ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Ihre E-Mail wurde erfolgreich gesendet. Bitte prüfen Sie Ihren Maileingang.

Leider ist ein Fehler beim E-Mail-Versand aufgetreten. Bitte versuchen Sie es erneut.

Vorgang fortführen?

Exportieren
Filter
  • ASTROPHYSICS  (1.120)
  • 1995-1999
  • 1980-1984  (578)
  • 1975-1979  (542)
  • 1983  (578)
  • 1979  (542)
Sammlung
Schlagwörter
Erscheinungszeitraum
  • 1995-1999
  • 1980-1984  (578)
  • 1975-1979  (542)
Jahr
  • 1
    facet.materialart.
    Unbekannt
    Precise determination of the distances of galaxies (1979)
    In:  CASI
    Details
    Publikationsdatum: 2006-01-16
    Beschreibung: The use of the Space Telescope in the determination of the distances of galaxies is examined. The Space Telescope can check the local extragalactic distance scale to within 10-15 percent. The determination of relative distances of cosmic standard candles, viz. brightest M-supergiants and SNe I in E galaxies, is discussed. The M-supergiants map the velocity field out to v sub o approx. 3000 km s(-1) thus providing a firm basis for the determination of H sub o (global) from local distances, and the possibility to derive precise distances of all nearby field galaxies from their recession velocities. Photometry of the SNe I out to z = 0.5 leads to a direct determination of q sub o via the Hubble diagram, and the form of their light curves offers a fundamental test on the nature of redshifts. Other calculations are discussed.
    Schlagwort(e): ASTROPHYSICS
    Materialart: NASA. Marshall Space Flight Center Sci. Res. with the Space Telescope; p 263-293
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 2
    facet.materialart.
    Unbekannt
    Requirements for predictions and real-time monitoring for the study of travelling interplanetary phenomena (1979)
    In:  CASI
    Details
    Publikationsdatum: 2006-01-16
    Beschreibung: Physical processes within quiescent as well as disturbed flows of solar wind plasma, energetic particles, and magnetic and electric fields from the Sun are considered. Specifically, travelling interplanetary phenomena to be studied during the years of the solar maximum of solar cycle 21 are covered. It is noted that predictions, while needed for long range, logistical planning, is secondary to the requirements of synoptic real time monitoring over a wide range of particle energies and spectral bandwidths.
    Schlagwort(e): ASTROPHYSICS
    Materialart: NASA. Marshall Space Flight Center Solar-Terrest. Predictions Proc., Vol. 2; p 340-345
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 3
    facet.materialart.
    Unbekannt
    The problems of cosmology (1979)
    In:  CASI
    Details
    Publikationsdatum: 2006-01-16
    Beschreibung: Three examples that illustrate the expected role of the Space Telescope in cosmological investigations are described addressing the distribution of globular star clusters, universe expansion, and other classical cosmological problems.
    Schlagwort(e): ASTROPHYSICS
    Materialart: NASA. Marshall Space Flight Center Sci. Res. with the Space Telescope; p 295-312
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 4
    facet.materialart.
    Unbekannt
    The central regions of active galaxies and quasars (1979)
    In:  CASI
    Details
    Publikationsdatum: 2006-01-16
    Beschreibung: Theories describing the central regions of nonthermal extragalactic sources (radio galaxies, Seyfert nuclei, quasars, etc.) are examined in the light of the experimental possibilities afforded by the Space Telescope. In particular, the theory which proposes the accretion of stars or gas onto a black hole as the explanation of the central engine is discussed. Planned observations directed towards the problem of the mass, size, and structure of the central engine, and the phenomenological questions regarding the general environment of the central engine are outlined.
    Schlagwort(e): ASTROPHYSICS
    Materialart: NASA. Marshall Space Flight Center Sci. Res. with the Space Telescope; p 197-214
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 5
    facet.materialart.
    Unbekannt
    Luminosity functions and evolution of globular clusters (1979)
    In:  CASI
    Details
    Publikationsdatum: 2006-01-16
    Beschreibung: The stellar dynamics of globular clusters are addressed in terms of luminosity functions, chemical topics, and dynamical topics
    Schlagwort(e): ASTROPHYSICS
    Materialart: NASA. Marshall Space Flight Center Sci. Res. with the Space Telescope; p 139-150
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 6
    facet.materialart.
    Unbekannt
    X-ray spectra of young supernova remnants (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: Einstein solid-state-spectrometer (SSS) spectra are presented for the Crab Nebula, Cas A, SN 1006, the Tycho SNR, and the Kepler SNR. The history of X-ray observations of SNRs is reviewed; the SSS instrument is briefly characterized; a reduction technique which accounts for all background sources in the 0.5-4.5-keV band is applied; and the physical models of SNRs constructed to reproduce the refined spectra are discussed. The limitations of the modeling methods and the need for further observations, especially of localized regions, are indicated.
    Schlagwort(e): ASTROPHYSICS
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 7
    facet.materialart.
    Unbekannt
    Magnetic topology and the heating of extended chromospheres (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: New data indicate that red giants are surrounded by geometrically thick chromospheres of several stellar radii extent. Such chromospheres occur among stars which apparently lack coronae. Maintenance of this extended warm region may require non-compressional wave heating of a magnetic character, and this may provide a crucial clue to the mechanism of rapid mass loss from red giant stars.
    Schlagwort(e): ASTROPHYSICS
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 8
    facet.materialart.
    Unbekannt
    A note on the oxygen gradient in NGC 628 (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: The Kitt Peak 2.1-m telescope and Intensified Image Dissector Scanner have been used to gather spectrophotometric data in the 3600-5200 A spectral region for five H II regions in the spiral galaxy NGC 628. The Pagel et al (1979) technique was then applied to determine the relative number abundances of O to H in each of the H II regions. An examination of the abundance values obtained as a function of the radial coordinate yields an O gradient of -0.05 + or - 0.03 dex/kpc.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astronomical Society of the Pacific, Publications (ISSN 0004-6280); 95; 986-988
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 9
    facet.materialart.
    Unbekannt
    Testing for a cosmological influence on local physics using atomic and gravitational clocks (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: The existence of a possible influence of the large-scale structure of the universe on local physics is discussed. A particular realization of such an influence is discussed in terms of the behavior in time of atomic and gravitational clocks. Two natural categories of metric theories embodying a cosmic infuence exist. The first category has geodesic equations of motion in atomic units, while the second category has geodesic equations of motion in gravitational units. Equations of motion for test bodies are derived for both categories of theories in the appropriate parametrized post-Newtonian limit and are applied to the Solar System. Ranging data to the Viking lander on Mars are of sufficient precision to reveal (1) if such a cosmological influence exists at the level of Hubble's constant, and (2) which category of theories is appropriate for a descripton of the phenomenon.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Physical Review D - Particles and Fields, 3rd Series (ISSN 0556-2821); 28; 1822-182
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 10
    facet.materialart.
    Unbekannt
    Observations of NGC 7027 from 5.2 to 7.5 microns - The detection of Ni II and additional dust features (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: NGC 7027 was observed with a multichannel grating spectrometer from 5.2 to 7.5 microns at a spectral resolving power of 120-200. Two new dust emission features are resolved at 5.62 and 6.95 microns, and for the first time the Ni II fine-structure line at 6.64 microns is detected. It is shown that a single molecular dust constituent might account for six of the nine observed dust features between 2 and 14 microns. The strength of the Ni II line indicates either that Ni is not depleted in the neutral gas, or that the line is formed at high density.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 274; 666-670
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 11
    facet.materialart.
    Unbekannt
    A new calibration of the extragalactic distance scale using Cepheids and RR Lyrae stars (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: Visual absolute magnitudes of classical Cepheids, metal-poor RR Lyrae stars and short-period type II Cepheids have been determined with very high precision by combining a large number of old and new astrophysical data. Five independent methods (four observational and one theoretical) have been successfully used: (1) secular and statistical parallaxes; (2) moving-group parallaxes; (3) cluster main-sequence fitting; (4) the Baade-Wesselink method and its modifications; and (5) light-curve and velocity-curve fitting (the theoretical method). With these five adopted methods, the zero point of the galactic and extragalactic distance scale can be set on a relatively firm and self-consistent basis. Classical Cepheids and RR Lyrae stars now provide essentially identical distances to nearby galaxies: the distance modulus to the Large Magellanic Cloud is 18.5 and to the Small Magellanic Cloud is 18.8, both with an uncertainty of 0.1. The distance to the center of our Galaxy is 8.6 plus or minus 0.5 kiloparsecs. The major uncertainty in these values lies in the correction for interstellar extinction.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 274; 20-30
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 12
    facet.materialart.
    Unbekannt
    On the line profile coefficient for stimulated emission (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: It is pointed out that the line profile coefficients for spontaneous and stimulated emission are identical in low-intensity radiation fields. In more intense radiation fields, however, the stimulated emission profiles in the radiative transfer equation and in the rate equations for the atomic level populations may differ from each other, owing to their different physical nature. A seeming discrepancy between the stimulated emission profiles of the usual semi-classical aproach and a recent quantum mechanical approach by Cooper et al. (1982), which should also be valid for intense 'broadband' fields, is discussed and shown to have negligible consequences for low-intensity radiation fields.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astronomy and Astrophysics (ISSN 0004-6361); 127; 1, Oc; 224-226
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 13
    facet.materialart.
