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Title:
Discovery of low-redshift X-ray selected quasars - New clues to the QSO phenomenon
Authors:
Grindlay, J. E.; Forman, W. R.; Steiner, J. E.; Canizares, C. R.; McClintock, J. E.
Affiliation:
AA(Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass.), AB(Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass.)
Publication:
Astrophysical Journal, Part 2 - Letters to the Editor, vol. 239, July 15, 1980, p. L43-L48. Research supported by the Fundacao de Amparo a Pesquisa do Estado de Sao Paulo; (ApJ Homepage)
Publication Date:
07/1980
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
QUASARS, RED SHIFT, STELLAR SPECTRA, STELLAR SPECTROPHOTOMETRY, EMISSION SPECTRA, LINE SPECTRA, LUMINOSITY, PROPORTIONAL COUNTERS, TELESCOPES
Comment:
A&AA ID. AAA028.141.056
DOI:
10.1086/183288
Bibliographic Code:
1980ApJ...239L..43G

Abstract

The identification of six X-ray sources discovered by the Einstein Observatory with X-ray quasars is reported, and the properties of these X-ray selected quasars are discussed. The four high-latitude fields of 1 sq deg each in which the Einstein imaging proportional counter detected serendipitous X-ray sources at intermediate exposures of 10,000 sec were observed by 4-m and 1.5-m telescopes, and optical sources with uv excesses and emission line spectra typical of many low-redshift quasars and Seyfert 1 galaxies were found within the 1-arcsec error boxes of the X-ray sources. All six quasars identified were found to be radio quiet, with low redshift and relatively faint optical magnitudes, and to be similar in space density, colors and magnitude versus redshift relation to an optically selected sample at the same mean magnitude. X-ray luminosity was found to be well correlated with both continuum and broad-line emission luminosities for the known radio-quiet quasars and Seyfert 1 galaxies, and it was observed that the five objects with the lowest redshifts have very similar X-ray/optical luminosity ratios despite tenfold variations in X-ray luminosity. It is concluded that photoionization by a continuum extending to X-ray energies is the dominant excitation mechanism in radio-quiet quasars.

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