  (Abridged) We report the results of a 20 ks Chandra ACIS-S observation of the
interacting galaxy pair NGC 4485/4490. A total of 29 discrete X-ray sources are
found coincident with NGC 4490, but only one is found within NGC 4485. The
sources range in observed X-ray luminosity from ~ 2 x 10^37 to ~ 4 x 10^39
erg/s. Extensive diffuse X-ray emission is detected coincident with the disk of
NGC 4490, and in the tidal tail of NGC 4485, which appears to be thermal in
nature and hence the signature of a hot ISM in both galaxies. However, the
diffuse component accounts for only ~ 10% of the total X-ray luminosity of the
system (2 x 10^40 erg/s, 0.5 - 8 keV), which arises predominantly in a handful
of the brightest discrete sources. This diffuse emission fraction is unusually
low for a galaxy pair that has many characteristics that would lead it to be
classified as a starburst system, possibly as a consequence of the small
gravitational potential well of the system. The discrete source population, on
the other hand, is similar to that observed in other starburst systems,
possessing a flat luminosity function slope of ~ -0.6 and a total of six
ultraluminous X-ray sources (ULX). Five of the ULX are identified as probable
black hole X-ray binary systems, and the sixth (which is coincident with a
radio continuum source) is identified as an X-ray luminous supernova remnant.
The ULX all lie in star-formation regions, providing further evidence of the
link between the ULX phenomenon and active star formation. Importantly, this
shows that even in star forming regions, the ULX population is dominated by
accreting systems. We discuss the implications of this work for physical models
of the nature of ULX, and in particular how it argues against the
intermediate-mass black hole hypothesis.
