  The low mass X-ray binary 2A 1822-371 is an eclipsing system with an
accretion disc corona and with an orbital period of 5.57 hr. The primary is an
0.59 s X-ray pulsar with a proposed strong magnetic field of 10^10-10^12 G. In
this paper we study the spin evolution of the pulsar and constrain the geometry
of the system. We find that, contrary to previous claims, a thick corona is not
required, and that the system characteristics could be best explained by a thin
accretion outflow due to a super-Eddington mass transfer rate and a
geometrically thick inner accretion flow. The orbital, spectral and timing
observations can be reconciled in this scenario under the assumption that the
mass transfer proceeds on a thermal timescale which would make 2A 1822-371, a
mildly super-Eddington source viewed at high inclination angles. The timing
analysis on 13 years of RXTE data show a remarkably stable spin-up that implies
that 2A 1822-371, might quickly turn into a millisecond pulsar in the next few
thousand years.
