Sensitive Chandra coverage of a representative sample of weak-line
  quasars: revealing the full range of X-ray properties
  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
timescale for an X-ray flux variation by a factor of $\gtrsim$ 9 further
supports the thick disk 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.
