2.7 Intermediate mass binary pulsars

The range of white dwarf masses observed is becoming broader. Since this article originally appeared [221], the number of “intermediate-mass binary pulsars” [54] has grown significantly [58Jump To The Next Citation Point]. These systems are distinct to the millisecond pulsar–white dwarf binaries in several ways:
  1. The spin period of the radio pulsar is generally longer (9 – 200 ms).
  2. The mass of the white dwarf is larger (typically ≳ 0.5 M ⊙).
  3. The orbit, while still essentially circular, is often significantly more eccentric (e ≳ 10 −3).
  4. The binary parameters do not necessarily follow the mass–period or eccentricity–period relationships.

It is not presently clear whether these systems originated from low- or high-mass X-ray binaries. It was suggested by van den Heuvel [383] that they have more in common with high-mass systems. Subsequently, Li proposed [213] that a thermal-viscous instability in the accretion disk of a low-mass X-ray binary could truncate the accretion phase and produce a more slowly spinning neutron star.


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