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4U 1210-64 is a peculiar X-ray binary that was first discovered in 1978 bythe Uhuru satellite. The analysis of the X-ray data revealed a 6.7-day orbitalperiod and an additional long-term modulation that is manifested as low andhigh flux states. Based on the previous classification of the donor star fromthe analysis of its optical spectra, the system has been suggested to be ahigh-mass X-ray binary. We re-visit the optical classification where, based onthe spectra from the Southern African Large Telescope (SALT), we conclude thatthe donor star is of spectral class A8 III-IV, making it a member of the rareintermediate-mass X-ray binaries. We perform radial velocity analysis using theSALT spectra where we consider circular and eccentric orbits. From the massfunction derived and the mass constraints of the donor star, we demonstratethat a neutron star is favoured as the compact object in the binary system. Weshow, for the first time, the folded optical lightcurves, whose shape isinterpreted to be due to a combination of ellipsoidal variations, irradiationof the donor star, and mutual eclipses of the star and accretion disk.

4U 1210-64: a new member of the rare intermediate-mass X-ray binary subclass