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  • ASTROPHYSICS  (2,970)
  • ASTRONOMY  (1,733)
  • 1980-1984  (4,703)
  • 1
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    The PDS-VAX intelligent plate scanning system of Trieste Astronomical Observatory (1984)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: An intelligent subsystem for interfacing a PDS1010A digital microdensitometer to a DEC DR11W DMA 16 bit UNIBUS port in DEC VAX VMS environment was tested. The subsystem employs two MOTOROLA M68000 microprocessors with 128 KB data memory. The PDS primitives and the user defined high level scanning functions and preprocessing modules are loaded from the host computer into two 8 KB RAM memories in the microprocessors using a dedicated PDS control language. The subsystem is planned to employ a nonstandard photomultiplier electronics. Two design schemes were tested: (1) based on three amplifiers of gain 10 cascaded and multiplexed to a 12 bit AD converter, and (2) based on a single amplifier of gain 100 and two 14 bit AD converters.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Astron. Microdensitometry Conf.; p 175-187
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  • 2
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    Space debris impact experiment (S0001) (1984)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: The specific objectives of this experiment are to establish the population and size distribution of meteoroids in the mass range from 10 to the minus 10 power to 10 to the minus 4 power G, to establish the current population of man-made debris in the same mass range, and to obtain data on the physical properties (composition and density) of meteoroids.
    Keywords: ASTROPHYSICS
    Type: Long Duration Exposure Facility (LDEF); p 136-137
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  • 3
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    Interplanetary dust experiment (A0201) (1984)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: The objective of this experiment is to study interplanetary dust, variously referred to as cosmic dust, cometary dust, zodiacial dust, or meteoric dust particles. Specific objectives are to obtain information regarding particle mass and velocity, and to undertake correlative analyses with other experiments, both on LDEF or near the time of the LDEF flight.
    Keywords: ASTROPHYSICS
    Type: Long Duration Exposure Facility (LDEF); p 134-135
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  • 4
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    Attempt at dust debris collection with stacked detectors (A0138-2) (1984)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: The primary objective of this experiment is to investigate the feasibility of future missions of multilayer thin-film detectors acting as energy sorter to collect micrometeoroids, if not in their original shape, at least as fragments suitable for chemical analysis. It is expected that this kind of particle collector will help in solving one of the most puzzling topics in cosmic-dust studies: the mineralogical and chemical composition of the particles. This is a matter of great interest in the study of the origin and evolution of the solar system.
    Keywords: ASTROPHYSICS
    Type: NASA. Langley Research Center Long Duration Exposure Facility (LDEF); p 124-126
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  • 5
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    STEP flight experiments Large Deployable Reflector (LDR) telescope (1984)
    In:  CASI
    Details
    Publication Date: 2006-04-03
    Description: Flight testing plans for a large deployable infrared reflector telescope to be tested on a space platform are discussed. Subsystem parts, subassemblies, and whole assemblies are discussed. Assurance of operational deployability, rigidization, alignment, and serviceability will be sought.
    Keywords: ASTRONOMY
    Type: NASA. Langley Research Center STEP Expt. Requirements; p 257-278
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  • 6
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    Interstellar-gas experiment (A0038) (1984)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: The objectives of this experiment are to collect and isotopically analyze interstellar gas atoms around the orbit of the Earth for the purpose of obtaining new data relevant to understanding nucleosynthesis, and to study the dynamics of the interstellar wind inside the heliosphere and the isotopic composition of the interstellar medium outside the heliosphere. The experiment hardware will act as a set of simple cameras with high-purity copper-beryllium collecting foils serving as the film. The experiment housing will mount and thermally control the foils, establish the viewing angles and viewing direction, provide baffling to reject ambient neutral particles, provide a voltage grid to reject ionospheric charged particles, sequence collecting foils, control exposure times, and protect the foils from contamination during the deployment and retrieval of the LDEF. After being returned to Earth, the entrapped atoms can be analyzed by mass spectroscopy to determine the relative abundance of the different isotopes of helium and neon. An attempt will also be made to detect argon.
    Keywords: ASTROPHYSICS
    Type: NASA. Langley Research Center Long Duration Exposure Facility (LDEF); p 98-100
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  • 7
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    Infrared mapping of galaxian centers: Star forming regions with kiloparsec scale sizes (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: A 1 to 20 micron mapping of the centers of galaxies encompassing the regions that extend out to several kiloparsecs from the nuclei is reviewed. Power emerging at or = 5 microns is a direct measure of the number of young stars present. This conclusion is strongly supported by the large-scale association of the infrared-emitting regions with visual continuum and line emission indicative of young stars, and by the similarity of the energy distributions to those of Galactic HII region/molecular cloud complexes. Much of the young-star activity is completely hidden from view. At shorter wavelengths, a variety of processes, including bremsstrahlung, are evident.
    Keywords: ASTRONOMY
    Type: Royal Observatory Star Formation Workshop; p 183-198
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  • 8
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    High spatial resolution IR observations of young stellar objects - A possible disk surrounding HL Tauri (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: High spatial resolution images of the T Tauri star HL Tau were obtained at 1.6 microns and 2.2 microns. The original images as well as maximum entropy image reconstructions reveal a circumstellar envelope structure, similar at both wavelenghts, and extended along P.A. = 112 deg; the 10 percent width of the structure is 1.9 sec (300 AU at 160 pc). The extended structure is interpreted as light scattered toward earth by dust in a disk surrounding this young stellar object. Polarization measurements made at 2.2 microns support this hypothesis. The total solid particle mass is, at minimum, 5 x 10 to the -7th solar mass.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 283; L57-L61
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  • 9
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    Very slow classical Cepheids - Theoretical models with periods longer than 50 days (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Systematics of the light curves of classical Cepheids with the longest known periods have been investigated with the help of full-amplitude models of pulsating stellar envelopes. For periods exceeding about 60 days, flat-topped light curves of the S Vul type are found to replace the smooth, asymmetric light curves characteristic of the slightly faster Cepheids. Predicted light and velocity amplitudes (although not the predicted radius amplitudes) agree well with observations. Variables with fluctuating light minima are observed to lie well off the mean period-luminosity relation, as are a few other (more stable?) variables with similarly long periods. The explanation for the long periods is probably low effective temperature rather than a low stellar mass. Because of the abnormal slowness of the classical Cepheids with periods longer than about 100 days, it is recommended that these variables not be used to calibrate the mean period-luminosity relation. Analogies between the slow classical Cepheids and the slow Population II Cepheids are drawn.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 281; 811-814
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  • 10
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    On the '3 kiloparsec arm' - Resonance excitation of linear and nonlinear waves by an oval distortion in the central region (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The mechanism responsible for the massive rapidly expanding Galactic feature known as the 3-kpc arm (Rougoor and Oort, 1960) is investigated theoretically in the framework of a density-wave model of the Galaxy. The arm is attributed to outgoing waves excited at the outer Lindblad resonance (OLR) of a small rotating oval distortion near the Galactic center. Linear and nonlinear models are developed, and it is shown that a density crest at 3.5 kpc with expansion velocity 53 km/s can be generated by a distortion turning at 118 km/s kpc with a 10-percent perturbation of the main gravitational field at the OLR (located at 3 kpc). The wave character of the nonlinear solution is found to be the same as that of the linear solution and to give good agreement with the observations in terms of expansion velocity, size, shape, and mass; only the observed asymmetry of the arm is not reproduced.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 281; 600-613
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  • 11
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    The Gamma-Ray Observatory mission objectives and its significance for gamma-ray astronomy (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The Gamma Ray Observatory (GRO) is an approved NASA mission, programmed for launch in 1988. Its complement of four detectors has established goals: (1) to study the nature of compact gamma-ray sources such as neutron stars and black holes, or objects whose nature is yet to be understood; (2) to search for evidence of nucleosynthesis especially in the regions of supernovae; (3) to study structural features and dynamical properties of the Galaxy; (4) to explore other galaxies, especially the extraordinary types such as radio, Seyferts, and quasars; and (5) to study cosmological effects by examining the diffuse radiation in detail. This paper discusses the design, objectives, and expected scientific results of each of the GRO instruments in view of the GRO mission goals.
    Keywords: ASTRONOMY
    Type: Advances in Space Research (ISSN 0273-1177); 3; 10-12
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  • 12
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    Superclustering and the large-scale structure of the Universe (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A complete redshift survey of nearby rich galactic clusters is analyzed in terms of a spatial correlation function, the growth of supercluster, the presence of superclusters around the Bootes void and the discovery of a 300 Mpc void. Abell's (1958) statistical sampling of rich clusters is used for the study. Attention is given to the dependence of the correlation function on the richness of the system, with finding that chances are greater of finding rich neighbors closer together than poor neighbors. Samples of redshifts of 4 or less correlate well with clusters of redshift 5 or more. The size of intergalactic voids is proportional to the surrounding galactic excesses. Finally, the superclusters exist on scales of about 100 Mpc/h, which is larger than expected.
