Soft X-ray emission and optical multicolors of faint QSOs in the Selected Area 57.
Abstract
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-X-ray spectral index α_ox_ 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 α_ox_ is found to be correlated with the U-J-F+N color, by a combined effect of α_ox_ 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.
- Publication:
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Astronomy and Astrophysics
- Pub Date:
- July 1997
- Bibcode:
- 1997A&A...323L..37M
- Keywords:
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- GALAXIES: ACTIVE;
- X-RAYS: GENERAL