With long-term hard X-ray monitoring, observations on high mass X-ray binary GX 301-2 from 2003-2011 performed by INTEGRAL/IBIS, we first systematically studied its spectral properties in different accreting luminosities and orbital phases. The cyclotron resonant scattering feature ( CRSF) at energies from 35-47 keV was detected in the hard X-ray spectra, suggesting the magnetic field of 5 × 1012 Gs. The variations of the CRSF show no relation to the X-ray luminosity while the line centroid energy of the CRSF has a positive correlation to the photon index and spectral cutoff energy, and there also exists a weak correlation between the absorption depth and cutoff energy. These relations support the idea that the spectral cutoff in accreting X-ray pulsars is strongly affected by the cyclotron resonant scattering. The correlation between the ratio of the line width to the centroid energy and absorption depth implies a tall cylindrical accreting column on the surface of the neutron star in GX 301-2. The explanation of the long spin period in GX 301-2 requires a strong surface magnetic field at least higher than 2 × 1014 Gs which is contradict with the measured value based on the cyclotron line energy. The line-forming region with a height at least larger than two neutron star radii is proposed to resolve the contradiction. This scenario is supported by the tall cylindrical accreting column on the neutron star surface in GX 301-2 according to the variation patterns of the CRSF. In addition, the possible evolution scenario of accreting magnetars like GX 301-2 is briefly discussed, and GX 301-2 would be an accreting magnetar in the equivalence phase.%利用INTEGRAL/IBIS卫星2003~2011年对X射线双星GX 301-2的观测数据, 系统研究了GX 301-2在不同吸积光度和轨道相位的谱性质, 得到GX 301-2的回旋吸收线的性质与X射线光度无关,其能量在35~47 keV之间, 且能量与光指数和截断能量正相关, 回旋吸收线的深度与截断能量有弱正相关, 这表明在吸积X射线脉冲星中, 回旋共振散射线对截断能量有很大影响. 而回旋吸收线宽度与能量比值和深度正相关, 这表明在GX 301-2表面存在一个吸积柱. 由GX 301-2的自旋周期得到表面磁场强度大约为2 × 1014 Gs, 与通过回旋吸收线得到的磁场强度不符, 但可以用吸积柱模型很好地解释.
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