Evolutionary selfenergyloss effects in compact binary systems. Importance of rapid rotation and of equation of state
Abstract
The spindown of a millisecond pulsar in a compact binary system leads to selfenergy losses, that cause the binary's orbital period to increase (the effect being of first postNewtonian (1PN) order). If the pulsar's periodderivative is not exceedingly small, this effect can become measurable in longterm highprecision timing measurements of the binary's orbital motion. We use rotating compressible spheroids to obtain an approximate, explicit expression for the orbital period derivative, due to spindown, valid to 1PN order. This expression can be used to observationally constrain the pulsar's moment of inertia, and, combined with other observations, the highdensity equation of state of compact stars. We apply our expression to representative models of millisecond pulsars in binary systems and demonstrate the importance of including higherorder rotational effects as well as the importance of the choice of equation of state, which both have been neglected, so far, in the literature. The computed increase in orbital period is larger, by as much as 32%, when the higherorder rotational effects are included, while it can change by more than a factor of two between different plausible equations of state.
 Publication:

Astronomy and Astrophysics
 Pub Date:
 February 2001
 DOI:
 10.1051/00046361:20000230
 arXiv:
 arXiv:astroph/0009244
 Bibcode:
 2001A&A...366..598S
 Keywords:

 EQUATION OF STATE;
 STARS: EVOLUTION;
 PULSARS: GENERAL;
 ROTATION;
 Astrophysics
 EPrint:
 7 pages, submitted to Astronomy and Astrophysics