The Rossi X-ray Timing Explorer ( RXTE ) spacecraft observed the X-ray pulsar GX 1+4 for a period of 34 hours on July 19/20 1996 .
The source faded from an intensity of \sim 20 mcrab to a minimum of \leq 0.7 mcrab and then partially recovered towards the end of the observation .
This extended minimum lasted \sim 40,000 seconds .
Phase folded light curves at a barycentric rotation period of 124.36568 \pm 0.00020 seconds show that near the center of the extended minimum the source stopped pulsing in the traditional sense but retained a weak dip feature at the rotation period .
Away from the extended minimum the dips are progressively narrower at higher energies and may be interpreted as obscurations or eclipses of the hot spot by the accretion column .
The pulse profile changed from leading-edge bright before the extended minimum to trailing-edge bright after it .
Data from the Burst and Transient Source Experiment ( BATSE ) show that a torque reversal occurred < 10 days after our observation .
Our data indicate that the observed rotation departs from a constant period with a \dot { P } / P value of \sim - 1.5 % per year at a 4.5 \sigma significance .
We infer that we may have serendipitously obtained data , with high sensitivity and temporal resolution about the time of an accretion disk spin reversal .
We also observed a rapid flare which had some precursor activity , close to the center of the extended minimum .