Phase-Resolved Spectroscopy of the High-Mass Binary 2S 1845-024

This work is devoted to a detailed study of radiation properties of the X-ray transient pulsar in the binary system 2S 1845-024. The main part of the work is based on the pulsar observation during an outburst on April 14, 2017 with the astrophysical observatory NuSTAR. Were also used data from public archives of other missions: Chandra, XRT and XMM-Newton. A detailed analysis in the wide energy band 3-79 keV of the averaged spectra was carried out with NuSTAR. In addition, phase-resolved spectroscopy with high temporal and spectral resolution was obtained for the first time. Studies have shown the absence of linear properties (except for the photoionization radiation 〖Fe〗_α) in all spectra. In particular, we did not detect cyclotron absorption lines. From which we can conclude that the magnitude of magnetic field of the neutron star lies in the ranges B ≤ 〖10〗^12 G and B ≥ 〖10〗^13 G. According to the early studies of 2S 1845-024, the source was assigned to the class of massive Be-systems. However, we have shown that the system probably belongs to the wind class. This is evidenced by a number of observational facts. For example, in the power spectrum, we did not find a break corresponding to the Keplerian rotation frequency on the inner edge of the accretion disk. This is evidence that neutron star accretes matter not from the disk, but from the wind. We also demonstrated that emission of all orbital phases is essentially obscured that is untypical for Be-systems. There is nothing to do with the absorption of all orbital phases. Good resolution spectra near the iron line energy also indicate the presence of wind. The ratio of the intensities of the lines 〖Fe〗_α and 〖Fe〗_β indicates that the radiation passes through a region with a partially ionized plasma. And we conclude that the source is most likely a system with a supergiant and accreting from the wind.