    Unbekannt
    Observational tests of baryon symmetric cosmology (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: Observational evidence for Baryon symmetric (matter/antimatter) cosmology and future observational tests are reviewed. The most significant consequences of Baryon symmetric cosmology lie in the prediction of an observable cosmic background of gamma radiation from the decay of Pi(O)-mesons produced in nucleon-antinucleon annihilations. Equations for the prediction of the gamma ray background spectrum for the case of high redshifts are presented. The theoretical and observational plots of the background spectrum are shown to be in good agreement. Measurements of cosmic ray antiprotons and the use of high energy neutrino astronomy to look for antimatter elsewhere in the universe are also addressed. Previously announced in STAR as N83-10996
    Schlagwort(e): ASTROPHYSICS
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 14
    facet.materialart.
    Unbekannt
    Interacting binary stars - Freaks or rosetta stones (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: Attention is given to semidetached binaries of the Algol type and to related interacting systems, such as Beta Lyrae and the W Serpentis stars. A brief description is given of observational problems. The basic properties of the Algol variables are satisfactorily explained by means of evolutionary models that assume considerable mass transfer between the components. It is pointed out that ultraviolet spectra obtained with the IUE satellite corroborate the view that the present subgiant secondary component was initially the more massive star and that it has been stripped of a large fraction of its mass so that the deep layers affected by CNO processing are now denuded. It is believed that the present-day 'classical' Algols must have undergone a phase of rapid mass transfer in the past and that Beta Lyrae and the W Serpentis stars are probably closer to that stage than ordinary Algols. Around the accreting star a complex structure is formed, and an induced stellar wind may blow a large part of the transferred matter out of the system.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Royal Astronomical Society of Canada, Journal (ISSN 0035-872X); 77; 283-304
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 15
    facet.materialart.
    Unbekannt
    What causes the buoyancy reversal in compressible convection? (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: The problem posed by the existence of a negative buoyancy work region at the top of cellular type convection in a deeply stratified superadiabatic layer (Massaguer and Zahn, 1980) is addressed. It is approached by studying two-dimensional cellular compressible convection with different physical parameters. The results suggest that a large viscosity, together with density stratification, is responsible for the buoyancy reversal. The numerical results obtained are analyzed. It is pointed out, however, that in an astrophysical situation a fluid involved in convection will generally have very small viscosity. It is therefore thought unlikely that buoyancy reversal occurs in this way.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysics and Space Science (ISSN 0004-640X); 95; 2, Se; 453-457
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 16
    facet.materialart.
    Unbekannt
    On a vibronic origin for the diffuse band spectrum (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: Duley (1982) has proposed that many of the diffuse interstellar bands in the wavelength interval 542-677 nm arise from vibronic transitions of Cr (3+) ions in MgO grains. No explanation has been offered for the fact that as many as 85 of the possible 108 transitions of this system have not been observed in the interstellar medium. Moreover, the relative intensities of the diffuse bands which are observed appear to be inconsistent with their assignment. It is therefore concluded that this model is not consistent with the observations.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysics and Space Science (ISSN 0004-640X); 95; 1, Se
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 17
    facet.materialart.
    Unbekannt
    A note on the composition and structure of interstellar grains (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: The plausibility of relatively pure diatomic oxide crystals forming in the expanding atmospheres of cool stars is commented on, and the likelihood of SiO grains condensing is discussed on the basis of laboratory nucleation experiments. Results of annealing experiments are used to consider the further evolution of silicon oxide and silicate grains. The evidence shows that SiO solids form only when SiO condenses directly onto surfaces, and that the probability of pure crystalline SiO grains forming is rather small.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysics and Space Science (ISSN 0004-640X); 95; 1, Se
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 18
    facet.materialart.
    Unbekannt
    Planetary nebulae and stellar evolution (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: Newly defined characteristics of planetary nebulae (PN) derived from analysis of a photometric survey of 57 PN are reported. The data were combined with measurements of 27 other PN made since 1918 and were found to indicate core masses ranging from 0.55-1.0 solar mass. N/O elemental abundance ratios observed were correlated with the planetary nuclei masses, and were in direct proportion. IUE data on PN that overlapped a large part of the survey indicated that the PN in the galactic disk are more massive than PN in the halo. It is suggested that PN evolve into white dwarfs, a hypothesis supported by astrometric solutions for three nearby visual binaries featuring white dwarfs with well-determined masses. It is noted, however, that PN with masses exceeding one solar mass have been sighted in the Magellanic Clouds.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Nature (ISSN 0028-0836); 305; 670
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 19
    facet.materialart.
    Unbekannt
    Two new possible planetary nebulae (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: Two new possible planetary nebulae have been identified using the Parker, Gull, and Kirshner (1979) emission-line survey of the galactic plane. Both objects exhibit very strong forbidden O III lambda 5007 line emission, a symmetrical morphology, and a faint blue central star.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astronomical Society of the Pacific, Publications (ISSN 0004-6280); 95; 614-618
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 20
    facet.materialart.
    Unbekannt
    Ultraviolet observations of M1-2 (= VV 8) (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: First IUE spectrograms of the peculiar emission-line object M1-2 (= VV 8) are presented. In the wavelength region 1150-3200 A this object is characterized by emission lines superposed on a moderately strong continuum. Some ultraviolet and optical properties of M1-2 are discussed in the context of symbiotic stars and protoplanetary and planetary nebulae. An E(B-V) extinction of 0.37 mag is obtained from the ratio of the He II flux at 1640 and 4686 A and is compared with values derived from other parameters. The ultraviolet observations suggest that M1-2 is a young, high-density planetary nebula of excitation class 5 or 6 with characteristics similar to IC 4997.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 275; 628-635
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 21
    facet.materialart.
    Unbekannt
    The origin of the Gum nebula (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: Obsrvations and theoretical investigations of the Gum nebula (GN) since about 1971 are reviewed. Direct observations of the GN, the Vela X supernova remnant (SNR), the Vela pulsar, and other stars in or near the GN are discussed with those of related phenomena such as the radio loops and known SNRs; the emphasis is on studies of the interstellar absorption lines, the evidence for hot gas in the GN, and the extended diffuse emission. The four basic models proposed for the GN are considered: a fossil Stromgren sphere, an old SNR, an H II region, or a superbubble. The GN physical parameters predicted by each model are listed in a table and compared. A minimum explanation which attributes the 36 x 36-deg filamentary structure and the 125-pc radius structure to the action of the stellar winds from Zeta Pup and Gamma-2 Vel (and perhaps the effect of a Vel X supernova explosion 20,000 years ago) is found most appropriate, at least until the questions of the net expansion rate of the GN (about 20 km/sec or about zero?) and the existence of the diffuse emission beyond the filamentary structure are resolved by observations.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Comments on Modern Physics, Part C - Comments on Astrophysics (ISSN 0146-2970); 10; 1-14
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 22
    facet.materialart.
    Unbekannt
    Electron velocity distributions near interplantary shocks (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: Previous work on electron heating mechanisms operating at the supercritical earth's bow shock is extended to the generally lower Mach number interplanetary shocks. This is done by studying electron velocity distributions observed both upstream and downstream of interplanetary shocks observed by ISEE 3 between August 1978 and December 1979. It is found that perpendicular heating accompanied by little or no parallel heating occurs at the weaker shocks but that parallel heating is dominant for the stronger shocks. When perpendicular heating is dominant, downstream velocity distributions are for the most part Gaussian at low energies (core) and Lorentzian at high energies (halo). When parallel heating is dominant, however, these distributions are flat-topped at low energies, having power law extensions to higher energies. At the weaker shocks, the observations are consistent with electron heating resulting from conservation of the magnetic moment, whereas at the stronger shocks the heating is quite similar to that observed at the earth's bow shock.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 88; 9949-995
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 23
    facet.materialart.
    Unbekannt
    Sharp shortward-shifted features in the spectra of O subdwarfs (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: Preliminary inspection of archival high-dispersion ultraviolet spectra obtained by the International Ultraviolet Explorer reveal sharp shortward-shifted features in the spectra of O subdwarfs. In three examples presented here, BD + 75.325 deg, HD 128220 B, and BD + 28.4211 deg, stable, multiple, discrete shortward-shifted components of the N V, C IV, and Si IV resonance doublets are seen. The available data suggest that some of these features are persistent, being relatively stable in velocity and intensity over at least 9 months. It is tentatively suggested that the mechanism, or mechanisms, producing these discrete features operates universally in hot stars, from luminous O and B stars down through the O subdwarfs to include the hot white dwarfs. If true, this has important ramifications for current knowledge of mass loss in hot stars.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 274; L87-L91
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 24
    facet.materialart.
    Unbekannt
    Images in the rocket ultraviolet - The starburst in the nucleus of M83 (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: Ultraviolet images of the SAB(s)c I-II galaxy M83 (NGC 5236) obtained with a rocketborne telescope in broad bandpasses centered at 1540 A and 2360 A show a bright resolved nuclear source which accounts for approximately 20 percent of the flux of the galaxy in both bandpasses. Low-resolution International Ultraviolet Explorer spectra of this source reveal an energy distribution similar to that of the starburst nucleus of NGC 7714. Strong blueshifted absorption lines can be interpreted as evidence for a nuclear wind powered by supernovae. Observations from UV, X-ray, optical, and far-infrared bandpasses are consistent with a starburst approximately one-sixth as strong as that in M82. A scaling of the M82 models of Rieke et al. (1980) predicts that the nucleus of M83 contains 10 to the 6th - 3 x 10 to the 7th solar masses in young stars and has a supernova rate of approximately 0.01 per yr.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 274; L53-L56
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 25
    facet.materialart.
