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Description
Some accreting neutron stars in massive and low-mass X-ray binaries exhibit flaring activity. The flares are accompanied by changes in spectra, pulsation profiles, and the long-term luminosity of the system. The flares themselves vary in duration and peak luminosity. Different flares have different origins; however, in many cases, the nature of the flares is unknown. In this work, we describe the behavior of the massive X-ray binary LMC X-4 during flaring activity. We demonstrate that the variability properties and the pulsar’s behavior during the flares are incompatible with most of the previously proposed mechanisms for flare production. Our analysis is based on the study of the neutron star spin dynamics and the regularity of changes in the pulse profile shape, performed using a long RXTE observation that shows four flares. In particular, our analysis demonstrate that the changes in the pulse profile shape during flares occur regularly, which contradicts models of material capture onto the neutron star magnetic field lines or the Rayleigh–Taylor instability.