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  • ASTRONOMY  (2)
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  • 1
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    Initial results from a ROSAT deep survey in Lynx (1992)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: Preliminary results from a deep (70 ksec) Rosat survey of the high galactic latitude selected area Lynx.3A are presented. Lynx.3A sensitivity was previously studied in both the optical radio, with deep Westerbork surveys and deep multicolor Charge Couple Device (CCD) images form the Palomar 200 inch Four-Shooter. About 70 x-ray sources were detected within the central 40 foot diameter region of the Position Sensitive Proportional Counter (PSPC), observed surface densities of approximately 200 x-ray sources/sq deg are suggested, and these x-ray sources alone account for approximately 30 percent of the cosmic x-ray background (0.9 to 2.2 keV). An initial look at the observed x-ray logN - logS curve is presented, but a detailed assessment requires further study. The 4 sigma limit of about 7 times 10 to the minus 15th power erg/s.sq cm (0.5 to 2.0 keV) is considerably deeper then the Einstein deep surveys, and of comparable sensitivity to the deepest current Rosat surveys. Cross correlation with our Four Shooter optical catalogs yields at least one likely optical candidate for nearly all of the Rosat x-ray sources; a number of the likely optical identifications have colors of quasi-stellar objects (and stellar PSF), but in other cases galaxies/groups are also viable candidates.
    Keywords: ASTRONOMY
    Type: MPI fuer Extraterristrische Physik, X Ray Emission from Active Galactic Nuclei and the Cosmic X Ray Background; p 227-230
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Deep UBVRI photometric calibration of high-latitude fields: SA 57 (1307+30) and Hercules (1720+50) (1994)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: We present CCD photometric calibration sequences in the magnitude range V = 17-22 for two fields at high Galactic latitude: SA 57 (at the North Galactic Pole) and Hercules (l = 77, b = 35). Photometry to a precision of about 0.02 mag at V = 20 and, in general, better than 0.10 mag at V = 22 was obtained in the Johnson UBV as well as the Kron-Cousins R and I bands. These data are suitable for setting magnitude zero-points in catalogues of faint stars, galaxies, and QSOs, and we apply them to our own photographic catalogs in these two fields. We also note a significant deviation in the (V-R, R-I) color-color diagram for the locus of faint (V is greater than 20) M dwarfs compared to the locus provided by much brighter M dwarfs. This deviation may indicate differences in spectral properties between Population I and older populations of late dwarfs; however we do not discount the possibility that this locus for the faint stars, which appears as a saturation in V-R color with increasing R-I color, is the result of systematic photometric error.
    Keywords: ASTRONOMY
    Type: Astronomical Society of the Pacific, Publications (ISSN 0004-6280); 106; 706; p. 1258-1270
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    NASA TECHNICAL REPORTS
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