    Keywords: ASTROPHYSICS
    Type: Advances in Space Research (ISSN 0273-1177); 3; 10-12
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  • 13
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    Ultraviolet spectral morphology of the O stars - The remarkable luminosity dependence of the Si IV stellar wind effect (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: An extensive survey of ultraviolet O type spectra, by means of high-resolution data from the International Ultraviolet Explorer archives, shows a strong correlation between both the photospheric and stellar wind features, and the optical spectral types. In particular, the stellar wind effect in the Si IV resonance doublet displays a strong luminosity dependence which has not been completely described before: there is no effect anywhere on the main sequence, but it develops gradually through the intermediate luminosity classes into a full P Cygni profile in the supergiants. This behavior is in sharp contrast to that of the C IV and N V, which have strong P Cygni profiles throughout most of the O type domain, including the main sequence. The Si IV effect simultaneously provides a sensitive classification criterion and poses an outstanding problem for detailed astrophysical interpretation. In addition, a new emission feature at 1574 A, possibly due to N III or to N IV forbidden line, is reported.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 280; L27-L30
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  • 14
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    Do bipolar magnetic regions exist on the surfaces of early-type stars? (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The observations of relatively narrow absorption components of the UV resonance lines in the spectra of early-type stars are reviewed, and some new observational data are presented for Rho Leo (B1 Ib). It is shown that the discrete components which are seen in the UV resonance lines of early-type stars are a result of ejection from local spots above the photospheres of hot stars. It is suggested that localized ejection is caused by magnetic flux lines associated with a bipolar magnetic region on the surface of the star.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 280; 712-728
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  • 15
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    Models of the hard X-ray spectrum of AM Herculis and implications for the accretion rate (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Phenomenological fits to the hard X-ray spectrum of AM Hercules have failed to explain the high equivalent width (0.8 + or - 0.1 keV) of Fe K-alpha emission. The scattering and fluorescent line production in a cold or partially ionized accretion column of hard X-rays emitted at the base are investigated using the Monte Carlo method. It is shown that the Fe emission equivalent width observed in the spectrum of AM Her can be explained without resorting to an overabundance of Fe in the accreting material. For sufficient optical depth across the accretion column, equivalent widths of K-alpha emission even larger than the observed values can be obtained. The accretion rate and gravitational power can be deduced from the optical depth across the column, if the column size is known, and, together with the observed hard X-ray and polarized light luminosities, imply a lower limit for the luminosity in the UV to soft X-ray range, for which the observations give model-dependent values.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 280; 734-743
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  • 16
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    Disappearance and disintegration of comets (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The present investigation has the objective to provide a summary of the existing evidence on the disappearance of comets and to draw conclusions regarding the physical processes involved in the disappearance. Information concerning the classification of evidence and the causes of apparent disappearance of comets is presented in a table. Attention is given to the dissipating comets, the headless sungrazing comet 1887 I, and the physical behavior of the dissipating comets and the related phenomena. It is found that all comets confined to the planetary region of the solar system decay on astronomically short time scales. However, only some of them appear to perish catastrophically. Some of the observed phenomena could be successfully interpreted. But little insight has been obtained into the character of the processes which the dissipating comets experience.
    Keywords: ASTROPHYSICS
    Type: Icarus (ISSN 0019-1035); 58; 81-100
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  • 17
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    X-ray spectral signatures of accreting black holes (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The X-ray properties of the binary black hole candidates include distinctive bimodal spectral behavior where the X-ray spectra switch between being very soft (alpha greater than 3) and hard (alpha about 0.7). It is pointed out that this spectral transition occurs at about 1 percent L(edd) (for accretion onto a 10 solar masses black hole), and that this corresponds to the luminosity where an optically thick electron-positron pair plasma will form. Active galactic nuclei (AGN) are often considered to be accreting black holes. An X-ray spectral similarity between the above binary sources and both the Seyfert I and BL Lac classes of AGN is demonstrated. As many of these objects radiate most of their luminosity as X-rays, such a similarity may be expected if the underlying mechanisms are similar.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 133; 2, Ap
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  • 18
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    Spectral analysis of magnetohydrodynamic fluctuations near interplanetary shocks (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Preliminary results of an investigation of magnetic fluctuations seen upstream of two interplanetary shocks are presented. The spectral analysis includes calculation of the normalized reduced magnetic helicity spectrum, the normalized reduced cross-helicity spectrum, and the Alfven ratio as discussed by Matthaeus and Goldstein (1982). Minimum variance methods are used to compute wave polarization as a function of frequency. The Taylor 'frozen in flow' hypothesis is assumed to convert frequencies to wave vectors. Some of the basic properties of the waves, including the probable mode of propagation in association with both quasi-parallel forward and reverse shocks, are described. A comparison with previous results on the generation of waves at interplanetary and planetary shocks is presented.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 89; 3762-377
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  • 19
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    The S201 far-ultraviolet imaging survey. II - A field in Cygnus (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Far-ultraviolet imagery of a region in Cygnus, a 20 deg diameter field centered near (1950) R. A. 21 h 31.2 m decl. +37 deg 25 arcmin, was obtained by the S201 far-ultraviolet camera during the Apollo 16 mission. In a 10 minute exposure covering the 1250-1600 A wavelength range (effective wavelength 1400 A), 730 star images can be detected, corresponding to a limiting ultraviolet magnitude of about m (1400) = 10. Assuming nominal interstellar extinction values in this region near the galactic plane, this result corresponds to the detection of A0 V stars to a distance of 300 pc and of B0 V stars to 1500 pc. Uncertainties in spectral classification and interstellar extinction for individual objects are probably more significant than calibration or measurement errors. Most of the objects detected are identified with stars in the Smithsonian Astrophysical Observatory Star Catalog (1966), or the Catalog of Stellar Identifications (1979) or both, but 87 objects remain unidentified (or are identified with late-type stars).
    Keywords: ASTRONOMY
    Type: Astrophysical Journal Supplement Series (ISSN 0067-0049); 54; 271-290
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  • 20
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    HEAO 3 observations of the Crab pulsar (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The Crab pulsar (PSR 0531+21) is the only pulsar which has been observed throughout almost the entire electromagnetic spectrum from 0.5 keV to over 2000 GeV. In general, the emission from the Crab nebula and its pulsar has been remarkably constant in time (except for the pulsations). However, several recent observations, especially of gamma-ray line emission, indicate possible time variations. The present investigation is concerned with the data obtained with the HEAO C-1 experiment. The data have been studied with the hope of finding information regarding a number of questions, taking into account the existence of line emission from the pulsar, the variation of the shape of the light curve with time, and the spectral variations as a function of pulsar phase. The spectrum of the total phase-averaged pulsed emission is found to be consistent with a single power-law spectrum from 50 keV to 10 MeV.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 278; 784-790
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  • 21
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    X-ray observations of X Persei (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The HEAO 2 Einstein Observatory was used to confirm the identification of 4U 0352 + 30 with X Per. The HEAO 2 data were analyzed in order to determine an additional point in the pulse period history of the X-ray source and to search for short binary periods. In addition, a majority of the historical X-ray observations was reanalyzed and more refined values for the pulse period as a function of time were obtained. The period history possess significant scatter, but no evidence for a measurable long-term spin-up trend is found, and hence a lower limit to the spin-up time scale is set. This lower limit is consistent with the presence of a neutron star, but it does not rule out a degenerate dwarf. The period history was also searched for evidence of binary motion, and upper limits to a(x) sin i were obtained.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 278; 711-715
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  • 22
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    Variable ultraviolet emission in SY Muscae (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The results of continued IUE monitoring of the symbiotic variable SY Muscae, following an earlier report of a radical enhancement in UV emission from the star, are reported. Over the course of one year, the prominent emission lines of N V, O V, C IV, and He II appear to be gradually decreasing in absolute intensity. This appears to coincide with a steady decline in electron density in the emission line forming region. The data are consistent with a sudden ejection event in which material expelled from the surface of a hot subdwarf has exposed the underlying UV continuum of the star. A number of strong emission lines that are photoexcited by the intense radiation field of the secondary also exhibit broad pedestal emission that suggests turbulent velocities of about 150-300 km/s in an expanding shell or possibly in an accretion disk.
    Keywords: ASTROPHYSICS
    Type: Royal Astronomical Society, Monthly Notices (ISSN 0035-8711); 207; 575-583
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  • 23
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    The remarkable ultraviolet spectrum of the planetary nebula Abell 30 (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Abell 30 has been identified as a planetary nebula in which the nucleus has experienced a final helium shell flash after ejection of the original, outer envelope. Around the central star of the nebula, four knots of material are observed. In view of the importance of the chemical composition of the ejected material for studies of advanced stages of stellar evolution, clarification of the physical conditions in the knots is vital. Data obtained of Abell 30 with the aid of the International Ultraviolet Explorer (IUE) satellite are discussed along with aspects of extinction, the He II flux, ionic abundances, the C II lambda 4267 line, questions regarding the existence of a carbon-rich core in the knot, the heating of the nebular gas, the central star, and heating by suprathermal particles from the stellar wind. The UV spectrum of the inner nebulosity of Abell 30 indicates that an extraordinary amount of energy is being deposited in the gas.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 277; 716-724
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  • 24
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    Determining asteroid masses from perturbations on Mars (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The orbit of Mars is perturbed more than 5 m, a value compatible with the accuracy of the Viking Lander ranging data, by about three dozen asteroids. In addition to larger asteroids throughout the belt, significant perturbations of long period are generated by smaller objects near commensurabilities with Mars. The largest periodic terms induced by 1 Ceres and 2 Pallas have amplitudes of 0.8 and 0.2 km, respectively, both with 10-year periods. Due to a near commensurability, 4 Vesta causes a 5-km, 52-year term. While the Viking ranges will yield significant mass determinations for the largest three asteroids, and some of the smaller bodies should be detectable, it will be difficult to separate the smaller bodies with useful accuracies. Accurate discrimination must await range data from future missions to Mars or other bodies in the neighborhood of the asteroid belt. The Viking ranges can also yield improved masses for the outer planets (except Pluto), an application which is being exploited by groups analyzing these data. Uncertainties in the asteroid masses limit the ultimate accuracy of the Viking determinations of both the long time scale motion of the system of the inner four planets with respect to an inertial frame and the rate of change of the gravitational constant.
