X-Ray Evidence Against the Hypothesis that the Hyper-Luminous z=6.3
  Quasar J0100+2802 is Lensed
  The $z=6.327$ quasar SDSS J010013.02+280225.8 (hereafter J0100+2802) is
believed to be powered by a black hole more massive than $10^{10}\ {\rm
M}_\odot$, making it the most massive black hole known in the first billion
years of the Universe. However, recent high-resolution ALMA imaging shows four
structures at the location of this quasar, potentially implying that it is
lensed with a magnification of $\mu\sim450$ and thus its black hole is
significantly less massive. Furthermore, for the underlying distribution of
magnifications of $z\gtrsim6$ quasars to produce such an extreme value,
theoretical models predict that a larger number of quasars in this epoch should
be lensed, implying further overestimates of early black hole masses. To
provide an independent constraint on the possibility that J0100+2802 is lensed,
we re-analyzed archival XMM-Newton observations of the quasar and compared the
expected ratios of X-ray luminosity to rest-frame UV and IR luminosities. For
both cases, J0100+2802's X-ray flux is consistent with the no-lensing scenario;
while this could be explained by J0100+2802 being X-ray faint, we find it does
not have the X-ray or optical spectral features expected for an X-ray faint
quasar. Finally, we compare the overall distribution of X-ray fluxes for known,
typical $z\gtrsim6$ quasars. We find a $3\sigma$ tension between the observed
and predicted X-ray-to-UV flux ratios when adopting the magnification
probability distribution required to produce a $\mu=450$ quasar.
