X-ray reprocessing in accreting pulsar GX 301-2 observed with Insight-HXMT

L. Ji, V. Doroshenko, V. Suleimanov, A. Santangelo, M. Orlandini, J. Liu, L. Ducci, S. N. Zhang, A. Nabizadeh, D. Gavran, S. Zhang, M. Y. Ge, X. B. Li, L. Tao, Q. C. Bu, J. L. Qu, F. J. Lu, L. Chen, L. M. Song, T. P. Li, Y. P. Xu, X. L. Cao, Y. Chen, C. Z. Liu, C. Cai, Z. Chang, T. X. Chen, Y. P. Chen, W. W. Cui, Y. Y. Du, G. H. Gao, H. Gao, Y. D. Gu, J. Guan, C. C. Guo, D. W. Han, Y. Huang, J. Huo, S. M. Jia, W. C. Jiang, J. Jin, L. D. Kong, B. Li, C. K. Li, G. Li, W. Li, X. Li, X. F. Li, Z. W. Li, X. H. Liang, J. Y. Liao, B. S. Liu, H. X. Liu, H. W. Liu, X. J. Liu, X. F. Lu, Q. Luo, T. Luo, R. C. Ma, X. Ma, B. Meng, Y. Nang, J. Y. Nie, G. Ou, X. Q. Ren, N. Sai, X. Y. Song, L. Sun, Y. Tan, Y. L. Tuo, C. Wang, L. J. Wang, P. J. Wang, W. S. Wang, Y. S. Wang, X. Y. Wen, B. Y. Wu, B. B. Wu, M. Wu, G. C. Xiao, S. Xiao, S. L. Xiong, R. J. Yang, S. Yang, Yan-Ji Yang, Yi-Jung Yang, Q. B. Yi, Q. Q. Yin, Y. You, F. Zhang, H. M. Zhang, J. Zhang, P. Zhang, W. Zhang, W. C. Zhang, Yi Zhang, Y. F. Zhang, Y. H. Zhang, H. S. Zhao, X. F. Zhao, S. J. Zheng, Y. G. Zheng, D. K. Zhou

Published 2020-12-04Version 1

We investigate the absorption and emission features in observations of GX 301-2 detected with Insight-HXMT/LE in 2017-2019. At different orbital phases, we found prominent Fe Kalpha, Kbeta and Ni Kalpha lines, as well as Compton shoulders and Fe K-shell absorption edges. These features are due to the X-ray reprocessing caused by the interaction between the radiation from the source and surrounding accretion material. According to the ratio of iron lines Kalpha and Kbeta, we infer the accretion material is in a low ionisation state. We find an orbital-dependent local absorption column density, which has a large value and strong variability around the periastron. We explain its variability as a result of inhomogeneities of the accretion environment and/or instabilities of accretion processes. In addition, the variable local column density is correlated with the equivalent width of the iron Kalpha lines throughout the orbit, which suggests that the accretion material near the neutron star is spherically distributed.