    Keywords: ASTRONOMY
    Type: Icarus (ISSN 0019-1035); 57; 1-13
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  • 25
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    A search for the 10-micron silicate feature in periodic Comet Grigg-Skjellerup (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A 10-micron spectrum of periodic Comet Grigg-Skjellerup was obtained on 22 June 1982 with the UCL array spectrometer at the United Kingdom Infrared Telescope, Mauna Kea. No emission feature is obvious in the spectrum. The observed spectrum can be fit equally well by a model of small hot absorbing grains or by a composite model with less than or equal to 30 percent (3sigma) warm, 'dirty' silicate grains. The latter model is consistent with the silicate abundance in Comet Kohoutek, which did display an emission feature at 10 microns.
    Keywords: ASTRONOMY
    Type: Astronomical Journal (ISSN 0004-6256); 89; 170
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  • 26
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    Broad band X-ray astronomical spectroscopy (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The Broad Band X-Ray Telescope (BBXRT) experiment has been designed for high sensitivity, moderate resolution spectrophotometry of cosmic sources in the range 0.5 to 12 keV. Principal elements are two co-aligned imaging telescopes with cooled Si(Li) detectors at each focus. The mirror design uses an approximate geometry of tightly nested, conical, foil reflectors that allow a large filling factor (high throughput) at small grazing angles (high energy response). Each detector consists of a cluster of five elements defined with grooves on a single crystal. This arrangement affords some spatial resolution as well as a means of substantial background reduction. Shuttle borne measurements will typically be of 2000 s duration for sources with a flux of 10 to the -12 erg/sq cm-s.
    Keywords: ASTRONOMY
    Type: IEEE Transactions on Nuclear Science (ISSN 0018-9499); NS-31; 786-790
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  • 27
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    Ultraviolet spectra of planetary nebulae. X - Physical conditions in the compact planetary nebula Sw St 1 (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Photoelectric visual and ultraviolet observations of the compact planetary nebula Sw St 1 are analyzed. The electron density, determined from the C III 1907/1909 A line ratio, is N(e) = (1.1 + or - 0.1) x 10 to the 5th/cu cm, consistent with the high emission measure and high critical frequency determined from observations of the thermal radio emission. The C/O abundance ratio in the nebula is found to be N(C)/N(O) = 0.72 + or - 0.1, i.e. the envelope is oxygen-rich, as suggested by the identification of the silicate feature in the 8-13 micron infrared spectrum. Difficulties remain in accurately determining the reddening constant to the nebula and its electron temperature.
    Keywords: ASTRONOMY
    Type: Royal Astronomical Society, Monthly Notices (ISSN 0035-8711); 206; 293-304
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  • 28
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    A study of extreme carbon stars. I - Silicon carbide emission features (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: 10-micron spectra of many extreme carbon stars reveal a prominent emission feature near 11 microns. This is compared with laboratory spectra of SiC grains. Two distinct types of features are found, perhaps indicative of different mechanisms of grain formation in different stars. Estimates are made of probable column densities and total masses of SiC in the circumstellar shells.
    Keywords: ASTROPHYSICS
    Type: Royal Astronomical Society, Monthly Notices (ISSN 0035-8711); 206; 137-147
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  • 29
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    MHD processes in the outer heliosphere (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The magnetic field measurements from Voyager and the magnetohydrodynamic (MHD) processes in the outer heliosphere are reviewed. A bibliography of the experimental and theoretical work concerning magnetic fields and plasmas observed in the outer heliosphere is given. Emphasis in this review is on basic concepts and dynamical processes involving the magnetic field. The theory that serves to explain and unify the interplanetary magnetic field and plasma observations is magnetohydrodynamics. Basic physical processes and observations that relate directly to solutions of the MHD equations are emphasized, but obtaining solutions of this complex system of equations involves various assumptions and approximations. The spatial and temporal complexity of the outer heliosphere and some approaches for dealing with this complexity are discussed.
    Keywords: ASTROPHYSICS
    Type: Space Science Reviews (ISSN 0038-6308); 39; 255-316
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  • 30
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    Cosmogony as an extrapolation of magnetospheric research (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A theory of the origin and evolution of the Solar System which considered electromagnetic forces and plasma effects is revised in light of information supplied by space research. In situ measurements in the magnetospheres and solar wind can be extrapolated outwards in space, to interstellar clouds, and backwards in time, to the formation of the solar system. The first extrapolation leads to a revision of cloud properties essential for the early phases in the formation of stars and solar nebulae. The latter extrapolation facilitates analysis of the cosmogonic processes by extrapolation of magnetospheric phenomena. Pioneer-Voyager observations of the Saturnian rings indicate that essential parts of their structure are fossils from cosmogonic times. By using detailed information from these space missions, it is possible to reconstruct events 4 to 5 billion years ago with an accuracy of a few percent.
    Keywords: ASTROPHYSICS
    Type: Space Science Reviews (ISSN 0038-6308); 39; 65-90
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  • 31
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    Abundances in galactic H II regions. III - G25.4-0.2, G45.5+0.06, M8, S159, and DR 22 (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Measurements of the ARII (6.99 microns), ArIII (8.99 microns), NeI (12.81 microns), SIII (18.71 microns), and SIV (10.51 microns) lines are presented for five compact HII regions along with continuum spectroscopy. From these data and radio data, lower limits to the elemental abundances of Ar, S, and Ne were deduced. The complex G25.4-0.2 is only 5.5 kpc from the galactic center, and is considerably overabundant in all these elements. Complex G45.5+0.06 is at seven kpc from the galactic center, and appears to be approximately consistent with solar abundance. The complex S159 in the Perseus Arm, at 12 kpc from the galactic center, has solar abundance, while M8 in the solar neighborhood may be somewhat overabundant in Ar and Ne. Complex DR 22, at 10 kpc from the galactic center in the Cygnus Arm, is overabundant in Ar. A summary of results from a series of papers on abundances is given.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 285; 174-180
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  • 32
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    Intense X-ray flares from active stellar systems - EV Lacertae and HD 8357 (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The HEAO A-1 Sky Survey Experiment included X-ray data used to define light curves for the flare star EV Lac and for X-ray flares observed in the binary system HD 8357. The data were taken during flare events and were detailed enough to calculate the flare rates and flaring luminosities. The peak luminosities during flares were several times the luminosities in normal X-ray flares emitted by the objects. Peak luminosities reached 30-50 times the normal variations and were associated with an order of magnitude increase in energy output. EV Lac was sufficiently active to be recommended for inclusion in future X-ray monitoring programs.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 284; 270-277
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  • 33
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    Regularized Monte-Carlo calculations of the optical polarization induced by scattering in X-ray binaries (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The results of regularized Monte Carlo calculations of the optical polarization Stokes parameters expected as a result of scattering from gas streams or accretion wakes in close binary systems whose properties resemble those of X-ray binaries are presented. The physical processes occurring in the system are represented by a model which follows a selected sample of individual photon paths from each emitting element on the surface of the primary to the photon's detection at earth. The result represents the variations in the intensity from each individual emitting element caused by the effects of limb darkening, gravity darkening, and variation in the projected area of the emitting element as seen from the scattering element.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 138; 1, Se
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  • 34
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    Radioastronomical observations of comets IRAS-Araki-Alcock (1983d) and Sugano-Saigusa-Fujikawa (1983e) (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Continuum and spectral-line radio observations of the comets IRAS-Araki-Alcock and Sugano-Saigusa-Fujikawa obtained at a number of observatories during May and June, 1983, are compiled in tables and briefly characterized. The species NH3, H2O, CO, and HCN are considered in detail; visible-range observations of CN are compared; and the implications of the results and the experience gained in performing and coordinating the observations for the detection of important species in other comets, especially Halley's Comet, are explored.
