  The transient ULX in M83 that went into outburst in or shortly before 2010 is
still active. Our new XMM-Newton spectra show that it has a curved spectrum
typical of the upper end of the high/soft state or slim-disk state. It appears
to be spanning the gap between Galactic stellar-mass black holes and the
ultraluminous state, at X-ray luminosities $\approx (1$-$3) \times 10^{39}$ erg
s$^{-1}$ (a factor of two lower than in the 2010-2011 Chandra observations).
From its broadened disk-like spectral shape at that luminosity, and from the
fitted inner-disk radius and temperature, we argue that the accreting object is
an ordinary stellar-mass black hole with $M \sim$$10$-$20 M_{\odot}$. We
suggest that in the 2010-2011 Chandra observations, the source was seen at a
higher accretion rate, resulting in a power-law-dominated spectrum with a soft
excess at large radii.
