Rapid quasi-periodic reconfiguration of the accretion column in pulsar 1A 0535+262

Journal article

Accretion onto strongly magnetised 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 synchronised 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.

Authors: Kong, L; Dai, X; Santangelo, A; Ji, L; Suleimanov, VF

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Nature Research
• Journal: Nature Communications
• Volume: 17
• Issue: 1
• Publication date: 2026-07-09
• Acceptance date: 2026-06-25
• DOI: 10.1038/s41467-026-75290-4
• EISSN: 2041-1723
• ISSN: 2041-1723
• Language: English
• Keywords: Pulsar; Luminosity; Cyclotron; Millisecond pulsar; Line (geometry); Radiation pressure; Neutron star; Magnetic field; Accretion (finance)