The Discovery of Soft X-ray Loud Broad Absorption Line Quasars

TL;DR

This paper reports the discovery of a rare class of broad absorption line quasars that are unexpectedly bright in soft X-ray emissions, challenging existing models of quasar absorption and wind-driving mechanisms.

Contribution

It introduces the first known sample of soft X-ray loud BALQSOs, including a LoBALQSO, with no intrinsic soft X-ray absorption, contradicting previous assumptions about BALQSO X-ray attenuation.

Findings

Identified 3 soft X-ray loud BALQSOs with no intrinsic absorption.

Found that these BALQSOs have high X-ray luminosity and hard ionizing spectra.

Challenged the current understanding of BALQSO wind ionization and driving forces.

Abstract

It is been known for more than a decade that BALQSOs (broad absorption line quasars) are highly attenuated in the X-ray regime compared to other quasars, especially in the soft band ($< $ 1 keV). Using X-ray selection techniques we have found "soft X-ray loud" BALQSOs that, by definition, have soft X-ray (0.3 keV) to UV ($3000 \AA$) flux density ratios that are higher than typical nonBAL radio quiet quasars. Our sample of 3 sources includes one LoBALQSO (low ionization BALQSO) which are generally considered to be the most highly attenuated in the X-rays. The three QSOs are the only known BALQSOs that have X-ray observations that are consistent with no intrinsic soft X-ray absorption. The existence of a large X-ray luminosity and the hard ionizing continuum that it presents to potential UV absorption gas is in conflict with the ionization states that are conducive to line driving forces within BAL winds (especially for the LoBALs).