  Building on recent work by Chandar et al. (2020), we construct X-ray
luminosity functions (XLFs) for different classes of X-ray binary (XRB) donors
in the nearby star-forming galaxy M83 through a novel methodology: rather than
classifying low- vs. high-mass XRBs based on the scaling of the number of X-ray
sources with stellar mass and star formation rate, respectively, we utilize
multi-band Hubble Space Telescope imaging data to classify each
Chandra-detected compact X-ray source as a low-mass (i.e. donor mass <~ 3 solar
masses), high-mass (donor mass >~ 8 solar masses) or intermediate-mass XRB
based on either the location of its candidate counterpart on optical
color-magnitude diagrams or the age of its host star cluster. In addition to
the the standard (single and/or truncated) power-law functional shape, we
approximate the resulting XLFs with a Schechter function. We identify a
marginally significant (at the 1-to-2 sigma level) exponential downturn for the
high-mass XRB XLF, at logLx ~ 38.48^{+0.52}_{-0.33} (in log CGS units). In
contrast, the low- and intermediate-mass XRB XLFs, as well as the total XLF of
M83, are formally consistent with sampling statistics from a single power-law.
Our method suggests a non-negligible contribution from low- and possibly
intermediate-mass XRBs to the total XRB XLF of M83, i.e. between 20 and 50%, in
broad agreement with X-ray based XLFs. More generally, we caution against
considerable contamination from X-ray emitting supernova remnants to the
published, X-ray based XLFs of M83, and possibly all actively star-forming
galaxies.
