# X-ray Insights into the Nature of Quasars with Redshifted Broad Absorption Lines

## TL;DR

This study uses Chandra X-ray observations to analyze redshifted broad absorption line quasars, revealing heavy X-ray absorption and supporting a rotationally-dominated outflow model over binary quasar models.

## Contribution

First X-ray analysis of RSBAL quasars showing heavy absorption, spectral properties, and implications for their physical models.

## Key findings

- RSBAL quasars are X-ray weak and heavily absorbed.
- Detected RSBAL quasars show hard X-ray spectra with low photon indices.
- Results favor a rotationally-dominated outflow model for RSBAL quasars.

## Abstract

We present $Chandra$ observations of seven broad absorption line (BAL) quasars at $z=0.863$-2.516 with redshifted BAL troughs (RSBALs). Five of our seven targets were detected by $Chandra$ in 4-13 ks exposures with ACIS-S. The $\alpha_{\rm ox}$ values, $\Delta\alpha_{\rm ox}$ values, and spectral energy distributions of our targets demonstrate they are all X-ray weak relative to expectations for non-BAL quasars, and the degree of X-ray weakness is consistent with that of appropriately-matched BAL quasars generally. Furthermore, our five detected targets show evidence for hard X-ray spectral shapes with a stacked effective power-law photon index of $\Gamma_{\rm eff}=0.5^{+0.5}_{-0.4}$. These findings support the presence of heavy X-ray absorption ($N_{\rm H}\approx 2 \times 10^{23}$ cm$^{-2}$) in RSBAL quasars, likely by the shielding gas found to be common in BAL quasars more generally. We use these X-ray measurements to assess models for the nature of RSBAL quasars, finding that a rotationally-dominated outflow model is favored while an infall model also remains plausible with some stipulations. The X-ray data disfavor a binary quasar model for RSBAL quasars in general.