Journal Article

An evolutionary scenario for short-period millisecond binary pulsars

Ene Ergma and Marek J. Sarna

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 280, issue 4, pages 1000-1006
Published in print June 1996 | ISSN: 0035-8711
e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1093/mnras/280.4.1000
An evolutionary scenario for short-period millisecond binary pulsars

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We present numerical calculations that simulate the evolution of a low-mass (1-M⊙) star transferring mass to a compact object. Mass transfer starts when the low-mass star (secondary) turns off the main sequence (having a small helium core). We have calculated five evolutionary sequences with the assumption of non-conservative evolution and one sequence with conservative evolution. We can conclude that near the bifurcation point the evolution is very sensitive to: (i) the assumption of conservative or non-conservative evolution; (ii) the structure of the mass-losing star. Small changes in the initial period when the secondary fills its Roche lobe will lead to large changes in the final period and mass of the remnant. Our calculations support the model of Kluźniak, Czerny & Ray in which the secondary star of PSR 1744 — 24A fills its Roche lobe when it turns off the main sequence. Owing to the low accretion rate the system is in the ‘propeller’ phase which may explain its very erratic eclipsing behaviour. The orbital parameters of PSR J0751 + 18 may be explained if we assume non-conservative evolution starting from an initial period (Pi) of 1.05 d. After the accretion stops near 0.343 d the system will evolve because of gravitational wave radiation (GWR), and after ∼7.5 × 109 yr its orbital parameters will be as observed. We can explain the orbital parameters of PSR J1012 + 5307 if we again assume non-conservative evolution but this time starting with an initial period between 0.53 and 0.63 d. Since the orbital period is relatively large, GWR is ineffective, and the orbital period of the system will be as it was when the system detached.

Keywords: binaries: close; stars: evolution; pulsars: general; pulsars: individual: PSR J1744 - 24A; pulsars: individual: PSR J0751 + 18; pulsars: individual: PSR J1012 + 5307

Journal Article.  0 words. 

Subjects: Astronomy and Astrophysics

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