    Keywords: ASTRONOMY
    Type: Icarus (ISSN 0019-1035); 60; 215-220
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  • 35
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    Precession model for the nucleus of periodic Comet Kopff (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The existing data base on certain characteristics of the periodic Comet Kopff, a candidate for a NASA rendezvous mission in the 1990s, is summarized. The comet was discovered in 1906. The data are used to calculate limits to the nuclear mass (0.7-1.5 x 10 to the 16th g), equatorial radius (1.26-1.64 km), and a geometric albedo of 0.08. An equatorial rotation velocity of 8.1-10.7 hr is projected. The estimates are highly dependent on the present photometric data, which in turn depend on the insolation rate, which if different than assumed could mean that all parameters would be revised upward significantly.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 89; 1573-158
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  • 36
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    The H flux peak and the hydrogen abundance in N type carbon stars (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: For galactic N and late R type irregularly variable carbon stars, a comparison is made of airborne infrared spectrophotometry to spectral flux distributions derived from model atmospheres. Although the agreement is good in several respects, the H(-) emission peak at 1.6 microns, so prominent in the models, is significantly weakened in the stellar spectrophotometry. It seems unlikely that molecular bands in the stars can completely obliterate this peak. A plausible explanation is that hydrogen is deficient in these stars, most probably from an episode of mass loss. The resultant cold shells surrounding these stars should be amenable to observation by IRAS, or other far-infrared observatories.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 284; L39-L42
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  • 37
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    A search at the millijansky level for milli-arcsecond cores in a complete sample of radio galaxies (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A complete sample of 26 extended radio galaxies was observed at 2.29 GHz with the Mark III VLBI system. The fringe spacing was about 3 milli-arcsec, and the detection limit was about 2 millijanskys. Half of the galaxies were found to possess milli-arcsec radio cores. In all but three sources, the nuclear flux density was less than 0.04 of the total flux density. Galaxies with high optical luminosity (less than -21.2) were more likely than less luminous galaxies to contain a detectable milliparcsec radio core (69 percent vs. 20 percent). For objects with arcsec cores, 80 percent were found to have a milli-arcsec core, even though the milli-arcsec object did not always contribute the greater part of the arcsec flux density.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 284; 519-522
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  • 38
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    An X-ray survey of variable radio bright quasars (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A sample consisting primarily of radio bright quasars was observed in X-rays with the Einstein Observatory for times ranging from 1500 to 5000 seconds. Detected sources had luminosities ranging from 0.2 to 41.0 x 10 to the 45th power ergs/sec in the 0.5 to 4.5 keV band. Three of the fourteen objects which were reobserved showed flux increases greater than a factor of two on a time scale greater than six months. No variability was detected during the individual observations. The optical and X-ray luminosities are correlated, which suggests a common origin. However, the relationship (L sub x is approximately L sub op to the (.89 + or - .15) found for historic radio variables may be significantly different than that reported for other radio bright sources. Some of the observed X-ray fluxes were substantially below the predicted self-Compton flux, assuming incoherent synchrotron emission and using VLBI results to constrain the size of the emission region, which suggests relativistic expansion in these sources. Normal CIV emission in two of the sources with an overpredicted Compton component suggests that although they, like BL Lac objects, have highly relativistic material apparently moving at small angle to the line of sight, they have a smaller fraction of the continuum component in the beam.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 284; 491-496
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  • 39
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    Some properties of the filamentary nebula at 1723 - 46 (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: High resolution spectra of the interstellar NaI D2 absorption line have been obtained for seven B-type stars aligned with an extensive filamentary nebula. Very fine filaments have now been found on a high contrast print of a deep H-alpha and forbidden N II plate, making identification as a fossilized remnant probable but uncertain. The inferred age is about 20,000 yr, the distance less than 200 pc, the diameter less than 17.5 pec, but the initial energy is only about 2 x 10 to the 47th erg.
    Keywords: ASTROPHYSICS
    Type: Royal Astronomical Society, Monthly Notices (ISSN 0035-8711); 210; 693-699
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  • 40
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    Grain destruction in interstellar shocks (1984)
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    Publication Date: 2011-08-18
    Description: The destruction of interstellar grains by nonthermal sputtering, thermal sputtering, and grain-grain collisions is discussed. It is concluded that large grains are easily destroyed by shocks in the interstellar medium, but that small grains are much more persistent. Since the MRN model has many more small grains than large ones, this means that the total number of grains is not significantly reduced even when half or more of the grain material is returned to the gas phase. Thus, the small grains are always available as condensation cores for mantle formation or redepletion of refractory grain materials.
    Keywords: ASTROPHYSICS
    Type: Royal Observatory Lab. and Observational Infrared Spectra of Interstellar Dust; p 26-32
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  • 41
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    New infrared observations of IRS1, IRS3, and the adjacent nebula in the OMC-2 cluster (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Observations of the infrared cluster of low luminosity protostars in Orion Molecular Cloud 2 (OMC2) are reported. Results show that the asymmetric distribution of the extended emission seen about IRS1 is another infrared reflection nebula. Energy distributions show that the spectral shape is fairly constant throughout the nebula which indicates there is little internal extinction within this region. Integrated surface brightness values show that the nebula is 5 times brighter than IRS1 at K. Energy distributions show that IRS1 has a more pronounced ice band absorption feature at 3.1 micron; suggesting that there is more extinction along the direct line of sight to IRS1 than along a line from IRS1 to the scattering grains and then to the observer. The distribution of the extended emission around IRS1 is similar to the reflection nebula seen in NGC 7538 (Werner et al. 1979). The asymmetric shapes of the two nebulae are similar and in each case there is excess extinction along line of sight to the illuminating source.
    Keywords: ASTRONOMY
    Type: Royal Observatory Lab. and Observational Infrared Spectra of Interstellar Dust; p 162-166
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  • 42
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    Transient dips of Cygnus X-1 observed from Tenma (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The transient intensity dips of the binary system Cyg X-1 have been observed, using the gas scintillation proportional counter (GSPC) array onboard the Tenma X-ray astronomy satellite. The duration of the dips was in the range from several seconds to 10 minutes, with several dips occurring as much as 15 h before the superior conjunction. Within the dips, complex structures were observed with time scales of several seconds, and, in at least one case, shorter than two seconds. For a dip lasting longer than 10 minutes, a high-quality spectrum was obtained which reveals the K-absorption edge of iron at 7.18 + or - 0.18 keV. On the basis of the observed absorption, it is suggested that the dips are caused by absorption due to relatively cool matter (less than about 30,000 k); the low-energy excess observed during the dips is due either to an extended soft X-ray emitting corona or to partial obscuration of the X-ray source by multiple blobs. From the time structure of the dip, a blob size of the order of 10 to the 9th cm is derived.
    Keywords: ASTRONOMY
    Type: Astronomical Society of Japan, Publications (ISSN 0004-6264); 36; 4, 19
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  • 43
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    Thermal modeling of Halley's Comet (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The comet thermal model of Weissman and Kieffer is used to calculate gas production rates and other parameters for the 1986 perihelion passages of Halley's Comet. Gas production estimates are very close to revised pre-perihelion estimates by Newburn based on 1910 observations of Halley; the increase in observed gas production post-perihelion may be explained by a variety of factors. The energy contribution from multiply scattered sunlight and thermal emission by coma dust increases the total energy reaching the Halley nucleus at perihelion by a factor of 2.4. The high obliquity of the Halley nucleus found by Sekanina and Larson may help to explain the asymmetry in Halley's gas production rates around perihelion.
    Keywords: ASTROPHYSICS
    Type: Advances in Space Research (ISSN 0273-1177); 4; 9, 19; 221-224
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  • 44
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    IRAS observations of cometary dust (1984)
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    Publication Date: 2011-08-19
    Description: It is pointed out that solid material present in the coma and tail of a comet is revealed by the scattering of sunlight and thermal emission of absorbed solar radiation. The large beam size and low background of the cold Infrared Astronomy Satellite (IRAS) telescope make it extremely well suited to the measurement of faint diffuse thermal emission from solid grains associated with comets. The IRAS project was conducted jointly by the Netherlands, the United Kingdom, and the U.S. Its basic objective involved a survey of the sky in four wavelength regions centered on 12, 25, 60, and 100 microns. The present paper is mainly concerned with IRAS observations of the coma-nucleus regions as defined by the maximum in the intensity distribution. Attention is given to circumstances of comet observations, dust production rates, and a discussion of the results.
    Keywords: ASTROPHYSICS
    Type: Advances in Space Research (ISSN 0273-1177); 4; 9, 19
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  • 45
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    A comparison of the dust properties in recent periodic comets (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Measurements of the thermal emission from the cometary dust coma can be used to derive the rate of dust production from the nucleus as well as the size distribution of absorbing grains. More than ten short-period comets have now been observed in the infrared over a wide range in heliocentric distance. Dust production rates are derived for these comets based on theoretical models of the thermal emission from small absorbing grains and calculations of dust grain velocities. The mean size and albedo of the dust grains is similar in these comets, with the exception of Comet Crommelin, which seems to have had larger, darker grains.
    Keywords: ASTROPHYSICS
    Type: Advances in Space Research (ISSN 0273-1177); 4; 9, 19; 189-196
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  • 46
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    A new calibration of the semi-empirical photometric theory for Halley and other comets (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The semiempirical photometric theory of gas and dust production in comets (Newburn, 1979, 1981, and 1982) is recalibrated on the basis of the 17-comet compilation of spectrophotometric data of Newburn and Spinrad (1984). The results are presented in graphs and tables, and it is shown that no corrections are required for the constant R and the function delta, but that the mixing ratios (obtained as functions of heliocentric distance) can be improved, with implications for the visual-photometric comet model. Recently calculated light curves for comet Halley are compared, and the use of the nearly identical curves of Bortle and Morris (1984) and Marcus (1983) is recommended.
