No evidence for an Eddington-ratio dependence of X-ray weakness in BALQSOs

TL;DR

This study investigates whether the Eddington ratio influences X-ray weakness in BALQSOs and finds no strong evidence for such a dependence, despite correlations with UV absorption features.

Contribution

First to analyze the relationship between Eddington ratio and X-ray properties in BALQSOs using a combined sample including new observations.

Findings

No strong correlation between Eddington ratio and X-ray suppression.

X-ray weakness correlates with UV absorption strength.

Results confirmed with mini-BALQSO sample.

Abstract

Several works have studied the relation between X-ray, UV, and wind properties in broad absorption line quasars (BALQSOs), generally concluding that the formation of strong winds is tightly connected with the suppression of the ionizing EUV/X-ray emission. The Eddington ratio ($\lambda_{Edd}$), which measures the accretion rate, is also known to be related with outflow and emission-line properties in the general quasar population. Moreover, models describing quasar accretion depend on $\lambda_{Edd}$, which can thus possibly affect the relative production of accelerating UV and ionizing EUV/X-ray radiation. In this work, for the first time, we investigated whether BALQSO X-ray properties are related with the Eddington ratio. We selected a sample of 30 BALQSOs with accurate measurements of black-hole mass and BAL properties from the literature, and we complemented it with 4 additional BALQSOs we observed with \xmm\, to populate the low and high Eddington-ratio regimes. We did not find evidence for a strong relation between $\lambda_{Edd}$ and X-ray suppression, which however shows a significant correlation with the strength of the UV absorption features. These findings are confirmed also by considering a sample of mini-BALQSOs collected from the literature.