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  • Other Sources  (566)
  • NASA Technical Reports  (566)
  • Bibliography of Innovation Network of Climate Change Adaptation Brandenburg Berlin
  • ASTROPHYSICS  (566)
  • 1980-1984  (566)
  • 1955-1959
  • 1980  (566)
Collection
  • Other Sources  (566)
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  • NASA Technical Reports  (566)
  • Bibliography of Innovation Network of Climate Change Adaptation Brandenburg Berlin
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  • 1980-1984  (566)
  • 1955-1959
Year
  • 101
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    Superluminal motion in compact radio sources (1980)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: The observations of radio sources whose components appear to move superluminally are now sufficient to eliminate certain theoretical models. However, a number of models might be still relevant. The models which involve relativistic bulk motions of the radio components seem to provide the most likely explanation of apparent superluminal motion. A summary of observational predictions of various models for superluminal motions is included.
    Keywords: ASTROPHYSICS
    Type: Astronomical Society of the Pacific; vol. 92
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  • 102
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    The settling of helium and the ages of globular clusters (1980)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Model low-mass globular-cluster stars were evolved with their helium allowed to diffuse under the influence of gravity, thermal diffusion, and concentration gradient. The evolution tended to speed up. Also, the turnoff point moved toward lower luminosity and slightly lower surface temperature. If the luminosity at turnoff is used as the sole criterion for determining the age of a globular cluster, the inferred ages of such clusters are reduced by about 22% from starting values in the vicinity of 15 billion years.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 237
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  • 103
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    Cold dense photoionized universes (1980)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: This investigation employs a computer code, initially constructed for modeling the evolution of a hot dense intergalactic medium (IGM), to study some properties of a cold dense IGM photoionized by QSOs. Within the observational constraints set by flux measurements in the far-ultraviolet, night sky brightness, and hard X-ray region, and the optical depth limits on various QSO spectra, it determines some allowable scenarios for a range of QSO spectral indices (alpha) and cutoff energies. With H(0) = 50 km/s-Mpc, closure density of an IGM (composed of H and He in their cosmic ratio) is possible only if alpha is greater than or equal to 0.1, a circumstance not likely to prevail; the most probable value, alpha = -0.7, implies an upper limit density about 0.35 of closure, which is somewhat larger than previous estimates. These estimates are substantially independent of whether or not QSOs produce the observed diffuse extragalactic X-ray background; such QSO spectral details are critical, however, in determining the ionization of heavy elements that are expected to contaminate a pure primeval plasma.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 237
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  • 104
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    The observations of the X-ray source HZ Herculis/Hercules X-1 (1980)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: The results of a campaign of monitoring HZ Her with the IUE satellite are presented. The spectrum and light variation outside of eclipse are consistent with the Milgrom and Salpeter model for emission from the X-ray heated photosphere of the primary. Near eclipse there is UV flux in excess of the prediction of the heated photosphere model, which shows significant 35 day variations and is consistent with an origin in a precessing disk, as described by Gerend and Boynton. The spectrum shows the strong emission lines of N V and C IV, which generally vary in the sense of the continuum. The N V/C IV ratio is greater than 2 near orbital phase 0.5 and approaches unity near eclipse. It is suggested that these emission lines are optically thick and arise from both the heated photosphere and the accretion disk.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 237
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  • 105
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    High energy X-ray and radio studies of Scorpius X-1 (1980)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: The results from extended high energy X-ray observations of Scorpius X-1 from the OSO 8 satellite are reported. The source was observed for a total of 15 days in 1975, 1977, and 1978. Simultaneous 10.7 GHz and 4.75 GHz radio data were obtained during the 1978 observation, and low energy X-ray data during the 1975 and 1978 observations. Detailed studies of the data reveal a lack of any correlation between the high energy X-rays and the other energy ranges. A 3 sigma upper limit of 22% was obtained for any modulation of the high energy flux with the binary period. No high energy tail was observed at any time.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 237
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  • 106
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    Helium synthesis, neutrino flavors, and cosmological implications (1980)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: The problem of the production of helium in the big bang is reexamined in the light of several recent astrophysical observations. These data, and theoretical particle-physics considerations, lead to some important inconsistencies in the standard big-bang model and suggest that a more complicated picture is needed. Thus, recent constraints on the number of neutrino flavors, as well as constraints on the mean density (openness) of the universe, need not be valid.
    Keywords: ASTROPHYSICS
    Type: Physical Review Letters; 44; May 5
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  • 107
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    An investigation of previously derived Hyades, Coma, and M67 reddenings (1980)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: New Hyades polarimetry and field star photometry were obtained to check the Hyades reddening, which was found to be nonzero in a previous study (Taylor, 1978). The new Hyades polarimetry implies essentially zero reddening. Four photometric techniques which are assumed to be insensitive to blanketing are used to compare the Hyades to nearby field stars and are found to yield essentially zero reddening. A simultaneous solution for the Hyades, Coma, and M67 reddenings is made, and the results are E(B-V) = 3 plus or minus 2(sigma) mmag, -1 plus or minus 3(sigma) mmag, and 46 plus or minus 6(sigma) mmag, respectively.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal; 85; Mar. 198
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  • 108
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    Galaxy spectral synthesis. II - M32 and the ages of galaxies (1980)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: The paper presents a population synthesis performed on absolute spectrophotometry for the central 31 in. of M32. The metallicity of M32 is solar with 0.1 dex, implying that major star formation continued in M32 until 5 Gyr ago, or 10 Gyr after the oldest globular clusters formed. The synthesis models predict that the rate of mass return to the interstellar medium in M32 from evolving stars is about 0.0008 solar mass/yr; however, the upper limit for star formation during the past 1 Gyr is about 0.003/yr, showing that the available optical observations do not exclude complete recycling of gas lost during stellar evolution into new generations of stars.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 236
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  • 109
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    Theoretical mean colors for RR Lyrae variables (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A hydrodynamically pulsating 0.6 solar mass model of a typical RR Lyrae variable was studied with a radiation transport-hydrodynamic computer program to predict theoretical T sub 3 and colors at many phases and to find the proper methods for getting mean colors and the consequent mean effective temperatures. The variable Eddington radiation approximation method was used with gray and with multifrequency absorption coefficients to represent the radiation flow in the outer optically thin layers. Comparison between observed and computed B-V colors indicate that these low Z population 2 models are reasonably accurate using King 1A composition opacities. The well known Oke, Giver, and Searle relation between B-V and T sub e reproduced. Mean colors were found by four different averaging methods. The method that gives a mean color and the mean T sub e closest to the nonpulsating model was the separate intensity means of B and V.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center Current Probl. in Stellar Pulsation Instabilities; p 293-310
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  • 110
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    Observations of classical cepheids (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The observations of classical Cepheids are reviewed. The main progress that has been made is summarized and some of the problems yet to be solved are discussed. The problems include color excesses, calibration of color, duplicity, ultraviolet colors, temperature-color relations, mass discrepancies, and radius determination.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center Current Probl. in Stellar Pulsation Instabilities; p 1-23
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  • 111
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    Evidence for the existence of nonradial solar oscillations: Solar rotation (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The coherent properties of six oscillations over a two week period in which seven days of equatorial diameter measurements were analyzed, are confirmed by the addition of an extra day of data. The two large 1 (the principal order number in the spherical harmonic expansion of the eigenfunction) g-mode oscillations may be candidates for the slowly rotating mode locked structures. For the four low frequency p-modes, periodic nature is observed in the daily power levels, varying with periods of several days. This is attributed to beating between rotationally split m states for a given 1 value. Nonradial modes are a major contribution to the observed solar oscillations. The nonradial character of the observed modes allows the depth dependence of the internal solar rotation to be investigated.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center Current Probl. in Stellar Pulsation Instabilities; p 665-675
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  • 112
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    Velocity structure in long period variable star atmospheres (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A regression analysis of the dependence of absorption line velocities on wavelength, line strength, excitation potential, and ionization potential is presented. The method determines the region of formation of the absorption lines for a given data and wavelength region. It is concluded that the scatter which is frequently found in velocity measurements of absorption lines in long period variables is probably the result of a shock of moderate amplitude located in or near the reversing layer and that the frequently observed correlation of velocity with excitation and ionization are a result of the velocity gradients produced by this shock in the atmosphere. A simple interpretation of the signs of the coefficients of the regression analysis is presented in terms of preshock, post shock, or across the shock, together with criteria for evaluating the validity of the fit. The amplitude of the reversing layer shock is estimated from an analysis of a series of plates for four long period variable stars along with the most probable stellar velocity for these stars.
