Soft X - ray emission and optical multicolors of faint QSOs in the Selected Area 57
نویسنده
چکیده
We present the ROSAT HRI X-ray measurements of 19 spectroscopically confirmed optically-selected QSOs in the 12′ radius region in the Selected Area 57. The optical-to-Xray spectral index αox ranges from 1.25 to 1.7, consistent with brighter QSOs. We have investigated the relationship between soft X-ray emission observed with the ROSAT HRI and optical colors (UJFN) of optically-selected QSOs in SA57. The optical to X-ray spectral index αox is found to be correlated with the U − J − F + N color, by a combined effect of αox and U , N excess correlations. Possible explanations are the physical link between broad emission-lines/Balmer continuum, and the ionizing radiation source seen in X-ray and/or a geometrical effect.
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