Chandra observations and classification of AGN-candidates correlated
  with Auger UHECRs
  We report on Chandra X-ray observations of possible-AGNs which have been
correlated with Ultra-high Energy Cosmic Rays (UHECRs) observed by the Pierre
Auger Collaboration. Combining our X-ray observations with optical
observations, we conclude that one-third of the 21 Veron-Cetty Veron (VCV)
galaxies correlating with UHECRs in the first Auger data-release are actually
not AGNs. We review existing optical observations of the 20 VCV galaxies
correlating with UHECRs in the second Auger data-release and determine that
three of them are not AGNs and two are uncertain. Overall, of the 57 published
UHECRs with |b|>10 degrees, 22 or 23 correlate with true AGNs using the Auger
correlation parameters. We also measured the X-ray luminosity of ESO139-G12 to
complete the determination of the bolometric luminosities of AGNs correlating
with UHECRs in the first data-set. Apart from two candidate sources which
require further observation, we determined bolometric luminosities for the
candidate galaxies of the second dataset. We find that only two of the total of
69 published UHECRs correlate with AGNs (IC5135 and IC4329a) which are powerful
enough in their steady-state to accelerate protons to the observed energies of
their correlated UHECRs. The GZK expectation is that about 45% of the sources
of UHECRs above 60 EeV should be contained within the z<0.018 volume defined by
the Auger scan analysis, so an observed level of 30-50% correlation with weak
AGNs is compatible with the suggestion that AGNs experience transient
high-luminosity states during which they accelerate UHECRs.
