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| Autores principales: | , , , , , , , , , , , , , , |
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| Formato: | Preprint |
| Publicado: |
2026
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| Materias: | |
| Acceso en línea: | https://arxiv.org/abs/2606.01625 |
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- Accretion onto strongly magnetized neutron stars is commonly interpreted using quasi-steady models, in which the accretion-column structure adjusts smoothly to the mass inflow rate. The cyclotron line in the X-ray spectrum, whose centroid energy traces the magnetic field strength and thus the height of the line-forming region, provides a key diagnostic of this structure. Whether this simple quasi-steady description remains valid on short dynamical timescales has remained uncertain. Here we show that, during a giant outburst of the X-ray pulsar 1A~0535+262, quasi-periodic hard X-ray flux variations are accompanied by synchronized oscillations of the cyclotron line energy, with amplitudes exceeding those expected from simple accretion-rate fluctuations. The anti-correlation between cyclotron energy and apparent flux provides direct spectral-timing evidence for rapid changes in the line-forming region, which we interpret as geometric reconfiguration of the accretion column. The variability emerges in the luminosity regime where radiation pressure becomes dynamically important. These results reveal limitations of a simple quasi-steady interpretation for this source and suggest that radiation-supported columns can enter intrinsically dynamical states in high-luminosity accreting pulsars.