    Keywords: ASTROPHYSICS
    Type: NASA Goddard Space Flight Center Current Probl. in Stellar Pulsation Instabilities; p 577-609
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  • 113
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    Light curves for bump Cepheids computed with a dynamically zoned pulsation code (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The dynamically zoned pulsation code developed by Castor, Davis, and Davison was used to recalculate the Goddard model and to calculate three other Cepheid models with the same period (9.8 days). This family of models shows how the bumps and other features of the light and velocity curves change as the mass is varied at constant period. The use of a code that is capable of producing reliable light curves demonstrates that the light and velocity curves for 9.8 day Cepheid models with standard homogeneous compositions do not show bumps like those that are observed unless the mass is significantly lower than the 'evolutionary mass.' The light and velocity curves for the Goddard model presented here are similar to those computed independently by Fischel, Sparks, and Karp. They should be useful as standards for future investigators.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center Current Probl. in Stellar Pulsation Instabilities; p 175-186
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  • 114
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    Optical observables in stars with non-stationary atmospheres (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Experience gained by use of Cepheid modeling codes to predict the dimensional and photometric behavior of nuclear fireballs is used as a means of validating various computational techniques used in the Cepheid codes. Predicted results from Cepheid models are compared with observations of the continuum and lines in an effort to demonstrate that the atmospheric phenomena in Cepheids are quite complex but that they can be quantitatively modeled.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center Current Probl. in Stellar Pulsation Instabilities; p 199-236
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  • 115
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    A discussion of Cepheid masses (1980)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: Masses and compositions of Cepheids are essential to map the places in the Hertzsprung-Russell diagram where various radial pulsation modes occur. Luminosity observations and stellar evolution theory give masses for Cepheids which range from 10 percent to a factor of four more than those given by pulsation theory. Combining the evolution and pulsation theories, a theoretical mass was determined using only the period and an approximate surface effective temperature. The ratio of the theoretical to evolutionary masses averaged 0.99 + or - 0.07 for 16 Cepheids.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center Current Probl. in Stellar Pulsation Instabilities; p 69-95
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  • 116
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    Pulsation and mass loss in Mira variables (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The behavior of pulsation in the outer layers of a typical Mira variable was studied in the adiabatic and isothermal limits. A shock wave propagates outward once per period and the radial velocity obtained from observations of hydrogen emission lines is identified with the velocity of gas in the post shock region. In the adiabatic case, mass loss in the form of a steady stellar wind was produced. In the isothermal case, no continuous mass loss was produced but occasional ejection of shells occur. Pulsation introduced into a star undergoing steady mass loss as a result of radiation pressure acting on grains caused the mass loss rate to increase by a factor of approximately 40, while the terminal velocity of the flow was almost unaltered.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center Current Probl. in Stellar Pulsation Instabilities; p 611-628
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  • 117
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    Zeeman observations of W Sgr (1980)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: A new precise method for measuring magnetic fields on Zeeman plates of the southern Cepheid 'W Sgr' is reviewed. Ten plates over the 7.6(d) period of pulsation show two extrema in the measured values of the effective magnetic field. The method has a precision of + or - 0.4 microns in the Zeeman shift corresponding to + or - 50 Gauss (g). A negative spike of -220 g occurred at the time of arrival of the compressional wave of pulsation at the stellar surface. A positive field of +270 g occurred at the phase of most rapid contraction near the temperature minimum of the pulsation cycle.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center Current Probl. in Stellar Pulsation Instabilities; p 57-67
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  • 118
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    The periods and amplitudes of TU Cas (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Light curve observations of the double-mode Cepheid TU Cas obtained by 10 different sets of observers on several photometric systems over a time span of 67 years were carefully studied to determine the fundamental and first overtone periods and their amplitudes on the V magnitude scale. The presence of a second overtone radial pulsation is discussed, and it is concluded that a previous detection of this mode was spurious due to the lack of a proper zero point correction for two groups of observations. The amplitudes of the two modes are shown to possibly vary during the entire observing period with the fundamental mode amplitude of 0.69 + or - 0.03 and the overtone amplitude decreasing about 0.2 or 0.3 magnitude. If this Cepheid displays the two pulsation modes because it is mode switching, this switching time scale might be less than a hundred years.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center Current Probl. in Stellar Pulsation Instabilities; p 25-40
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  • 119
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    Mira variables: An informal review (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The structure of the Mira variables is discussed with particular emphasis on the extent of their observable atmospheres, the various methods for measuring the sizes of these atmospheres, and the manner in which the size changes through the cycle. The results obtained by direct, photometric and spectroscopic methods are compared, and the problems of interpretation are addressed. Also, a simple model for the atmospheric structure and motions of Miras based on recent observations of the doubling of infrared molecualr times is described. This model, consisting of two atmospheric layers plus a circumstellar shell, provides a physically plausible picture of the atmosphere which is consistent with the photometrically measured magnitude and temperature variations as well as the spectroscopic data.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center Current Probl. in Stellar Pulsation Instabilities; p 533-566
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  • 120
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    The pulsating white dwarfs (1980)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: The characteristics of variable white dwarfs are presented through an examination of observational data. The variable white dwarfs are normal, single, DA white dwarfs. The variations are caused by pulsations, but the pulsations are nonradial rather than radial pulsations. The periods are all very long. Excluding harmonics and cross frequencies, the shortest period is 114 sec and the longest period is 1186 sec. Without exception every variable is multiperiodic. The stability of the periods varies from extremely high to very low; the low stability of many of the variables perhaps being due to incomplete data. Finally, there is a strong correlation between the amplitude of the variations and their remaining properties. The higher amplitude variables have more periods in their light curves and the periods are more unstable.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center Current Probl. in Stellar Pulsation Instabilities; p 423-451
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  • 121
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    Pulsation of late B-type stars (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Radial velocity observations of three of the brightest stars in the Pleiades, Alcyone, Maia and Taygeta, made during the course of one night, 25 October 1976, are discussed. All three stars were discovered to be pulsating with periods of a few hours. Analysis of all published radial velocities for each star, covering more than 70 years and approximately 100,000 cycles, has established the value of the periods to eight decimal places, and demonstrated constancy of the periods. However, amplitudes of the radial velocity variations change over long time intervals, and changes in spectral line intensities are observed in phase with the pulsation. All three stars may also be members of binary systems.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center Current Probl. in Stellar Pulsation Instabilities; p 409-420
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  • 122
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    The evolutionary stage of an RRs star SX Phe (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The evolutionary stage for a short period variable SX Phe was investigated. It was assumed that SX Phe is a mixed star with low metal abundance in which the material was mixed after the star evolved off the main sequence, and is in the second hydrogen burning stage. The validity of this hypothesis was examined by constructing two evolutionary sequences with (X,Z,M/solar mass) = (0.5,0.004,0.75) and (0.5,0.001,0.70) in the hydrogen burning phase and computed the pulsation period. Agreement between theoretical results and observational data was sufficient to conclude that the mixed model is actually adequate for SX Phe. The applicability of this model to other RRs stars is briefly discussed.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center Current Probl. in Stellar Pulsation Instabilities; p 317-327
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  • 123
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    On the origin of period changes in RR Lyrae stars (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The observed period changes are explained with respect to the behavior of the semiconductive zone (SCZ) within the core of an RR Lyrae star. General consideration are given which suggest that the composition changes occuring within the SCZ during the horizontal-branch evolution result from many small mixing events, each of which slightly perturbs the pulsation period. Results indicate that small mixing events within the core of an RR Lyrae star can produce changes in the pulsation period comparable with those typically observed. It is further indicated that these mixing events together with the nuclear burning between them can produce period changes of both signs.
    Keywords: ASTROPHYSICS
    Type: Current Probl. in Stellar Pulsation Instabilities; p 271-291
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  • 124
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    Mode identification in Beta Cephei stars (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The essential observational characteristics related to mode identification are summarized. Major emphasis is placed on the following: both light and velocity amplitudes; typical periods in both light and radial velocity; the light curve for Beta Cephei stars in comparison to the classical Cepheids and RR Lyrae stars; the van Hoof effect with respect to the radial velocity curves in many Beta Cephei stars; and the line profiles of many Beta Cephei stars.