    Keywords: ASTROPHYSICS
    Type: Advances in Space Research (ISSN 0273-1177); 4; 9, 19; 185-188
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  • 47
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    On Bowen enhancement of the N III spectrum under solar and nebular conditions (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Expected enhancement of the N III emission-line spectrum by the Bowen He II to O III to N III resonant photoexcitation process is computed using a six-configuration model. Preliminary comparisons with available solar and nebular observations indicate that the process may play only a small role, although photoexcitation quenching of the N III and O III far-infrared fine-structure lines is noted as a possibly important mechanism. Some features are discussed in connection with the nebular emission at 1750 A, which is suggested as an indicator of excitation class for planetary nebulae.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 287; 945-951
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  • 48
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    The 41.5 day binary X-ray pulsar 4U 1223 - 62 (GX 301 - 2) (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Ariel 5 and SAS 3 X-ray pulse timing data for the 700 s X-ray pulsar 4U 1223 - 62 (GX 301 - 2) are reexamined in order to deduce the orbital elements of this system. The Ariel 5/SAS 3 arrival times are first reanalyzed to obtain the best solution for an orbital period close to 41.5 days and to estimate the uncertainties in it caused by unknown variations in the underlying pulse period. Spectral measurements by OSO 8 and HEAO 1 at a variety of orbital phases are presented and the origin of an unabsorbed, unpulsed soft component is discussed. OSO 8 observations of occasions when the amplitude and shape of the pulse profile changed dramatically are discussed. The global X-ray properties of the system are explained in terms of a simple stellar wind accretion model, and the interaction of the inflowing material with the neutron star magnetosphere is considered.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 287; 856-867
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  • 49
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    Similar photospheres, different mantles - A study of four O stars (1984)
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    Publication Date: 2011-08-19
    Description: The present investigation is concerned with a comparison of the spectra of four O stars (10 Lac, S Mon, HD 46223, and Zeta Pup) which have similar effective temperatures, taking into account an attempt to find the reason for differences regarding the spectral type of the stars. The photospheres of the stars are examined, taking into account the effective temperatures, radii, speed of rotation, and masses. Information is presented about the equivalent widths and profiles of strong lines in the visible and ultraviolet spectra of each star. It is found that the four stars have similar photospheres but different mantles. The stars are assigned different spectral types because the empirically selected lines used for determining spectral type in class O are sensitive primarily to conditions in the mantle of the star and not to conditions in the photosphere. Questions concerning the reasons for the differences regarding the mantles are also explored.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 287; 874-891
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  • 50
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    Absorption features in the 5-8 micron spectra of protostars (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: High signal-to-noise ratio spectra in the range of 5-8 microns of four sources embedded in molecular clouds are examined using low-temperature laboratory measurements of the 5-8-micron spectra of simple molecules and their mixtures. The absorption, apparent in all four sources, is characterized by highly distinct features ranging from two relatively narrow bands at 6.0 and 6.8 microns in W33A to a broad, shallow, and partially structured feature extending from 5.2 to 7.8 microns in Mon R2-IRS2, BN, and NGC2264. The first feature (W33A) is explained by the OH bending mode in H2O and the CH deformation modes in saturated hydrocarbons; while the second feature (Mon R2-IRS2-type) is explained by the presence of a mixture of saturated and unsaturated hydrocarbons possibly containing strongly electronegative groups.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 287; 697-706
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  • 51
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    IUE observations of the 'Butterfly' Nebula M2-9 (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: IUE observations of the peculiar 'Butterfy' nebula M2-9 indicate that it is not a normal planetary nebula. The ultraviolet spectrum is characterized by few emission lines and a weak continuum. Mg II 2800 A is the strongest emission line present and may be indicative of a binary nucleus. Lines of N v, Q I, N III, N IV, Si III, and C III are seen, but C IV and O III are conspicuous by their absence. T(e) = 10,250 + or - 400 K was determined for the core. Nitrogen in the core is found to be overabundant by about a factor of 5 over the solar value. M2-9 may be an object in the early stages of becoming a planetary nebula.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 287; 353-358
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  • 52
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    Self-absorption of high-energy Gamma-rays in Cygnus X-3 (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Absorption of high-energy gamma-rays from Cyg X-3 in its own photon field by the reaction gamma + gamma yields e(+) + e(-) is considered. It is found that gamma rays with an energy around 10 to the 12th eV are attenuated, and the observed flux has to be corrected. Gamma rays with energy greater than 10 to the 15th eV which are observed are not affected by the photon field.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 287; 338-340
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  • 53
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    Monte Carlo shock-like solutions to the Boltzmann equation with collective scattering (1984)
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    Publication Date: 2011-08-19
    Description: The results of Monte Carlo simulations of steady state shocks generated by a collision operator that isotropizes the particles by means of elastic scattering in some locally defined frame of reference are presented. The simulations include both the back reaction of accelerated particles on the inflowing plasma and the free escape of high-energy particles from finite shocks. Energetic particles are found to be naturally extracted out of the background plasma by the shock process with an efficiency in good quantitative agreement with an earlier analytic approximation (Eichler, 1983 and 1984) and observations (Gosling et al., 1981) of the entire particle spectrum at a quasi-parallel interplanetary shock. The analytic approximation, which allows a self-consistent determination of the effective adiabatic index of the shocked gas, is used to calculate the overall acceleration efficiency and particle spectrum for cases where ultrarelativistic energies are obtained. It is found that shocks of the strength necessary to produce galactic cosmic rays put approximately 15 percent of the shock energy into relativistic particles.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 286; 691-701
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  • 54
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    The collapse of the cores of slowly rotating isothermal clouds (1984)
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    Publication Date: 2011-08-19
    Description: A generalized model which accounts for the effects of initially uniform and slow rotation is defined for the spherical collapse of a singular isothermal sphere such as protosolar and binary nebulae. An initial unstable equilibrium state is described for a sound speed of 0.35 km/sec and a rotation rate of 10 to the -14th/sec for the molecular cloud surrounding the accreting core. The total angular momentum and mass of the inner cloud is set equal to solar system values. The evolution of the collapse is traced by applying a perturbation analysis to the similarity solution for a nonrotating condition, and matched asymptotic expansions solve the hydrodynamic equations. The model is concluded a valid tool for studying star and nebular disk formation.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 286; 529-551
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  • 55
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    Evidence for a supersonic turbulent velocity gradient in the outer photosphere of the supergiant alpha Cygni (A2Ia) (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The balloon-borne UV Stellar Spectrometer's high resolution, near-UV spectra of the supergiant Alpha Cyg are subjected to analysis in order to determine the average microturbulent line-of-sight velocity component. A value of 15.0 + or - 0.5 km/sec is obtained, which is close to the 13.7 km/sec local sound velocity, and is consistent with the view that shock waves are the dominant structure in the outer photosphere of Deneb, so that shock wave dissipation determines the thermal structure of the photosphere.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 141; 2, De
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    Cometary showers and unseen solar companions (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The possibility that an invisible solar companion passing through the Oort cloud every 28 Myr precipitates a sufficiently high rate of cometary collisions with the earth to account for periodic mass species extinctions recorded in the fossil record is discussed. A Monte Carlo simulation shows that any hypothesized 'death star' with a 28 Myr orbit would experience an average 10 percent change in period per orbit. Production of an 18-fold increase in cometary impacts would be associated with a 0.055 probability that a 10 km nucleus would hit the earth in a shower once every 510 Myr, longer than the proposed extinction periodicity. However, if the death star orbit has a 0.6 eccentricity and the Oort cloud is sufficiently densely populated, a 2 billion comet shower may be possible. A survey of large terrestrial impact craters indicates that 6-12 craters with diameters over 10 km originated in periodic showers. The extinctions in any case occur at 26 Myr periods and cannot be correlated with the 33 Myr period of recrossing the galactic plane, or with any other known phenomena.
    Keywords: ASTRONOMY
    Type: Nature (ISSN 0028-0836); 312; 380; Rep
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    Vibrational and rotational excitation of CO in comets Nonequilibrium calculations (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Ultraviolet observations of atomic carbon in cometary comae show that carbon-bearing compounds must comprise a significant fraction (approximately equal to or greater than 10 percent) of the volatiles. One likely source is CO. This compound is an important constituent of at least some cometary nuclei, even though it may not be the ultimate source of atomic carbon in all comets. Feldman (1983) has suggested that the relative abundance of CO may be one of the few fundamental characteristics which distinguish one comet from another. The present investigation is, therefore, concerned with the vibrational and rotational excitation of the CO molecule in cometary comae. Two previously neglected factors are taken into account in the study. The fractional populations of CO as solutions to time-dependent differential equations are derived, and a nonisothermal and cold kinetic temperature profile for the inner coma is considered.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 285; 858-869
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  • 58
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    The ultraviolet variability of early-type supergiants (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Four early-type supergiants - HD 79186 (B5 Ia), HD 96919 (B9 Ia), HD 105056 (ON9.7 Iae), and HD 148379 (B2 Iae) - have been observed with the low-resolution spectrographs of IUE in the large aperture on 14 days. The behavior of the ultraviolet fluxes with time is studied. The light from all four stars seems to vary. Typically the dispersion about the mean magnitude at any wavelength corresponds to + or - 0.085, + or - 0.080, + or - 0.101, and + or - 0.106 mag, respectively. These amplitudes exceed the typical uncertainty in an IUE measurement of flux by about a factor of 3; they are somewhat larger than the variations known in the visible wavelength range. There are insufficient data to investigate periodicity in the observed light changes. The effective temperatures and angular diameters of the stars have been estimated using the present ultraviolet photometry, published UBV and uvby photometry, and the model-atmosphere fluxes reported by Kurucz in 1979. The program stars have dimensions typical for their spectral types. A brief discussion is given of possible causes of the variability of hot supergiants.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 285; 668-673
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  • 59
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    Modification to shock fitting program (1984)
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    Publication Date: 2011-08-19
    Description: A modified form of the Lepping-Argentiero single spacecraft, shock normal determination procedure is presented. The modified method incorporates a simple predictor-corrector algorithm which allows a faster convergence rate and the use of average values of the parameters for the starting vector.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 89; 11004-11
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  • 60
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    Large-scale interplanetary magnetic fields - Voyager 1 and 2 observations between 1 AU and 9.5 AU (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The large-scale radial and temporal variations of the interplanetary magnetic field strength B observed by Voyagers 1 and 2 are discussed. Two components of the magnetic field strength were considered: (1) an average component, B sub zero, based on solar rotation averages, and (2) a fluctuation component, delta B, expressed by 10- or 24-hour averages of B normalized by the best-fit average field for the corresponding time and distance. Observations of the sector structure, interfaces, and shocks are presented to further describe magnetic field strength.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 89; 10659-10
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  • 61
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    Evidence for material between Saturn's A and F rings from the Voyager 2 photopolarimeter experiment (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The region in the Saturn system between the F ring and the outer edge of the A ring is an area that appears, in images from the imaging experiment, to be virtually devoid of material except for three small satellites. Near the orbit of 1980S28, Atlas - the innermost satellite - the Voyager Photopolarimeter Stellar Occultation data show a discontinuity in count rate which marks a boundary between the tenuous material near the outer edge of the A ring and the orbit of Atlas. The data pertaining to this region have been examined with the aid of statistics and models generated from other similar ring structures. It is concluded that the discontinuity is real, implying the existence of tenuous material of normal optical depth of 0.01 to 0.006 in this region.