    Unbekannt
    X-ray observations of LMC X-3 with the monitor proportional counter aboard the HEAO 2 Einstein observatory - A comparison with Cygnus X-1 (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: A comparison is presented of the black hole candidates LMC X-3 and Cygnus X-1 based on Einstein observations of LMC X-3 with the monitor proportional counter. A spectral analysis shows LMC X-3 to be more like the typical bright galactic X-ray source than Cygnus X-1. A search for periodic pulsations over a period range from 0.2 ms to over 1000 s set upper limits at the 90 percent confidence level of the order of 10 percent. An analysis of the aperiodic variability of LMC X-3 shows none of the shot noise behavior characteristic of Cygnus X-1. The absence of distinctive X-ray properties common to both sources suggests that the identification of black hole candidates on the basis of X-ray properties similar to Cygnus X-1 (or LMC X-3) is not reliable.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 274; L65-L69
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 26
    facet.materialart.
    Unbekannt
    Stellar evolution in N-body simulations of disk galaxies. I (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: The Kalnajs (1972, 1976) Omega models of global mass and velocity distributions are employed in the present two-dimensional N-body simulation, which allows for a spectrum of particle masses, stellar explosions, explosion remnant interactions with an interstellar medium, and the creation of new stars from the gas. Two sequences of runs using the Omega values of 0.8 and 0.9 examine the separate and combined effects of particle mass distribution, the gravitational influence of an interstellar gas distribution on the N-body particles, and stellar evolution, allowing for stellar explosions and star formation from the gas. It is found that both Omega values' nonequilibrium results dramatically change when evolution is allowed to occur. These results call for more realistic coupled N-body and evolution simulations in order to improve the understanding of disk galaxy evolution.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 274; 595-610
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 27
    facet.materialart.
    Unbekannt
    The (an)isotropy of the X-ray sky (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: An assessment is made of the extent to which the study of the isotropy of the X-ray sky has contributed to the present understanding of the structure of the universe at moderate redshifts. It is, of course, the anisotropic character of the sky flux that is valuable in this context. Although it is not currently possible to undertake measurements with the precision and small solid angles that are typically achieved in the microwave range, the comparatively crude limits from the X-ray fluctuations place limits on the largest scale structure of the universe. After indicating the nature of measurements made, with the HEAO 1 A-2 experiment, of the X-ray sky and its anisotropies, it is shown how these place limits on the origin of the X-ray sky and on any large scale structure of the universe.
    Schlagwort(e): ASTROPHYSICS
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 28
    facet.materialart.
    Unbekannt
    Comments concerning magnetic fields as a possible cause of rapid, irregular variability of early-type stars (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-19
    Beschreibung: It is noted that it is helpful to divide the atmosphere of an early-type star into two parts: a photosphere and a mantle. The photosphere can be modeled satisfactorily by normal model-atmosphere procedures. When modeling the mantle, one must take account of the deposition of nonradiative heat and momentum and one should recognize that the mantles of hot stars do not appear to be uniform or spherically symmetric. Five areas of discrepancy between classical theory and observation are noted and a possible way of modeling the mantles of early-type stars is outlined. The model consists of arcades of magnetic loops which form helmet-type structures in the equatorial band of the star, and of coronal-hole-type structures emmanating from weak unipolar regions which are chiefly distributed at polar latitudes.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Hvar Observatory, Bulletin (ISSN 0351-2651); 7; 1, 19
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 29
    facet.materialart.
    Unbekannt
    Observational knowledge about the physical properties of O stars (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-19
    Beschreibung: Information about the effective temperatures, radii, and masses of O-type stars is presented. It is argued that rapid variations in the amount of light from O stars and the spectral distribution are a result chiefly of changes which occur in the envelope of the star. The stability of the photospheric layers of O stars against convection is reviewed and it is noted that late O stars and early B stars have a convection zone in the deeper parts of the photosphere. This convection zone is due to the second ionization of helium. Evidence is reviewed that most of the line-profile changes seen for O stars are generated by changes in the physical state of the mantle of the star, that is of the outer atmosphere where the deposition of non-radiative energy and momentum controls the physical state of the atmosphere. The physical state of the mantle may change in response to changes in the upper envelope of a star with a different time constant than the photosphere does.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Hvar Observatory, Bulletin (ISSN 0351-2651); 7; 1, 19; 1-15; Di
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 30
    facet.materialart.
    Unbekannt
    The X-ray spectrum of 3C 273 (1979)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-17
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 232
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 31
    facet.materialart.
    Unbekannt
    Interstellar C2 molecules toward Zeta Persei (1979)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-17
    Beschreibung: A search for absorption by interstellar C2 molecules, conducted at the (2-0) Phillips band near 8760 A, is reported for three stars. No interstellar absorption is seen in the spectra of 20 Tau and Epsilon Aur, at upper limits of approximately 5 mA and 1 mA, respectively. Toward Zeta Per, however, the R(0), Q(2), and Q(4) lines are detected, and a useful upper limit on the Q(6) line is obtained. The resulting column density, 1.4 x 10 to the 13th to 2.0 x 10 to the 13th per sq cm, and the excitation temperature, T = (78 plus or minus 25) K, show acceptable agreement with an existing theoretical model of the absorbing cloud.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 232
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 32
    facet.materialart.
    Unbekannt
    Galaxies and gamma-ray astronomy (1979)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-17
    Beschreibung: The nature of the high-energy spectra of several types of active galaxies and their contribution to the measured diffuse gamma-ray emission between 1 and 150 MeV are considered, using X-ray spectra of active galaxies and SAS 2 data regarding the intensity upper limits to the gamma-ray emission above 35 MeV. It is found that a substantial increase in slope of the photon energy spectrum must occur in the low energy gamma-ray region for Seyfert galaxies, BL Lac objects, and emission line galaxies; the power-law spectra observed in the X-ray range must steepen substantially between 50 keV and 50 MeV. In addition, a cosmological integration shows that Seyfert galaxies, BL Lac objects, and quasars may account for most of the 1-150 MeV diffuse background, even without significant evolution.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 232
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 33
    facet.materialart.
    Unbekannt
    Magnetic Cepheids (1979)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-17
    Beschreibung: The role of a magnetic field in the pulsational behavior of classical Cepheids has been studied by computing linearized models of pulsating stellar envelopes pervaded by a well-tangled magnetic field. It is found that the 'pulsational' masses of Cepheids that are implied by the theoretical values of the quantities Q(0), P(1)/P(0), and (possibly) P(2)/P(0) can be brought into line with the large 'evolutionary' masses, if the pressure due to the postulated magnetic field is assumed to be comparable to the thermodynamic pressure everywhere in the pulsating layers. The field strengths that are required - several hundred gauss at the surface and several ten thousand gauss at the base - are quite reasonable from the point of view of the observed magnetic fields in Cepheids. The influence of the magnetic field on the location of the blue edge of the instability strip in the H-R diagram is estimated to be very slight.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 234
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 34
    facet.materialart.
    Unbekannt
    Numerical models for cometary dust environments (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: The development of a numerical model for the dust environment near a comet is described. The major components of the model are a simple treatment of the acceleration of the dust by the gas outflow from an isothermal icy nucleus, a detailed treatment of the dust particle trajectories controlled by solar gravity and radiation pressure, including the formation of the dust envelope and tail, and a simple treatment of the radiation from the dust in the visible and thermal infrared. The results of recent comet observations are used to estimate parameter values for the model, including dust-to-gas ratios by light and by mass, the distribution of dust and gas emission on the nuclear surface, the distributions of dust particle size, density, mass, and radiative properties, and other quantities. Gas and dust production rates as functions of time are derived from observed light curves using the simple photometric theory. Sample results are presented for the dust concentration, flux and fluence along the trajectory of a spacecraft which flies by Comet P/Halley in 1986.
    Schlagwort(e): ASTROPHYSICS
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 35
    facet.materialart.
    Unbekannt
    An outer ion coma model in two dimension (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: A simple cometary outer ion coma model is constructed by adopting published results from numerical MHD computations. The ion composition and density distributions so derived are used to highlight some of the basic features of cometary plasma flows and the need for cometary ion observations with absolute brightness calibration.
    Schlagwort(e): ASTROPHYSICS
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 36
    facet.materialart.
    Unbekannt
    Search for hydrogen atoms and the noble gas abundances in the head of Comet Schwassmann - Wachmann 1 (1974 II) from Voyager 2 UVS spectra (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Schlagwort(e): ASTROPHYSICS
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 37
    facet.materialart.
    Unbekannt
    The nature of cometary dust from remote sensing (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: Observational data on the thermal emission from cometary dust grains and theoretical models constructed to explain them are reviewed. Consideration is given to grain temperature, the size distribution of the grains, thermal-emission models, the silicate component, dust-grain albedo, and icy grains; model predictions and observations are compared in graphs. It is pointed out that no unambiguous detection of icy grains has been achieved, probably because these grains are vaporized within a few hundred km of the nucleus when the comet is within 2.5 AU of the sun.
    Schlagwort(e): ASTROPHYSICS
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 38
    facet.materialart.
