical error analyses, it has been demonstrated that the 1980 apparition of comet Encke is an excellent opportunity for a cometary flyby space probe. For this particular apparition, a flyby to within 1,000 km of comet Encke seems possible without the use of sophisticated and expensive onboard navigation instrumentation.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Study of Comets, Part 2; p 983-995
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  • 103
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    History of the dust released by comets (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The Finson-Brobstein theory is used to examine production and history of dust released from periodic comets and to compare dust size distribution in relation to the Zodiacal cloud. Results eliminate all of the bright new comets from contributors to the Zodiacal cloud. Among the periodic comets, all particles of size much smaller than 10 micrometer are also lost. Only the large particles remain as possible contributors.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Study of Comets, Part 2; p 943-948
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  • 104
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    The wind-sock theory of comet tails (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A method is reported for calculating the shapes of ionic comet tails that use the magnetic field along the tail to channel the tail plasma. The local momentum field in the solar wind determines magnetic field line locations along the tail. Thus, the magnetic field acts as a transparent wind sock in trapping field lines in the cometary plasma around the nucleus long enough to be effectively fastened to the comet's head.
    Keywords: ASTROPHYSICS
    Type: The Study of Comets, Part 2; p 878-892
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  • 105
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    Particles from comet Kohoutek detected by the micrometeoroid experiment on HEOS 2 (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: HEOS B measurements on particles ejected from comet Kohoutek reflect average particle rate as a function of particle speed and mass in relation to random distribution with known speed from the interplanetary region. The micrometeoroid experiment detector onboard the satellite passed through the orbital plane of the comet and encountered ejected particles for approximately two months.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Study of Comets, Part 2; p 949-961
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  • 106
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    Analysis of NH spectrum (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The A3Pi to X3Sigma- transition of NH is a common feature of cometary spectra. Since the NH molecule is likely to be formed by photodissociation of molecules such as ammonia or hydrazine, identifying the final states of the photolysis would shed light on the identity of the parent. It is shown that the transition rate for the a 1Delta to X3Sigma- transition is sufficiently fast to deplete any a1Delta concentration formed in the original photolysis process. This analysis focused on experimental spectra obtained for the comet Kohoutek. The fluorescence pumping of the NH molecule is calculated for November 29, 1973 and January 25, 1974 using the model of radiative equilibrium which assumes no collisions.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Study of Comets, Part 2; p 848-852
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  • 107
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    Interpretation of comet spectra (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The spectra of comets are discussed by considering successively a number of molecules that have been studied recently: CN, CH, C2, C3, OH, CH(+). The first two of this list, CN and CH, have been analyzed in greatest detail. A classification of the spectra of cometary heads is introduced.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Study of Comets, Part 2; p 797-838
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  • 108
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    Neutral temperature of cometary atmospheres (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Spectral analyses of the coma and type I tails of a comet indicate that the main constituent of a cometary atmosphere is H2O and that cometary nuclei are composed of dirty ice containing mainly CO and N2. Thermochemical calculations on strong infrared coupling between H2O and dust grains explain the dependence of atmospheric temperature on the distance of the comet from the sun considering the strong cooling effect of H2O. It is concluded that atmospheric temperatures of comets cannot be so high as 1500 K.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Study of Comets, Part 2; p 763-772
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  • 109
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    Gas phase chemistry in comets (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The significance of gas phase reactions in determining the nuclear structure of comets is discussed. The sublimation of parent molecules such as H2O, CH4, CO2, and NH3 from the surface of the nucleus and their subsequent photodissociation and ionization in forming observed cometary molecular species are elaborated.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Study of Comets, Part 2; p 753-762
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  • 110
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    The neutral coma of comets: A review (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The hypothesis that water snow controls the vaporization of the nucleus of some comets seems verified from the general order of magnitude of the size of their nucleus and of their nuclear albedo; the largest observed production rates are H and OH which both seem to originate from the photodissociation of H2O, as also confirmed by the scale length of the invisible parent molecule producing OH. However, comet Encke is not uniformly covered by water snow, as it produces only one tenth of the expected vaporization. Early results on comet Kohoutek suggest that the conclusions could be slightly different for some of the new comets in Oort's sense. If the far ultraviolet observations confirm the early assessments of the production rates of C, O and H, then at least another major constituent competing with water has not yet been detected. Such a major constituent is suggested by the ratios C/O = 0.24 and H/O = 2.5.
    Keywords: ASTROPHYSICS
    Type: The Study of Comets, Part 2; p 711-752
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  • 111
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    Laboratory observations of the photochemistry of parent molecules: A review (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The photochemistry of possible parent molecules of comets has been reviewed. Quantum yields for many of the primary processes are unknown. Energy partitioning among the fragments has not been extensively investigated. A few of the studies have been performed as a function of the number of collisions that the excited molecules undergo, so that possible differences that may occur in a cometary environment may be ascertained.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Study of Comets, Part 2; p 679-704
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  • 112
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    Laser induced photoluminescence spectroscopy of cometary radicals (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Flash photolysis together with laser excitation of the product fragments was used in laboratory studies of cometary radicals. The LIPS method has been applied to the CN radical to determine: (1) Radiative lifetimes of individual rotational levels in the zeroth vibrational level of the B state; (2) energy partitioning during photodissociation of C2N2; and (3) vibrational and rotational excitation during formation of CN radicals in the photodissociation of dicyanoacetylene.
    Keywords: ASTROPHYSICS
    Type: The Study of Comets, Part 2; p 706-710
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  • 113
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    Comets, interstellar clouds and star clusters (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The association of comets with star formation in clusters is elaborated. This hypothesis is also used to explain origin and evaluation of the Oort cloud, the composition of comets, and relationships between cometary and interstellar molecules.
    Keywords: ASTROPHYSICS
    Type: The Study of Comets, Part 2; p 663-672
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  • 114
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    On the origin of comets (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Physico-chemical processes leading to the dynamic formation and physical evolution of comets are reviewed in relationship to the various theories that propose solar origins, protoplanetary origins, planetary origins and interstellar origins. Evidence points to the origins of comets by the growth and agglomeration of small particles from gas and dust at very low temperatures at undetermined regions in space.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Study of Comets, Part 2; p 638-662
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  • 115
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    A continuing controversy: Has the cometary nucleus been resolved? (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Evidence is presented for classifying cometary nuclei into two basic types, described by core mantle and coreless models. Mass loss related nongravitational effects in a comet's motion as a function of time are included in considering gradual evaporation of an icy envelope surrounding the meteoric matrix in the core of the nucleus.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Study of Comets, Part 2; p 537-585
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  • 116
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    Review of investigations performed in the USSR on close approaches of comets to Jupiter and the evolution of cometary orbits (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Methods are reviewed for calculating the evolution of cometary orbits with emphasis on the orbital changes that take place when comets pass within the spheres of action of giant planets. Topics discussed include: differences and difficulties in methods used for the calculation of large perturbations by Jupiter; the construction of numerical theories of motion covering the whole period of observations of each comet, allowing for planetary perturbations and the effects of nongravitational forces; and investigations of the evolution of cometary orbits over the 400 year interval 1660-2060. The classical theory of cometary capture is briefly discussed.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Study of Comets, Part 1; p 490-536
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  • 117
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    The evolution of comet orbits (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The origin of comets and the evolution of their orbits are discussed. Factors considered include: the law of survival of comets against ejection on hyperbolic orbits; short-period comets are not created by single close encounters of near-parabolic comets with Jupiter; observable long-period comets do not evolve into observable short-period comets; unobservable long-period comets with perihelia near Jupiter can evolve into observable short-period comets; long-period comets cannot have been formed or created within the planetary region of the solar system (excluding the effects of stellar perturbations); it is possible that some of the short-period comets could have been formed inside the orbit of Neptune; circularly-restricted three-body problem, and its associated Jacobi integral, are not valid approximations to use in studying origin and evolution of comets.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Study of Comets, Part 1; p 445-464
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  • 118
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    Nongravitational forces on comets (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Methods are presented and discussed for determining the effects of nongravitational forces on the orbits of comets. These methods are applied to short-period and long-period comets. Results are briefly described.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Study of Comets, Part 1; p 465-488
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  • 119
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    Luminosity and astrometry of comets: A review (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Visual and photographic observations of the brightness of comets are reviewed including methods and sources of errors. Nuclear magnitude estimates are discussed and interpreted in relation to determination of appropriate exposure times for photographic observations. The importance of brightness ephemarides is emphasized.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Study of Comets, Part 1; p 380-409
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  • 120
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    Comet brightness parameters: Definition, determination, and correlations (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The power-law definition of comet brightness is reviewed and possible systematic influences are discussed that can affect the derivation of m sub o and n values from visual magnitude estimates. A rationale for the Bobrovnikoff aperture correction method is given and it is demonstrated that the Beyer extrafocal method leads to large systematic effects which if uncorrected by an instrumental relationship result in values significantly higher than those derived according to the Bobrovnikoff guidelines. A series of visual brightness parameter sets are presented which have been reduced to the same photometric system. Recommendations are given to insure that future observations are reduced to the same system.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Study of Comets, Part 1; p 410-444
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  • 121
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    A kinematographic study of the tail of comet Kohoutek (1973f) (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Observations of comet Kohoutek made in the Southwest U.S., Alaska and Hawaii were combined to produce a movie of the cometary tail. Plasma tail motions seen in the movie are described. Features of the plasma tail discussed include: tail rays; wave trains; and condensations and kinks.
