Tidal Dissipation In Millisecond Pulsar Binaries

The first derivative of orbital period,Pb,can be measured accurately in many pulsar binaries through timing observation.It has normally been attributed to the combination of only transverse motion(Shklovskii effect),the acceleration along the sight of line and gravitational wave radiation.Thus Pb has been recognized as a useful tool to test fundamental physics.However,there are still some pulsar binaries,Pb of which can not be explained by such three effects,it implies there are other effects in pulsar binaries.The largest possible samples of binary pulsars with measured Pb are collected,which are all millisecond pulsar binaries.After counting out two observation effects from the observed value,the residual value should be negative if it come form gravitational radiation.Further,after subtracting the gravitational terms,the residual Pb represent the term of unknown effect.However,a weird distribution appears which is half negative and half positive,which likely come from tidal dissipation.By simply assuming the tidal effect is responsible for the residual Pb,the tidal response parameter of samples is calculated.After comparing with the tidal model,we found that the dynamical tidal model on white dwarf is sufficient to reproduce residual Pb of millisecond pulsar-white dwarf binaries and equilibrium tidal model on main-sequence star is sufficient to reproduce residual Pb of millisecond pulsarmain-sequence star binaries.And for one of millisecond pulsar-main-sequence star binaries in sample,the Love number of companion can be derived k2=0.31 ± 0.04,which is a reasonable value for main-sequence star.Moreover,a weak power law correlation between tidal parameter and orbital period is found,and such a correlation also implies a new correlation on the spin of companion stars of millisecond pulsar binaries,which likely corresponds to a tidal process occurring in the recycling stage worthy of further investigation.