Is the binary pulsar PSR 1718–19 formed by accretion induced collapse?
A possible model for the binary pulsar PSR 1718–19 in the globular cluster NGC 6342 is discussed. This is a 6.2 hour eclipsing binary system with a rotational period of 1 s, a magnetic field of ≈ 1012 G and the mass of the companion is only 0.1 – 0.2M ⊙. We have used the original idea by Schatzman (1974) that in this system the neutron star has been formed through accretion-induced collapse of the white dwarf. To explain the source of material in this eclipsing system two main stages of thermal evolution of the secondary are proposed. 1. Before the collapse a massive white dwarf is the X-ray source with an X-ray luminosity of more than 1033 erg/s. Due to the short orbital separation, a ≈ (4 – 6) 1010 cm, the flux at the surface of the companion will be more than 1010 erg/s cm 2. If such heating occurs during several hundred Myr then the secondary will greatly expand and violent mass transfer will start which leads to an increase in the orbital separation. 2. After the pulsar spin-down to its current rotational period the pulsar action will switch off. Since the thermal timescale of the companion is much longer (≈ 100 Myr) than the system timescale (≈ 10 Myr) the secondary is out of thermal equilibrium. The companion may slightly underfill its Roche lobe and the stellar wind from the bloated secondary may be a source of material in the system.
KeywordsNeutron Star White Dwarf Roche Lobe Binary Pulsar Significant Mass Loss
Unable to display preview. Download preview PDF.
- Canal, R. and Schatzman, E., 1974a, C.R.Acad. Sci. Paris, 279, B-681.Google Scholar
- Ergma, E., 1993, Astron. Astrophys., 273, L38.Google Scholar
- Frank, J., King, A.R. and Lasota, J.P., 1992, Astrophys. J., 385, L45.Google Scholar
- Nomoto K. and Yamaoka, H., 1991, in X ray Binaries and Recycled Pulsars ed.E.P.J.van den Heuvel and S.A.Rappaport, p.189.Google Scholar
- Schatzman, E. 1974, Presented at Int.Sch.Cosmol. Gravit., Erice, ItalyGoogle Scholar
- Tutukov, A.V., Fedorova, A.V., Ergma, E. and Yungelson, L.R., 1985, Sov. Asron. Lett., 11, 123.Google Scholar
- Wijers, R.A.M.J. and Paczynski, B., 1993, Astrophys. J., 415, L115.Google Scholar
- Zwitter, T., 1993, Mon. Not. R. astr. Soc., 264, L3.Google Scholar