    Unbekannt
    Electromagnetically-tracked free-mass gravitational wave antennas (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: The response to a gravitational wave of two free masses whose relative motion is monitored with an electromagnetic tracking signal is derived. The results indicate a two-feature signature in one-way data and a three-feature signature in two-way data. The effect is applied to gravitational wave experiments using laser interferometers, spacecraft Doppler tracking, planetary ranging, and pulsar timing analysis. Actual results are presented from spacecraft Doppler experiments and from pulsar timing data analysis, with new upper limits being set on a possible cosmic gravitational wave background via the pulsar data.
    Schlagwort(e): ASTROPHYSICS
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 39
    facet.materialart.
    Unbekannt
    Infrared properties of extragalactic H II complexes (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: Infrared observations of relatively isolated giant H II complexes in the LMC and the spiral arms of M33 and M101 are discussed, and complexes which extend over several kiloparsecs near the galactic centers are examined. The 30 Doradus nebula is emphasized, showing the variation of the 50-100 micron color temperature with position in that object. Ten-micron scans through the nucleus of NGC 1097 are compared to a visual photograph, showing the enhanced infrared emission which occurs at the nucleus and at the ring of H II regions about 1 kpc from the nucleus.
    Schlagwort(e): ASTROPHYSICS
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 40
    facet.materialart.
    Unbekannt
    X-ray emission from pre-main-sequence stars, molecular clouds and star formation (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: The pre-main sequence X-ray emitting stars observed in molecular clouds appear to provide the bulk of the ionization. Newly forming stars therefore control the coupling of the magnetic field to the cloud. Since this coupling itself is believed to be responsible for the rate of cloud collapse, it is suggested that there is a natural feedback mechanism, involving observed X-rays, which is capable of regulating molecular cloud evolution and the rate of star formation.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 272; Sept. 15
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 41
    facet.materialart.
    Unbekannt
    A note on compressibility and energy cascade in turbulent molecular clouds (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: Observed velocity-size correlations are reexamined in the light of an improved theory of turbulent energy cascade that is developed. It is shown that observed velocity-size correlations cannot be compared with the Kolmogorov law, which is based on incompressible turbulent flow. The fact that the log v-log(l/rho) scaling law (v the turbulent velocity, l the associated region size, and rho the fluid density) predicted for compressible energy cascade is always steeper than that observed in molecular clouds indicates the injection rather than the dissipation of mechanical energy at smaller scales of motion. It is also shown that the concept of strict energy cascade may not be generally applicable in the interstellar medium. The agreement between theory and observation turns out to be best for small cool clouds and cloud cores, suggesting that, for these regions at least, the dominant process in establishing the observed v-l-rho correlation is a turbulent energy cascade.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 272; Sept. 15
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 42
    facet.materialart.
    Unbekannt
    A large molecular cloud toward the SNR W50 and SS 433 (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: The CO 1 yields 0 transition at 115 GHz has been mapped over an area of more than 6 deg sq toward W50, the extended SNR surrounding the peculiar object SS 433. W50 is found to lie at the end of a filamentary molecular cloud 4 deg long and 1 deg wide that closely matches a conspicuous dust lane on the Palomar Sky Survey; the cloud's kinematic distance is within 0.7 of 2.2 kpc, in agreement with the distance 2-3.3 kpc estimated for the SNR, and its mass is about 120,000 solar masses. Though there is little evidence of star formation in the molecular filament, or evidence of an interaction between the filament and W50 (or SS 433), the positional coincidence of the two, their similar distance, and their displacement nearly two molecular scale heights from the plane all suggest a physical relationship or common origin. One possibility is that both the molecular filament and the stellar progenitor of W50 were ejected from a large active molecular complex lying in the plane at l = 40 deg.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 272; Sept. 15
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 43
    facet.materialart.
    Unbekannt
    Correlated particle and magnetic field observations of a large-scale magnetic loop structure behind an interplanetary shock (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: From a survey of observations on ISEE-3, an example of correlated particle and magnetic field observations of a large-scale magnetic loop structure is presented. Bidirectional proton fluxes were observed for a period of 40 hours in the energy range 35-1600 keV approximately 12 hours after the passage of the interplanetary shock of December 11, 1980, and directly after the passage of a discontinuity. For each of the eight logarithmically spaced energy channels, a three-dimensional anisotropy analysis reveals streaming along both directions of the magnetic field. The magnetic field rotated slowly but steadily through approximately 180 deg during this same 40-hour period; this is consistent with the existence of a large-scale loop with extent greater than 0.5 AU. The observations suggest that the particles are being injected into the loop sunward of the spacecraft; they appear as bidirectional fluxes in the outermost regions of the loop arising from a combination of focusing and near scatter-free transport.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Geophysical Research Letters (ISSN 0094-8276); 10; Sept
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 44
    facet.materialart.
    Unbekannt
    The effect of MHD instabilities on the flaring of cometary plasma tails (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: The hypersonic pressure balance model of flaring in cometary plasma tails of Ershkovich et al. (1982) has been modified to include the effects of magnetohydrodynamic (MHD) instabilities occurring along the ionopause in the outer-tail regions. The effect of instability is to mix the solar-wind and comet-tail plasmas, increasing the tail magnetic field strength above that calculated from magnetic flux conservation. The earlier model assumed the ionopause to be a tangential discontinuity surface (flux conserving) at all distances, with the result that the magnetic field approached zero in the outer regions of strongly flaring tails. The present model is more realistic and is in better agreement with measurements of cometary plasma tail widths and flaring angles. This agreement leads to an important conclusion that the magnetic flux is not conserved in distant comet tails.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 272; Sept. 1
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 45
    facet.materialart.
    Unbekannt
    On searches for periodic pulsed emission - The Rayleigh test compared to epoch folding (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: The Rayleigh test has been recently invoked as a method of searching a time series for periodic pulsations. In this paper, this technique is discussed and compared to epoch folding, a technique which has had widespread use in X-ray astronomy. It is found that the Rayleigh test provides a more sensitive approach to the search for periodic pulsations when the pulses are sinusoidal or of broad duty cycle, such as those typical of the pulsing X-ray sources. Epoch folding, on the other hand, is more sensitive to the narrow pulses typical of radio pulsars.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 272; Sept. 1
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 46
    facet.materialart.
    Unbekannt
    Electrodynamic coupling in magnetically confined X-ray plasmas of astrophysical origin (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: Explicitly magnetic field-independent relationships that quantitatively connect the thermodynamic state of the confined beta-less-than-one X-ray plasma to the confining magnetic loop characteristics and the stressing velocity at beta greater than about one are presented. The derived relations fall into two categories: (1) diffuse heating resulting from efficient transport of energy throughout the magnetic loop volume, and (2) isolated heating within the electrodynamic dissipation shell. For each of these cases the Joule dissipation, shear viscous dissipation, and compressional dissipation are considered. Each of these models is characterized by three thermodynamic scalings that are parametrized by the magnetic loop properties and by the stressing velocity. Eliminating the magnetic field intermediary from these relations and normalizing the inverse aspect ratio and the magnetic expansion factor with respect to solar conditions results in a single, unique velocity scaling law for each model.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 271; Aug. 15
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 47
    facet.materialart.
    Unbekannt
    The detection of H2 in cool carbon stars (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: Spectra of several carbon stars in the two micron region are examined and compared with synthetic spectra from model atmospheres. Molecular hydrogen has been directly observed in carbon stars for the first time through the quadrupole 1-0 S(1) line at 4712.9/cm. It is definitely present in several Mira variables, and is definitely not present in several irregular variables and one Mira variable. A discrepancy between the predicted and observed line depths at different temperatures is shown. Resolution of the discrepancy by change of temperature alone would require an upward revision of the present effective temperature scale by at least 600 K. Several possible resolutions of the dilemma are briefly examined.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 270; July 15
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 48
    facet.materialart.
    Unbekannt
    Very long baseline interferometry at a wavelength of 3.4 mm (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: The first detection of interference fringes by VLBI at a wavelength of 3.4 mm during observations of 3C84 are reported. The compact source in the nucleus of 3C84 was observed for a 9-hr period on the 485 km baseline between the Owens Valley Radio Observatory and the Hat Creek Observatory. The fringe data are given and the derivation of the correlated flux densities is described. The findings are discused in the context of previous obervations. The results demonstrate that there are no unforeseen technical difficulties associated with millimeter VLBI, and that the sensitivity of existing systems is sufficient to observe objects brighter than a few Jy. The observations are consistent with the millimeter wavelength radio structure of 3C84 being more compact than its centimeter wavelength structure.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Nature (ISSN 0028-0836); 303; June 9
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 49
    facet.materialart.
    Unbekannt
    Comment on 'A comparative study of rotational properties of high-velocity and low-velocity early-type stars' (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 267
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 50
    facet.materialart.
    Unbekannt
    Theoretical study of silicon dicarbide (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: Silicon dicarbide was first observed in 1926 in spectra of cool carbon stars. The carrier of these bands around 5000 A was tentatively identified as SiC2 by Kleman (1956) who produced similar spectra by inserting silicon into the graphite tube of a King furnace heated to over 2500 K. This identification was strengthened by subsequent mass spectral studies which showed SiC2 as a major molecular component of vaporized silicon carbide. The present investigation is concerned with calculations which were initiated in an attempt to understand more recent astronomical observations of unidentified lines in the millimeter-wave region of the spectrum. The calculations were designed to determine the ground state equilibrium structure and to obtain vibrational and rotational constants. Calculations for estimating the positions and structure of low-lying electronic states were also performed. Self-consistent field (SCF) calculations were performed assuming a closed-shell electronic structure analogous to that in C3. Calculations were conducted for symmetric CSiC, and asymmetric SiCC forms.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 266
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 51
    facet.materialart.