    Keywords: ASTROPHYSICS
    Type: The Study of Comets, Part 1; p 370-377
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  • 122
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    Review: Observations of recent comets, ion tails (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Photographic plates of the moving structures in the cometary tail are examined. Several divergent explanations for the case of comet Kohoutek are presented. It is suggested that these hypotheses be tested by observing the motion of the material spectroscopically by means of the Doppler effect.
    Keywords: ASTROPHYSICS
    Type: The Study of Comets, Part 1; p 361-369
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  • 123
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    Photometric observations of recent comets (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Infrared observations of comet Bennett, Kohoutek, Bradfield, and Encke are analyzed with emphasis on the detection of the silicate emission feature. Results are summarized.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Study of Comets, Part 1; p 334-356
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  • 124
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    Radio detection of H2O in comet Bradfield (1974b) (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Results of observations of comet Bradfield using the Haystack telescope are summarized with emphasis on the detection of the 1.35 cm emission line of water in the comet. The excitation of water and methyl cyanide in comets is briefly considered.
    Keywords: ASTROPHYSICS
    Type: The Study of Comets, Part 1; p 272-280
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  • 125
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    Spectrophotometry of comet Kohoutek (1973f) during pre-perihelion period (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Scans of the head of comet Kohoutek obtained during the pre-perihelion period with a photoelectric spectrum scanner are discussed. The mean relative flux distributions and the continuum energy distribution of the head of comet Kohoutek are given and normalized to 479 nm. The emission features of CN, C3, Ch, and the principal Swan band sequences of C2 and Na are identified and discussed. The adopted monochromatic values relative to 479 nm are given and plotted along with the energy distribution of the sun.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Study of Comets, Part 1; p 220-231
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  • 126
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    H2O(+) ions in comets: Comet Kohoutek (1973f) and comet Bradfield (1974b) (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The image tube Cassegrain slit spectra of comet Kohoutek and Bradfield calibrated and reduced to relative intensities are discussed. Monochromatic changes in the surface brightness for various neutral and ionized molecules are determined. The intensities of C2 and CN decreased approximately four times faster than the intensity change for the H2O(+) features. It is shown that the excitation mechanism for the observed H2O(+) bands is by fluorescent scattering of the incident solar radiation. The effects of solar activity on the photoionization rate of H2O in a comet are discussed. Observations of another bright comet at the time of maximum solar activity are needed to determine changes in band intensities of comet tail ions due to solar activity.
    Keywords: ASTROPHYSICS
    Type: NASA Goddard Space Flight Center The Study of Comets, Part 1; p 199-205
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  • 127
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    Spectroscopic observations of comet Kohoutek (1973f), 2 (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Spectroscopic observations of comet Kohoutek at the Asiago Astrophysical Observatory are described. Spectra cover six nights before perihelion and five nights after perihelion. The spectra of the coma and tail of comet Kohoutek are characterized by fairly strong, asymmetric H2O(+) emissions in the red and the near infrared spectral regions and by the appearance of the 01 forbidden lines at 6300-6364 A, already at heliocentric distance r=1.55 A.U. These peculiarities suggest that some differences in chemical abundances or in physical conditions exist between comet Kohoutek and other comets.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Study of Comets, Part 1; p 185-198
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  • 128
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    Spectroscopic observations of comet Kohoutek (1973f) (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Coude spectrograms of comet Kohoutek obtained with the ESO 152-cm telescope in La Silla, Chile are discussed. Emission features of the C3, CH, and CO(+) molecules found in the blue region of the spectrum are considered along with measured emissions in the visual region of the spectrum. The observational and cometary data are given in tabular form.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Study of Comets, Part 1; p 159-181
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  • 129
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    Review of cometary spectra (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The spectra of comet Kohoutek, comet Bradfield, and comet Mrkos are reviewed and compared in relation to stellar spectroscopy and evolution. The possibility of observing the absorption spectrum of a comet and direct measurement of Doppler shifts due to expansion or streaming motions in comets are considered along with the spectra of giant comets, such as, comet Minkowski, comet Baade, and comet Lovas. A speculative explanation for possible intrinsic abundance differences between comets is given.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Study of Comets, Part 1; p 136-158
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  • 130
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    Comet data collections (1976)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: Various collections of comet observational material are discussed in terms of developing a data base. Emphasis is placed on observational material buried in the archives of the older observatories.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Study of Comets, Part 1; p 127-135
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  • 131
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    Narrow band photometry of comet Kohoutek (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Photometric observations of the coma of comet Kohoutek were made at the Cassegrain focus of a 36-inch telescope. The observations consisted of one wide (visual, 5454 A) and six narrow (CN, 3879 A; C3, 4057 A; C2, 4732 A, 5165 A, 5634 A; continuum, 5200 A) band interference filters. In addition each filter was used with six diaphragms. Good quality data were obtained on 13 days between November 1973 and February 1974. A small flare was observed on 1 December for all filters, a CN flare on 13 January, and a visual flare on 28 January. The data were reduced to absolute narrow band magnitudes of the comet for the 13 days. The radial dependence of the surface brightness was derived from the set of diaphragms and future work will be directed toward using these results for modeling density distributions for the coma.