    Keywords: ASTROPHYSICS
    Type: Current Probl. in Stellar Pulsation Instabilities; p 331-361
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  • 125
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    Microturbulence and Wesselink radii (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Using the calibration of Bell and Parsons (1974), the effects of changes in microturbulence and surface gravity throughout the cycles of delta Cephei and eta Aquilae are estimated. When the changes in microturbulence are considered, Wesselink radii for these stars are reduced 20%.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center Current Probl. in Stellar Pulsation Instabilities; p 237-246
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  • 126
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    Dependence of red edge on eddy viscosity model parameters (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The dependence of the red edge location on the two fundamental free parameters in the eddy viscosity treatment was extensively studied. It is found that the convective flux is rather insensitive to any reasonable or allowed value of the two free parameters of the treatment. This must be due in part to the fact that the convective flux is determined more by the properties of the hydrogen ionization region than by differences in convective structure. The changes in the effective temperature of the red edge of the RR Lyrae gap resulting from these parameter variations is quite small (approximately 150 K). This is true both because the parameter variation causes only small changes and because large changes in the convective flux are required to produce any significant change in red edge location. The possible changes found are substantially less than the approximately 600 K required to change the predicted helium abundance mass fraction from 0.3 to 0.2.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center Current Probl. in Stellar Pulsation Instabilities; p 113-120
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  • 127
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    The period structure of the ZZ Ceti variables (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The current observational status of the period structure of ZZ Ceti stars is reviewed, and in particular those features which appear to be the most important for theory to explain, or which may be relevant to the directions of theoretical development are discussed. Mechanisms to explain the broad range of period structure are suggested. Multiple nonradial modes, probably corresponding to different radial overtones, may be simultaneously excited in each star. The excitation energy of individual stars is distributed among permitted modes by nonlinear resonant coupling. In addition, rotational splitting of the nonradial modes can produce closely spaced periods which results in modulation of the light curve. Amplitude/spectral complexity correlation results from the appearance in the power spectrum of harmonics and cross-frequencies which are the effects brought on by increasing nonlinearity of the pulsations.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center Current Probl. in Stellar Pulsation Instabilities; p 501-512
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  • 128
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    Some evolutionary considerations of Beta Cephei stars (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The evolutionary aspects of massive population 1 stars were investigated. Semiconvection was treated in two different ways, and included mass loss both in the early as well as later spectra stages. The effect of rotation was taken into account and the time evolution of angular momentum of these models was studied. The effect of differential rotation due to the faster rotating interiors and slowed down surface layers are briefly described.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center Current Probl. in Stellar Pulsation Instabilities; p 363-380
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  • 129
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    Population of the lower part of the instability strip: Delta Scuti stars and dwarf Cepheids (or AI Velorum) (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Some of the properties of the atmospheric variations in delta Scuti stars were investigated with emphasis on the amplitude and the shape of both light curves and radial velocity curves. It is shown that these curves are small and rapidly variable in the case of dwarf Scuti stars; for the evolved stars the situation is more complex. The relation between variables and nonvariables, and also the results on abundances in the atmospheres of these stars were surveyed with respect to the hydrodynamics of their envelopes. The abundance anomalies of Am stars were qualitatively examined. The coexistence of abundance anomalies and variability among giants were also studied. Attempts were made to relate the variability to the hydrogen ionization zone in an envelope deprived of helium. Specific results are reported.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center Current Probl. in Stellar Pulsation Instabilities; p 247-270
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    The radii of SU Cas and TU Cas (1980)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: It is possible to obtain the masses of Cepheid variables by several methods involving the pulsation theory. However, these masses are frequently smaller than those indicated by the theory of stellar evolution. The cause of this discrepancy is not fully understood. Since the pulsation theory indicates that there is a relation among the mass, the radius and the period, the discrepancy also manifests itself in the radii of these stars. With this in mind, radius determinations for two Cepheids, SU Cas and TU Cas, were undertaken. It is concluded that because of the agreement between the present radius and the beat radius of TU Cas, the pulsation theory is giving correct information about the radii of beat Cepheids. This implies that the luminosities of short period Cepheids have been overestimated. Thus, the solution to the mass discrepancy should perhaps be sought in the theory of stellar evolution or in the possibility of mass loss.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center Current Probl. in Stellar Pulsation Instabilities; p 41-54
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  • 131
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    X-ray observations of the Seyfert 1 galaxies AKN120 and MCG8-11-11 (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A new X-ray source, H0523-00, with the optically variable Seyfert 1 galaxy AKN 120 is identified. The source has a 2-10 keV X-ray flux of 2 x 10 to the -11th ergs/sq cm s which corresponds to a 2-10 keV X-ray luminosity of 10 to the 44th ergs/s. X-ray observations over a 1.5 year time span combined with contemporaneous optical photometry show a decrease in the optical with no corresponding decrease in the X-ray. In contrast, similar observations of MCG 8-11-11 show a contemporaneous decrease in optical and X-ray fluxes. It is noted that the infrared and X-ray spectral slopes for these two objects are similar, with the optical being steeper by roughly one unit.
    Keywords: ASTROPHYSICS
    Type: NASA-TM-80663 , NAS 1.15:80663
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  • 132
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    Colors and magnitudes predicted for high redshift galaxies (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Ultraviolet observations of nearby galaxies with the ANS are used to derive ultraviolet spectra for different galaxy types. These spectra are used with existing visible spectrophotometry to calculate K-corrections, and to predict colors and magnitudes for various galaxy types as a function of redshifts, to z = 2. No evolutionary effects are considered. It appears that the first-ranked cluster galaxies on blue emulsions should be spirals for z greater than or approximately equal to 0.5.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal Supplement Series; 43; July 198
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  • 133
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    Surface composition changes in massive star evolution with mass loss (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A series of evolutionary models of 40-100 solar mass objects undergoing mass loss are constructed with the explicit inclusion of the surface composition of H, He, C, N, O elements. Mass loss rates similar to those observed in Of stars, 4 to 7 x 10 to the -6th solar masses/yr, result in an appearance at the surface of equilibrium CNO products, i.e. enhanced nitrogen and diminished carbon, while that star is still burning hydrogen in the core. This result obtains because the initial convection core is a relatively large fraction of the total mass and rather modest loss exposes levels of anomalous composition. It is suggested that these objects might reasonably be identified as those luminous late type WN stars still containing surface hydrogen.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics; 92; 3, De; Dec. 198
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  • 134
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    On equilibrium states of heated self-gravitating gas clouds cooling by conduction in an external gravitational field (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Exact analytic solutions are presented for equilibrium states of a self-gravitating one-dimensional cloud of gas, embedded in an external gravitational field due to a plane of 'stars' being heated at a rate proportional to the local gas density, and cooling by thermal conduction. It is found that the general topology of the solutions is such that the gas density has a minimum on the plane of 'stars', rising to an infinite but integrable peak away from the plane so that the total mass of gas in the cloud is finite. The results may be of interest in investigations of interstellar molecular clouds and of filamentary structures in supernova remnants as well as in the modeling of gas distributions around 'cocoon' protostars.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 242
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  • 135
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    Formation of chromospheric resonance line profiles in supergiants (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The formation of chromospheric resonance line profiles is examined for the case of the relatively low-density atmospheres appropriate to late-type supergiants. The effects of partial frequency redistribution control the emergent line profiles, to the extent that even an isothermal atmosphere can give rise to apparent emission features. Schematic model chromospheres are used to demonstrate the effects of different velocity fields and temperature-density structures on the line profiles, as a first step toward a clearer understanding of the chromospheric line profiles and why supergiants have broad emission lines (the Wilson-Bappu effect). Neither the Doppler nor the mass column density explanation alone can explain the Wilson-Bappu effect in supergiants, but both theories may play a role.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 242
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  • 136
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    The rate of mass loss and variations in the wind from the Be star Delta Centauri (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 242
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  • 137
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    On the albedo of the interplanetary dust (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The zodiacal light brightness and measured spatial density of the interplanetary dust lead to a mean geometric albedo of 0.24 for the dust particles near 1 AU; whereas the composition of collected micrometeroids suggests a geometric albedo of less than or approximately equal to 0.1. The data do not support the very low albedo (0.01 or less) proposed by Cook (1978). The evidence is against a change in the mean particle albedo between 0.1 and 2 AU. Beyond 2 AU, the data are unclear and a change in albedo is not ruled out.
