Publications
of the
MPIfR
Optical & Infrared
Interferometry Group
O. Loehmer, M. Kramer, T. Driebe, A. Jessner, D. Mitra,
A.G. Lyne
The Parallax, Mass and Age of the PSR
J2145-0750 binary system
Astronomy and Astrophysics, 426, 631
(2004)
Abstract.
We present results of timing measurements of the binary millisecond
pulsar PSR J2145-0750. Combining timing data obtained with the
Effelsberg and Lovell radio telescopes 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 $\dot x=1.8(6)\times 10^{-14}$ lt-s s$^{-1}$, where
$x=(a_{\rm p}\sin i)/c$, is caused by the proper motion of the system.
With this measurement we can constrain the orbital inclination angle to
$i<61\degr$, with a median likelihood value of $46\degr$ 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,
$m_2$, 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 $0.7 M_\odot\leq m_2\leq 1.0
M_\odot$. 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 $T_{\rm eff}=5750\pm600$ K
and a cooling age of $\tau_{\rm cool}=3.6(2)$ 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 $P_0=13.0(5)$ ms,
which is very close to the current period.
You can get this publication ...