    Keywords: ASTROPHYSICS
    Type: The Study of Comets, Part 1; p 70-91
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  • 132
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    Photoelectric photometry of comet Kohoutek (1973f) (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Comet Kohoutek was observed with the 50 cm (f/15) reflecting telescope of the European Southern Observatory, La Silla, Chile, on fourteen nights between January 16 and 30, when the heliocentric and geocentric distances of the comet were r=0.66 - 1.00 A.U. and delta=0.81 - 0.96 A.U., respectively. The 40 inch and 80 inch diaphragms were used for the photometry of the cometary head in the UBV system and with six interference filters. The atmospheric conditions were good but the accuracy of observations was low due to large extinction and twilight. The mean error of one measurement of log F in all but Na 5893 A filters can be estimated at plus or minus 0.02, whereas the accuracy through the Na filter was substantially lower.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Study of Comets, Part 1 1976; p 50-69
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  • 133
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    Photometry of the cometary atmosphere: A review (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Photometry and polarimetry of the cometary heads one of the most important sources of information about the physical processes in comets is reviewed. Methods of inspection discussed include: narrow band photometry, wide band photometry, color photography, tilting filter techniques, and photoelectric spectrum scanning. Results of photoelectric observations of comets are described including photoelectric and infrared measurements of comet Kohoutek. Photometric profiles of the coma in monochromatic light are used to determine the lifetime of the parent molecules for the observed radicals, CN and C2.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Study of Comets, Part 1; p 1-49
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  • 134
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    Velocity dispersions in galaxies. V - The nuclei of M31 and M32 (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Stigmatic spectra between 4160 and 4385 A of the central regions of M31 and M32 as well as the K0 III star 51 Ori are presented which were obtained using a SEC-vidicon integrating television tube and the coude spectrograph of the Hale telescope. Line-of-sight velocity dispersions of approximately 130 and 55 km/s are determined for the nuclei of M31 and M32, respectively, by directly comparing their spectra with Gaussian-broadened spectra of 51 Ori. The analytical techniques are outlined, and alternative methods for estimating velocity dispersions are evaluated, including least-squares fitting of intensities and division of Fourier transforms. It is noted that the broadened spectrum of 51 Ori fits the nucleus of M32 and the bulge of M31 much better than the nucleus of M31 in the region between 4180 and 4370 A.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 205; Apr. 1
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  • 135
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    Optical and infrared spectrophotometry of 18 Markarian galaxies (1976)
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    Publication Date: 2019-06-27
    Description: Slit spectra, spectrophotometric scans, and infrared broad-band observations are presented for 18 Markarian galaxies with emission lines. Eight of the program galaxies can be classified as Seyfert galaxies. Arguments are given that thermal, nonthermal, and stellar radiation components are present. Broadly speaking, one group of Seyfert galaxies is characterized both by the presence of a high-density region of gas and by a continuum dominated by nonthermal radiation. The continua of the remaining program Seyferts, which do not have a high-density region of gas, are dominated by thermal radiation from dust and a stellar continuum. The 10 galaxies which are not Seyfert galaxies are shown to be examples of extragalactic H II regions; there is evidence for thermal emission from dust being present at 10 microns in four of these galaxies.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 205; Apr. 1
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  • 136
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    Encounters of spherical galaxies. I - Galaxy models with one stellar population. II - Galaxy models with two stellar populations (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Close encounters between two spherical galaxies of equal size and consisting of only one stellar population are calculated using models of elliptical galaxies constructed according to King's (1966) method. The mass loss and the change in internal energy are computed under the assumption that the stars do not change their velocity or density distributions during the encounters. The results for a specific case are compared with the calculations of Gallagher and Ostriker (1972), who employed the observed brightness distribution and the derived density distribution of the E1 galaxy NGC 3379. For models with one stellar population, the results suggest that the radius of a galactic halo would have to be at least 200 kpc for appreciable mass loss to occur over the history of a galaxy in a rich cluster. The calculations are then extended to include a halo population characterized by a high central velocity dispersion. In this case, it is found that the halo population of sufficiently large galaxies can be dispersed without appreciably affecting the main population. It is suggested that the missing mass of many clusters of galaxies may be located in an intergalactic sea of faint stars making up an envelope for the centrally located gE galaxies.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics; 48; 2, Ap; Apr. 197
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  • 137
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    2290-MHz flux densities of 52 high-declination radio sources (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal; 81; Apr. 197
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  • 138
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    The detection of interstellar OH absorption in the Zeta Ophiuchi cloud (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 204; Mar. 15
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  • 139
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    H2CO emission at 2 millimeters in dark clouds (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The paper reports the detection of the 2-mm emission line due to the 2(12)-1(11) transition of H2CO at two positions in the Taurus dark cloud and one position in the dark cloud L134 N. The profiles of the observed emissions are plotted, and peak radiation temperatures at 2 mm are determined for the three positions. These radiation temperatures are used along with data on the 2-mm H2CO absorption line and computed cross sections for H2-H2CO collisions to deduce the molecular hydrogen density and the ortho-H2CO column density in the two clouds. The results are shown to support previous theoretical estimates of the H2CO/H2 and the H2(C-12)O/H2(C-13)O ratios. It is concluded that if the abundances of CS and HCN in the clouds are equal to that of H2CO, emissions from these molecules should be easily detectable.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 204; Mar. 15
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  • 140
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    Detection of X-ray emission from the remnant of the supernova 1006 A.D. (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Results are reported for OSO-7 observations which positively identify the supernova remnant SN 1006 as a weak source of X-ray emission. Acceptable fits to the spectrum are obtained for both a power law with an energy index of about -2.3 and for thermal bremsstrahlung at a temperature corresponding to about 4 keV. The X-ray intensity over the range from 1 to 10 keV is found to be about 9 by 10 to the -11th power erg/sq cm per sec, and it is assumed that the X-rays originate in a plasma shell 4.4 pc in radius and heated by an expanding blast wave. The distance of SN 1006 is estimated as 1.2 kpc, its X-ray luminosity (1-10 keV) as about 1.6 by 10 to the 34th power erg/sec, and its initial kinetic energy as of the order of 10 to the 50th power ergs. It is noted that the reverse-shock model of X-ray production is also consistent with the data and that SN 1006 is the only supernova remnant for which both X-ray and radio emission have been detected, but no optical filaments have been observed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 204; Mar. 15
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  • 141
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    Copernicus observations of Betelgeuse and Antares (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The Mg II h and k lines were observed strongly in emission by Copernicus scans of the M supergiants alpha Ori and alpha Sco. The striking symmetry in the k line as contrasted with the symmetric h line, as observed previously was confirmed. Estimates of absolute chromospheric fluxes were obtained. Measured values for the widths of the h and k lines do not follow a Wilson-Bappu relationship. Upper limits determined for other chromospheric lines of alpha Ori tend to exclude the existence of extensive and/or hot regions surrounding this supergiant. Observed weakening by fluorescence of the Fe L 4307 A line is good evidence that the Mn I and Fe I resonance transitions overlying the Mg II k-line profile are responsible for the strong asymmetry of this line in the two stars. However, quantitative study shows that the absorption provided by the cool circumstellar shells is insufficient to provide the observed asymmetry. Additional absorption may be provided by a cool turbulent region at the top of the chromosphere.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 204; Mar. 15
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  • 142
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    An analysis of the interstellar material in the line of sight toward Omicron Persei (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Chemical abundances and physical conditions in the interstellar gas toward Omicron Per are analyzed using Copernicus UV spectrophotometric data on 69 lines due to ions and atoms as well as 19 lines of H2 and HD. The UV extinction toward the star is determined along with the column densities of atomic and molecular hydrogen, the atomic column densities and temperature in the H I region, and the nature of the ionized regions along the line of sight. It is concluded that: (1) Omicron Per is apparently embedded in the near edge of an extended dense molecular cloud, the outer parts of which give rise to the observed absorption lines; (2) the H I region may consist of more than one cloud; (3) the far-UV extinction rise is unusually steep, indicating a high proportion of small grains; (4) the element depletions are somewhat greater than in Zeta Oph, particularly for sulfur and argon; and (5) the molecular abundances are generally consistent with gas-phase formation models rather than with molecular formation on grain surfaces, unless a substantial amount of small grains is present to increase the available surface area.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 204; Mar. 15
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  • 143
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    On the existence of molecular hydrogen along lines of sight with low reddening (1976)
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    Publication Date: 2019-06-27
    Description: The existence of molecular hydrogen along lines of sight with low reddening (B-V color excesses not exceeding 0.03) is discussed for the stars HD 28497, Mu Col, Alpha Vir, Beta Cen, and Lambda Sco. The main observations are of the R(1) features, which for effective rotational temperatures above 200 K are the dominant source of H2 transitions. If the formation process for molecular hydrogen is similar to that for regions of greater reddening, the observations indicate that the neutral gas outside standard clouds may be partially in small clouds, though a more diffuse component seems to exist in some cases. Extremely high rotational temperatures are inferred for the H2 toward HD 28497. The possibility of formation of H2 through the reaction H(-) + H yields H2 + e(-) is briefly discussed. In any case, only small regions seem to contribute to the observed H2 column density.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 204; Mar. 15
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  • 144
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    Components in interstellar molecular hydrogen (1976)
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    Publication Date: 2019-06-27
    Description: Results are reported for precise spectrophotometric measurements of the profiles of selected Lyman absorption lines produced by hydrogen molecules in various rotational levels along the line of sight to 13 stars which have shown some evidence for an increase in line width with increasing rotational quantum number (J). The line profiles were measured by multiple scans with the Copernicus satellite telescope. Based on analysis of the radial velocities, derivations of the column densities, and line-profile fitting, the following conclusions are made: (1) the increase in interstellar H2 line width with increasing J results from the presence of the most shortward component, which is relatively weak at low J but becomes more important at higher J; (2) the relative column densities found for the different J levels in each component may be fitted by a theoretical model in which rotational excitation is due to absorption of UV photons followed by radiative quadrupole spontaneous transitions or collisionally induced downward transitions between different J levels; (3) the atomic hydrogen density is between 300 and 1000 per cu cm in the most shortward component for each of three stars; (4) the approaching gas which produces each shortward component must be in the form of thin sheets; and (5) the sheets are the compressed gas behind a shock front moving through the interstellar medium.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 204; Mar. 15
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  • 145
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    Jupiter's magnetotail as the source of interplanetary Jovian MeV electrons observed at earth (1976)
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    Publication Date: 2019-06-27
    Description: The source of interplanetary Jovian MeV electron enhancements observed at earth is found to be Jupiter's magnetotail. If an average solar wind speed of 400 km/sec is assumed, the main region of emission extends from about 1.0 AU downstream from Jupiter to about 2.0 AU beyond the planet. (If a value of 350 km/sec is assumed, it extends from about 0.4 AU to about 1.2 AU.) Individual 'active' zones are about 0.2 AU in length. It is proposed that interplanetary magnetic field line connection with the tail is the mechanism providing the Jovian electrons observed at earth.
