Sensitive Chandra coverage of a representative sample of weak-line quasars: revealing the full range of X-ray properties
Date Issued
2022
Author(s)
Ni, Q.
•
Brandt, W. N.
•
Luo, B.
•
Garmire, G. P.
•
Hall, P. B.
•
Plotkin, R. M.
•
Shemmer, O.
•
Timlin, J. D.
•
•
Wu, J.
•
Yi, W.
Abstract
We present deeper Chandra observations for weak-line quasars (WLQs) in a representative sample that previously had limited X-ray constraints, and perform X-ray photometric analyses to reveal the full range of X-ray properties of WLQs. Only 5 of the 32 WLQs included in this representative sample remain X-ray undetected after these observations, and a stacking analysis shows that these 5 have an average X-ray weakness factor of >85. One of the WLQs in the sample that was known to have extreme X-ray variability, SDSS J1539+3954, exhibited dramatic X-ray variability again: it changed from an X-ray normal state to an X-ray weak state within ≈3 months in the rest frame. This short time-scale for an X-ray flux variation by a factor of ≳9 further supports the thick disc and outflow (TDO) model proposed to explain the X-ray and multiwavelength properties of WLQs. The overall distribution of the X-ray-to-optical properties of WLQs suggests that the TDO has an average covering factor of the X-ray emitting region of ~0.5, and the column density of the TDO can range from $N_{\rm H}\, \sim 10^{23-24}~{\rm cm}^{-2}$ to $N_{\rm H}\, \gtrsim 10^{24}~{\rm cm}^{-2}$, which leads to different levels of absorption and Compton reflection (and/or scattering) among WLQs.
Volume
511
Issue
4
Start page
5251
Issn Identifier
0035-8711
Ads BibCode
2022MNRAS.511.5251N
Rights
open.access
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