The parallax, mass and age of the PSR J2145-0750 binary system

• Published in: Astronomy and astrophysics (Berlin) 2004-11, Vol.426 (2), p.631-640
• Main Authors: LÖHMER, O, KRAMER, M, DRIEBE, T, JESSNER, A, MITRA, D, LYNE, A. G
• Format: Article
• Language: English
• ISSN: 0004-6361; 1432-0746
• DOI: 10.1051/0004-6361:20041031

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 x = 1.8(6) x 10 super(-14) It-s s super(-1), where x = (a sub(p) sin i)/c, is caused by the proper motion of the system. With this measurement we can constrain the orbital inclination angle to i < 61 degree , with a median likelihood value of 46 degree 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, m sub(2), 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 0.7 M sub( ) less than or equal to m sub(2) less than or equal to 1.0 M sub( ). 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 T sub(eff) = 5750 plus or minus 600 K and a cooling age of tau sub(cool) = 3.6(2) 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 P sub(0) = 13.0(5) ms, which is very close to the current period.