    Keywords: ASTROPHYSICS
    Type: Geophysical Research Letters; 3; Apr. 197
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  • 146
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    Radio continuum measurements of compact H II regions and other sources (1976)
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    Publication Date: 2019-06-27
    Description: Results are reported for measurements of the flux densities of 33 sources at wavelengths of 13, 4, and 2 cm, which were conducted using the NASA/JPL Deep Space Network 64-m antenna at Goldstone, Calif. Besides compact H II regions, the sources included five Uhuru X-ray sources, several IR sources, an extragalactic radio source, and a H2O maser. The Lyman continuum flux is derived from the measured radio flux and the assumed distance and temperature for 10 possible H II regions; the spectra of previously known sources are extended to higher frequencies, and upper limits are placed on the flux densities for the five X-ray sources. New compact H II regions are found in the bright nebula M78, the nebula K5, and the Ophiuchus dark cloud/IR region.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal; 81; Mar. 197
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  • 147
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    Studies of the average pulse shape of Centaurus X-3 in the 2-20 keV range (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 204; Mar. 1
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  • 148
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    On the flux and the energy spectrum of interstellar ions in the solar system (1976)
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    Publication Date: 2019-06-27
    Description: The flux density of ions created by ionization of interstellar neutral particles in the solar system and picked up by the solar wind is calculated as a function of the neutral particles. For atomic hydrogen the flux density is estimated to exceed 10,000/sq cm/sec over the distance range from a few to nearly 100 AU. The velocity space distribution of the interstellar ions is calculated under the assumption of no significant energy diffusion but with inclusion of adiabatic effects as well as a possible strong pitch angle diffusion. The energy spectrum is highly nonthermal and much broader than that of the solar wind ions; interstellar protons are easily distinguishable from solar wind protons by their location in velocity space. If charge exchange is an important contributor to the ionization of hydrogen, the observed local intensity of interstellar protons should exhibit time variations correlated with the density changes of the solar wind stream structure.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research; 81; Mar. 1
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  • 149
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    High-resolution radio observations of three supernova remnants (1976)
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    Publication Date: 2019-06-27
    Description: The paper presents and discusses radio observations of three supernova remnants (G21.5-0.9, G29.7-0.3, and 3C 391) made at 3.7 and 11.1 centimeters. The supernova remnant G21.5-0.9 has an elliptical brightness distribution and is similar to the Crab Nebula as well as 3C 58 in appearance and spectrum. The two remnants G29.7-0.3 and 3C 391 both show a broken shell structure typical of most galactic supernova remnants.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 204; Mar. 1
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  • 150
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    Magellan - A balloon-borne collection technique for large cosmic dust particles (1976)
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    Publication Date: 2019-06-27
    Description: The paper describes a balloon-borne system for collecting large (50 to a few hundred micrometers in the major dimension) solid particles falling through the atmosphere at an altitude of about 30 km which are postulated to be fragments of larger cosmic particles or bodies which disintegrate on entering the atmosphere. The major component of the system is the collection surface - a funnel, 7.2 m in diameter, fabricated from mylar, 12 microns thick, and lightly coated with aluminum. Also described is the sample collector, which collects the particles gathered in the apex of the cone. Two successful flights of short duration using zero-pressure balloons have been achieved. Some examples of particles collected are shown. Mg, Al, Si, S, K, Ca, Ti, and Fe have been detected in these particles by energy dispersive X-ray analysis.
    Keywords: ASTROPHYSICS
    Type: Canadian Journal of Physics; 54; Feb. 1
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  • 151
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    On the detection of a cometary mass distribution (1976)
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    Publication Date: 2019-06-27
    Description: The problem of detecting a possible cometary distribution on the fringes of the solar system is examined. The acceleration of a space probe due to a hypothetical cometary mass distribution with the surface density rising to a maximum and subsequently falling off with increasing distance from the sun is analyzed. The total minimum detectable cometary mass for the Pioneer and Mariner spacecraft is estimated on the basis of this model to be on the order of 1000 earth masses. Precision tracking of deep space probes is less sensitive by three orders of magnitude for the detection of an unseen cometary mass distribution at the fringes of the solar system than are the secular perturbations of long-period comets.
    Keywords: ASTROPHYSICS
    Type: Icarus; 27; Jan. 197
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  • 152
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    An observation of the diffuse soft X-ray/extreme-ultraviolet background (1976)
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    Publication Date: 2019-06-27
    Description: Results are reported for observations of diffuse radiation in the spectral bands from 114 to 150 A and from 44 to 120 A, which were made with rocket-borne proportional counters in areas of the sky near galactic coordinates 150 deg longitude, -15 deg latitude and 189 deg longitude, 3 deg latitude. The observed fluxes are 0.125 photon per sq cm/s/sr/eV at 180 eV, which is consistent with previous measurements, and 3.2 photons per sq cm/s/sr/eV at 100 eV, which indicates a steeply rising spectrum. It is noted that these fluxes are significantly smaller than those detected by Yentis et al. (1972), and the differences are attributed to either a terrestrial origin of the fluxes or the direction of observation. Constraints are placed on the parameters of simple emission models of celestial origin, and a rigorous upper limit is determined for the space density of white dwarfs at a blackbody temperature of at least 100,000 K.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 204; Feb. 15
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  • 153
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    Radiative cooling of a low-density plasma (1976)
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    Publication Date: 2019-06-27
    Description: The paper extends and improves the radiative cooling coefficient calculations of Cox and Tucker (1969) and Cox and Daltabuit (1971) for a low-density optically thin plasma with no molecules or dust, of cosmic abundances in the range from 10,000 to 100,000,000 K. Earlier rates applied to a plasma containing H, He, C, N, O, Ne, Mg, Si, and S; the present study added Ca, Fe, and Ni. For the elements included, many individual lines are calculated which previously has been averaged together. The cooling processes considered are permitted, forbidden, and semiforbidden line transitions, including contributions from dielectronic recombination and bremsstrahlung, radiative recombination, and two-photon continua. The ionization balance is calculated in collisional equilibrium using an approximate auto-ionization following inner-shell excitation and the low-density limit for the dielectronic recombination rate. Cooling in various observational bands in the soft X-ray region is determined.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 204; Feb. 15
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  • 154
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    A statistical method for treating molecular line opacities (1976)
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    Publication Date: 2019-06-27
    Description: A method for treating atomic and molecular line opacities in cool stellar atmospheres by a statistical opacity sampling is investigated. Under the usual assumptions of plane-parallel geometry, radiative equilibrium, hydrostatic equilibrium, and LTE, each radiative quantity is computed monochromatically at each chosen frequency and depth without any averaging of the opacity. The number of frequencies needed to allow an accurate integration of the energy flux over a given spectral interval is investigated as a function of depth, including opacity for both CN and C2. This method is extended to the calculation of a model atmosphere of a star, and the effect of the number and placement of frequency points is studied. The method is applied to treating molecular lines of CO, C2, and CN in a cool carbon star. Significant advantages of the opacity sampling method are its flexibility, which permits computation of models having arbitrary variations of chemical composition and of opacity with wavelength and depth, and generalizability to include departures from LTE.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 204; Feb. 15
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  • 155
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    Interstellar molecular hydrogen toward zeta Puppis (1976)
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    Publication Date: 2019-06-27
    Description: This paper reports the measurement of some 136 interstellar H2 absorption lines found in a continuous scan of the far-ultraviolet spectrum of zeta Pup at 0.05-A resolution with the Copernicus telescope. Absorptions from only the rotational levels 0 to 5 of the lowest vibrational state of the ground electronic state were observed. The total H2 column density is 2.8 by 10 to the 14th power molecules/sq cm; the ratio of H nuclei in H2 to the number in H I plus molecules is 6 by 10 to the -6th power; the population of the rotational levels can be represented by a single excitation temperature of 1120 (plus or minus 80) K. The radial velocities of all rotational levels were the same within 7 km/s and differed from most atoms and first ions by no more than 4.5 km/s on the average. The tables also list the best available data on wavelengths, oscillator strengths, and radiative damping constants for all the H2 lines with zero vibrational level likely to be observed in the interstellar gas.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 204; Feb. 15
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  • 156
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    New test of the equivalence principle from lunar laser ranging (1976)
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    Publication Date: 2019-06-27
    Description: An analysis of six years of lunar-laser-ranging data gives a zero amplitude for the Nordtvedt term in the earth-moon distance yielding the Nordtvedt parameter eta = 0.00 plus or minus 0.03. Thus, earth's gravitational self-energy contributes equally, plus or minus 3%, to its inertial mass and passive gravitational mass. At the 70% confidence level this result is only consistent with the Brans-Dicke theory for omega greater than 29. We obtain the absolute value of beta - 1 less than about 0.02 to 0.05 for five-parameter parametrized post-Newtonian theories of gravitation with energy-momentum conservation.
