Timing models for the long-orbital period binary pulsar PSR B1259-63
N. Wex (Max-Planck Society, Research Unit Theory of Gravitation, Germany),
S. Johnston (RCfTA, University of Sydney, Australia),
R. N. Manchester (ATNF, CSIRO, Australia),
A. G. Lyne (NRAL, University of Manchester, Jodrell Bank, UK.),
B. W. Stappers (MSSSO, ANU, Australia),
M. Bailes (University of Melbourne, Australia).
Abstract
The pulsar PSR B1259-63 is in a highly eccentric 3.4-yr orbit with the Be
star SS 2883. Timing observations of this pulsar, made over a 7-yr period
using the Parkes 64-m radio telescope, cover two periastron passages, in 1990
August and 1994 January. The timing data cannot be fitted by the normal pulsar
and Keplerian binary parameters.
A timing solution including a (non-precessing) Keplerian orbit and timing
noise (represented as a polynomial of fifth order in time) provide a
satisfactory fit to the data. However, because the Be star probably has a
significant quadrupole moment, we prefer to interpret the data by a
combination of timing noise, dominated by a cubic phase term, and omega-dot
and x-dot terms. We show that the omega-dot and x-dot are likely to
be a result of a precessing orbit caused by the quadrupole moment of the
tilted companion star.
We further rule out a number of possible physical effects which could
contribute to the timing data of PSR B1259-63 on a measurable level.
Key words:pulsar timing -- timing noise -- binary pulsars -- classical spin-orbit coupling -- pulsars: individual (PSR B1259-63)