On the orbital properties of millisecond pulsar binaries.
HUI C.Y., WU K., HAN Q., KONG A.K.H. and TAM P.H.T.
Abstract (from CDS):
We report a detailed analysis of the orbital properties of a binary millisecond pulsar (MSP) with a white dwarf (WD) companion. Positive correlations between the orbital period Pb and eccentricity ε are found in two classes of MSP binaries with a He WD and with a CO/ONeMg WD, though their trends are different. The distribution of Pb is not uniform. Deficiency of sources at Pb ∼ 35-50 days (Gap 1) have been mentioned in previous studies. On the other hand, another gap at Pb ∼ 2.5-4.5 days (Gap 2) is identified for the first time. Inspection of the relation between Pb and the companion masses Mc revealed the subpopulations of MSP binaries with a He WD separated by Gap 1, above which Pb is independent of Mc (horizontal branch) but below which Pb correlates strongly with Mc (lower branch). A distinctive horizontal branch and a lower branch separated by Gap 2 were identified for the MSP binaries with a CO/ONeMg WD at shorter Pb and higher Mc. Generally, Mc are higher in the horizontal branch than in the lower branch for the MSP binaries with a He WD. These properties can be explained in terms of a binary orbital evolution scenario in which the WD companion was ablated by a pulsar wind in the post-mass-transfer phase.