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  • ASTRONOMY  (4)
  • Chaperone
  • Condensed Matter: Electronic Properties, etc.
  • 1990-1994  (1)
  • 1975-1979  (3)
  • 1
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    A deep x ray survey in the Lockman hole and the soft x ray log N - log S (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The longest pointed observation (152 ksec) with the Rosat position sensitive proportional counter in the direction of the absolutely lowest neutral hydrogen column density is discussed. 26 shallower fields from the Rosat medium sensivity survey are analyzed. 1176 X-ray sources were detected in at least one Rosat energy band in these fields covering a total solid angle of 9.3 deg; 661 of these sources constitute a statistically complete sample detected in the hard band with 0.5 to 2 keV fluxes greater than 2.5 times 10 to the power of minus 15 erg/sq cm s. The faintest limiting flux of the survey is analyzed. Detailed simulations show that confusion effects and other selection biases are relatively small and can be corrected for in the sample. From an analysis in the Lockman field, a best fit slope of approximately 1.8 is found for the extrapolation of the differential X-ray counts below 2.5 times 10 to the power of minus 15 erg/sq cm s. On the basis of this analysis an upper limit of approximately 25% can be found for a truly diffuse background component in the Rosat hard band.
    Keywords: ASTRONOMY
    Type: NASA-CR-194698 , NAS 1.26:194698 , MPE-PREPRINT-238
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  • 2
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    Observations of an isolated compact infrared source in Perseus (1975)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 202; Dec. 1
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  • 3
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    Optical studies of 10 high galactic latitude X-ray sources (1975)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Optical studies are reported for a representative sample of 10 unidentified high galactic latitude X-ray sources that are north of declination minus 25 deg and that have 3U error boxes less than or of the order of 0.5 square degrees. The source 3U 1410-03 is identified with a peculiar emission-line spiral galaxy, NGC 5506, and a distance group 4 rich cluster of galaxies, Abell 2142, is suggested as a possible identification for 3U 1555+27. It is shown that very few of the unidentified high galactic latitude sources are quasi-stellar sources brighter than 17.5 mag, although one possible X-ray quasar, NAB 0137-01, is reported.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 199; July 1
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  • 4
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    IUE observations of the quasar 3C 273 (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: IUE observations indicate that the spectrum of 3C 273 is similar to that of other large-redshift quasars. There is a large excess of flux in the range 2400 A to 5300 A, which encompasses the Balmer jump region but which does not appear to be explainable by Balmer emission. The intensity ratio of Lyman-alpha to H-beta is 5.5, in agreement with other measures and a factor 6 smaller than the recombination value. The only absorption lines in the spectrum are due to our Galaxy. There is marginal evidence for a depression of the continuum shortward of the Lyman-alpha emission line, but the errors are too large to warrant any conclusion that 3C 273 has a rich absorption-line spectrum such as that seen in large-redshift quasars. The absence of emission and absorption lines of Fe II leads to the conclusion that resonance fluorescence probably produces the visual Fe II emission lines.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 230
    Format: text
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