    Keywords: ASTRONOMY
    Type: Icarus (ISSN 0019-1035); 60; 409-415
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  • 62
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    1984 AB - A unique Mars-crossing asteroid (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Asteroid 1984 AB, discovered in January 1984, proved to be a unique object with a close dynamical relationship to Mars. A brief history of the discovery and subsequent 'evolution' of the orbit as it was refined is presented. The preliminary orbit of 1984 AB indicated that it might be a Mars Trojan, and an extended discussion of this interesting possibility is presented, but this hypothesis had to be dismissed after further observations had refined the orbit. The semimajor axis and orbital eccentricity are very similar to that of Mars. No other known Mars-crossing asteroid exists with an orbit as closely associated to Mars.
    Keywords: ASTRONOMY
    Type: Icarus (ISSN 0019-1035); 60; 404-408
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  • 63
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    A radar study of Comet IRAS-Araki-Alcock 1983d (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Radar echoes from Comet IRAS-Araki-Alcock at wavelengths 3.54 and 12.9 cm indicate that the comet's nucleus is very rough on a scale larger than the radar wavelengths; however, the low polarization ratio (25 percent at 3.54 cm) indicates that the scattering is not dominated by multiple reflections, internal reflections, or large abundances of sharp edges, cracks, and pits. The shape of the nucleus probably departs greatly from a sphere with average radii near 3-4 km. The nucleus does not appear to look significantly different from a number of Apollo and Amor asteroids except that: (1) there is a suggestion that minor structure moves rapidly across the spectra, and (2) the debris not gravitationally bound to the comet was detected, and contributes 25 percent of the total radar cross section at the 12.9-cm wavelength. Other considerations suggest that the pole was at least 45 deg away from the line of sight on two days of observation, and that the rotation period is approximately 1-2 days.
    Keywords: ASTRONOMY
    Type: Astronomical Journal (ISSN 0004-6256); 89; 1745-175
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  • 64
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    Cyclotron emission near stellar mass black holes (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Cyclotron emission in the inner regions of an accretion disk around a matter accreting black hole can be appreciable. In the case of the X-ray source Cyg X-1, cyclotron emission may provide the soft photons needed for 'Comptonization' to produce high energy X-rays. The inverse correlation between the fluxes of high energy and low energy X-rays during the 'high' and 'low' states of Cyg X-1, may be understood as a result of the variation of the rate of accretion and the Compton scattering of the cyclotron photons. In the case of the X-ray source GX 339-4, the observed optical flux during the high states does not seem to be due to cyclotron emission, but probably due to reprocessing of high energy X-rays by the outer regions of the disk.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 139; 2, Oc
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  • 65
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    Submillimeter wavelength survey of the galactic plane from l = -5 deg to l = +62 deg - Structure and energetics of the inner disk (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Observational results are presented from a new large-scale survey of the first quadrant of the galactic plane at wavelengths of 150, 250, and 300 microns, with a 10 x 10 arcmin beam. The emission detected in the survey arises from compact sources, most of which are identified with known peaks of 5 GHz or CO emission, or both, and from an underlying diffuse background with a typical angular width of about 0.9 deg (FWHM) which accounts for most of the emission. A total of 80 prominent discrete sources are identified and characterized, of which about half have not previously been reported at far-infrared wavelengths. The total infrared luminosity within the solar circle is about 1 to 2 x 10 to the 10th solar luminosity, and is probably emitted by dust that resides in molecular clouds.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 285; 74-88
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  • 66
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    The variable component of the NGC 4151 IUE spectrum - Evidence for an expanding spherical emission shell (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The profile of the forbidden line of C III (1909) is the same in two pseudo-trailed, low-resolution SWP spectra of the nucleus of the Seyfert galaxy NGC 4151 obtained with the IUE in November 1980 and December 1982, respectively. In the 1980 spectrum, the C III forbidden line profile is also very nearly the same as that of the resonance line C IV (1550). In the 1982 spectrum, the continuum is 5 times higher and C IV is both much broader and much brighter. In the difference spectrum, which is interpreted to be the spectrum of a time-variable component, C IV (1550) is the only strong emission feature. The profile of this line closely resembles that of a spherical shell surrounding a less dense gas uniformly expanding from a central opaque object. From values of the profile parameters and from the observed time variability of the object, it is inferred that the shell has a radius of about 10 to the 15th cm, a mass of 0.25 solar mass, an expansion velocity of 13,000 km/s, and an electron density of 10 to the 11th per cu cm. From the line profile and the continuum, it is inferred that the opaque central source has approximate radius of 10 to the 14th cm and temperature 23,000 K.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 285; 69-73
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  • 67
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    A solar spectral line list between 10 and 200 A modified for application to high spectral resolution X-ray astronomy (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A spectral line list for the 10-200 A range is developed from existing solar spectra for application to high spectral resolution measurements of astrophysical plasmas. The solar spectral line lists are merged into a single comprehensive list. The effect of the solar emission measure distribution is removed from the line intensities, which results in a set of emission rates for the lines that can be applied to many optically thin, low density high temperature plasmas in ionization equilibrium. In addition to the measured solar lines, 250 theoretical lines are added to this list. These lines fall in wavelength regions where the existing solar lists have few lines because of limitations in instrumental sensitivity. Also, some lines have been added because the sun has very little plasma at temperatures of about one million K, and consequently these lines are weak or absent in solar spectra. The entire list contains about 600 lines. Finally, predicted spectra of the two RS CVn stars, alpha Aur (Capella) and UX Ari, are presented at 1 and 0.25 A spectral resolution. Also, the solar spectrum is shown at 1 A resolution, and the emission rate spectrum (spectrum not modified by an emission measure distribution) is shown at very high spectral resolution. The predicted spectra for Capella and UX Ari are based on results obtained from the Einstein and International Ultraviolet Explorer (IUE) spacecraft.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal Supplement Series (ISSN 0067-0049); 56; 67-89
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  • 68
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    Gamma rays from atomic and molecular gas in the large complex of clouds in Orion and Monoceros (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A comparison of COS-B gamma-ray observations of the large complex of interstellar clouds in Orion and Monoceros with the Columbia CO and Berkeley H I surveys of this region reveals a good correlation between gamma-ray emission and total gas distribution. The observed gamma-ray emission is explainable in terms of interactions of cosmic rays that are uniformly distributed in this region with the interstellar gas. The correlation is used as the basis of a calibration of the ratio between H2 column density and the integrated CO line intensity; the value of (2.6 + or - 1.2) X 10 to the 20th mol/sq cm K km s thereby obtained is consistent with the value derived from a similar analysis for the inner galaxy.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 139; 1, Oc
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  • 69
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    On the orbit improvement results obtained by referring old cometary observations to the SAO Star Catalog (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: An algorithm is presented for the automatic reduction to the SAO Star Catalog of old micrometer cometary observations of the type comet minus star. Results of a numerical test are presented showing the distinct influence of such a reduction on orbit determination results.
    Keywords: ASTROPHYSICS
    Type: JPL Cometary Astrometry; p 203-206
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  • 70
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    Reduction of astrographic catalogues (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: An automatic program for the reduction of overlapping Carte du Ciel plates is described. The projection and transformation equations are given and the RAA subprogram flow is outlined. The program was applied to two different sets of data, namely to nine overlapping plates of the Cape Zone of the CdC, and to fifteen plates taken with the CIDA-refractor of the open cluster Tr10.
    Keywords: ASTRONOMY
    Type: JPL Cometary Astrometry; p 99-104
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  • 71
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    Obtaining accurate comet positions despite some inaccurate catalog stars (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: From an astrographic negative a grid is determined from measurement of all the reference stars and using their catalog positions, and other grids from selections of reference stars. These grids are determined from many stars, and individual stars will have errors with respect to the grid. There are ways to identify stars X that are not at their cataloged position: (1) determine the focal length of the telescope from the measurements of each pair of stars and look for discordant results; (2) stars X are several arcseconds off the grid, and the other stars fit better when stars X do not help determine the grid; and (3) the grid is stretched or distorted to include the stars X. Fifteen to twenty percent of the stars in the S.A.O. catalog are 1.5 seconds or more off their catalog positions. An interactive session with a computer can find and eliminate these errant stars and result in more accurate comet positions.
    Keywords: ASTRONOMY
    Type: JPL Cometary Astrometry; p 96-98
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  • 72
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    Desired characteristics of catalogs for cometary astrometry (1984)
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    Publication Date: 2011-08-19
    Description: Reference star catalogs for cometary astrometry have to provide an all-sky coverage with suitable stellar density and limiting magnitude on a fundamental coordinate system. A general catalog meeting all these requirements will not be available for a foreseen timescale. The suitability of various existing catalogs for cometary astrometry is discussed.
    Keywords: ASTRONOMY
    Type: JPL Cometary Astrometry; p 87-92
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    The astrometry network of observers in USSR (1984)
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    Publication Date: 2011-08-19
    Description: A list of observatories included in the Soviet Astrometry Network is given. Some aspects of Astrometry Network activity are discussed. The Comet Halley star catalog is outlined.
    Keywords: ASTRONOMY
    Type: JPL Cometary Astrometry; p 76-83
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    The IHW reference star catalogs for Comets Halley and Giocobini-Zinner (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The general categories of catalogs are observed and compiled. Observed catalogs are tabulations of positions determined with a single instrument (transit circle or astrograph) at a single location with a single approximate mean epoch. Compiled catalogs are produced from a combination of observed catalogs and have the advantage of many more observations per star. In addition, catalogs may be classified according to their density and type of instrument used to produce them. The specific catalogs that should be used for Halley's Comet and Giaobini-Zinner Comet are described.