    Unbekannt
    A two-component X-ray spectrum from SMC X-1 (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: HEAO 1 A-2 and Einstein Solid State Spectrometer (SSS) observations of SMC X-1 are presented. An unpulsed soft component is found with a blackbody temperature of 0.16 keV and an area for the emission region of 10 to the 15th to 10 to the 17th sq cm. The hard X-ray component is pulsed; the phase-averaged spectrum is a power law with alpha of about 0.5 up to 17 keV, above which it steepens. The SSS sets an upper limit of less than 4 x 10 to the 21st H/sq cm to any absorption, and is consistent with that expected from the wind of Sk 160. Absorption dips with a timescale of several hundred seconds are seen immediately following an eclipse exit, and are probably caused by inhomogeneities in the wind of Sk 160.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 266
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 52
    facet.materialart.
    Unbekannt
    NGC 315 - High-velocity H I in an active elliptical galaxy (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: The detection of high-velocity H I in absorption against the nuclear continuum source in the giant elliptical galaxy NGC 315 is reported. The absorption line is found to be highly blueshifted in the reference frame of the galaxy with a projected velocity toward the galaxy of 490 km/s. The absorption line is very strong (244 + or - 4 mJy), consisting of two components with very narrow velocity widths of 2.5 km/s (FWHM) each and peak optical depths of 0.9 and 0.2. The kinetic temperature must be 150 K if the line widths are due entirely to thermal broadening, while the neutral gas column densities implied are 2-5 x 10 to the 20th hydrogen atoms/sq cm. No OH in absorption was detected in these clouds to a limiting peak optical depth of 0.04, although this result is consistent with either a galactic or extragalactic origin of the clouds. It is suggested that these clouds may have condensed out of a large unobserved galactic halo of gas, or they may reside in or have been captured from the intracluster medium.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 266
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 53
    facet.materialart.
    Unbekannt
    The angular diameters, effective temperatures, radii, and luminosities of 10 Wolf-Rayet stars (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: The effective temperature of a normal star with an absorption-line spectrum is a parameter which represents the total amount of radiative energy emerging from each square centimeter of surface of the star. Effective temperatures have been obtained for 10 Wolf-Rayet stars by means of ultraviolet energies determined from high-resolution International Ultraviolet Explorer (IUE) spectra and energies determined from observations made in the visible range. It is essential to use high-resolution IUE spectra in order to resolve the continuum from many emission lines which are present, particularly shortward of 1900 A. The results confirm what was found earlier, namely that the effective temperatures of Wolf-Rayet stars are similar to those of early B stars. The effective temperature of the central star of the planetary nebula BD 30 deg 3639, HD 184738, is found to be 18,000 K.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 266
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 54
    facet.materialart.
    Unbekannt
    Axions and the evolution of structure in the universe (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: A cosmological scenario where axions provide the dark matter in the universe is considered. Fluctuations in the axion-field energy denisty produced by domain walls and strings cause the appearance of 'axion clumps' of masses of order 10 to the 6th solar masses which most likely collapse to black holes by or at the time that the universe becomes axion dominated at T approximately 10 eV. These objects form the building blocks for the clustering hierarchy theory of galaxy and supercluster formation on scales up to about 10 Mpc and 10 to the 15th solar masses.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Physical Review Letters; 50; Mar. 21
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 55
    facet.materialart.
    Unbekannt
    On searches for pulsed emission with application to four globular cluster X-ray sources - NGC 1851, 6441, 6624, and 6712 (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: Periodic pulsations have been sought in the NGC 1851, 6441, 6624, and 6712 globular cluster sources' X-ray emission, using the Einstein Observatory's Monitor Proportional Counter. Special attention is given to features of the present methods of analysis, which correctly account for several effects that have been routinely overlooked by other researchers. No pulsed emission was detected in the periods searched, which covered from 1 msec to about 500 sec. The 90% confidence upper limits for the pulsed fraction are given.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 266
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 56
    facet.materialart.
    Unbekannt
    Possible mechanisms for the Hubble-Sandage /S Doradus/ variables (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: The unexplained long-term variability of the light of the brightest nonexplosive stars known, namely the Hubble-Sandage (or S Doradus) variables, is investigated in terms of the following mechanisms: (1) episodic, nearly catastrophic mass loss, perhaps accompanied by temporary shrinkage of the stellar radius, in a luminous supergiant; (2) flickering of a hydrogen-burning or helium-burning shell; (3) hydrogen flashing in an evolved stellar core; (4) pulsation of a luminous supergiant envelope near the Eddington limit of radiative stability; (5) pulsation of a dense circumstellar gas or dust cloud; (6) overturning of giant convection cells (or some other kind or nonradial oscillation) in a luminous supergiant envelope; or (7) vibrational instability and mass outflow in an extremely massive main-sequence star. It is believed that the second and third suggestions can all but definitely be ruled out and that the sixth and seventh are rather unlikely. Preference is given to the notion that a sudden, massive outflow of matter may sometimes occur from the surface of an evolved supergiant of very high mass.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 264
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 57
    facet.materialart.
    Unbekannt
    Methanol in Orion A - Simultaneous observations of corresponding rotational transitions in the ground and torsionally excited states (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 264
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 58
    facet.materialart.
    Unbekannt
    Hf chronometer for the early solar system (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: It is now widely believed that Al-26 (half-life, 7.2 x 10 to the 5th yr) and Pd-107 (half-life, 6.5 x 10 to the 6th yr) were present in the early solar system. The nucleosynthetic event responsible for the production of these nuclei must therefore have occurred no more than a few million years before the formation of solid bodies. It is possible that this event also gave a rise to the I-129 believed to be present in the early solar system. The last event to contribute Pu-244 to the solar system, however, occurred approximately 10 to the 8th yr before the time of solidification. It is noted that this latter time scale is also consistent with the lack of evidence for a Cm-247 chronometer. It is proposed that Hf-182 (half-life, 9 x 10 to the 6th yr) can resolve the question whether heavy-element nonactinide nucleosynthesis occurred during the (Al-26)-producing event. It is believed that an answer to this question will help to clarify the chronology of the formation of the solar system and will help to determine the astrophysical sites of heavy-element nucleosynthesis.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Nature (ISSN 0028-0836); 304; Aug. 11
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 59
    facet.materialart.
    Unbekannt
    Accretion powered X-ray pulsars (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: The current theoretical understanding of the properties of X-ray pulsars is assessed through a comparison with unified descriptions of 14 such systems, extending over six orders of magnitude in luminosity, in whose phase averaged spectra the only notable trend is a less abrupt high energy cutoff in the lower luminosity systems. Detailed pulse phase spectroscopy is given for five of the systems. A reexamination of the pulse phase spectra of 4U 0115 + 63 has uncovered electron cyclotron lines at 11.5 and 23 keV that appear to be in absorption at pulse peak and in emission during an interpulse. Spectral hardening regions such as those from Her X-1 are a common feature in the low energy pulse of many pulsars, and may represent the passage of the magnetic axis through the observer's line of sight. Attention is given to the nature of the beaming from Her X-1, and it is concluded that a pencil beam configuration represents the simplest explanation of the overall properties of the pulse.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 270; July 15
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 60
    facet.materialart.
    Unbekannt
    Scalloped disk galaxies - A Kelvin-Helmholtz instability? (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: The scalloped outermost edge of the Galaxy may be driven by a Kelvin-Helmholtz interface instability if the disk and halo components of the Galaxy at large galactocentric distances do not corotate. The range of unstable wavelengths is found to be 10-23 kpc, in good agreement with the observed wavelength, 19 kpc.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 270; July 15
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 61
    facet.materialart.
    Unbekannt
    Fragmentation of a nonisothermal protostellar cloud (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: The collapse of a very low thermal energy, rotating cloud results in fragmentation to a binary protostellar system even in the nonisothermal regime. The solar system therefore probably did not form from a fragmentation hierarchy involving ejection of the presolar nebula from a multiple system.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Icarus (ISSN 0019-1035); 55; July 198
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 62
    facet.materialart.
    Unbekannt
    The partial phase of the eclipse of epsilon Aurigae (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: Ultraviolet spectra of the peculiar eclipsing binary Epsilon Aurigae (FO Ia + ?) were obtained with the International Ultraviolet Explorer at pre-eclipse and ingress partial phases. The results show a wavelength dependence of the eclipse in contrast to the grayness (non-wavelength dependence) of the eclipse observed in visible light. From the current results, incorporating previous observations, it is suggested that: (1) the obscuration of the light of the F supergiant by the disk proposed by Huang (1965) is the result of electron scattering in visible light; (2) the increase in the eclipse depths toward shorter wavelengths observed in the ultraviolet is caused by dust; and (3) the temperature of the disk is in the range from 1000 to 2000 K.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 269; June 1
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 63
    facet.materialart.