    Keywords: ASTROPHYSICS
    Type: Icarus; 43; Sept
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  • 138
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    Observations of the motion and distribution of the ionized gas in the central parsec of the Galaxy. II (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Observations of infrared fine-structure line emission from compact clouds of ionized gas within Sgr A West are presented. These clouds have diameters of 0.1-0.5 pc, internal velocity dispersions of 100 km/s (FWHM), and line center velocities up to + or - 260 km/s. Their masses are not accurately determined but are probably between 0.1 and 10 solar masses. They are ionized by radiation like that of stars of effective temperature not greater than 35,000 K. The clouds are shown to have lifetimes of 10,000 yr and so must be generated and dissipated at a rate of a few per 1000 yr. From analysis of the distribution of the velocities of the clouds, a most probable mass distribution is derived which includes a central pointlike mass of several x 10 to the 6th solar masses in addition to several x 10 to the 6th solar masses of stars within 1 pc of the center.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 241
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  • 139
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    The striated dust tail of Comet West 1976 VI as a particle fragmentation phenomenon (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The motions of 16 striae in the dust tail of Comet West are studied. It is found that all 16 striae have originated from particle ejections, and that the particles responsible for the formation of a discrete striae must be emitted simultaneously, be subjected to the same repulsive acceleration in the tail, and break up simultaneously. A strong correlation is found between the ejection times and the times of known explosive events. The repulsive accelerations of particle fragments in the striae vary from 0.6 to 2.7 times the solar attraction, indicating submicron grains of strongly absorbing materials. The repulsive acceleration of parent particles range from 0.55 to 1.10, which is only slightly smaller than those of their fragments and suggests highly nonspherical shapes of parents. The mass of dust in an average striae is estimated to be one-billion grams. Rotational bursting is discussed as a possible fragmentation mechanism. The absence of measurable effects of the Lorentz force indicate an upper limit of a few volts for the electric charge of the fragments.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal; 85; Nov. 198
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  • 140
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    Interstellar depletions and far-ultraviolet extinction in the Rho Ophiuchi cloud (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Copernicus ultraviolet data on six stars embedded in the well-studied Rho Ophiuchi cloud complex have been analyzed for interstellar abundances, densities, and far-ultraviolet extinction parameters, in an effort to determine how interstellar depletions depend on physical conditions. While there are variations within the cloud in the overall depletions, the pattern of depletions from element to element is constant for all six lines of sight. A picture is suggested in which the cloud core has a small velocity dispersion or is either so strongly depleted or so dense (hence not ionized) that the lines of first ions of heavy elements do not arise there, but rather form in a less-dense or less-depleted outer region. The cloud as a whole has substantial depletions, average to low far-ultraviolet extinction, and a low ratio of molecular to atomic hydrogen.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 241
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  • 141
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    The continuous spectrum of Markarian 421 during periods of X-ray satellite observations (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: New UBVRI photometry of Mrk 421 obtained during periods of X-ray satellite observations are presented. An X-ray light curve for 1977 November from the HEAO A-1 experiment is also given. The decomposition of the UBVR fluxes into a compact nonthermal component and an extended galactic component shows that there are coordinated variations in the optical nonthermal and X-ray emission. The data are consistent with the hypothesis that the mini-BL Lac object is emitting by the synchrontron-self-Compton process. The host galaxy of this composite source has properties like those of a giant elliptical.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 241
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  • 142
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    Gravitational radiation quadrupole formula is valid for gravitationally interacting systems (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: An argument is presented for the validity of the quadrupole formula for gravitational radiation energy loss in the far field of nearly Newtonian (e.g., binary stellar) systems. This argument differs from earlier ones in that it determines beforehand the formal accuracy of approximation required to describe gravitationally self-interacting systems, uses the corresponding approximate equation of motion explicitly, and evaluates the appropriate asymptotic quantities by matching along the correct space-time light cones.
    Keywords: ASTROPHYSICS
    Type: Physical Review Letters; 45; Dec. 1
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  • 143
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    Search for far-infrared emission from young supernova remnants (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A search has been conducted for 80-350 micron emission from the Tycho, Kepler, and Cas A supernova remnants. The bolometric fluxes are less than 5 x 10 to the -11th, 4 x 10 to the -12th, and 9 x 10 to the -12th W/sq m, respectively, for the entire radio shell, corresponding to luminosities less than 25,000, 1100, and 1500 solar luminosities (within 2 standard deviations). The ratio of dust to gas in Cas A is at least 10 times less than the 'normal' ratio.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 240
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  • 144
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    33 second X-ray pulsations in AE Aquarii (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The discovery of 33-s pulsations in the 0.1-4.0 keV light curve of the nova-like variable AE Aquarii is reported. These pulsations agree in period and phase with the optical pulsations. The periodicity probably originated from an accretion-induced hot spot on a rapidly rotating, magnetized white dwarf. It is possible that transient pulsations at nearby periods, similar to those seen in the optical light curve, are also present in the X-ray light curve.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 240
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  • 145
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    Hercules X-1 hard X-ray pulsations observed from HEAO 1 (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The 1.24-sec pulsations of Her X-1 in the energy range 13-75 keV have been analyzed in data obtained from the UCSD/MIT experiment on HEAO 1 during observations of the source on three dates in February 1978 and three in August 1978. Observational results are (1) the main pulse broadens somewhat with increasing energy; (2) the pulsation light curve undergoes pronounced changes at the leading edge of the main pulse from day to day; (3) spectral hardening within the main pulse is confirmed; (4) a 40-60 keV spectral feature in the spectrum is confirmed; (5) this feature is resolved, the pulse width broadening is greater than 20%, and its centroid varies with pulsation phase; and (6) the 13-75 keV spectrum does not noticeably vary from day to day, except for an overall intensity factor. Some implications of these results for the prevailing models of Her X-1 and the HZ Her-Her X-1 system are briefly discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 240
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  • 146
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    Photometric studies of composite stellar systems. IV - Infrared photometry of globular clusters in M31 and a comparison with early-type galaxies (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 240
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  • 147
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    Infrared photometry of the semistellar nucleus of M31 (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: New broad-band infrared JHK data and narrow-band CO and H2O indices for the semistellar nucleus of M31 are presented. The data were obtained specifically to test a prediction of a recent synthesis model by Faber and French in which the ratio of dwarf-to-giant light increases strongly in going from the bulge to the nucleus of M31. The new infrared data do not support such a model. Some alternative explanations for the behavior of the various indices are given, but the apparent conflict between the Faber-French interpretation of the strength of the Na I 8190 A feature and our data is not satisfactorily resolved.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 240
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  • 148
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    The abundance of CO in diffuse interstellar clouds - An ultraviolet survey (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: CO was detected in 17 directions and its upper limits were estimated in 21 directions by a UV survey carried out with the Copernicus satellite in the C-X 1088 A and E-X 1076 A lines toward 48 bright stars. The CO column densities range from 10 to the 12th to 10 to the 17th/sq cm and correlate with C I and H2. The tendency of the C I/CO ratio to be about 10 follows the ratio of particular atomic and molecular cross-sections and the physical parameters of interstellar clouds. Finally, the connection between UV observations in diffuse clouds and radio observations of (C-13)O in dark clouds is discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 242
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  • 149
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    Observations of outbursts from the recurrent X-ray transient A0538-66 and LMC X-4 (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Nine X-ray outbursts from the LMC have been observed with the HEAO 1 Large-Area Sky Survey Instrument. Some are shown to originate in the recurrent transient A0538-66, confirming the proposed 16 day periodicity and showing that the duration of the events can be as long as 14 days or as short as a few hours. Deviations from precise periodicity can be attributed to phase jitter or to a change in period occurring around the time of an exceptionally long outburst. Other outbursts which are irregular and consistently shorter originate in LMC X-4. A long-term light curve indicates that the LMC X-4 outbursts occur only when the source is in a high state, but are not strongly correlated with the binary phase.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 240
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  • 150
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    Models of molecular clouds and the abundances of H2CO and HCO/+/ (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Observations of HCO(+) and H2CO in a sample of 13 molecular clouds have been analyzed by construction of uniform, spherical cloud models. The total densities and the abundance of HCO(+) and H2CO relative to H2 which result from these models fall into two domains: one group of clouds has a low temperature, moderate density, and high abundances; the other group has higher temperature and density, but lower abundances. The factor distinguishing these groups may be depletion onto grains in the denser sources.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 240
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  • 151
