We present the results of an in-depth study of the long-period X-ray pulsar GX 301 - 2 .
Using archival data of INTEGRAL , RXTE ASM , and CGRO BATSE , we study the spectral and timing properties of the source .
Comparison of our timing results with previously published work reveals a secular decay of the orbital period at a rate of \simeq - 3.25 \times 10 ^ { -5 } \mathrm { d yr } ^ { -1 } , which is an order of magnitude faster than for other known systems .
We argue that this is probably result either of the apsidal motion or of gravitational coupling of the matter lost by the optical companion with the neutron star , although current observations do not allow us to distinguish between those possibilities .
We also propose a model to explain the observed long pulse period .
We find that a very strong magnetic field B \sim 10 ^ { 14 } G can explain the observed pulse period in the framework of existing models for torques affecting the neutron star .
We show that the apparent contradiction with the magnetic field strength B _ { \mathrm { CRSF } } \sim 4 \times 10 ^ { 12 } G derived from the observed cyclotron line position may be resolved if the line formation region resides in a tall accretion column of height \sim 2.5–3 R _ { \mathrm { NS } } .
The color temperature measured from the spectrum suggests that such a column may indeed be present , and our estimates show that its height is sufficient to explain the observed cyclotron line position .