    Keywords: ASTROPHYSICS
    Type: Physical Review Letters; 36; Mar. 15
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  • 157
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    On the detectability of gravitational waves from W Ursae Majoris binary stars (1976)
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    Publication Date: 2019-06-27
    Description: The possibility is considered of using the collective gravitational radiation from all the W UMa binary stars in the Galaxy for critical tests of gravitational theories. The class of detectors which respond to the Riemann tensor is briefly examined, and the detectability of the cited radiation is analyzed. It is shown that the random stress field due to gravitational waves from all the W UMa binaries in the Galaxy will not be detectable in the near future because of interference from local gravity gradients.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 203; Feb. 1
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  • 158
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    The dynamics of the intergalactic medium in the vicinity of clusters of galaxies (1976)
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    Publication Date: 2019-06-27
    Description: Numerical solutions to the problem of infall of matter into clusters of galaxies are presented. It is assumed that the universe can be described by a Friedmann cosmological model with a Hubble constant 50 km/s/Mpc. It is found that physically reasonable models having a deceleration parameter of 1/2 lead to excessive X-ray emission from clusters of galaxies. Models including a heat flux due to thermal conduction, heating of the intracluster medium by galaxy motions, and a gas outflow from the galaxies in the cluster are discussed, and the results are compared with the observational data in both the X-ray and radio bands. It is concluded that the density parameter must be less than 0.2 in order that the predicted X-ray emission not exceed that observed. No models have been found which give a good description of the observed cluster X-ray sources, with the exception of a fully adiabatic model in a high-density universe.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 203; Feb. 1
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  • 159
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    On the masses of the quasi-stellar objects (1976)
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    Publication Date: 2019-06-27
    Description: Current estimates of quasar masses are based on the idea that the objects are outbursts involving galaxies or on the argument that the conversion of mass into radiant energy requires a minimum mass. These estimates are contrasted with those that can be obtained by considering the dynamics of the gas in the regions surrounding the highly compact nonthermal central source. In the analysis, it is assumed that absorption arises in gas clouds associated with quasars and that the emission- and absorption-line regions are being driven by radiation pressure. The results demonstrate that the masses of cosmologically distant quasars must lie between 50 million and 2 billion solar masses and that the mass-loss rate should be about one ten-millionth part per year. If the quasars are local objects, the upper mass limit is reduced to about 20 million solar masses. It is noted that these masses are significantly less than the masses of galaxies, but might be appropriate for galactic nuclei.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 205; Apr. 15
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  • 160
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    Absolute measurement of the photoionization cross section of atomic hydrogen with a shock tube for the extreme ultraviolet (1976)
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    Publication Date: 2019-06-27
    Description: The paper reports an experiment which is part of a program to measure the absolute values of the atomic photoionization cross sections of astrophysically abundant elements, particularly in stars and planetary atmospheres. An aerodynamic pressure-driven shock tube constructed from stainless steel with a quadratic cross section was used to measure the photoionization cross section of H I at 19 wavelength points from 910 to 609 A with experimental uncertainties between 7 and 20%. The shock tube was used to produce fully dissociated hydrogen and neon mixtures for the photoabsorption measurements.
    Keywords: ASTROPHYSICS
    Type: Physical Review A - General Physics; vol. 13
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  • 161
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    Resonance-line transfer with partial redistribution. VIII - Solution in the comoving frame for moving atmospheres (1976)
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    Publication Date: 2019-06-27
    Description: The effects of partial frequency redistribution in the scattering process for lines formed in moving atmospheres are analyzed using a general method that allows the transfer equation to be solved in the comoving frame of the gas. The same chromospheric and atomic model studied by Cannon and Vardavas (1974) is employed in the calculations, but a depth scale with logarithmically spaced points is adopted. It is found that in both static and moving atmospheres, the profiles obtained with complete and partial frequency redistribution are virtually identical. The large differences in profiles obtained by Cannon and Vardavas when they used complete and partial redistribution are shown to be spurious (and physically unreal) effects resulting from angle averaging in the observer's frame instead of the comoving frame.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 205; Apr. 15
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  • 162
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    Color gradients in the nuclear region of M31 (1976)
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    Publication Date: 2019-06-27
    Description: Spectrophotometric measurements of the nuclear region of M31 under conditions of excellent seeing with M31 near the zenith and using a 3.8-9.9-in. diameter entrance annulus for the bulge along with a 3.6-in. aperture for the nucleus, show that the nuclear region is only slightly redder and shows marginally stronger CN blends than the bulge. The data can be interpreted in terms of an increase in heavy-element abundance toward the center of M31 by a factor substantially less than two.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 205; Apr. 15
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    The interpretations of ultraviolet observations of comets (1976)
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    Publication Date: 2019-06-27
    Description: The paper summarizes recent cometary UV observations, most of which were made in Ly-alpha light with instruments aboard earth-orbiting satellites. These include OAO-2 observations of comets Bennett and Tago-Sato-Kosaka, OGO-5 observations of comets Bennett and Encke, and numerous observations of comet Kohoutek. Models for the production of cometary hydrogen atoms are described, including the fountain, syndyname, and parent-daughter models. Calculations of emission line profiles and multiple-scattering effects are also discussed. Results of observations and interpretations are reviewed for each cited comet, far-UV observations in other emission lines are noted, and the use of comets as solar-wind probes is considered. It is concluded that the results of the present cometary Ly-alpha observations strongly support the concept of an icy conglomerate solid cometary nucleus and suggest water to be one of the most abundant molecules in comets.