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    Galactic and extragalactic contributions to the far-ultraviolet background (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Data from the 1350-1550 A bandpass channel of the 2.5-deg angular resolution extreme-ultraviolet telescope on the Apollo-Soyuz mission have been analyzed for stellar and airglow radiation contributions for the galactic latitude range above 30 deg. At intermediate latitudes, the resulting diffuse background is found to be correlated with the neutral hydrogen column density as determined by 21 cm radio data. This result, together with the observed anisotropy and mean intensity of the radiation field, is consistent with the hypothesis that scattering of galactic-plane starlight off dust grains having an albedo of 0.5 and a phase function coefficient of 0.5 is the primary source of the observed radiation field at the intermediate latitudes. The background intensity near the poles is, however, higher than expected from the H I column density and extinction measurements.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 240
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  • 152
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    Behavior of molecules on interstellar grains - Application of the Langevin equation and iterative extended Hueckel (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The Langevin equation was used to explore an adsorbate desorption mechanism. Calculations were performed using iterative extended Hueckel on a silica model site with various small adsorbates, e.g., H, CH, OH, NO, CO. It was found that barriers to free traversal from one site to another are substantial (about 3-10 eV). A bootstrap desorption mechanism for some molecules in the process of forming at a site also became apparent from the calculations. The desorption mechanisms appear to be somewhat balanced by a counterforce - the attraction of sites for the newly desorbed molecule. The order of attraction to a silica grain site for the diatomic molecules considered was OH greater than CH greater than CO greater than NO, when these entities were sufficiently distant. The nature of the silica grain and that of the 'cold' desorption mechanism, when considered together, suggest that the abundance of very small grains might be less common than anticipated.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 242
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  • 153
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    Criteria for fragmentation in a collapsing rotating cloud (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The isothermal collapse of a rotating protostar with pressure and self-gravity is calculated by a hydrodynamic computer code that treats three space dimensions. A number of initial conditions are tested to determine the conditions under which a cloud is unstable to fragmentation. It is shown that fragmentation does not proceed to a significant extent during the first free-fall time, but that in most cases fragmentation has occurred by 1.5 to 2 times the initial free-fall time. The extent to which the density in the fragments is enhanced over that in their surroundings on this time scale depends on the initial ratio of thermal to gravitational energy, but is only weakly dependent on the type and amplitude of the perturbation and on the initial rotational energy.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 242
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  • 154
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    Transient mass transfer caused by local surface heating in close binaries (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The surge of mass from one component of a binary system resulting from local surface heating is analyzed. The impact of such surges on the companion can produce transient phenomena such as those seen in X-ray binaries, RS CVn objects, and cataclysmic variables. The heating may be caused by nonlinear g-mode oscillations or by X-ray heating by the companion in X-ray binaries, among other possible mechanisms. As an example, model calculations have been performed for a surge, triggered by a relatively moderate local heating, in a hypothetical X-ray binary; the results show that such a surge can account for X-ray turn-ons.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 240
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  • 155
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    Resonant electrodynamic heating of stellar coronal loops: An LRC circuit analogue (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The electrodynamic coupling of stellar coronal loops to underlying beta velocity fields. A rigorous analysis revealed that the physics can be represented by a simple yet equivalent LRC circuit analogue. This analogue points to the existence of global structure oscillations which resonantly excite internal field line oscillations at a spatial resonance within the coronal loop. Although the width of this spatial resonance, as well as the induced currents and coronal velocity field, explicitly depend upon viscosity and resistivity, the resonant form of the generalized electrodynamic heating function is virtually independent of irreversibilities. This is a classic feature of high quality resonators that are externally driven by a broad band source of spectral power. Applications to solar coronal loops result in remarkable agreement with observations.
    Keywords: ASTROPHYSICS
    Type: NASA-TM-82065
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  • 156
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    Pulsar gamma-rays: Spectra luminosities and efficiencies (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The general characteristics of pulsar gamma ray spectra are presented for a model where the gamma rays are produced by curvature radiation from energetic particles above the polar cap and attenuated by pair production. The shape of the spectrum is found to depend on pulsar period, magnetic field strength, and primary particle energy. By a comparison of numerically calculated spectra with the observed spectra of the Crab and Vela pulsars, it is determined that primary particles must be accelerated to energies of about 3 x 10 to the 7th power mc sq. A genaral formula for pulsar gamma ray luminosity is determined and is found to depend on period and field strength.
    Keywords: ASTROPHYSICS
    Type: NASA-TM-82026
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  • 157
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    An X-ray survey of nine historical novae (1980)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: The Einstein Observatory imaging proportional counter was used to search for X-ray emission from nine nearby historical novae. Six of the novae were detected with estimated X-ray intensities between .1 to 4 keV of 10 to the -13th power to 10 to the -11th power ergs/sq cm-s, comparable to the intensities of previously detected cataclysmic variables. The X-ray intensity of one of the novae, V603 Aql, varies over times of several hundred seconds. The data suggest a correlation between the decay rate of the historical outburst and the current X-ray luminosity. Alternatively, the X-ray luminosity may be related to the inclination of the binary system.
    Keywords: ASTROPHYSICS
    Type: NASA-TM-82014
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  • 158
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    Magnetic field directional discontinuities. 2: Characteristics between 0.46 and 1.0 AU (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The characteristics of directional discontinuities (DD's) in the interplanetary magnetic field are studied using data from the Mariner 10 primary mission between 1.0 and 0.46 AU. Statistical and visual survey methods for DD identification resulted in a total of 644 events. Two methods were used to estimate the ratio of the number of tangential discontinuities (TD's) to the number of rotational discontinuities (RD's). Both methods show that the ratio of TD's to RD's varied with time and decreased with decreasing radial distance. A decrease in average discontinuity thickness of approx. 40 percent was found between 1.0 and 0.72 AU and approx. 54 percent between 1.0 and 0.46 AU, independent of type (TD or RD). This decrease in thickness for decreasing r is in qualitative agreement with Pioneer 10 observations between 1 and 5 AU. When the individual DD thickness are normalized with respect to the estimated local proton gyroradius (RA sub L), the average thickness at the three locations is nearly constant, 43 + or - 6 R sub L. This also holds true for both RD's and TD's separately. Statistical distributions of other properties, such as normal components and discontinuity plane angles, are presented.
    Keywords: ASTROPHYSICS
    Type: NASA-TM-82036 , REPT-695
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  • 159
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    Motion about the stable libration points in the linearized, restricted three-body problem (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The motion of a point particle in the neighborhood of a triangular libration point (L sub 4 or L sub 5) in the linearized, restricted problem of three bodies in the plane is described. The derivation of the equations of motion is standard. From these equations, three invariants of the motion are obtained; the Jacobi integral is expressed linearly in terms of two of these. The trajectories for varied initial conditions are drawn, and a complete geometric description of the particle motion is given in elementary terms. Each trajectory has an exterior boundary curve; its equation is found. An approximation to this boundary curve was known; the two curves are compared graphically. For certain initial conditions, there is an interior region from which the trajectory is excluded; the equation of the boundary of this region is given.
    Keywords: ASTROPHYSICS
    Type: NASA-RP-1065 , S-500
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  • 160
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    Stellar chromospheres (1980)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: Developments in the understanding and use of chromospheric diagnostics are discussed with emphasis on the following aspects: (1) trends emerging from semiempirical models of single stars; (2) the validity of claims that theoretical models of chromospheres are becoming realistic; (3) the correlation between the widths of Ca 2 H and K line emission cores and stellar absolute luminosity extending over 15 magnitudes (Wilson-Bappu relation); and (4) the existence of systematic flow patterns in stellar chromospheres.
    Keywords: ASTROPHYSICS
    Type: NASA-CR-163715
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  • 161
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    Gravitational radiation and the ultimate speed in Rosen's bimetric theory of gravity (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: In Rosen's bimetric theory of gravity the (local) speed of gravitational radiation is determined by the combined effects of cosmological boundary values and nearby concentrations of matter. It is possible for the speed of gravitational radiation to be less than the speed of light. It is here shown that the emission of gravitational radiation prevents particles of nonzero rest mass from exceeding the speed of gravitational radiation. Observations of relativistic particles place limits on the speed of gravitational radiation and the cosmological boundary values today, and observations of synchroton radiation from compact radio sources place limits on the cosmological boundary values in the past.
    Keywords: ASTROPHYSICS
    Type: Annals of Physics; 125; Mar. 198
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  • 162
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    Pristine nature of comets as revealed by their UV spectrum (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Satellite and rocket VUV observations of comets are discussed with reference to observations of OH and NH; the Lyman-alpha halo of hydrogen; and C, O, S atoms, ions, and molecules. Attention is also given to the study of production rates, and elemental and molecular abundances. It is shown that the observation of the VUV spectrum of comets has revealed new clues about comets, which could serve as a link between interstellar molecules and planetary atmospheres as well as between stellar and planetary astrophysics.
