A possible model A possible model of pulsar timingof pulsar timing

Biping GongBiping Gong

Collaborator Yaping LiCollaborator Yaping Li

KIAA Oct 19, 2012

quasi-periodic feature?

Possible mechanisms

free precession

un-modeled companion exact period

Random processes

quasi-periodic feature? multi-planets ?

Long-term orbital Long-term orbital effects?effects?

geodetic precession of spin axis , geodetic precession of spin axis , BO equationBO equation

Like the effect of free precession, it also predicts a periodic timing delay, without considering the motion of the orbital plane.

BO’s two-body equation BO’s two-body equation

negligible

AK’sAK’s two-body equationtwo-body equation (J=const)(J=const)

（ J=const ? ）

Just with the basic Just with the basic binary parameters binary parameters like, orbital like, orbital period, mass, and period, mass, and spin parametersspin parameters like, spin angular like, spin angular momentum, we have the following results.momentum, we have the following results.

J=L+S=constJ=L+S=const

PSR B1540-06PSR B1540-06

PSR B1828-11PSR B1828-11

PSR B0919+06PSR B0919+06

PSR B1826-17PSR B1826-17

PSR J1931+2421PSR J1931+2421

Companion star?Companion star?

Spin angular momentumSpin angular momentum ， ， --

Orbital period ， 0.20-0.34 hr

Companion mass ， 0.16-0.68 solar mass

Are there binary pulsars with Are there binary pulsars with

orbital period less than 90min ?orbital period less than 90min ?

4U 1626-67 an evidence 4U 1626-67 an evidence of such of such

a scenario?a scenario?

Thanks!