    Unbekannt
    Effects of the Kelvin-Helmholtz surface instability on supersonic jets (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: An exact numerical calculation is provided for of linear growth and phase velocity of Kelvin-Helmholtz unstable wave modes on a supersonic jet of cylindrical cross section. An expression for the maximally unstable wavenumber of each wave mode is found. Provided a sharp velocity discontinuity exists all wave modes are unstable. A combination of rapid jet expansion and velocity shear across a jet can effectively stabilize all wave modes. The more likely case of slow jet expansion and of velocity shear at the jet surface allows wave modes with maximally unstable wavelength longer than or on the order of the jet radius to grow. The relative energy in different wave modes and effect on the jet is investigated. Energy input into a jet resulting from surface instability is discussed. Previously announced in STAR as N83-17379
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 269; June 1
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 64
    facet.materialart.
    Unbekannt
    Observations of the line profile of Paschen alpha in 3C 273 (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: Within the uncertainties, the P-alpha line profile is the same as those of H-beta, L-alpha, and C IV. It is therefore contended that if current models of broad-line-emitting clouds in quasars are correct, then the similarity of the P-alpha line profile to the L-alpha profile argues against a velocity field dominated by radial inflow or outflow. It is noted, however, that if the cloud motions are predominantly due to radial inflow or outflow, then the clouds must radiate more isotropically in L-alpha then current models predict. The observed similarity of the line profiles of P-alpha at 1.875 microns and of C IV at 1550 A leads to the conclusion that there is no differential reddening caused by dust between clouds moving at different velocities within the broad line region of 3C 273.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astronomical Society of the Pacific, Publications (ISSN 0004-6280); 95; May 1983
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 65
    facet.materialart.
    Unbekannt
    Energy dynamics in stressed magnetic fields - The filamentation and flare instabilities (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: The thermal and tearing instabilities are believed to be the two primary temperature modification mechanisms in sheared astrophysical magnetic fields. The former gives rise to the formation of cool filaments and the latter to the release of magnetic energy. It has long been known that these processes are interrelated, most conspicuously in the case of the solar corona where prominences often precede flares within the same magnetic structure. It is also clear, from first principles, that the energy transport underlying the thermal instability should have a strong effect on the resistivity which facilitates magnetic tearing, and that the energy release of the latter should affect the temperature drop of the former. This paper describes some results of the first calculations which attempt to unify the dynamic treatment of these two coexisting instabilities. Growth rates as a function of resistivity, and examples of the primary mode structures are provided, along with a discussion of some critical aspects of the interaction of these two astrophysical energy flux mechanisms.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 268; May 15
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 66
    facet.materialart.
    Unbekannt
    Blue compact dwarf galaxies. II - Near-infrared studies and stellar populations (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: An IR photometric survey was performed of 36 blue compact dwarf galaxies (BCDG) where intense bursts of star formation have been observed. The survey covered the J, H, and K lines, with all readings taken at the level of a few mJy. Although the near-IR fluxes observed in the galaxies are due to K and M giants, the bursts have calculated ages of less than 50 million yr. However, the BCDG galaxies surveyed are not young, with the least chemically evolved galaxy observed, I Zw 18, featuring 50 pct of its stars formed prior to its last burst, but with a missing mass that is not accounted for by H I interferometric observations. It is concluded that the old stars must be more spatially extended than the young stars, and a mixture of OB stars with the K and M giants is projected as capable of displaying the colors observed. The star formation processes in the BCDG galaxies is defined as dependent on the total mass of the galaxies, with low mass galaxies having a high ratio of star formation, compared to their previous rates.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 268; May 15
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 67
    facet.materialart.
    Unbekannt
    Observation of ice mantles toward HD 29647 (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: The water ice absorption band at 3.1 microns has been observed in HD 29647, which is a late B type star with an anomalous ultraviolet extinction curve. The interpretation is that ice mantles are present on the dust grains in the intervening cloud and that these mantles are responsible for suppressing the 2200 A interstellar absorption feature. This is the first observation of both the 2200 A region and the 3.1 micron interstellar absorption feature toward the same star. A comparison of recent UV laboratory data of water ice with the UV spectrum of HD 29647 further supports the presence of water ice mantles in the same column density as that observed in the infrared. The diffuse interstellar features have been reported to be weakened in this star, consistent with their origin being on grain core surfaces, rather than in mantles or gaseous molecules.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 268; May 1
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 68
    facet.materialart.
    Unbekannt
    The kinetic temperature and density of the Sagittarius B2 molecular cloud from observations of methyl cyanide (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: Observations of the K components of the CH3CN J = 4-to-3 rotational transition at 73.6 GHz, the 6-to-5 transition at 110.4 GHz, and the 7-to-6 transition at 128.7 GHz, yield a mean kinetic temperature value of 85 + or - 10 K and a mean H2 density of 110,000 + or - 50,000/cu cm for the central 2.0 arcmin of the Sgr B2 molecular cloud. Within the K = zero-to-4 ladders of CH3CN in Sgr B2, the populations of the radiatively coupled J levels are relaxed and exhibit a rotational temperature of about 16 K, which is similar to that of several linear molecules.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 266
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 69
    facet.materialart.
    Unbekannt
    Development of a mass spectrometer system for the measurement of inert gases in meteorites (1983)
    In:  CASI
    Details
    Publikationsdatum: 2016-06-07
    Beschreibung: The study of the inert gases in meteorites has provided many clues as to the origin and evolution of the solar system. Particularly crucial and complex are the gases krypton and xenon. To accurately measure the isotopic compositions of these gases requires a mass spectrometer of high sensitivity and resolution. A previously unused and largely untested mass spectrometer system was brought to the point where it was ready for routine sample analyses. This involved, among other things, focusing the ion beam for optimal peak shape and sensitivity, documenting the instrument's response to a series of characteristic tests such as multplier gain checks, and interfacing the instrument to a computer to run the sample analyses. Following this testing and setting up, three iron meteorite samples were to be analyzed for argon, krypton, and xenon. The three samples were shown in prior work to possibly contain primordial heavy inert gases. Although these analyses have not yet been carried out, it is anticipated that they will be completed in the near future.
    Schlagwort(e): ASTROPHYSICS
    Materialart: NASA. Johnson (Lyndon B.) Space Center The 1983 NASA/ASEE Summer Faculty Fellowship Research Program Research Reports; NASA. Johnson (Lynd
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 70
    facet.materialart.
    Unbekannt
    Some applications of Lie groups in astrodynamics (1983)
    In:  CASI
    Details
    Publikationsdatum: 2016-06-07
    Beschreibung: Differential equations that arise in astrodynamics are examined from the standpoint of Lie group theory. A summary of the Lie method is given for first degree differential equations. The Kepler problem in Hamiltonian form is treated by this method. Extension of the Lie method to optimal trajectories is outlined.
    Schlagwort(e): ASTROPHYSICS
    Materialart: NASA. Johnson (Lyndon B.) Space Center The 1983 NASA/ASEE Summer Faculty Fellowship Research Program Research Reports; NASA. Johnson (Lynd
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 71
    facet.materialart.
    Unbekannt
    Pair production in superstrong magnetic fields (1983)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: The production of electron-positron pairs by single photons in magnetic fields 10 to the twelth power G was investigated in detail for photon energies near threshold as well as for the asymptotic limit of high photon energy. The exact attenuation coefficient, which is derived and then evaluated numerically, is strongly influenced by the discrete energy states of the electron and positron. Near threshold, it exhibits a sawtooth pattern as a function of photon energy, and its value is significantly below that predicted by the asymptotic expression for the attenuation coefficient. The energy distributions of the created pair are computed numerically near threshold and analytic expressions are derived in the asymptotic limit. These results indicate that as field strength and photon energy increase, it becomes increasingly probable for the pair to divide the photon energy unequally. This effect, as well as the threshold behavior of the attenuation coefficient, could have important consequences for pulsar models.
    Schlagwort(e): ASTROPHYSICS
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 72
    facet.materialart.
    Unbekannt
    Introductory Comments on Stellar Atmospheric Structure and Its Modeling (1983)
    In:  CASI
    Details
    Publikationsdatum: 2014-09-10
    Beschreibung: A general historical perspective on stellar atmospheric models is presented. Some comments on the priori speculative-theoretical modeling of the star, its atmosphere, and its environment are made. In contrast to this more speculative type of investigation, an empirical-theoretical program is defined. The objectives of the program are to delineate atmospheric structural patterns, properties of the local stellar environment, and some necessary characteristics of subatmospheric structure as inferred from the observations of nonthermal fluxes and phenomena, and thermodynamic self consistency.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Stellar Atmospheric Struct. Patterns; p 3-18
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 73
    facet.materialart.
    Unbekannt
    HEAO 1 observations of the X-ray pulsar 4U 1626-67 (1979)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-17
    Beschreibung: Results are reported for an observation of the 7-s pulsar 4U 1626-67 with the A-2 experiment on HEAO 1. The phase-averaged X-ray spectrum between 0.7 and 60 keV is complex, as are the constituent spectra, which change radically as a function of pulse phase. Included in this spectral change is the sudden appearance and subsequent decay of a continuum or emission feature with a mean energy of 19 keV, which contains about one-half the power in this spectral range. Pulse-timing results include a new determination of the pulse period and a factor of 8 reduction in the upper limit for the light travel time for orbital periods between 1 and 7 hours. These findings are discussed and compared with the general nature of pulsar spectra.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 231
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 74
    facet.materialart.
    Unbekannt
    Statistical equilibrium in cometary C2. II - Swan/Phillips band ratios (1979)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-17
    Beschreibung: Statistical equilibrium calculations have been made for both the triplet and ground state singlets for C2 in comets, using the exchange rate as a free parameter. The predictions of the results are consistent with optical observations and may be tested definitively by accurate observations of the Phillips and Swan band ratios. Comparison with the one reported observation indicates compatibility with a low exchange rate and resonance fluorescence statistical equilibrium.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 231
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 75
    facet.materialart.