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  • 163
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    X-ray properties of quasars (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The X-ray properties of 111 catalogued quasars have been examined with the imaging proportional counter on board the Einstein Observatory. Thirty-five of the objects, of redshift between 0.064 and 3.53, were detected as X-ray sources. The 0.5-4.5-keV X-ray properties of these quasars are correlated with their optical and radio continuum properties and with their redshifts and variability characteristics. The X-ray luminosity of quasars tends to be highest for those objects which are bright in the optical and radio regimes and which exhibit optically violent variability. These observations suggest that quasars should be divided into two classes on the basis of radio luminosities, spectra, evolution and underlying morphology and that quasars can make up a significant portion of the diffuse soft X-ray background only if the slope of the optical quasar log N-log S relation is steeper than 2 to m sub b of about 21.5.
    Keywords: ASTROPHYSICS
    Type: Nature; 288; Nov. 27
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  • 164
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    Interstellar gas in the Gum Nebula (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A survey of the interstellar gas near the Gum Nebula by optical observation of 67 stars at Ca II, 42 stars at Na I, and 14 stars in the UV with the Copernicus satellite provided radial velocities and column densities for all resolved absorption components. Velocity dispersions for gas in the Gum Nebula are not significantly larger than in the general interstellar medium; the ionization structure is predominantly that of an H II region with moderately high ionization. Denser, more highly ionized clouds are concentrated toward the Gum Nebula; these clouds do not show the anomalously high ionization observed in the Vela remnant clouds.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 240
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  • 165
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    Molecule formation and infrared emission in fast interstellar shocks. II - Dissociation speeds for interstellar shock waves (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The postshock destruction of molecules is examined, including the processes of (1) collisions with neutral hydrogen atoms and molecules, (2) electronic collisions, and (3) neutral chemical reactions with atoms, particularly atomic hydrogen. By using conservative estimates of collisional dissociation rates from individual vibrational states, it is found that process (1) leads to the destruction of molecular hydrogen behind shocks with speeds equal to or greater than 25 km/s if the preshock molecular gas has hydrogen nucleus densities of equal to or greater than 10 to the 4th/cu cm. At lower densities (100 per cu cm), destruction occurs for shock speeds equal to or greater than 50 km/s and process (2) dominates. Dissociation of molecules such as CO, H2O, and O2 follows the destruction of H2, as the resultant hydrogen atoms chemically dissociate the metal atoms from their bonds (process 3) in the hot postshock gas. These results demonstrate that many of the observed high-speed interstellar molecules, if shock accelerated, must have dissociated and reformed in the postshock gas.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 241
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  • 166
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    X-rays from G74.9 + 1.2 - An elderly Crab Nebula (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The supernova remnant G74.9 + 1.2, which resembles the Crab Nebula in many of its radio properties, has been detected in 0.15-3 keV X-rays with the Imaging Proportional Counter on the Einstein Observatory. The intrinsic luminosity of the object is about 100 times weaker than the Crab Nebula in this band. The X-ray morphology is centrally brightened (not a shell) with a total extent about 5 arcmin (17 pc). The nearby, intense, compact radio source 2013 + 370 is also probably detected as an extended X-ray source. It is argued that G74.9 + 1.2 represents an object similar to the Crab Nebula but of age 4000-7000 years. If this is the case, the period of the pulsar or neutron star (whose loss of rotational energy fuels the nebula) is predicted to be 0.1-0.2 s.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 241
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  • 167
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    The approximation of radiative effects in relativistic gravity - Gravitational radiation reaction and energy loss in nearly Newtonian systems (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: An argument is presented to determine the accuracy with which a solution of Einstein's field equations of gravitation must be approximated in order to describe the dominant effects of gravitational radiation emission from weak-field systems. Several previous calculations are compared in the light of this argument, and some apparent discrepancies among them are resolved. The majority of these calculations support the 'quadrupole formulae' for gravitational radiation energy loss and radiation reaction.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 242
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  • 168
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    Neutrinos and the age of the universe (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The age of the universe should be calculable by independent methods with similar results. Previous calculations using nucleochronometers, globular clusters and dynamical measurements coupled with Friedmann models and nucleosynthesis constraints have given different values of the age. A consistent age is reported, whose implications for the constituent mass density are very interesting and are affected by the existence of a third neutrino flavor, and by allowing the possibility that neutrinos may have a non-zero rest mass.
    Keywords: ASTROPHYSICS
    Type: Nature; 288; Nov. 13
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  • 169
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    X-ray observations of Seyfert galaxies with the Einstein Observatory (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Thirty-seven Seyfert galaxies have been observed with the Imaging Proportional Counter on the Einstein Observatory. X-ray emission from 20 Seyfert 1 galaxies, three of which have been previously detected, and from four Seyfert 2 galaxies. Significant correlations are found between the 2 keV X-ray flux and the nonstellar continuum near 3.5 microns, the nonstellar B band continuum, and the H-beta line flux, and also between 0.5-4.5 keV X-ray luminosity and the zero intensity width of the H-beta emission line and the H-beta forbidden O III ratio. These correlations apply to both types of Seyfert galaxy, as well as the X-ray selected QSOs of Gindlay et al., suggesting that the same physical process operates in each one over a continuous range of intrinsic luminosity.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 242
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  • 170
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    The infrared echo of a supernova in a dust cloud (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A simple model is given for the infrared light-echo from a supernova explosion in a molecular cloud. The color temperature is determined by the vaporization temperature of the dust grains, and the time scale is given by the light travel time across the distance to which grains are vaporized. For typical parameters, a supernova exploding in a cloud with a density of approximately 10,000/cu cm at a distance of 10 kpc produces a flux of approximately 60,000 Jy at 3.5 microns for 150 days.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 242
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  • 171
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    On the origin of striae in cometary dust tails (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: It has been argued by Sekanina that the so-called striae or pseudo-synchronic bands observed in the dust tails of several comets are a consequence of the sudden disruption of elongated or chainlike parent grains in the tail. The present paper offers a specific mechanism for this disruption process, that is, electrostatic disruption following sudden charging to high electrostatic potentials. Assuming the grains to be prolate spheroids, it is shown that they can attain potentials in the range -60 V to -300 V when subject to energetic electron beams (1-10 keV). The energy source for these electrons is the interaction of the solar wind with the cometary ionosphere producing currents and associated electrostatic double layers.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 242
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  • 172
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    X-ray line emission from the Cygnus Loop (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The HEAO 1 satellite has observed the X-ray spectrum of the Cygnus Loop in the 0.1-2.0 keV band. The observed count-rate spectrum is deconvolved by the Kahn and Blissett technique to demonstrate conclusively the presence of oxygen- and iron-line emission between 0.6 and 0.9 keV. The spectrum has been fitted with single- and two-component Raymond-Smith plasma emission models. The best-fit dominant X-ray temperature is approximately 3,200,000 K, and the best-fit interstellar column density is approximately a few times 10 to the 20th/sq cm.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 242
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  • 173
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    4U 1626-67 and the character of highly compact binary X-ray sources (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 240
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  • 174
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    A magnetic study of spotted UV Ceti flare stars and related late-type dwarfs (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A multichannel photoelectric Zeeman analyzer has been used to investigate the magnetic nature of the spotted UV Ceti flare stars. Magnetic observations were obtained on a sample of 19 program objects, of which 5 were currently spotted dKe-dMe stars, 7 were normal dK-dM stars, 7 were UV Ceti flare stars, and 1 was a possible post-T Tauri star. Contrary to most previously published observations and theoretical expectations, no magnetic fields were detected on any of these objects from either the absorption lines or the H-alpha emission line down to an observational uncertainty level of 100-160 gauss (standard deviation).
