LMXB AND IMXB EVOLUTION: I. THE BINARY RADIO PULSAR PSR J1614–2230

We have computed an extensive grid of binary evolution tracks to represent low- and intermediate-mass X-ray binaries (LMXBs and IMXBs). The grid includes 42,000 models which cover 60 initial donor masses over the range of 1-4 M{sub sun} and, for each of these, 700 initial orbital periods over the range of 10-250 hr. These results can be applied to understanding LMXBs and IMXBs: those that evolve analogously to cataclysmic variables, that form ultracompact binaries with P{sub orb} in the range of 6-50 minutes, and that lead to wide orbits with giant donors. We also investigate the relic binary recycled radio pulsars into which these systems evolve. To evolve the donor stars in this study, we utilized a newly developed stellar evolution code called 'MESA' that was designed, among other things, to be able to handle very low mass and degenerate donors. This first application of the results is aimed at an understanding of the newly discovered pulsar PSR J1614-2230 which has a 1.97 M{sub sun} neutron star, P{sub orb} = 8.7 days, and a companion star of 0.5 M{sub sun}. We show that (1) this system is a cousin to the LMXB Cyg X-2; (2) for neutron stars of canonicalmore » birth mass 1.4 M{sub sun}, the initial donor stars which produce the closest relatives to PSR J1614-2230 have a mass between 3.4 and 3.8 M{sub sun}; (3) neutron stars as massive as 1.97 M{sub sun} are not easy to produce in spite of the initially high mass of the donor star, unless they were already born as relatively massive neutron stars; (4) to successfully produce a system like PSR J1614-2230 requires a minimum initial neutron-star mass of at least 1.6 {+-} 0.1 M{sub sun}, as well as initial donor masses and P{sub orb} of {approx}4.25 {+-} 0.10 M{sub sun} and {approx}49 {+-} 2 hr, respectively; and (5) the current companion star is largely composed of CO, but should have a surface H abundance of {approx}10%-15%.« less