    Unbekannt
    Pioneer 10 studies of interplanetary shocks at large heliocentric distances (1979)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-17
    Beschreibung: Pioneer 10 Ames plasma analyzer data collected in the 6.1 to 12.6 AU range of heliocentric distances (November 1974 to April 1977) have been examined for interplanetary shock waves. Eighteen shock signatures have been identified, with four of these being of the reverse type and the remainder the forward type. Sonic Mach numbers in the range from 3 to 10 are estimated for these events.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Geophysical Research Letters; 6; June 197
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 76
    facet.materialart.
    Unbekannt
    Discovery of two distorted interstellar bubbles (1979)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-17
    Beschreibung: During an extensive program of direct imagery of emission nebulae, arcuate structures have been found around two stars. A well-defined shocklike structure is found about the T Orionis variable LL Ori, located to the side of the Orion Nebula. A less extensive shocklike structure is also found about the runaway star Zeta Oph. These structures can be best described in terms of distorted interstellar bubbles. A direct consequence of this interpretation is an independent estimate of the rates of mass loss for these stars.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 23
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 77
    facet.materialart.
    Unbekannt
    An upper limit for the total energy of relativistic particles contained in the early stages of supernova explosions (1979)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-17
    Beschreibung: A model is proposed for the emission of X-rays from supernova explosions wherein the thermal distribution of photons from a supernova photosphere is inverse Compton scattered by relativistic electrons within or near the surface of the star. Using this model, upper limits for the number of relativistic electrons and their total energy are established on the basis of upper limits to the observed X-ray luminosity of a supernova during maximum light. These upper limits, in conjunction with radio frequency upper limits obtained by Brown and Marscher, strongly suggest that supernovae do not produce significant numbers of relativistic particles until at least 70 years after the initial outburst. This, in turn, implies that young supernovae cannot account for the radio and X-ray variability of active galactic nuclei and quasars.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 230
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 78
    facet.materialart.
    Unbekannt
    Gamma rays from accretion onto rotating black holes (1979)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-17
    Beschreibung: Ionized matter falling onto an isolated rotating black hole will be heated sufficiently that proton-proton collisions will produce mesons, including neutral pions, which decay into gamma rays. For massive (1000-solar mass) black holes, the resulting gamma-ray luminosity may exceed 10 to the 36th erg/s with a spectrum peaked near 20 MeV.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astronomy and Astrophysics; 74; 1, Ap; Apr. 197
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 79
    facet.materialart.
    Unbekannt
    Sporadic mass ejection in red supergiants (1979)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-17
    Beschreibung: A general mechanism first proposed by Burke (1969) is applied to red supergiants for determining the spin-down rate and angular-momentum loss of rotating stars. This model relies principally on sporadic mass ejection, which is assumed to be the result of turbulent elements accelerating material in cool supergiant atmospheres. Mass is preferentially expelled in the forward direction of rotation, resulting in a rapid loss of angular momentum on time scales of 10,000 to 1 million years in the supergiant evolutionary phase. Such rotational breaking will occur if the turbulent elements have characteristic sizes a few percent of the stellar radius and rms velocities one-third the escape speed of the star. This model predicts the formation of a cool silicate disk or torus around the star because of the preferred expulsion of material near equatorial regions of the supergiant.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 228
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 80
    facet.materialart.
    Unbekannt
    Absorption models for low-frequency variability in compact radio sources (1979)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-17
    Beschreibung: The consequences of the most plausible version of the absorption model for low-frequency variability in compact extragalactic radio sources are considered. The general restrictions placed on such a model are determined, and observational tests are suggested that can be used either to support the model or to discriminate among its various versions. It is shown that low-frequency variability in compact radio sources can be successfully explained by a class of models in which the flux is modulated by changes in free-free optical depth within an intervening ionized medium. Two versions of such a model are distinguished, one involving large changes in optical depth and the other, small changes. It is noted that while absorption effects are capable of causing rapid flux and structural variations at centimetric wavelengths, the models predict detailed behavior that is in direct conflict with observational data.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 228
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 81
    facet.materialart.
    Unbekannt
    Comptonization of X-rays by low-temperature electrons (1979)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-17
    Beschreibung: A method is described for calculating the spectrum that results from the Compton scattering of a monochromatic source of X-rays by low-temperature electrons, both for initial-value relaxation problems and for steady-state spatial diffusion problems. The method gives an exact solution of the inital-value problem for evolution of the spectrum in an infinite homogeneous medium if Klein-Nishina corrections to the Thomson cross section are neglected. This, together with approximate solutions for problems in which Klein-Nishina corrections are significant and/or spatial diffusion occurs, shows spectral structure near the original photon wavelength that may be used to infer physical conditions in cosmic X-ray sources. Explicit results, shown for examples of time relaxation in an infinite medium and spatial diffusion through a uniform sphere, are compared with results obtained by Monte Carlo calculations and by solving the appropriate Fokker-Planck equation.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 228
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 82
    facet.materialart.
    Unbekannt
    Photoneutrino reactions in a superstrong magnetoactive plasma (1979)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-17
    Beschreibung: The neutrino luminosity due to the photoneutrino process in the presence of a superstrong magnetoactive electron plasma appropriate for neutron stars is computed. The results indicate that for relatively low temperatures, between 100 million and 500 million K, the energy loss rate is significantly reduced both in the low-density regime below about 10 million g/cu cm (by the magnetic field) and in the high-density regime above that value (by plasmon excitations). These effects are temperature dependent, and they are less pronounced when the temperature is in the range from 500 million to 1 billion K.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 227
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 83
    facet.materialart.
    Unbekannt
    Detection of HC/O-18//plus/ in Sagittarius B2 (1979)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-17
    Beschreibung: Line emission at 85.1 GHz attributed to the J equals 1-0 rotational transition of the formyl ion HC(O-18)(plus) has been detected in Sgr B2 (OH). The double isotopic ratio (O-16/O-18)/(C-12/C-13) in the formyl ion in Sgr B2 is estimated to be in the range 5-10, hence within a factor 2 of the terrestrial value of 5.5. This determination implies that the C-13/C-12 ratio near the galactic center does not differ greatly from that in local molecular clouds.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 227
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 84
    facet.materialart.
    Unbekannt
    Galactic distribution models of gamma-ray burst sources (1979)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-17
    Beschreibung: The log N-log S relationships for several galactic distribution models of gamma-ray burst sources are derived. The resulting curves are substantially different from the galactic curves usually assumed (slope = -1). There is a relatively weak dependence on the radial distribution assumed but a strong dependence on scale height. Available observational data from several experiments appear to rule out both thin disk distributions and extended halo distributions which have a strong radial density dependence. The prospects are good for obtaining self-consistent distribution data from future large-area detectors.
    Schlagwort(e): ASTROPHYSICS
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 85
    facet.materialart.
    Unbekannt
    Scale covariance and G-varying cosmology. II - Thermodynamics, radiation, and the 3 K background (1979)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-17
    Beschreibung: Within the framework of a scale-covariant theory of gravitation, a semiclassical description of particles and photons is given. Thermodynamic relations consistent with the modified conservation equations are derived. Application to a system of radiation shows that the observed 3-K background radiation can be interpreted, within the present framework, as a remnant of equilibrium radiation in the past. As the theory postulates a nonstandard coupling between gravitation and electrodynamics, the assumption that Einstein's theory of gravitation is unchanged forces modifications at the atomic level. The use of Minkowskian spacetime in atomic physics is found to be adequate only over small, but not large, time scales compared with the age of the universe. As a result, a relation between energy and the frequency of a free photon is demonstrated. Possible observational consequences of this relation are discussed.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal Supplement Series; 41; Oct. 197
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 86
    facet.materialart.
    Unbekannt
    Large-scale structure of X-ray clusters of galaxies (1979)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-17
    Beschreibung: Observations from the A-2 experiment on HEAO-1 are used to search for very large-scale structure (exceeding a degree) in 40 X-ray sources in clusters of galaxies. Significant evidence for extension is found only in the relatively nearby Perseus and Virgo clusters. For the remainder of the sources the results place stringent limits on the flux in any very large component.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Royal Astronomical Society; vol. 189
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 87
    facet.materialart.
    Unbekannt
    The violent interstellar medium (1979)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-17
    Beschreibung: Observational evidence for high-velocity and high-temperature interstellar gas is reviewed. The physical processes that characterize this gas are described, including the ionization and emissivity of coronal gas, the behavior and appearance of high-velocity shocks, and interfaces between coronal gas and cooler interstellar gas. Hydrodynamical models for the action of supernova explosions and stellar winds on the interstellar medium are examined, and recent attempts to synthesize all the processes considered into a global model for the interstellar medium are discussed.
    Schlagwort(e): ASTROPHYSICS
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 88
    facet.materialart.
    Unbekannt
    HEAO 1 observations of 4U1232+07 (1979)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-17
    Beschreibung: An analysis of the NRL HEAO 1 observations of the Virgo cluster and 3C 273 has revealed X-ray emission from a region between these two objects. The most satisfactory explanation is the presence of two weak X-ray sources, for which error boxes have been obtained. One source is likely to be the peculiar galaxy IC 3576, suggested by Margon et al. (1972) as the source 2U 1231+07=4U 1232+07. The error box resulting from combining the present observations with the 4U data strengthen the X-ray identification with this extremely interesting galaxy. There are numerous possibilities for the other X-ray source, including the interacting pair of galaxies NGC 4410a and NGC 4410b (NGC 4410a/b).
