The parallax, mass and age of the PSR J2145-0750 binary system
Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany e-mail: email@example.com
2 University of Manchester, Jodrell Bank Observatory, Macclesfield, Cheshire SK11 9DL, UK
Accepted: 22 June 2004
We present results of high-precision timing measurements of the binary millisecond pulsar PSR J2145-0750. Combining 10 yrs of radio timing data obtained with the Effelsberg 100-m radio telescope and the Lovell 76-m radio telescope we measure a significant timing parallax of 2.0(6) mas placing the system at 500 pc distance to the solar system. The detected secular change of the projected semi-major axis of the orbit lt-s s-1, where , is caused by the proper motion of the system. With this measurement we can constrain the orbital inclination angle to , with a median likelihood value of which is consistent with results from polarimetric studies of the pulsar magnetosphere. This constraint together with the non-detection of Shapiro delay rules out certain combinations of the companion mass, m2, and the inclination, i. For typical neutron star masses and using optical observations of the carbon/oxygen-core white dwarf we derive a mass range for the companion of . We apply evolutionary white dwarf cooling models to revisit the cooling age of the companion. Our analysis reveals that the companion has an effective temperature of K and a cooling age of Gyr, which is roughly a factor of three lower than the pulsar's characteristic age of 10.4 Gyr. The cooling age implies an initial spin period of ms, which is very close to the current period.
Key words: astrometry / stars: neutron / stars: white dwarfs / stars: binaries: general / stars: pulsars: individual: PSR J2145-0750
© ESO, 2004