High-Mass X-ray binaries in the Small Magellanic Cloud
  The last comprehensive catalogue of high-mass X-ray binaries in the Small
Magellanic Cloud (SMC) was published about ten years ago. Since then new such
systems were discovered, mainly by X-ray observations with Chandra and
XMM-Newton. For the majority of the proposed HMXBs in the SMC no X-ray
pulsations were discovered as yet, and unless other properties of the X-ray
source and/or the optical counterpart confirm their HMXB nature, they remain
only candidate HMXBs. From a literature search we collected a catalogue of 148
confirmed and candidate HMXBs in the SMC and investigated their properties to
shed light on their real nature. Based on the sample of well-established HMXBs
(the pulsars), we investigated which observed properties are most appropriate
for a reliable classification. We defined different levels of confidence for a
genuine HMXB based on spectral and temporal characteristics of the X-ray
sources and colour-magnitude diagrams from the optical to the infrared of their
likely counterparts. We also took the uncertainty in the X-ray position into
account. We identify 27 objects that probably are misidentified because they
lack an infrared excess of the proposed counterpart. They were mainly X-ray
sources with a large positional uncertainty. This is supported by additional
information obtained from more recent observations. Our catalogue comprises 121
relatively high-confidence HMXBs (the vast majority with Be companion stars).
About half of the objects show X-ray pulsations, while for the rest no
pulsations are known as yet. A comparison of the two subsamples suggests that
long pulse periods in excess of a few 100 s are expected for the "non-pulsars",
which are most likely undetected because of aperiodic variability on similar
timescales and insufficiently long X-ray observations. (abbreviated)
