2018MNRAS.479..353B

The accreting pulsar GX 1+4 is a symbiotic X-ray binary system with an M-type giant star companion. The system has a spin period of about 150 s and a proposed strong magnetic field of 10¹²-10¹⁴G. In this paper we study the coherent variability of the source and attempt to find a phase-coherent solution for the pulsar. We also test for the presence of a pulse phase-flux correlation, similar to what is observed for the accreting millisecond X-ray pulsars, in order to test whether this feature is dependent on the magnetic field strength. We find that no phase coherent solution exists, which suggests that the pulsar is accreting plasma from a wind rather than an accretion disc. We also find evidence that the pulse phase is not correlated with the X-ray flux, which strengthens the idea that such relation might be present only in weak magnetic field sources like accreting millisecond pulsars.