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  • Other Sources  (3)
  • 1990-1994  (3)
  • 1960-1964
  • 1994  (1)
  • 1992  (2)
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  • 1990-1994  (3)
  • 1960-1964
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  • 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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    NASA TECHNICAL REPORTS
  • 2
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    Tuning CAS Application using AIMS: An Automated Instrumentation and Monitoring System (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-08-13
    Description: To bring together NASA's scientists and engineers and their counterparts in industry, other government agencies, and academia working in the Computational AeroSciences (CAS) field. This workshop is part of the technology transfer plan of the High Performance Computing and Communications Program (HPCCP). Specific objectives of this Workshop are to: (1) communicate the goals and objectives of HPCCP in the area of CAS; (2) promote and disseminate CAS technology within the appropriate technical communities, including NASA, industry, academia, and other government labs; (3) help promote synergy among CAS scientists; and (4) permit feedback from peer researchers in issues pacing the CAS field in general and the HPCCP CAS program in particular.
    Keywords: Aeronautics (General)
    Type: NASA Computational Aerosciences Workshop; Mar 07, 1995 - Mar 09, 1995; Moffett Field, CA; United States
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    NASA TECHNICAL REPORTS
  • 3
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    Discovery of intermediate redshift galaxy clusters in the ROSAT NEP field (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-08-27
    Description: We report preliminary results from a program to identify optical counterparts of ROSAT sources in the North Ecliptic Pole (NEP) region. The most striking X-ray feature reported by Hasinger et al. (1991) is an extended low surface brightness region of X-ray emission. Within the two X-ray contours of highest count rate we find a cluster of galaxies at a redshift of 0.09 and an early-type galaxy at a redshift of 0.03. X-ray emission from these objects may provide an explanation for the observed X-ray morphology. We also find evidence that other X-ray sources in this region are coincident with clusters or groups of galaxies at redshifts between 0.08 and 0.09. The presence of at least five X-ray detected clusters or groups in this narrow redshift band within a 1.5 deg radius field seems to indicate the existence of a moderate redshift supercluster. The existence of these clusters will have major implications for the study of large-scale structure through X-ray surveys such as ROSAT.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 259; 1; p. L9-L11.
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