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 240
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  • 175
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    Iron K photons from weakly magnetized neutron stars in X-ray binaries (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The emission of iron K photons by the continuum X-ray source and the neutron star surface is considered. It is shown that the continuum sources of X-ray binaries produce negligible amounts of iron K photons because nearly all iron atoms in the continuum source are fully stripped due to the intense X-ray fluxes. In contrast, the atmosphere of the neutron star in an X-ray binary might be an important source of iron K photons (photon energy about 6.5 keV) because it is bombarded by a large number of hard X-rays capable of photo-ejecting K-shell electrons from iron atoms. Information is discussed concerning the magnetic field strength, the gravitational potential at the neutron star surface, and the direction of the magnetic dipole axis which are obtainable from the observations of K photons of the neutron star atmosphere.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 240
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  • 176
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    The discovery of an O subdwarf in the globular cluster NGC 6712 (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Spectral data for C49 in the globular cluster NGC 6712 are examined with reference to evolutionary models for low-mass stars that are contracting into white dwarfs. The spectrum of this star is found to be almost identical to that of the first sdO star found in a globular cluster, star A in NGC 6397. Analysis of the spectral data using nonlocal thermodynamic equilibrium models gives surface parameters T not less than 50,000 K, log g = 5.5 plus or minus 0.5, and N(He)/N(H) approximately equal to 0.1. The results are consistent with the models considered.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 240
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  • 177
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    Diffuse X-ray emission from the jets of SS 433 (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The detection of large-scale diffuse X-ray jets from the variable-emission-line object SS 433 is reported. Observations were made with the high resolution imager and imaging proportional counter on board the Einstein X-ray Observatory. The two diffuse X-ray features discovered are found to be aligned with both the central source of SS 433 and with the bulges of the shell of the huge supernova remnant W 50 associated with SS 433, thus confirming the detection of jets related to SS 433 and the link between SS 433 and W 50, establishing a minimum age of 1000 years for the jet phenomenon and offering an explanation of the size of W 50. Processes by which two oppositely directed beams of material from the SS 433 source region may emit the diffuse X-rays are then considered, including shock heating by interactions with the ambient medium and synchrotron radiation. Similarities between the morphologies of the diffuse X-ray emission and those of radio galaxies are also noted.
    Keywords: ASTROPHYSICS
    Type: Nature; 287; Oct. 30
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  • 178
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    The optical identification of H2252-035 with a cataclysmic variable (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: An improved position is presented for the X-ray source H2252-033 using the Ariel V Sky Survey Instrument, and precise positioning using the Scanning Modulation Collimator on HEAO-1. The source is identified optically with a 13th magnitude emission-line object, which is probably a white dwarf binary with a well formed accretion disk, with similarities to the dwarf novae (e.g., SS Cyg) at minimum.
    Keywords: ASTROPHYSICS
    Type: Royal Astronomical Society; vol. 193
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  • 179
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    Far-infrared polarization of the Kleinmann-Low Nebula (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Further data on the polarization of the far-infrared (wavelength greater than 40 microns) emission from the Orion Nebula shows no evidence for polarized emission by aligned grains. Results at wavelength about 71-115 microns are consistent with a small (about 1.5%) absorption-induced polarization with about the same position angle on the sky as the polarization measured at shorter wavelengths.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal; 85; Oct. 198
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  • 180
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    Stellar convection. III - Convection at large Rayleigh numbers (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The results of a numerical, three-dimensional study of convection in a self-gravitating sphere of Boussinesq fluid with a Rayleigh number of 10-billion and a Prandtl number of 1 are presented. The velocity and temperature are computed by using spectral methods in the horizontal and finite-differencing in the radial directions. An eddy viscosity and diffusivity are needed to model the subresolution flow. For Rayleigh numbers much less than 10-billion the flows do not have well-defined inertial ranges, and an eddy viscosity and diffusivity cannot be assigned in this self-consistent manner. By computing the energy spectra as well as the detailed energy budgets as a function of wavenumber, it is shown that for Rs = 10-billion there is an inertial range for the modes corresponding to spherical harmonics with l greater than 6.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 240
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  • 181
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    1.0 millimeter maps and radial density distributions of Southern H II/molecular cloud complexes (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Measurements of the 1.0-mm continuum emission from seven Southern Hemisphere H II region/molecular cloud complexes located in the inner part of the Galaxy near the galactic plane are presented. The sources were mapped based on observations made by a remote-controlled prime focus infrared photometer on the Cerro Tololo 4-m telescope at a resolution of 65 arcsec. The morphologies and physical characteristics of the sources investigated are found to be similar, with dust column densities of 0.006-0.030 g/sq cm, linear extents of 1.5-3 pc, total masses of 20,000-100,000 solar masses and infrared luminosities between 2 and 4 x 10 to the 6th solar luminosities. In all cases, the dense, extended dust envelopes are observed to be singly peaked and centered about one or more compact near-infrared sources, with a radial density distribution around the central peak proportional to the -1.5 power of the radius as in other extended 1.0-mm continuum sources.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 240
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  • 182
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    The Parker spiral configuration of the interplanetary magnetic field between 1 and 8.5 AU (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The magnetic field data from the Pioneer 10 and 11 spacecraft show that the field directions between 1 and 8.5 AU are in accordance with the Parker spiral directions within quiet and interaction regions. The included angle between the inward and outward sectored field directions is near 180 deg; the field direction manifests greater variability in quiet regions than in interaction zones. The fractional polarities below 10 deg heliographic latitude are dominated by temporal variations; however, dual-spacecraft investigations permitted a significant latitudinal gradient to be extracted. The sector structure extended occasionally to 16 deg heliographic latitude during the period of average current sheet inclination in 1976; it is proposed that the fast streams associated with interaction regions may move the current sheet to higher latitudes when the source of the fast plasma is in the southern solar hemisphere.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research; 85; Dec. 1
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  • 183
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    Some fluid dynamic problems in the studies of planetary collisions with cometary comas (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The flow field in a cometary coma varies from free molecular flow to transition flow and finally to continuum flow. General discussions of these flow regimes with two-phase effects are given. Some numerical results of similarity solution of a strong shock propagation in a two-phase flow are presented.
    Keywords: ASTROPHYSICS
    Type: Acta Astronautica; 7; Dec. 198
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  • 184
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    The outer atmospheres of cool stars. VII - High resolution, absolute flux profiles of the Mg II h and k lines in stars of spectral types F8 to M5 (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Keywords: ASTROPHYSICS
    Type: PB81-171449 , AD-A103917 , AFGL-TR-81-0240 , Astrophysical Journal Supplement Series; 44; Nov. 198
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  • 185
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    Abundances and excitation of interstellar methyl formate (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The detection of methyl formate (HCOOCH3) in four transitions toward Orion KL, in two transitions toward Sagitarrius B2, and in one transition toward W51 is reported. The column densities of HCOOCH3 are found to be surprisingly large (2-5 x 10 to the 14th per sq cm) in all three clouds. Stimulated emission in the 18 cm K doublet of HCOOCH3 toward Sagittarius B2 is clearly demonstrated. The relatively large column densities of HCOOCH3 in clouds outside the galactic-center region probably imply that this molecule is widely distributed in the galaxy, but the negative results in other clouds require lower column densities than in Orion by a factor of 0.5 or less. Two unidentified lines were detected in Orion, at approx. 91 and 99 GHz.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 241
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  • 186
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    Spectroscopic observations of the optical counterpart of Centaurus X-4 (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The optical spectrum of the transient X-ray burst source Centaurus X-4 was observed about 5 weeks after the source reached its maximum. The brightness of the optical counterpart had decreased to V = 18.2, and the star had become appreciably redder (B - V = 0.7) compared to its color at maximum. The spectrum of Centaurus X-4 is similar to that of cataclysmic variables showing strong emission lines of H-1 and weaker lines of He-1 and He-2. The N03 lambda 4640 line is not visible. The continuum energy distribution of Centaurus X-4 shows the presence of a main-sequence star in the system, with spectral type between K3 and K7. This is consistent with the orbital period of 8.2 hr proposed by Kaluzienski et al (1980), if the main-sequence star is close to filling its Roche lobe.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 241
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  • 187
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    On the origin and persistence of long-period pulsating X-ray sources (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Mounting observational evidence and theoretical results suggest that most pulsing X-ray sources, including those with massive companions, are disk fed when significant mass transfer is taking place. Regardless of whether or not substantial braking has occurred before the onset of disk accretion, once it begins the resulting strong braking torque on fast rotators is sufficient to spin-down a neutron star from an initial period approx. 1 sec to a period approx. greater than 100 sec in a time short compared to the main-sequence lifetime of a massive companion and even, in many cases, in a time short compared to the star's lifetime as a bright X-ray source. It is argued that sources with longer periods have larger magnetic moments, or lower mean luminosities, or both, whereas sources with shorter periods have smaller magnetic moments, or higher mean luminosities, or both.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 241
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  • 188
