Final answer:
Low-mass X-ray binaries have companion stars with masses typically less than the Sun, while high-mass X-ray binaries have companions with masses often exceeding 10 times the mass of the Sun.
Step-by-step explanation:
The masses of companion stars in low-mass X-ray binaries (LMXBs) are typically less than the mass of the Sun (M☉), whereas the companion stars in high-mass X-ray binaries (HMXBs) are often significantly more massive, sometimes exceeding 10M☉.
In LMXBs, the companion star is usually a late-type (cooler) main-sequence star, a subgiant or a white dwarf, while in HMXBs, the companion tends to be an early-type (hotter) main-sequence star, a supergiant, or a Be-type star. The distinction in mass affects the accretion process and the evolution of the binary system.
In HMXBs, the high mass of the companion leads to strong stellar winds that can feed the accretion onto the neutron star or black hole, causing intense X-ray emissions, whereas in LMXBs, the accretion is often driven by Roche lobe overflow.