    Keywords: ASTROPHYSICS
    Type: Space Science Reviews; 18; Mar
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    Effect of polarization on superfluidity in low density neutron matter (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The singlet-state quasi-particle interaction in neutron matter is examined on the basis of results of a detailed evaluation of the Landau Fermi-liquid parameters for pure neutron effects, including polarization effects. This means that the interaction induced by exchange of density and spin-density excitations is taken into account. It is shown that polarization actually works to suppress the pairing matrix elements, owing to the spin dependence of the quasi-particle interaction and, ultimately, the balance of attraction, repulsion, and spin dependence in the fundamental two-neutron interaction. Since the isotropic energy gap and the condensation energy in low-density neutron-star matter are extremely sensitive functions of the pairing matrix elements, they will also be suppressed by the polarizability of the neutron medium.
    Keywords: ASTROPHYSICS
    Type: Physics Letters; 61B; Apr. 12
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  • 165
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    On the nature of the anti-tail of Comet Kohoutek /1973f/. II - Comparison of the working model with ground-based photographic observations (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: On the basis of photographic observations made at the Cerro Tololo Inter-American Observatory, the radial and transverse brightness profiles and time variations in the surface brightness of the anti-tail of Comet Kohoutek were examined. In the process of photometric reduction one-dimensional radial tracings passing through the comet's nucleus and covering the entire anti-tail were used in the place of the standard two-dimensional scans. Each radial scan was defined by the position angle, and 'noise' variations were interpolated from the known field brightness outside the anti-tail. An analysis of the results provides quantitative support for a previously proposed model (Sekanina, 1974) suggesting that the dust particles in the anti-tail suffered a significant loss in radius due to evaporation near the perihelion passage. Preliminary calculations indicate that only particles initially larger than 100-150 micrometers in diameter survived. The emission rate of dust may be comparable to those derived for Comets Arend-Roland (1957 III) and Bennett (1970 II).
    Keywords: ASTROPHYSICS
    Type: Icarus; 27; Jan. 197
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  • 166
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    A probability of encounter with interstellar comets and the likelihood of their existence (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: A theory of the probability of encounter of the sun with an interstellar comet at a distance comparable to the earth-sun distance is formulated, and a general expression is derived establishing the relationship among the influx rate of interstellar comets, the perihelion distance, the space density of the comets, the Maxwellian distribution of comet velocities in the interstellar cloud, and the cloud's systematic velocity relative to the sun. An upper limit of .0006 solar mass per cubic parsec is established for the space density of interstellar comets. The theoretical distribution of semimajor axes of interstellar comets shows that a strong hyperbolic excess must be present in the orbits of a majority of interstellar comets regardless of the dynamical characteristics of the comet cloud, except when the cloud is moving along with the sun and the distribution of individual velocities has a very low dispersion. This case, however, implies a possibility of capture by the sun and thus becomes a problem of an Oort-type cloud.
    Keywords: ASTROPHYSICS
    Type: Icarus; 27; Jan. 197
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  • 167
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    Mass loss in red giants and supergiants (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The circumstellar envelopes surrounding 13 late-type giants and supergiants have been studied using a homogeneous collection of high-resolution, photoelectric scans of strong optical resonance lines. Various properties of the envelopes, including the mass loss rate, dilution factor, hydrogen density, and degree of ionization, have been determined quantitatively.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 204; Feb. 15
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  • 168
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    Gravitational-wave bursts from the nuclei of distant galaxies and quasars - Proposal for detection using Doppler tracking of interplanetary spacecraft (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: It is argued that the collapse which forms the supermassive black holes that are likely to exist in the nuclei of many quasars and galaxies, and collisions between those holes, should produce strong broadband bursts of gravitational waves. The mean time between such gravitational-wave bursts at earth is analyzed in terms of the present Hubble expansion rate, the present deceleration parameter of the universe, the redshift z = 2.5 (at which most of the bursts are assumed to have been generated), the present number density of 'centers' where the bursts originated, the mean number of bursts generated in each center during its active life, and the speed of light. The analysis shows that the range from one week to 300 years is reasonable for the time between bursts, although it is admitted that hardly any bursts at all is also reasonable. Expected characteristics of the bursts are deduced, and it is shown that the best detector for these bursts will probably be Doppler tracking of one or more interplanetary spacecraft.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 204; Feb. 15
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  • 169
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    Verification of the principle of equivalence for massive bodies (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Analysis of 1389 measurements, accumulated between 1970 and 1974, of echo delays of laser signals transmitted from earth and reflected from cube corners on the moon shows gravitational binding energy to contribute equally to earth's inertial and passive gravitational masses to within the estimated uncertainty of 1.5%. The corresponding restriction on the Eddington-Robertson parameters is 4(beta) - gamma 3 = -0.001 plus or minus 0.015. Combination with other results, as if independent, yields values for beta and gamma in accord with general relativity.
    Keywords: ASTROPHYSICS
    Type: Physical Review Letters; 36; Mar. 15
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  • 170
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    High-dispersion observations of emission lines in the postnova HR Delphini (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Results are reported for analysis of high-resolution line profiles obtained with an echelle spectrograph in the postnova HR Del. The investigated emission lines include H-alpha, the forbidden N II lines at 6548 and 6583 A, and the forbidden O III line at 5007 A. Heliocentric radial velocities of the line components are given along with their normalized relative intensities. The lines are found to have considerable structure which probably arises from condensations in the expanding nebula. It is shown that all the lines contain two major velocity groups, designated as shells A and B, and that shell B is more highly ionized and probably has a higher electron temperature. A large ratio between the intensities of the 6584-A and H-alpha lines is observed in shell A, and it is concluded that this is consistent with a nitrogen excess of a factor of two or more.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 203; Feb. 1
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  • 171
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    The time variability of Cygnus X-1 (1976)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The shot-noise character of the short-term time variations of Cyg X-1 is reviewed. Evidence for the systematic variation of these parameters with the binary period is presented.
    Keywords: ASTROPHYSICS
    Type: CONTRIB-119 , NASA. Goddard Space Flight Center X-ray Binaries; p 453-463
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  • 172
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    Formation of hard X-ray tails (1976)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: X-ray observations of Cygnus X-1 have shown a power-law spectrum. A natural way that this spectrum might arise is discussed. Inverse Compton scattering of a soft photon flux in a very hot accretion disk, kTe at approximately 100 keV is a possible cause. The slope of the spectrum may vary if source conditions vary.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 379-390
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  • 173
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    Information about accretion flows from X-ray timing of pulsating sources (1976)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The response was studied of a rotating neutron star to fluctuating torques and it was found that the observed variations in the pulsation periods of the compact X-ray sources Cen X-3 and Her X-1 could be caused by short time scale fluctuations in the accretion torques acting on the neutron stars. The sizes and rates of the required fluctuations are consistent with current accretion models. Such fluctuations can cause period variations either (a) directly, by causing a random walk of the star's angular velocity or (b) indirectly, by exciting a long-period mode of the neutron star, such as the Tkachenko mode of the rotating neutron superfluid. Phenomena in compact X-ray sources and cataclysmic variables which may be caused by fluctuating mass flow rates are also discussed.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 141-153
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  • 174
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    Intense soft X-ray flux from Her-1 (1976)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: An intense flux of soft X-rays extending up to at least 1 keV has been observed from Her X-1. If the soft X-ray intensity is corrected for interstellar absorption the luminosity between 0.16 and 1 keV is comparable to that from 2-10 keV. The soft X-rays are modulated with the 1.24 sec period observed at higher energies but are approximately 180 deg out of phase with the high energy flux. These results extend the detection of this flux to higher energy, a different binary phase, and to a time 19 periods (of the 35 day cycle) later. These observations suggest that this soft emission is a stable feature in the spectrum of this source during its X-ray on state and that this emission is local to Her X-1.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 119-125
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  • 175
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    Stellar crystal X-ray spectroscopy on OSO-8 (1976)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The large-area graphite crystal X-ray spectrometer on the OSO-8 satellite is described, and its response to stellar line and continuum radiation is discussed. A high resolution X-ray spectrum of Sco X-1 obtained from a preliminary analysis of quick look data shows a strong, smooth continuum with an absence of emission or absorption features over the energy range 2.2 to 8 keV. Upper limits are set on narrow line emission from highly ionized states of S, Ca, and Fe.