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    Upper limits on X-ray line emission from the Crab Nebula (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: X-ray emission lines from the Crab Nebula and the surrounding region have been searched with the Focal Plane Crystal Spectrometer (FPCS) on the Einstein Observatory. A 3 x 30 arcmin and a 6 arcmin diameter circular aperture were pointed at several positions centered on, and immediately to the north and south of, the nebula. Stringent upper limits are obtained for emission in lines of N-6 (0.43 keV), O-8 (0.65 keV), Fe-17 (0.83 keV), and others - most of which are prominent in the spectra of other supernova remnants and of the sun. The observed upper limits and standard models for the emission from a thermal plasma lead to upper limits on the quantity of hot plasma within or around the Crab. In particular, previously reported emission from a 7 arcmin diameter region surrounding the Crab is probably due to scattering of X-rays from the central source by interstellar dust in the line of sight and is certainly not due to emission from a thermal plasma.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 241
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  • 189
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    Radiative transfer in dusty nebulae. III - The effects of dust albedo (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The effects of an albedo of internal dust, such as ionization structure and temperature of dust grain, were studied by the quasi-diffusion method with an iterative technique for solving the radiative heat transfer equations. It was found that the generalized on-the-spot approximation solution is adequate for most astrophysical applications for a zero albedo; for a nonzero albedo, the Eddington approximation is more accurate. The albedo increases the average energy of the diffuse photons, increasing the ionization level of hydrogen and heavy elements if the Eddington approximation is applied; the dust thermal gradient is reduced so that the infrared spectrum approaches blackbody spectrum with an increasing albedo.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 241
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  • 190
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    Line formation in winds with enhanced equatorial mass-loss rates and its application to the Wolf-Rayet star HD 50896 (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A model having a spherically symmetric velocity distribution with a higher density at the equatorial region was developed to simulate the UV spectrum of the Wolf-Rayet star HD 50896. The spectrum showed P Cygni-shaped profiles whose emissions are stronger than expected in a spherically symmetric stellar wind. The model was studied varying the inclination angle of the star-wind system and the polar to equatorial density ratios; it was shown that HD 50896 could possess a nonspherically symmetric wind and that its symmetry axis is inclined between 60 and 90 deg. It is possible that the velocity distribution of the wind could include an inner constant velocity plateau beyond which the wind accelerates to its terminal velocity as indicated by infrared continuum investigations.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 241
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  • 191
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    A search for the lowest-energy conformer of interstellar glycine (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The first search for the lowest-energy conformation of interstellar glycine has been carried out. An emission line has been detected in Sgr B2 which is coincident in frequency with the J(K-K+) = 14(1, 14)-13(1, 13) transition of conformer I glycine; while the carrier of the observed line is uncertain, no other frequency-coincident species are known, and hence glycine cannot be ruled out. Several previously unidentified lines have been identified as methyl formate. Evidence for the existence of the elusive interstellar ethylene oxide, the only reported interstellar ring-structure molecule, is discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 241
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  • 192
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    The effect of solar-cycle ultraviolet flux variations on cometary gas (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The effects on comet gas of variations in the solar ultraviolet flux during solar cycle 21 are discussed. The photoionization, photodissociation, and resonance fluorescence and scattering rates of individual atoms and molecules increase by factors ranging up to 4, leading to potential order of magnitude variations in emission-line fluxes between minimum and maximum solar activity. These effects are illustrated for H2O and CO. Recent observations of comet Bradfield (1979) are discussed, and it is suggested that comets appearing near solar maximum be extensively observed to provide information on the response of cometary gas to solar flux variations, which can be used to discriminate between cometary models.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 241
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  • 193
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    Correlated observations of a spatially resolved type III solar radio burst group and the associated hard X-ray emission (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The first measurements of the spatial structure of a group of type III solar radio bursts associated with an impulsive hard X-ray burst are presented. At 169 MHz the radio source has been found to consist of two principal regions separated by about 300,000 km. The two regions together produced a total of four component bursts in good time correlation with spikes in the hard X-ray emission. The observations indicate that electron acceleration/injection occurs over a region which covers a wide range of magnetic field lines.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 241
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  • 194
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    An absorption line in the ultraviolet spectrum of 40 Eridani B (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Two excellent low-resolution spectra show an absorption line of equivalent width 3 A, near 1391 A, in the typical DA (hydrogen atmosphere) white dwarf 40 Eri B. The line is confirmed by a high-resolution spectrum and is the first seen in any DA star. Ultraviolet fluxes and the profile of Lyman-alpha confirm an effective temperature near 17,000 K. If the line is Si IV, it requires a temperature near 40,000 K. Unattractive possibilities are a hot circumstellar absorbing envelope dependent on accretion from companions, or formation at large optical depth in a transparent atmosphere with high Si/H. A suggestion that H2 should be considered leads to the possible interpretation as the (0, 5) transition of the Lyman band, formed at small optical depth. The band should be stronger in cooler DAs.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 241
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  • 195
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    Extended 20 micron emission from the center of NGC 1068 (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Multiaperture photometry of the Seyfert galaxy NGC 1068 is reported which demonstrates that significant 20 micron emission originates at positions located more than 3 arcsec, or 260 pc, from the nucleus. These observations strongly support arguments that most of the infrared flux is thermal emission from dust. It is argued that the dust giving rise to this extended emission cannot be heated solely by a compact nuclear object. It is suggested that there is a powerful energy-generation mechanism, possibly an enormous burst of star formation, operating on a scale much larger than that identified with the visible nucleus.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 241
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  • 196
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    Neutral cometary atmospheres. III - Acceleration of cometary CN by solar radiation pressure (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The acceleration of cometary CN radicals due to solar radiation pressure has been determined by fitting Monte Carlo models to nine observed sunward-tailward pairs of brightness profiles of the (0-0) band of CN at 3883 A. The profiles were determined from spectrograms of comets Bennett 1970 II and West 1976 VI. The values of the observed acceleration agree with those computed from resonance fluorescence calculations to within the expected uncertainties. This provides an independent confirmation of the identification of the observed scale lengths with the photochemical lifetimes and velocities associated with the production of observed cometary CN by the photodissociation of HCN. The ratio of the intensity of the (0-1) band of CN at 4216 A to the (0-0) band at 3883 A has been determined from spectrograms of comet West, and is compared with theoretical values.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 241
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  • 197
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    The very long type II X-ray bursts from the rapid burster (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Two very long type II bursts (greater than 200 sec) from the rapid burster (MXB 1730-335) have been observed on Mar. 3, 1979 UT. Similar long bursts were observed about five months later, in August 1979, by the Japanese satellite Hakucho. This new burst mode is possibly related to the early stage of the turn-on. In this paper, results of the analysis of the bursts from the rapid burster as observed by the SAS 3 X-ray observatory during Mar. 3-5, 1979 are presented.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 241
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  • 198
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    IUE ultraviolet spectra and chromospheric models of HR 1099 and UX Arietis (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: IUE spectra in the region 1150-3200 A of the RS CVn-type variables HR 1099 and UX Arietis are presented and analyzed in terms of chromospheric models. Measurements of Mg h and k lines and Ca II H-K and H alpha spectra are indicated which are found not to be correlated with orbital phase or radio flares and which suggest that the strong emission arises in the K star rather than the G star in these systems. Under the assumption that the UV emission lines are associated with the K star, surface gravities of log g = 3.6 and 3.4 and effective temperatures of 4850 and 5000 K are adopted for HR 1099 and UX Ari, respectively, along with solar metal abundances for each. Model calculations of the chromospheric structure necessary to account for observed C(+), Mg(+), Si(+) and Si(+2) line fluxes are presented which indicate that the transition region pressure lies in the range 0.18-1.0 dynes/sq cm, implying transition regions that are more extended than that of the sun and are not conductively heated. It is noted that pressure scaling laws and the use of Mg II and C II lines as pressure diagnostics may be invalid, possibly due to atmospheric inhomogeneities or gas flows.
    Keywords: ASTROPHYSICS
    Type: PB81-163032 , Astrophysical Journal; vol. 241
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  • 199
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    The interstellar material in front of Chi Ophiuchus. II - Ultraviolet observations (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The high-resolution UV spectrometer aboard the Copernicus satellite was used to observe the interstellar gas toward the moderately reddened star Chi Oph. The data are consistent with the hypothesis that the material in both the -6 and -12 km/s blend of gas and the -26 km/s cloud could have been affected by shock front activity, though the signatures of that activity are different in each case. These observations of the blend of gas establish that both low and high density neutral material must be present.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 241
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  • 200
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    The infrared emission of G333.6-0.2 - An extremely nonspherical H II region (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The southern H II region G333.6-0.2, which has a total luminosity of 3.3 million solar luminosities (for an assumed distance of 4 kpc) was mapped at 2.2, 10, 30, 50, and 100 microns. At all wavelengths, the surface brightness of the infrared radiation is unusually high and the structure of the source is compact and symmetrical. The present observations, along with previous data, suggest that G333.6-0.2 is excited by a single luminous object or a very compact cluster, which has formed on the front surface of a dense molecular cloud as seen from the earth. It is shown that the spectral and spatial characteristics of the infrared radiation can be understood in terms of this blister model.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 241
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