    Schlagwort(e): ASTROPHYSICS
    Materialart: Nature; 281; Oct. 11
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 89
    facet.materialart.
    Unbekannt
    VV 5-32-63/64 - The 'supermassive double galaxy' in Abell 1775 revisited (1979)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-17
    Beschreibung: Spectroscopy is presented for galaxies in A 1775, the cluster containing VV 5-32-63/64, an apparent double galaxy which has long been considered a gravitationally bound system with supermassive components (10 to the 13th solar masses). However, this model has run afoul of recent radio observations, which detected an extremely long straight radio tail emanating from the eastern galaxy in the pair. The present observations indicate that if both galaxies are members of the same cluster, the cluster radial-velocity dispersion (1522 km/sec) is large enough to account for the velocity difference between the two VV galaxies (1650 km/sec). It is therefore suggested that the VV galaxies are not gravitationally bound and need not be supermassive. The large velocity dispersion measured for A 1775 also strains suggested velocity dispersion vs X-ray luminosity relations for clusters of galaxies, as A 1775 has not yet been detected at X-ray wavelengths.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astronomical Society of the Pacific; vol. 91
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 90
    facet.materialart.
    Unbekannt
    Infrared spectroscopy of stars (1979)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-17
    Beschreibung: This paper reviews applications of IR techniques in stellar classification, studies of stellar photospheres, elemental and isotopic abundances, and the nature of remnant and ejected matter in near-circumstellar regions. Qualitative IR spectral classification of cool and hot stars is discussed, along with IR spectra of peculiar composite star systems and of obscured stars, and IR characteristics of stellar populations. The use of IR spectroscopy in theoretical modeling of stellar atmospheres is examined, IR indicators of stellar atmospheric composition are described, and contributions of IR spectroscopy to the study of stellar recycling of interstellar matter are summarized. The future of IR astronomy is also considered.
    Schlagwort(e): ASTROPHYSICS
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 91
    facet.materialart.
    Unbekannt
    Observed properties of interstellar dust (1979)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-17
    Beschreibung: Recent information on the observed properties of interstellar dust is reviewed, with an attempt made to clarify some of the observational uncertainties associated with obtaining dust parameters. Attention is given to interstellar extinction, the interstellar dust distribution, the dust-to-gas ratio, and light scattering by dust grains. Interstellar polarization is also examined, along with heavy-element depletion in the interstellar medium, thermal emission from interstellar dust grains, diffuse interstellar features, and the composition and origin of interstellar grains.
    Schlagwort(e): ASTROPHYSICS
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 92
    facet.materialart.
    Unbekannt
    Stellar magnetic fields - The role of a magnetic field in the peculiar M giant, HD 4174 (1979)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-17
    Beschreibung: Principles of coronal heating via basic electrodynamic effects, viz., resonant absorption of Alfven surface waves (quiescent) and magnetic tearing instabilities (impulsive), are detailed to argue three principles which may have application to late-type evolved stars. First, if one observes that B-squared/8 pi is much greater than rho times v-squared in a stellar atmosphere, then the observed magnetic field must originate in an interior dynamo. Second, low mass-loss rates could imply the presence of closed magnetic flux loops within the outer atmosphere, which constrain hydrodynamic flows when the magnetic body forces exceed the driving forces. Third, given that such magnetic loops effect an enhancement of the local heating rate, a positive correlation is predicted between the existence of a corona and low mass-loss rates. Application of these principles is made in the case of the peculiar M giant star HD 4174, which is purported to have a kilogauss magnetic field. Several of its spectroscopic peculiarities are shown to be consistent with the above principles, and further observational checks are suggested. Possible application to dMe and RS CVn objects is sketched.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astronomical Society of the Pacific; vol. 91
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 93
    facet.materialart.
    Unbekannt
    Physical parameter profiles of selected X-ray flares (1979)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-17
    Beschreibung: Soft X-ray proportional-counter data for nine X-ray flares of class C1 to M1 occurring during the Skylab mission, have been analyzed to yield temperature, volume emission measure, electron density and thermal energy content. Profiles of these quantities are presented, using 1-min averages of 2.5-s resolution data. The event profiles are discussed and comparisons with previous studies made.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astronomy and Astrophysics Supplement Series; 38; Oct. 197
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 94
    facet.materialart.
    Unbekannt
    Pulse-phase spectroscopy of Hercules X-1 (1979)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-17
    Beschreibung: The 6-18 keV and the 40-60 keV X-ray spectrum of Hercules X-1 were simultaneously observed with the A-2 experiment on HEAO-1. By combining these measurements with the results of an earlier observation of this X-ray pulsar, evidence was found for a component of emission above 40 keV which is above an extrapolation from lower energies, by a factor which depends on the phase of the pulse. These data were compared to previous hard X-ray observations and possible models were discussed.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Royal Astronomical Society; vol. 188
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 95
    facet.materialart.
    Unbekannt
    Cosmic far-ultraviolet background radiation - Probe of a dense hot intergalactic medium (1979)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-17
    Beschreibung: Line and continuum radiation fluxes have been computed for a wide range of enriched intergalactic medium (IGM) models. Observations of the diffuse extragalactic light at optical and far-ultraviolet wavelengths are found to provide a potentially important probe of a dense hot intergalactic medium. If the diffuse X-ray background is produced by this gas, the models constrain the cosmological density parameter (Omega) to be less than 0.4. The associated Compton distortions of the cosmic blackbody background radiation and the optical depths to distant quasars at X-ray wavelengths are also evaluated.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 231
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 96
    facet.materialart.
    Unbekannt
    Double core evolution and X-ray binaries (1979)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-17
    Beschreibung: The evolution of a 16-solar mass star and a 1-solar mass neutron star is followed through the common-envelope binary phase. It is found that the encounter of the neutron star with a yellow giant leads to coalescence of the two cores, while encounter with a red giant leads to hydrodynamic expansion and probable ejection of the common envelope. Within the context of the two rotation laws (1) uniform rotation (investigated in the present study), and (2) uniform specific angular momentum (considered in an earlier study), the results are independent of the choice for the angular-momentum distribution in the common envelope. Implications of the results for the binary pulsar phase are discussed.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Letters; 20; 2, 19; 1979
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 97
    facet.materialart.
    Unbekannt
    Reversal of the /O III/lambda 4363/H sub gamma lambda 4340 ratio in the planetary nebula IC 4997 (1979)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-17
    Beschreibung: Five image-tube spectrograms of the planetary nebula IC 4997 obtained during August 1977 show that the intensity forbidden ratio O III 4363 A/H-gamma 4340 A was equal to unity, but a sixth one obtained in April 1978 showed the ratio to be 0.91. These results represent a significant increase in the intensity ratio, which had been declining from 1895 to 1962 (when it was considerably less than unity), and is interpreted as resulting from a gradual increase in temperature of the nebula's central star accompanied by a transient event which led to a temporarily high value for the ratio in mid-1977.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal; vol. 231
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 98
    facet.materialart.
    Unbekannt
    X-ray observations of AM Herculis from OSO 8 (1979)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-17
    Beschreibung: X-ray observations of the white dwarf binary system AM Herculis in the range 2 to 250 keV, taken by OSO 8, are presented and compared with balloon and Ariel 5 measurements. The composite spectrum of the 2 to 40 and 20 to 250 keV fluxes determined by the proportional counter and the high energy scintillation spectrometer, respectively, on board the satellite is shown averaged over the entire binary cycle. Variations in spectral shape and intensity between the OSO 8 results and balloon measurements taken 10 to 20 days apart are observed. Results indicate the presence of a spectral break at about 15 keV on some occasions, similar to that seen in Her X-1, however presumably caused by a different mechanism than in the neutron star. It is also considered unlikely that the gamma-ray tail observed by Ariel 5 existed during OSO 8 observations.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Nature; 279; June 7
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 99
    facet.materialart.
    Unbekannt
    NGC 1275 /3C 84/ - Similar structure in the optical and 3-mm radio variations (1979)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-17
    Beschreibung: Optical and 3.3-mm data for the Seyfert galaxy NGC 1275 (3C 84) are compared. Similarities exist between the variations at the two wavelengths with regard to amplitude, time scale, and interval between events. The question is raised whether these similarities may be the result of a common triggering mechanism.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astronomical Society of the Pacific; vol. 91
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 100
    facet.materialart.
    Unbekannt
    An analysis of the infrared continuum of comets. II - Comet Kohoutek (1979)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-17
    Beschreibung: An analysis of the infrared observations of comet Kohoutek has been carried out on the basis of silicate grain models. The 'observed' grain temperature has been obtained as a function of the heliocentric distance, and it is compared with the expected distribution. In the visible region, one requires for the refractive index, (m = n-ik), n of about 1.6 and k less than 0.05. The total number of grains varies essentially as the inverse square of radial distance; the size of the particles in the antitail of the comet Kohoutek is greater than 5 microns. The ratio of infrared flux from grains to the incident solar flux at wavelengths of a few microns is calculated.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astronomical Journal; 84; May 1979
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
Schließen ⊗
Diese Webseite nutzt Cookies und das Analyse-Tool Matomo. Weitere Informationen finden Sie hier...