What is wrong with the binary millisecond pulsar J1903+0327?

The millisecond pulsar J1903+0327 is accompanied by an ordinary
G-dwarf star in an unusually wide and eccentric orbit.  The standard
model for producing MSPs fails to explain the orbital characteristics
of this extraordinary binary, and alternative binary models are unable
to explain the observables.  We present a triple-star model for
producing MSPs in relatively wide eccentric binaries with a normal
(main-sequence) stellar companion. We start from a stable triple
system consisting of a Low-Mass X-ray Binary with an orbital period of
at least 1day, accompanied by a G-dwarf in a wide and possibly
eccentric orbit.  Variations in the initial conditions naturally
provide a satisfactory explanation for the unexplained triple
component in the eclipsing soft X-ray transient 4U~2129+47 or the
cataclysmic variable EC 19314-5915.  The best explanation for J1903
however, results from the expansion of the orbit of the LMXB, driven
by the mass transfer from the evolving donor star to its neutron star
companion, which causes the triple eventually to becomes dynamically
unstable.  Using numerical computations we show that, depending on the
precise system configuration at the moment the triple becomes
dynamically unstable, the ejection of each of the three components is
possible. If the donor star of the LMXB is ejected, a system
resembling J1903 will result. If the neutron star is ejected, a single
MSP results.  This model therefore also provides a straightforward
mechanism for forming single MSP in the Galactic disk.  We conclude
that the Galaxy contains some 30--300 binaries with characteristics
similar to J1903 and about an order of magnitude fewer single
millisecond pulsars produced with the proposed triple scenario.