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  • 1
    Publication Date: 2019-06-28
    Description: X-ray spectra of GX 339-4 measured on three occasions in 1977 and 1978 are presented. These are the first reported measurements above 10 keV. The spectra can be described as the superposition of a soft component, which is dominant below about 20 keV, and a hard component at higher energy. Simultaneous measurements at lower energy show that the soft component vanished during the observation in early 1978. The behavior of these two components is similar to that of the spectrum of Cygnus X-1; this reinforces the previously noted resemblance in rapid X-ray variability.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 262
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  • 2
    Publication Date: 2019-07-13
    Description: The photon number spectrum integrated over the impulsive part of the event is shown to fit a thermal bremsstrahlung function with a temperature of 330 + or - 70 keV at energies between 151 and 487 keV. At lower energies, the data points lie considerably below this function, indicating a broad absorption feature extending down to values less than or equal to 28 keV, the lowest energy measured. The upper energy of this absorption feature varies from 100 to 150 keV on a time scale less than or equal to 0.5 s. This event is interpreted as a typical gamma ray burst, even though it is still considered remotely possible that it is of solar origin. The spectral features, together with their variability, are interpreted in terms of electron interactions at the cyclotron resonance frequency in magnetic fields of 10 to the 12th - 10 to the 13th gauss close to the surface of a neutron star.
    Keywords: ASTROPHYSICS
    Type: Gamma ray transients and related astrophysical phenomena; Workshop; Aug 05, 1981 - Aug 08, 1981; La Jolla, CA
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  • 3
    Publication Date: 2011-08-18
    Description: (Previously announced in STAR as N82-22136)
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 259
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  • 4
    Publication Date: 2011-08-18
    Description: (Previously announced in STAR as N82-13594)
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research; 87; June 1
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  • 5
    Publication Date: 2011-08-18
    Description: Airborne measurements of the Ar II (6.99 micron) and S II (18.7) micron lines for five compact H II regions in the solar neighborhood are presented, as well as 2-4 micron and 8-13 micron spectroscopy where available. From these data and radio data, lower limits to the elemental abundances of Ar, Ne, and S are deduced. Some of these H II regions suffer substantial nebular extinction, and some are extended. After correcting for beam size effects an extinction, it is found that four of the objects are consistent with standard abundances, within the uncertainties of correcting for unobserved ionization states. A Perseus arm object, S156, is apparently overabundant in sulfur.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 262
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  • 6
    Publication Date: 2011-08-18
    Description: The turbulent convection of a compressible fluid in a deep atmosphere is simulated by two-dimensional numerical computations, displaying coexisting 'cells' whose sizes range from the total depth of the convection zone to the smallest scale height at the top. While the largest cells traverse the entire zone, smaller ones are clustered near the top. The vertical correlation length of the vertical velocity is proportional to the local pressure or density scale height, in a way reminiscent of the concept of mixing length.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 263
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  • 7
    Publication Date: 2011-08-18
    Description: The description of the spin given here is classical in that it is intrinsic but not quantized. The approach in this matter is similar to, for example, the work of Bailey and Israel (1973, 1975, 1979), where the fluid particles, which have intrinsic spin, may be galaxies or clusters of galaxies. The elementary particles of these objects and the 'ferromagnetic alignment' of their quantum spins are not resorted to in order to describe a fluid with spin. Physically this means that the equation of motion for the spin tensor is a modified Fermi-Walker transport equation (Misner et al., 1973), arising as a direct result of the inclusion of spin as an intrinsic variable in the thermodynamic description of the internal energy. The variables in this description are classical variables throughout and are not microscopic fields. An improved perfect-fluid energy-momentum tensor that includes spin and torsion is presented. Use is made of a Lagrangian variational principle based on the tetrad formalism of Halbwach (1960) and the method od constraints of Ray (1972).
    Keywords: ASTROPHYSICS
    Type: Physical Review Letters; 49; Oct. 11
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  • 8
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    In:  Other Sources
    Publication Date: 2011-08-18
    Description: Statistical characteristics of magnetic clouds observed in the interplanetary medium near earth are investigated. Forty-five magnetic clouds are identified in which one component of B changes direction by rotating parallel to a plane, while the component of B normal to that plane is either constant or zero. Three classes of clouds are identified: clouds preceded by a shock, clouds followed by a stream interface, and clouds associated with a CME. In superposed epoch plots, the maximum field strength is found to be approximately the same for each class of clouds. Temperatures are all low, densities are somewhat high, and the pressure is higher that the ambient pressure in all three types of clouds. The physical characteristics of the magnetic clouds and their rate of occurrence suggests that many or all of the clouds may be related to coronal mass eject elements observed in white light data.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research; 87; Feb. 1
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  • 9
    Publication Date: 2019-06-28
    Description: Orion OB1 was the association most heavily observed by the Copernicus satellite UV spectrometer, which detected very unusual, strong interstellar UV absorption lines. Negative velocity gas at -100 km/sec was also noted, together with the absence of a corresponding, very high positive velocity feature. These and other characteristics have led to the present inferrence of a radially expanding, thin, uniform and low column density shell of fast moving gas which surrounds the Ori OB1 and Lambda Ori regions. Inside this shell is a more slowly moving inhomogeneous region of higher density gas which produces the more sporadically distributed gas at velocities in the 30-100 km/sec range. Within this framework, it is suggested that the most recent supernova is seen in the highest velocity gas, while the composite effects of the history of supernova formation lie in the denser, slower material.
    Keywords: ASTROPHYSICS
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  • 10
    Publication Date: 2019-06-28
    Description: Nearly complete 2 to 13 micron spectra are presented for 13 compact infrared sources associated with molecular clouds, along with partial spectra of six additional objects. The spectra are found to resemble blackbodies with superposed absorption features from 2.8 to 3.5 microns, at 6.0 and 6.8 microns, and in the silicate band centered near 9.7 microns. Correlations among the features are investigated in an attempt to confirm possible identifications. A good correlation between the deepest part of the absorption at 3.1 microns, its long wavelength wing, and the 6.0 micron features suggests that all may derive from large amorphous water ice particles. The relatively poor correlation between the 3.4 and 6.8 micron optical depths adds no evidence in support of the suggestion that these bands may be due to CH bonds
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 253
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