    Keywords: ASTRONOMY
    Type: JPL Cometary Astrometry; p 93-95
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    The astrometry network of observers in Japan (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The astrometric network of observers and the main telescopes for professional and amateur astronomers in Japan and their availability for the International Halley Watch (IHW) are described.
    Keywords: ASTRONOMY
    Type: JPL Cometary Astometry; p 74-75
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    The astrometry network of observers in China (1984)
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    Publication Date: 2011-08-19
    Description: In China, the Purple Mountain Observatory (32 deg. 04 min. N and 118 deg. 49 min. E), the Shanghai Observatory (31 deg 06 min N and 121 deg 11 min E), and the Qingdao Station (36 deg 05 min N and 120 deg 19 min E) will take part in the astrometry of Halley's Comet. The astrometric work together with the instrumentation used, is given.
    Keywords: ASTRONOMY
    Type: JPL Cometary Astrometry; p 71-73
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    The astrometry programme at Mt. John Observatory (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The comet (and minor planet) astrometry program uses one of two 0.6 meter (24 in.) Cassegrain telescopes at Mt. John University Observatory. For astrometric photographs of comets and minor planets a simple guide probe camera is attached to the Cassegrain. Frequently the Cassegrain field does not include sufficient cataloged stars for a satisfactory reduction. In these cases the comet position is transferred to an astrograph plate. Ephemeris data are calculated to the tenth of a day nearest the meridian transit of the object or for dusk or dawn twilight for low objects. Star measurement and identification are checked by reducing positions of cataloged stars.
    Keywords: ASTRONOMY
    Type: JPL Cometary Astrometry; p 66-70
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    Problems and procedures of cometary astometry (1984)
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    Publication Date: 2011-08-19
    Description: Photography of comets or asteroids for the purpose of astrometry requires consideration of a few details not met with in other astronomical problems. In the general case the object has a substantial non-sidereal motion and the decision must be made whether to track on the fiducial stars or on the object. The best method for introducing the required image motion compensation to the detector will depend on the focal plane facilities. Measurement of elongated images and the problems involved are discussed.
    Keywords: ASTRONOMY
    Type: JPL Cometary Astrometry; p 58-65
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  • 79
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    Kitt Peak measurements of P/Halley positions (1984)
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    Publication Date: 2011-08-19
    Description: Techniques used for the acquisition and reduction of imaging data for astrometric positions of comet Halley at Kitt Peak National Observatory are described. These techniques are applicable to the comet while it is fainter than magnitude V approximately 21. They yield positions that are uncertain by + or - 0.9 arcsec. The reliability and consistency of the positions already derived could be improved by as much as a factor of four in a more ambitious astrometric program.
    Keywords: ASTRONOMY
    Type: JPL Cometary Astrometry; p 48-57
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    Astrometric plates obtained at the primary focus of large aperture reflectors (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Coma, astigmatism, and great differences in stellar magnitudes between photographed object and reference stars constitute the main sources of errors in measuring positional plates. These three sources of error can easily be eliminated by the method used at the Klet Observatory for obtaining precise observations of faint objects. The astrometric plates are taken by the method of two diaphragms. The first diaphragm, with a small central aperture; is located in front of the photographic plate. The second diaphragm is situated in front of the mirror. By a very short (of the order of tens of seconds) exposure a sufficient number of reference stars can be obtained throughout the entire plate. The stars are very well defined to the very edge of the plate and are easy to measure. Moreover, this method makes it possible to use plates of larger dimensions than usual so that it is always possible to find the necessary reference stars.
    Keywords: ASTRONOMY
    Type: JPL Cometary Astrometry; p 45-47
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    Cometary astrometry with Schmidt cameras (1984)
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    Publication Date: 2011-08-19
    Description: A great many of the professional comet discoveries are made using wide field Schmidt telescopes. In particular the Palomar Schmidt, the ESO Schmidt in Chile and the UK Schmidt at Siding Spring Observatory in Australia. The wide field of view and fast f ratio are two of the distinctive features of this design which make it attractive for comet work. The techniques described refer to those in current use on the UK Schmidt. However in large part the methods described may be applied quite widely.
    Keywords: ASTRONOMY
    Type: JPL Cometary Astrometry; p 34-40
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  • 82
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    Scale lengths in quasi-parallel shocks (1984)
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    Publication Date: 2011-08-18
    Description: A review was carried out of ISEE and Voyager spacecraft magnetometer data to determine if quasi-parallel bow shocks are really broad, disordered regions. The key parameter was the deceleration scale (thickness, Lp) across which random energy would need to increase and a localized electrostatic field (E) would be present. Lp would define the breadth of the shock and be associated with a plasma deceleration. The ISEE 1 satellite collected data on the electron density, bulk speed, magnetic intensity, and electron temperature in November 1977 during five traverses of the bow shock. Similar data were gathered from an interplanetary shock wave in 1981. The evidence supported the concept of a plasma deceleration across a thin layer (Lp) in both types of shocks. The layers were about 50 times (interplanetary) and 20 times (earth) thinner than surrounding magnetic fluctuation regions. It is asserted that the regions of deceleration, although much thinner, are the actual shocks and not the entire regions of magnetic fluctuations.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 89; 7545-755
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  • 83
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    Experiments to test theoretical models of the polarization of light by rough surfaces (1984)
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    Publication Date: 2011-08-18
    Description: A number of attempts have been made to provide theoretical models of the physical processes involved in the polarization of light scattered by a rough surface, such as the regolith of an atmosphereless planet. Some laboratory experiments designed to test different aspects of these models are described. It is concluded that double Fresnel reflection is usually the dominant process in producing negative polarization, but that diffraction effects may play a significant part in double events involving small-scale surface features.
    Keywords: ASTRONOMY
    Type: Royal Astronomical Society, Monthly Notices (ISSN 0035-8711); 210; 89-112
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    Identification of the SiCC radical toward IC +10216 - The first molecular ring in an astronomical source (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: In the radio spectrum of the envelope of the evolved carbon star IRC +10216, the fraction of lines from exotic molecules seldom or never observed in the terrestrial laboratory is exceptionally high. At least 20 lines have not been identified, and it is not known whether one, two, or a number of new molecules are involved. It is shown in the present investigation that nine of the previously unidentified lines in IRC +10216 are produced by SiCC, a radical long known to exist in stellar atmospheres. The true ground-state geometry of this radical has only been obtained recently on the basis of an elegant two-photon ionization experiment in a supersonic molecular beam. Information regarding the molecular geometry and lower rotational levels of SiCC is presented in a graph. The intensities of the SiCC lines confirm the assignments, yield new data on the temperature and density in the envelope of IRC +10216, and indicate that the amount of SiCC there is substantial.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 283; L45-L48
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  • 85
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    Far-infrared and submillimeter survey of the galactic plane from l = 11.5 deg to l = 17.5 deg (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Medium resolution (11 min) maps of the galactic plane are presented from l = 11.5 deg to l = 17.5 deg at wavelengths of 93 microns, 154 microns, and 190 microns. The maps are interpreted in terms of the temperature and spatial structure of diffuse far-infrared/submillimeter sources associated with evolved H II regions and a continuous ridge of galactic emission. The emission regions are found to be more extended at the longer wavelengths which implies that there must be a range of dust temperatures in the sources. The properties of the galactic ridge are similar to those of the sources.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 283; 566-572
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  • 86
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    Mass extinctions and missing matter (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The possible influence of 'invisible matter' on the solar system's comet halo, and therefore on quasi-periodic cometary bombardment of the earth and consequent mass extinctions, is briefly addressed. Invisible matter consisting of small or cold interstellar molecular clouds could significantly modulate the comet background flux, while invisible matter consisting of a large population of old, dead stars with a relatively small galactic concentration probably could not. It is also shown that the downward force exerted by the Galaxy will perturb the halo, but will not produce any periodicity.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 311; 17
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  • 87
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    The remarkable infrared galaxy Arp 220 = IC 4553 (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: IRAS observations of the peculiar galaxy Arp 220 = IC 4553 show that it is extremely luminous in the far-infrared, with a total luminosity of 2 x 10 to the 12th solar luminosities. The infrared-to-blue luminosity ratio of this galaxy is about 80, which is the largest value of the ratio for galaxies in the UGC catalog, and places it in the range of the 'unidentified' infrared sources recently reported by Houck et al. in the IRAS all-sky survey. Other observations of Arp 220, combined with the luminosity in the infrared, allow either a Seyfert-like or starburst origin for this luminosity.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 283; L1-L4
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  • 88
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    183 GHz water line variation - An energetic outburst in Orion KL (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Observations of the 3(13)-2(20) transition of water vapor in the direction of Ori MC1 in 1980 February show a 50 percent flux increase and an apparent additional red shift of approximately 2 km/s relative to the line observed in 1977 December. From a detailed examination of the amplitude and frequency calibration, it appears unlikely that the effect is due to systematic error. The increase is attributed to the appearance of a new component at a velocity of 12 km/s with respect to the local standard of rest. The new component also has broad wings. Increased emission from a region in the high-velocity core of Ori MC1 can be due either to additional far-IR radiation to pump the 1983 GHz transition or to a change in the physical conditions in the gas. Statistical equilibrium calculations using the large-velocity-gradient formalism were carried out to develop a model for the emission. The calculations support a model in which the gas in the region of enhanced emission is hotter than the dust. The temporal coincidence between the 183 GHz increase and the 22 GH1 water maser outburst suggests a common, impulsive cause, which has heated the gas in a part of the HV source, enhancing the emission in both transitions.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 283; 106-116
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  • 89
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    Remarks on a vibronic origin for the diffuse band spectrum (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: It has been demonstrated that the diffuse band spectrum could not originate as a series of vibronic transitions from atomic impurities in interstellar MgO grains as has recently been proposed since laboratory spectra of such materials show no evidence for such complex structure. Furthermore, recent observational evidence indicates that the extinction feature at 160 nm in the standard interstellar extinction curve upon which the identification of interstellar MgO was founded is actually the result of a calibration error in the original observational data.
