Eclipsing binary millisecond pulsar PSR J1740-5340 -- evolutionary considerations and observational test

We perform evolutionary calculations for a binary system with initial parameters: $M_{sg,i}$= 1$M\odot$ and $M_{ns,i}$= 1.4 $M\odot$ and $P_{orb,i}(RLOF)$= 1.27 d to produce observed binary parameters for the PSR J1740--5340. Our calculations support model proposed by D'Amico et al. (2001) in which this binary may be progenitor of a millisecond pulsar + helium white dwarf system. We propose observational test to verify this hypothesis. If the optical companion lack of carbon lines in its spectrum shows but the oxygen and nitrogen lines are present then our model correctly describes the evolutionary stage of PSR J1740--5340.