    Keywords: ASTROPHYSICS
    Type: CONTRIB-116 , NASA. Goddard Space Flight Center X-ray Binaries; p 53-65
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  • 176
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    Ice in space: An experimental and theoretical investigation (1976)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The thermodynamics of water ice formation was experimentally investigated under a wide variety of conditions, including those of outer space. This information, and in particular, the lifetime of ice particles as a function of solar distance is an absolute requirement for proper interpretation of photometric profiles of comets. The sublimation of ice particles in a nonequilibrium situation was studied. An oscillating fiber microbalance was used to measure the sublimation rate of water droplets (which were suspended on a long quartz fiber which was oscillating in a vacuum chamber). The influence of particle size, surface temperature, and the index refraction from simulated solar radiation were studied in relation to ice formation. Also examined was the influence of impurities (clathrates) on ice formation. Windows in the vacuum chamber allowed the ice particles to be exposed to a 1 kilowatt xenon arc lamp which was used to simulate solar radiation. Ice is proposed as a possible energy source for comets, as amorphous water ice and ammonia in low temperature and pressure environments demonstrated a clear energy release upon warming. Motion pictures of ice formation were taken and photographs are shown.
    Keywords: ASTROPHYSICS
    Type: NASA-CR-144273
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  • 177
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    Mean lives of some astrophysically important excited levels in carbon, nitrogen and oxygen (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A number of astrophysically important mean lives of levels in carbon, nitrogen and oxygen were measured with the beam-foil technique. New values are reported and compared with earlier theoretical and experimental values. Direct references to astrophysical applications are listed.
    Keywords: ASTROPHYSICS
    Type: NASA-CR-146853
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  • 178
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    The earth's magnetosphere (1976)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The following aspects of the earth's magnetosphere were discussed: general structure, magnetic field merging and magnetospheric convection, time-varying convection and magnetospheric substorms, magnetic storms, and comparative magnetospheres. Solar flares and the magnetospheres of Mercury, Venus, Mars, Jupiter, Saturn, and Uranus were also described.
    Keywords: ASTROPHYSICS
    Type: NASA-CR-146803 , PPG-258
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  • 179
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    Science aspects of 1980 ballistic missions to comet Encke, using Mariner and Pioneer spacecraft (1976)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: Science aspects of a 1980 spacecraft reconnaissance of Comet Encke are considered. The mission discussed is a ballistic flyby (more exactly, a fly-through) of P/Encke, using either a spin stabilized spacecraft, without despin of instruments, or a 3-axis stabilized spacecraft.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Study of Comets, Part 2; p 1058-1070
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  • 180
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    A means of in-situ measurements of neutral H and He on an out-of-the-ecliptic mission (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: On an out-of-the-ecliptic mission, in situ measurements of densities and temperature of interstellar neutral H and He in the heliosphere should complement observations based on backscattered Lyman-alpha intensities. A means of performing the in situ measurements is briefly described.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center Proc. of the Symp. on the Study of the Sun and Interplanetary Medium in Three Dimensions; p 321-329
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  • 181
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    Strong scintillations in astrophysics. 4. Cross-correlation between different frequencies and finite bandwidth effects (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The cross correlation of the intensity fluctuations between different frequencies and finite bandwidth effects on the intensity correlations based on the Markov approximation were calculated. Results may be applied to quite general turbulence spectra for an extended turbulent medium. Calculations of the cross-correlation function and of finite bandwidth effects are explicitly carried out for both Gaussian and Kolmogorov turbulence spectra. The increases of the correlation scale of intensity fluctuations are different for these two spectra and the difference can be used to determine whether the interstellar turbulent medium has a Gaussian or a Kolmogorov spectrum.
    Keywords: ASTROPHYSICS
    Type: NASA-TM-X-71072 , X-602-76-35
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  • 182
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    Detection of molecular microwave transitions in the 3 mm wavelength range in comet Kohoutek (1973f) (1976)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: Observations of comet Kohoutek made with a 3-mm line receiver mounted on the 11-m NRAO radio dish at Kitt Peak are presented. The detection of line transitions of hydrogen cyanide and methyl cyanide is reported and discussed along with the variability of neutral gas jets. Microwave transitions in molecules of cometary origin are also examined.
    Keywords: ASTROPHYSICS
    Type: The Study of Comets, Part 1; p 258-271
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  • 183
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    On the cometary hydrogen coma and far UV emission (1976)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: Cometary hydrogen observations are reviewed with emphasis on observations of comet Bennett. The results are theoretically interpreted and a brief summary of ultraviolet observations other than Lyman alpha is given.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Study of Comets, Part 1; p 287-314
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  • 184
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    Radio detections of cometary molecular transitions: A review (1976)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: Radio detections of CH, OH, HCN, CH3CN, and several unidentified species in comet Kohoutek and the detection of H2O emission from comet Bradfield are discussed in terms of the similarities and differences between cometary molecules and interstellar molecules. Emphasis is placed on excitation and chemistry. The observed projected densities and resulting gas production rates are considered along with the feasibility of future radio molecular observations of comets.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Study of Comets, Part 1; p 232-252
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  • 185
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    Photoelectric polarimetry of the tail of comet Ikey-Seki (1975 VIII) (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Post-perihelion measurements of Comet 1965 VIII made on four nights in October-November 1965 using a Fabry photometer atop 3,052 m Mt. Haleakala, Hawaii are described. Detailed results of observations at 5300A on October 29, 1965 are presented.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Study of Comets, part 1; p 92-120
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  • 186
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    On the acceleration of energetic particles in the interplanetary medium (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Fermi scattering and transit time damping are two possible mechanisms for accelerating low energy protons (approximately 1 Mev) in co-rotating particle streams. Solutions to the equations which govern particle behavior in such streams are presented. It was found that acceleration by Fermi scattering requires a scattering mean-free path more than an order of magnitude smaller than the nominal value for low energy particles of 0.1 AU. Transit time damping of only the observed low level of magnitude fluctuations in the interplanetary magnetic field appears to yield the required acceleration rate. Measurements of the direction of the anisotropy in the particle streams could help in deciding which mechanism is operative. In the case of Fermi scattering the anisotropy must be in the heliocentric radial direction, whereas for transit time damping a significant azimuthal anisotropy could be present.
    Keywords: ASTROPHYSICS
    Type: NASA-TM-X-71077 , X-660-76-25
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    The acceleration of energetic particles in the interplanetary medium by transit-time damping (1976)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: Transit time damping is examined as a possible means for accelerating low energy particles in co-rotating streams and interstellar ions. Data show that: the protons in co-rotating streams may be accelerated by transient-time damping the small-scale variations in the field magnitude that are observed at a low level in the inner solar system. The interstellar ions may be accelerated by transit time damping large-scale field variations in the outer solar system.
    Keywords: ASTROPHYSICS
    Type: NASA-TM-X-71078 , X-660-76-26
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    Observations of the interplanetary magnetic field between 0.46 and 1 A.U. by the Mariner 10 spacecraft (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Almost continuous measurement of the interplanetary magnetic field (IMF) at a sampling rate of 25 vectors/sec was performed by the magnetic field experiment onboard the Mariner 10 spacecraft during the period November 3, 1973 to April 14, 1974, comprising approximately 5-2/3 solar rotations and extending in radial distance from the sun from 1 to 0.46 AU. A clearly discernible two-sector pattern of field polarity was observed during the last 3-1/2 months of the period, with the dominant polarity toward the sun below the solar equatorial plane. Two compound high-speed solar wind streams were also present during this period, one in each magnetic field sector. Relative fluctuations of the field in magnitude and direction were found to have large time variations, but on average the relative magnitude fluctuations were approximately constant over the range of heliocentric distance covered while the relative directional fluctuations showed a slight decrease on average with increasing distance. The occurrence rate of directional discontinuities was also found to decrease with increasing radial distance from the sun.
