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abstract
Ninety percent of the more than 1000 QSOs in the Large Bright Quasar Survey (LBQS), were observed in soft X-rays during the ROSAT All-Sky Survey (RASS). These data constitute among the largest, most homogeneous X-ray surveys of QSOs to date, and as such are well-suited to the study of the multiwavelength properties of QSOs. By stacking X-ray counts, we obtain effectively much more sensitive observations for an average QSO in bins of redshift or luminosity, and for several classes of QSOs. We confirm a correlation of $\alpha_{ox}$ with luminosity for the overall sample. For higher redshifts and optical luminosities, radio-loud QSOs appear to become progressively more luminous in X-rays than radio-quiet QSOs. The X-ray properties of a subsample of 36 BAL QSOs suggest that they may be unusually X-ray quiet, while a subsample of 22 FeII-strong QSOs is anomalously X-ray bright.
