Optical spectroscopy of 20 Be/X-ray Binaries in the Small Magellanic
  Cloud
  We present a large sample (20 in total) of optical spectra of Small
Magellanic Cloud (SMC) High-Mass X-ray Binaries obtained with the 2dF
spectrograph at the Anglo-Australian Telescope. All of these sources are found
to be Be/X-ray binaries (Be-XRBs), while for 5 sources we present original
classifications. Several statistical tests on this expanded sample support
previous findings for similar spectral-type distributions of Be-XRBs and Be
field stars in the SMC, and of Be-XRBs in the Large Magellanic Cloud and the
Milky Way, although this could be the result of small samples. On the other
hand, we find that Be-XRBs follow a different distribution than Be stars in the
Galaxy, also in agreement with previous studies. In addition, we find similar
Be spectral type distributions between the Magellanic Clouds samples. These
results reinforce the relation between the orbital period and the equivalent
width of the Halpha line that holds for Be-XRBs. SMC Be stars have larger
Halpha equivalent widths when compared to Be-XRBs, supporting the notion of
circumstellar disk truncation by the compact object.
