RADIO AND OPTICAL OBSERVATIONS OF THE PSR B1259-63/SS 2883 Be STAR
BINARY SYSTEM
Simon Johnston (ATNF, CSIRO, and RCfTA, University of Sydney, Australia),
R. N. Manchester (ATNF, CSIRO, Australia),
A. G. Lyne (NRAL, Jodrell Bank, UK),
L. Nicastro(IRA-CNR, Bologna, Italy.),
J. Spyromilio (Anglo-Australian Observatory, Australia.)
Abstract We report here on radio timing observations of the 47-ms pulsar PSR B1259-63 (PSR J1302-6350) and optical observations of its binary companion Be star, SS 2883. The two are in a highly eccentric orbit of period 3.4 yr. Radio observations over 1250 days with the Parkes radio telescope now permit a phase-connected solution which shows that the the next periastron is expected to occur on 1994 January 9.2 UT, and that the pulsar has a period derivative of 2.3x10^-15. The pulsar thus has a characteristic age of 0.33 Myr and a surface magnetic field strength of 3x10^11 G. Optical photometry of SS 2883 shows that the star is of spectral type of about B2e, indicating its mass to be 10 Msun and its radius 6 Rsun. The system can be no further than 1.5 kpc distant, substantially closer than the distance derived from the dispersion measure. High-resolution spectroscopy of the Balmer-series emission lines allows a determination of the underlying stellar rotation velocity, vsini, of 180 km s^-1. It is likely that the inclination of the plane of the orbit and the inclination of the circumstellar disc are similar at ~35 deg. The system is a likely progenitor of the high-mass X-ray binaries and double-neutron-star systems such as PSR B1913+16.