The relation between white dwarf mass and orbital period in wide binary radio pulsars

• Published in: Monthly notices of the Royal Astronomical Society 1995-04, Vol.273 (3), p.731-741
• Main Authors: Rappaport, S., Podsiadlowski, Ph, Joss, P. C., Di Stefano, R., Han, Z.
• Format: Article
• Language: English
• Subjects: binaries: general; pulsars: general; stars: evolution; stars: neutron; white dwarfs
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/273.3.731

We have re-examined a scenario for the evolution of a binary system, initially comprising a neutron star and a low-mass giant and ending as a wide binary containing a radio pulsar and a white dwarf in a nearly circular orbit. The evolution is driven by the nuclear evolution of the giant, which results in the stable transfer of much or all of the envelope of the giant to the neutron star. The angular momentum associated with the transferred mass may spin the neutron star up to high rotation rates, yielding a ‘recycled’ pulsar; the white dwarf, which had been the core of the giant progenitor, remains as a fossil relic of the giant. This scenario provides a unique test of the theory of advanced stages of stellar evolution, in that it predicts the existence of a testable relationship between observable quantities: the mass, Mwd, of the white dwarf and the orbital period, Porb, of the binary. The relationship arises because (1) stellar evolution theory predicts the existence of a rather tight relationship between the core mass, Mc, of a giant and the radius, Rg, of its envelope; and (2) in the scenario under consideration, the giant envelope is expected to fill its Roche lobe until the termination of mass transfer. The final orbital separation should thus be a well-defined function of Rg at the end of the mass-transfer phase (i.e. at the time when the envelope of the giant is exhausted), while Mwd will be essentially identical to the final value of Mc at the termination of mass transfer. Using refined stellar evolution calculations, we have redetermined the most likely value of Rg as a function of Mc for core masses in the range 0.15