    Keywords: ASTROPHYSICS
    Type: NASA-TM-X-71043 , X-692-76-2
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  • 189
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    High resolution measurements of the low state of Cyg X-1 (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Cyg X-1 was observed on two occasions separated by a year by the same X-ray rocket payload. High resolution temporal and spectral data reveal that Cyg X-1 was essentially unchanged in these two observations a year apart, with bursts of millisecond duration observed in the earlier flight and also, observed in the second. Analysis of these bursts has failed to reveal any internal temporal structure, either luminous or spectral. The shot noise character of temporal fluctuations on timescales approximately 1 second can be explained by the presence of exponential pulses with a fraction of a second time constant and a rate near 8 sec/1. The possible connection of these pulses with the bursts is examined.
    Keywords: ASTROPHYSICS
    Type: NASA-TM-X-71178 , X-661-76-179
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  • 190
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    Consequences of using nonlinear particle trajectories to compute spatial diffusion coefficients (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The propagation of charged particles through interstellar and interplanetary space has often been described as a random process in which the particles are scattered by ambient electromagnetic turbulence. In general, this changes both the magnitude and direction of the particles' momentum. Some situations for which scattering in direction (pitch angle) is of primary interest were studied. A perturbed orbit, resonant scattering theory for pitch-angle diffusion in magnetostatic turbulence was slightly generalized and then utilized to compute the diffusion coefficient for spatial propagation parallel to the mean magnetic field, Kappa. All divergences inherent in the quasilinear formalism when the power spectrum of the fluctuation field falls off as K to the minus Q power (Q less than 2) were removed. Various methods of computing Kappa were compared and limits on the validity of the theory discussed. For Q less than 1 or 2, the various methods give roughly comparable values of Kappa, but use of perturbed orbits systematically results in a somewhat smaller Kappa than can be obtained from quasilinear theory.
    Keywords: ASTROPHYSICS
    Type: NASA-TM-X-71188 , X-692-76-200
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  • 191
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    Interplanetary boundary layers at 1 AU (1976)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The structure and nature of discontinuities in the interplanetary magnetic field at 1 AU in the period March 18, 1971 to April 9, 1971, is determined by using high-resolution magnetic field measurements from Explorer 34. The discontinuities that were selected for this analysis occurred under a variety of interplanetary conditions at an average rate of 0.5/hr. This set does not include all discontinuities that were present, but the sample is large and it is probably representative. Both tangential and rotational discontinuities were identified, the ratio of TD's to RD's being approximately 3 to 1. Tangential discontinuities were observed every day, even among Alfvenic fluctuations. The structure of most of the boundary layers was simple and ordered, i.e., the magnetic field usually changed smoothly and monotonically from one side of the boundary layer to the other.
    Keywords: ASTROPHYSICS
    Type: NASA-TM-X-71171 , X-692-76-168
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  • 192
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    An X-ray red-shift test for clusters of galaxies up to Z greater than or equal to 1 (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Correlated measurements of red-shifted iron line emission and apparent surface brightness are suggested for unambiguously defining intrinsic X-ray characteristics for clusters of galaxies up to z greater than or equal to 1. If some of the weak unidentified high galactic latitude X-ray sources are clusters at z approximately 1-3, then such correlated measurements should be feasible witin the complement of instruments aboard the HEAO-B orbiting X-ray telescope observatory. In addition, those clusters at z less than 1 would require spectral data from broader bandwidth experiments, such as the all-sky survey to be provided by the proportional counters aboard the first mission of the High Energy Astronomy Observatory (HEAO-A).
    Keywords: ASTROPHYSICS
    Type: NASA-TM-X-71102
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  • 193
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    JPL Development Ephemeris number 96 (1976)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The fourth issue of JPL Planetary Ephemerides, designated JPL Development Ephemeris No. 96 (DE96), is described. This ephemeris replaces a previous issue which has become obsolete since its release in 1969. Improvements in this issue include more recent and more accurate observational data, new types of data, better processing of the data, and refined equations of motion which more accurately describe the actual physics of the solar system. The descriptions in this report include these new features as well as the new export version of the ephemeris. The tapes and requisite software will be distributed through the NASA Computer Software Management and Information Center (COSMIC) at the University of Georgia.
    Keywords: ASTROPHYSICS
    Type: NASA-CR-147923 , JPL-TR-32-1603
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    Progress in our understanding of cometary dust tails (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Various analytical techniques are employed to analyze observations on the character, composition, and size distribution of solid particles in cometary dust tails. Emphasized is the mechanical theory that includes solar gravitational attraction and solar radiation pressure to explain dust particle motions in cometary tails, as well as interactions between dust and plasma.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Study of Comets, Part 2; p 893-942
    Format: application/pdf
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  • 195
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    Cooling and recombination processes in cometary plasma (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The ion electron plasma in comets is examined for cooling processes which result from its interactions with the neutral coma. A cometary coma model is formulated that is composed predominantly of H2O and its decomposition products where electrons are cooled in a variety of processes at rates varying with energy. It is shown that solar plasma plus accumulated cometary ions and electrons is affected very strongly as it flows into the coma. The electrons are rapidly cooled and all but some 10% of the ions undergo charge exchange. Photodissociation of H2O is assumed where ion electron recombination is the dominant loss process.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Study of Comets, Part 2; p 856-876
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  • 196
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    Far ultraviolet excitation processes in comets (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Recent observations of atomic oxygen and carbon in the far ultraviolet spectrum of comet Kohoutek have demonstrated the existence of these atomic species in the cometary coma. However, in order to identify the source of their origin, it is necessary to relate the observed ultraviolet flux to the atomic production rate. Analyses of observed OI wavelength 1304 and CI wavelength 1657 A multiplets have been carried out using high resolution solar spectra. Also examined is the possibility of observing ultraviolet fluorescence from molecules such as CO and H2, as well as resonance scattering either from atomic ions for which there are strong corresponding solar lines (CII) or from atoms for which there is an accidental wavelength coincidence (SI).
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Study of Comets, Part 2; p 773-796
    Format: application/pdf
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  • 197
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    K I 7699 A emission from the Betelgeuse shell (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: A map of the circumstellar gas shell around Betelgeuse is presented from observations of the fluorescent emission in the K I 7699 A resonance line. The observations obtained at 3 sec and 5 sec from the star indicate approximate spherical symmetry in the 10 km/s expanding shell responsible for the blueshifted sharp cores seen in strong resonance and low excitation lines. Calculations show that the density of neutral K atoms is approximately constant between 3 sec and 5 sec from the star. The emission profiles in the west show a second, higher velocity, component at 5 sec from the star.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 210; Dec. 1
    Format: text
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  • 198
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    The dynamical interaction of a newly formed protostar with infalling matter - The origin of interstellar grains (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 210; Dec. 1
    Format: text
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  • 199
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    Interplanetary magnetic field power spectra - Mean field radial or perpendicular to radial (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: A detailed frequency analysis of Pioneer-6 interplanetary magnetic field data is carried out for 5 to 15 hour periods during which the mean interplanetary field is approximately radial or perpendicular to radial. The reason why these data sets were chosen is that by making the usual assumption that the phase speed of any wave present is much less than the mean solar wind speed, the measured frequency spectra can be interpreted in terms of the wave number parallel or perpendicular to the mean field, without such additional assumptions as isotropy or the dominance of a particular mode and without measurements of velocity and density. The details of the calculation of the magnetic field power spectra, coherencies, and correlation functions are discussed, along with results obtained directly from the data (such as spectra, slopes, anisotropies, and coherencies). The results are interpreted in terms of MHD theory, and are related to work in other areas.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research; 81; Nov. 1
    Format: text
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  • 200
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    On the interpretation of Fe II emission profiles in Seyfert galaxies and QSOs (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Recent high-resolution spectral scans of several QSOs and Seyfert galaxies show broad Balmer lines and permitted Fe II lines in emission. It is suggested that a careful comparison of the Fe II and Balmer profiles may distinguish between the different proposed mechanisms for broadening of the lines. For a suprathermal-particle model, the hydrogen and Fe II lines arise in the same region, with the Fe II emission produced by the dense ambient gas that is excited by the flux of suprathermal particles. Hence, such a model predicts that the Fe II lines are substantially narrower than the hydrogen lines.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 210; Nov. 15
    Format: text
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