Do Some AGN Lack X-ray Emission?
  $Context:$ Intermediate-Mass Black Holes (IMBHs) are thought to be the seeds
of early Supermassive Black Holes (SMBHs). While $\gtrsim$100 IMBH and small
SMBH candidates have been identified in recent years, few have been robustly
confirmed to date, leaving their number density in considerable doubt. Placing
firmer constraints both on the methods used to identify and confirm
IMBHs/SMBHs, as well as characterizing the range of host environments that
IMBHs/SMBHs likely inhabit is therefore of considerable interest and
importance. Additionally, finding significant numbers of IMBHs in metal-poor
systems would be particularly intriguing, since such systems may represent
local analogs of primordial galaxies, and therefore could provide clues of
early accretion processes.
  $Aims:$ Here we study in detail several candidate Active Galactic Nuclei
(AGN) found in metal-poor hosts.
  $Methods:$ We utilize new X-ray and optical observations to characterize
these metal-poor AGN candidates and compare them against known AGN luminosity
relations and well-characterized IMBH/SMBH samples.
  $Results:$ Despite having clear broad optical emission lines that are
long-lived ($\gtrsim$10--13\,yr), these candidate AGN appear to lack associated
strong X-ray and hard UV emission, lying at least 1--2 dex off the known AGN
correlations. If they are IMBHs/SMBHs, our constraints imply that they either
are not actively accreting, their accretion disks are fully obscured along our
line-of-sight, or their accretion disks are not producing characteristic high
energy emission. Alternatively, if they are not AGN, then their luminous broad
emission lines imply production by extreme stellar processes. The latter would
have profound implications on the applicability of broad lines for mass
estimates of massive black holes.