    Keywords: ASTROPHYSICS
    Type: Astrophysics and Space Science (ISSN 0004-640X); 103; 2, Au
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  • 90
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    Interplanetary radio storms. I - Extension of solar active regions through the interplanetary medium (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: About 100 storms of type-III solar radio bursts have been identified in the ISEE-3 radio-experiment data during the 4-yr period around the maximum of the 21st solar cycle. They demonstrate the very frequent presence of streams of suprathermal electrons. Their durations range from 1 to 10 d or more. They are observed up to 100-170 solar radii. Their rate of occurrence is 2 to 3 per solar rotation near solar maximum. It is shown that the time variations of the daily radio-emission intensities correlate with the sunspot-number variations and with the solar activity in general. More specifically, a very good correlation is found with the meter-wave type-III and type-I storms, which demonstrates that the suprathermal electrons responsible for the radio emission have been accelerated below 2 solar radii heliocentric. The different lags observed between the sunspot-number variations, the S-component, and the type-I and type-III storms are discussed.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 136; 2, Ju
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  • 91
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    Mass ejection from the peculiar emission star R Aquarii (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: It is pointed out that the composite emission object R Aquarii embodies a number of characteristic properties which distinguish it from other peculiar emission stars. The visual spectrum indicates the presence of a cool Mira variable in close association with a hot unresolved ionizing source of radiation which appears to be responsible for the high excitation nebular emission observed. It has been suggested by Hubble (1943) and Baade (1944) that the distinguishing meniscus-shaped nebula was formed by a nova outburst which occurred about 600 years ago. Wallerstein and Greenstein (1980) reported the appearance of a new feature in R Aquarii which resembles a brilliant 'spike' or 'jet' protruding a distance approximately 7 arcsec from the central compact region. Attention is given to several models which have been considered to explain the emission feature.
    Keywords: ASTROPHYSICS
    Type: Comments on Modern Physics, Part C - Comments on Astrophysics (ISSN 0146-2970); 10; 85-96
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  • 92
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    Cryogenic telescope on the Infrared Astronomical Satellite (IRAS) (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The Infrared Astronomical Satellite (IRAS) has completed an unbiased all-sky survey at wavelengths from 10 to 100 microns. The design and performance of the focal plane array is described with emphasis on in-orbit measurements of the sensitivity and stability. In the four broad spectral bands centered at 12, 25, 60, and 100 microns, the system noise equivalent flux density (NEFD) values are in Jy/(Square root of Hz), 0.03, 0.025, 0.046, and 0.21, respectively (Jansky = 10 to the -26th W/sq m/Hz). For point sources, a single scan at the survey rate of 3.8 arcmin/s yields limiting flux densities at the 3-sigma confidence level of 0.36, 0.30, 0.39, and 1.2 Jy. The dc stability of the junction field effect transistor (JFET) amplifiers and the excellent off-axis rejection of the telescope permit total flux measurements of extended infrared emission at levels below 6,000,000 Jy/sr. Response of the extrinsic silicon and germanium photo-detectors to ionizing radiation is described.
    Keywords: ASTRONOMY
    Type: Optical Engineering (ISSN 0091-3286); 23; 122-127
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  • 93
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    Preliminary scientific results from the first six months of the Infrared Astronomical Satellite (IRAS) (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The Infrared Astronomical Satellite (IRAS) was successfully launched on January 25, 1983. This paper presents results based on analysis of early scientific data returned from IRAS. Among the early results of IRAS are the discovery of comet IRAS-Araki-Alcock, evidence for a shell of large particles around the nearby bright star Vega, detection of stars in the process of formation, and detection of many infrared bright galaxies. These early results demonstrate that the IRAS data will be a treasure chest for astronomers for years to come.
    Keywords: ASTRONOMY
    Type: Optical Engineering (ISSN 0091-3286); 23; 128-130
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  • 94
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    The v = 0 - 0 spectrum of H2 (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Ground-state rotational parameters for molecular hydrogen are evaluated using a combination of laboratory and observational data. High-accuracy v = 0 - 0 S(0)-S(5) frequencies from infrared laboratory measurements are analyzed simultaneously with available observed frequencies for the S(8), S(9), S(12), S(13), S(14), and S(15) Orion emission lines. The laboratory and Orion measurements are consistent with each other within their measurement errors. The combined data set yields a determination of five v = 0 rotational parameters and an improvement in the high-J calculated line positions. The analysis produces the parameters (in per cm): B(0) = 59.334627(30), D(0) = 0.0456912(30), H(0) = 4.8974(90) x 10 to the -5th, L(0) = -6.320(110) x 10 to the -8th, M(0) = 7.19(30) x 10 to the -11th, where a correction is made for the estimated contribution of sixth and higher orders.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 282; L85-L88
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  • 95
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    Flatness of the universe - Reconciling theoretical prejudices with observational data (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Theoretical prejudices argue strongly for a flat universe; however, observations do not support this view. It is pointed out that this apparent conflict could be resolved if the mass density of the universe today were dominated by (1) relativistic particles produced by the recent decay of massive, relic particle species, or by (2) a relic cosmological constant. Scenario (1) has several advantages in the context of galaxy formation, but must confront the problem of a young universe.
    Keywords: ASTROPHYSICS
    Type: Physical Review Letters (ISSN 0031-9007); 52; 2090-209
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  • 96
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    Binary modulation and transient periodic variations in X-ray emission from the AM Her binary H 0139 - 68 (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A detailed timing analysis of HEAO-1 and Einstein satellite soft X-ray data on the AM Her-type binary H 0139 - 68 indicates that the X-ray flux is modulated at the 113.6363-min period of its optical counterpart, and that the X-ray source shows high and low states. Transient X-ray pulsations with a period of about 275 sec are noted in the Imaging Proportional Counter (IPC) data during the high state, and the rapid X-ray flickering observed in the IPC light curve is characterized by an average e-folding autocorrelation time of about 10-20 sec. The present optical and X-ray data preclude the presence of an accretion disk in the primary system.
    Keywords: ASTROPHYSICS
    Type: Royal Astronomical Society, Monthly Notices (ISSN 0035-8711); 208; 679-685
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  • 97
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    The unusual 8-13 micron spectrum of Markarian 231 (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: An 8-13 micron spectrum was obtained of the Seyfert galaxy Markarian 231 with a spectral resolution of 0.22 micron per point. The spectrum is unlike any previously published spectrum at these wavelengths. The spectrum can be attributed to a combination of absorption and reemission by crystalline silicates which must have formed under conditions quite different from those in which silicates form in the Galaxy. Comparison of the data with previously published data indicates that the infrared emission is extended and not dominated by a bright central source.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 281; L17-L19
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  • 98
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    A formula for the Shakura-Sunyaev turbulent viscosity parameter (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A formula for the Shakura-Suniaev alpha parameter is proposed in terms of the growth rate of the unstable modes of the physical mechanisms that generates turbulence. Turbulent convection is discussed as a particular example. The effect of rotation on turbulent viscosity is considered, and some remarks are made on convective fluxes, disk stability, and other types of instabilities.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 280; L55-L58
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  • 99
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    Soft X-ray spectral observations of quasars and high X-ray luminosity Seyfert galaxies (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Results of the analysis of 28 Einstein SSS observations of 15 high X-ray luminosity (L(x) 10 to the 435 power erg/s) quasars and Seyfert type 1 nuclei are presented. The 0.75-4.5 keV spectra are in general well fit by a simple model consisting of a power law plus absorption by cold gas. The average spectral index alpha is 0.66 + or -0.36, consistent with alpha for the spectrum of these objects above 2 keV. In all but one case, no evidence was found for intrinsic absorption, with an upper limit of 2 x 10 to the 21st power/sq cm. Neither was evidence found for partial covering of the active nucleus by dense, cold matter (N sub H greater than 10 to the 22nd power/sq cm); the average upper limit on the partial covering fraction is 0.5. There is no obvious correlation between spectral index and 0.75-4.5 keV X-ray luminosity (which ranges from 3 x 10 to the 43rd to 47th powers erg/s) or with other source properties. The lack of intrinsic X-ray absorption allows us to place constraints on the density and temperature of the broad-line emission region, and narrow line emission region, and the intergalactic medium. Previously announced in STAR as N84-14082
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 280; 499-515
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  • 100
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    The photometric method of detecting other planetary systems (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Rosenblatt (1971) has conducted an investigation regarding the use of photometric techniques to detect other planetary systems by searching for changes in starlight caused by the transit of a planet. The obtained results suggest that neither the intrinsic variation of the starlight nor the transmission fluctuations in the terrestrial atmosphere would prevent detection of planets as small as Mars with telescope apertures of 40 to 60 cm. The present investigation shows that Rosenblatt's results are too optimistic even for present-day differential photometric techniques. However, it appears that the detection of planets at least one-third the size of Jupiter is feasible, if a photometer with the required precision can be developed, taking into account the availability of a wide-angle telescope with a 1- to 2-m aperture.
    Keywords: ASTRONOMY
    Type: Icarus (ISSN 0019-1035); 58; 121-134
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