Eclipsing binary millisecond pulsar PSR J1740-5340 – evolutionary considerations andobservational test

We perform evolutionary calculations for a binary system to produce observed binary parameters for the PSR J1740–5340. Our calculations support the model proposed by D'Amico et al. (2001) in which this binary may be the progenitor of a millisecond pulsar + helium white dwarf system. We propose an observational test to verify this hypothesis. We propose that observations of abundances of C, N, O elements in the spectra of the optical companion of PSR J 1740–5340 may give additional information about the nature of the secondary being either i) a perturbed low–mass main–sequence star or ii) an evolved star with helium core and thin hydrogen envelope which has lost its main envelope during semi–detached evolution.