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  • ASTROPHYSICS  (6)
  • PHYSICS, ATOMIC, MOLECULAR, AND NUCLEAR  (4)
  • 1995-1999  (1)
  • 1990-1994  (5)
  • 1970-1974  (4)
  • 1950-1954
  • 1
    Publikationsdatum: 2019-06-27
    Beschreibung: We have calculated the polarization fraction of the Lyman-alpha radiation emitted in e/-/-H/1s/ collisions using the Glauber, Born, and various Vainshtein approximations, and have compared these predictions with observation. We find that the Born, Glauber and all forms of the Vainshtein yield results which are very close to each other and to the data in the energy range from 30 to 700 eV. The comparatively small differences between the various approximations are detailed in the text; also, the reason for the close agreement of the predicted polarization fractions - although the computed 1s-2p total and differential cross sections are not so close - is explained. With respect to the Glauber approximation, the importance of computing the phase integral along a direction perpendicular to the momentum transfer q at each value of q, is stressed.
    Schlagwort(e): PHYSICS, ATOMIC, MOLECULAR, AND NUCLEAR
    Materialart: Journal of Physics; vol. 5
    Format: text
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  • 2
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    In:  Other Sources
    Publikationsdatum: 2019-06-27
    Beschreibung: Glauber scattering amplitudes for atomic hydrogen excitation by electrons or protons, presenting closed form expressions requiring no numerical integration
    Schlagwort(e): PHYSICS, ATOMIC, MOLECULAR, AND NUCLEAR
    Materialart: ; - ASTRONOMY 1969- TE
    Format: text
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  • 3
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    In:  Other Sources
    Publikationsdatum: 2019-06-27
    Beschreibung: Glauber approximations for elastic and inelastic scattering of protons by ground state hydrogen atoms, comparing with measurements
    Schlagwort(e): PHYSICS, ATOMIC, MOLECULAR, AND NUCLEAR
    Materialart: ; 35 (
    Format: text
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  • 4
    Publikationsdatum: 2019-06-27
    Beschreibung: Glauber and Vainshtein approximations for cross sections of 1s-2p excitation during inelastic electron-atomic hydrogen scattering
    Schlagwort(e): PHYSICS, ATOMIC, MOLECULAR, AND NUCLEAR
    Materialart: ; UGREVUE(
    Format: text
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  • 5
    Publikationsdatum: 2019-07-12
    Beschreibung: Low-dispersion UV spectra taken by the IUE satellite of an S star HD 35155 are presented. It is shown that the spectra contain strong emission lines of multiply ionizes species and an excess continuous emission shortward of 2000 A. Because neither the photospheres nor chromospheres of S stars are expected to produce multiply ionized ions, the emission lines and the excess short-wave emission seen in the HD 35155 spectra are interpreted as an evidence of the presence of a hot nearby compact companion. Some inferences regarding the compact companion and the possible location of the source of the emission lines of multiply ionized ions are discussed.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 383; 842-852
    Format: text
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  • 6
    Publikationsdatum: 2019-08-27
    Beschreibung: Model calculation of inhomogenuous magnetized neutron star atmospheres are used to analyze the phase-dependent spectra of 4U 1538-52 and Vela X-1 taking into account general relativistic effects. A chi (exp 2) fitting procedure is used on the Ginga data for these objects to determine the geometry and the magnetic structure of the polar caps, as well as their size and location on the surface of the stars. Other parameters determined by the fit are the masses and radii of neutron stars, the accretion rates, and the rotation and magnetic inclination angles including an azimuthal offset to reproduce the asymmetry of the pulse shapes. We find that general relativistic effects play a significant role in determining the derived cap sizes, the fluxes, and the observational appearance of the pulses. There is evidence that the polar caps are unequal and nonantipodal, suggesting either an off-center or bent magnetic axis, or a strong nondipole component. The magnetic field structure is approximated by a two-component model. The rotation axes are inferred to be moderately close to the mean magnetic axes and seen at large inclinations with respect to the line of sight.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 444; 1; p. 405-414
    Format: text
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  • 7
    Publikationsdatum: 2019-07-13
    Beschreibung: We have obtained IUE spectra for 31 middle and late-type giant and supergiant stars whose TD-1 fluxes or ground-based spectra indicate the presence of a hot component, or whose radial velocities indicate an unseen component. Stellar components earlier than type F1 were detected in 22 cases. While 20 of the hot secondaries are seen weakly in optical spectra, two are UV discoveries: HD 58134 and HD 183864. The hot companions are classified accurately by temperature class from their far-UV spectra. The interstellar extinction of each system and the relative luminosities of the components are derived from the UV and optical fluxes, using a new grid of UV intrinsic colors for hot dwarfs. We find that many giant stars apparently have companions which are too hot and hence too luminous for consistency with the primary's spectral classification.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 412; 2; p. 814-826.
    Format: text
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  • 8
    Publikationsdatum: 2019-07-13
    Beschreibung: To test the popular hypothesis that technetium-deficient stars of spectral types S and MS are mass-transfer binaries, we have searched for ultraviolet light from the putative hot secondaries in spectra taken with the SWP spectrograph of IUE. Although most S and MS stars are apparently thermally pulsing AGB (asymptotic giant branch) stars whose surfaces have been enriched with s-process elements and carbon dredged up from the interior, those stars whose spectra show enhanced s-process elements but no Tc are widely believed to be cooler analogs of the Ba II stars, which apparently owe their unusual abundances to prior mass transfer, the Tc from which has decayed away. We report IUE observations of 15 S and MS stars with the SWP, including the identification of six hot companions. Assembling all the IUE observations made to date, we find clear support for the mass-transfer hypothesis, confirming evidence from other lines of research. We further discuss the ages of the companions and the implications of these discoveries for stellar evolution.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 402; 2; p. 667-679.
    Format: text
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  • 9
    Publikationsdatum: 2019-07-12
    Beschreibung: The K5 III star Alpha Tau was observed with the Goddard High Resolution Spectrograph on November 27, 1990 as part of the Science Assessment Program for the HST. The spectra show intersystem and permitted chromospheric emission lines of semiforbidden C II and Si II, Fe II, Fe I, Ni II, and Co II. Resolved profiles of the semiforbidden C II lines indicate a complex chromospheric turbulent velocity distribution with mean value of roughly 24 km/s, while their observed wavelengths indicate a 4 km/s downflow of the semiforbidden C II plasma. Twenty-five new emission lines have been found in the 2320-2370 A region, 17 of which have been identified with the aid of Skylab data obtained above the solar limb, including four lines from Co II (UV 8) and an Fe I (UV 12) line.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 377; L45-L48
    Format: text
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  • 10
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    In:  Other Sources
    Publikationsdatum: 2019-07-12
    Beschreibung: IUE ultraviolet spectral observations reveal that the F supergiant HD 51956 contains a hot companion star partially obscured by warm plasma. Variable absorption features are analogous to those in the strongly interacting system HD 207739. The F type component is apparently transferring matter to a subluminous B type star which originally was the primary component.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 364; L13-L15
    Format: text
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