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  • 1
    Publication Date: 2006-04-18
    Description: Preliminary results from the Bragg crystal spectrometer on the ANS satellite are given. No significant Si XIII and Si XIV narrow line emission has been detected from Cygnus X-1, -2, or -3.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 49-52
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  • 2
    Publication Date: 2011-08-17
    Description: 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.
    Keywords: ASTROPHYSICS
    Type: Astronomical Society of the Pacific; vol. 91
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  • 3
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    In:  Other Sources
    Publication Date: 2011-08-17
    Description: Observations made with the Rotation Modulation Collimator system (RMC) have revealed that X-ray source X-4 in the Large Magellanic Cloud (LMC X-4) is most likely part of a binary system. An analysis of the star's coordinates is presented, with attention given to orbital period and flux intensity variations. Stellar mass and orbital inclination angle are estimated for both X-4 and its companion star.
    Keywords: ASTRONOMY
    Type: Nature; 271; Jan. 5
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  • 4
    Publication Date: 2019-06-27
    Description: Cas A was observed with the imaging detectors on the Einstein X-ray Observatory. The mass of the expanding shell due to the interaction of the blast wave and the ambient medium is determined. This indicates that Cas A is probably not in the free expansion phase, but has not yet reached the adiabatic phase of expansion. Detailed comparison of X-ray, optical, and radio images shows various degrees of correlation, indicating that several processes for emission are present. An upper limit of 1,500,000 K is established for any stellar remnant that is below the expected temperature of a neutron star by a factor of about 5. The total mass of the SNR is found to be 10-30 solar masses
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 234
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  • 5
    Publication Date: 2019-06-27
    Description: The Einstein (HEAO 2) X-ray Observatory, launched in 1978, includes a fully imaging focusing X-ray telescope with an angular resolution of a few arc sec, a field of view of up to one deg, and a sensitivity several hundred times greater than previously available in any X-ray astronomy experiment. A high-resolution imager, an imaging proportional counter, a focal plane crystal spectrometer, and a monitor proportional counter are among the principal instruments on board the Einstein X-ray Observatory. About 20% of the total effective observing time in the first year of the X-ray astronomy experiment has been reserved for guest observers.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 230
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  • 6
    Publication Date: 2019-06-27
    Description: Formulae for the gravitational radiation due to the anisotropic axisymmetric emission of neutrinos from a small source are derived. We find that a burst of neutrinos released anisotropically from a supernova will generate a burst of gravitational radiation that may be comparable in amplitude and energy to the gravitational radiation generated by the fluid motion in the collapse of the supernova core.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 223
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  • 7
    Publication Date: 2019-06-27
    Description: Data on the X-ray structure of the Perseus cluster of galaxies in the energy range from 2 to 10 keV are analyzed which were obtained during a 12-day observation with the rotating modulation collimator aboard SAS 3. In particular, the nature of the compact X-ray source coincident with NGC 1275 is examined. The data are shown to confirm the presence of a diffuse region of X-ray emission surrounding the nucleus of NGC 1275; it is found that a model which also includes a point source at the nucleus is consistent with the data if the point contribution is no larger than 20% of the X-ray flux detected within 3 to 5 arcmin of the galaxy. The results suggest that NGC 1275 may have accreted a large amount of gas from the intracluster medium and that the flux from the possible point source is consistent with a synchro/Compton model.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 221
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  • 8
    Publication Date: 2019-06-27
    Description: Some of the effects of primordial inhomogeneities on the production of H-2, He-3, and Li-7 are investigated. For the most part, temperature fluctuations have only small effects on the abundances. The density fluctuations are modeled by a unimodal distribution so that the Universe is characterized by the mean density and the relative amplitude of the density variations. It has been found that the constraint which H-2 production imposes on the mean mass density is eased somewhat by allowing for density inhomogeneities. However, unless the composition of the interstellar matter is atypical of most of the matter in the Universe, the mass density will be at least a factor of 3 below the critical density. For reasonable estimates of the pregalactic abundances, sufficient He-3 and Li-7 cannot be produced in the same model universe. Production of both Li-7 and H-2 requires large-amplitude primordial fluctuations, while sufficient He-3 and H-2 can be formed in very low-density, fairly homogeneous universes.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 197; Apr. 15
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  • 9
    Publication Date: 2019-06-27
    Description: X-rays from a region containing the nucleus of the type 1 Seyfert galaxy 3C 120 have been detected using the rotating modulation collimator on board the SAS-3 X-ray observatory. The error circle has a 95% error radius of 1.0 arcmin. The measured X-ray (2-10 keV) flux is 5.4 by 10 to the -11th power erg/s per sq cm. The corresponding luminosity is 2.3 by 10 to the 44th power erg/s for the source at 200 Mpc. Synchrotron-Compton and hot plasma models are discussed.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 215
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  • 10
    Publication Date: 2019-06-27
    Description: Cygnus X-1 was observed from 3 November until 9 November 1974, using the hard X-ray (1-28 keV) and soft X-ray (1-8 keV) experiment on board the Astronomical Netherlands Satellite. On three occasions, on 4 and 5 November, the X-ray spectrum was observed to be harder, while the flux intensity in the 1-7 keV ranges decreased by about 50% from its quiescent value. These events occurred near and following the time of superior conjunction of the likely optical counterpart HDE 226 868. These events appear to be the same as previously reported absorption dips and reveal this phenomenon to be more complex than had been believed. A systematic study of the X-ray spectral variations in these energy bands, on a time scale of 64 seconds over the period of the spectroscopic binary, is presented.
    Keywords: ASTROPHYSICS
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