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We present results of the analysis of super-Eddington flares registered fromthe X-ray pulsar LMC X-4 by the NuSTAR observatory in the broad energy range3-79 keV. The pulsar spectrum is well described by the thermal comptonizationmodel both in a quiescent state and during flares, when the peak luminosityreaches values $L_{\rm x} \sim (2-4)\times10^{39}$ erg s$^{-1}$. An importantfeature, found for the first time, is that the order of magnitude increase inthe luminosity during flares is observed primarily at energies below 25-30 keV,whereas at higher energies (30-70 keV) the shape of the spectrum and the sourceflux remain practically unchanged. The luminosity increase is accompanied bychanges in the source pulse profile -- in the energy range of 3-40 keV itbecomes approximately triangular, and the pulsed fraction increases withincreasing energy, reaching 60-70% in the energy range of 25-40 keV. The paperdiscusses possible changes in the geometry of the accretion column, which canexplain variations in spectra and pulse profiles.

Peculiarities of super-Eddington flares from the X-ray pulsar LMC X-4 with NuSTAR