Bimodal Radio Bursts and Long-timescale State Switching in the Rotating Radio Transient J2237+2828

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Abstract Rotating radio transients (RRATs) represent a critical yet enigmatic population of neutron stars whose sporadic emission is driven by highly intermittent magnetospheric states. We present a high-sensitivity, multi-epoch polarimetric study of RRAT J2237+2828 using the Five-hundred-meter Aperture Spherical radio Telescope, uncovering a complex, nonstationary magnetospheric environment. Individual bursts exhibit high linear polarization (20%–60%) and frequent orthogonal polarization modes, suggesting a fundamental coherent emission mechanism similar to canonical pulsars. However, the emission clearly shows bimodal behavior: pulses cluster into a High-energy burst state (Mode B) and a low-energy recovery state (Mode A). We identify a profound temporal asymmetry in the state-switching dynamics. While the transition from Mode B to Mode A occurs abruptly within 1–2 pulsar periods, the transition back to Mode B requires an extensive waiting time spanning hundreds to thousands of seconds. A compelling positive correlation between the inter-burst waiting time and the subsequent burst fluence ( r s ≈ 0.45), coupled with a significant deviation from Poissonian statistics, strongly suggests that the system is regulated by an energy accumulation and release process. This long-term “system memory” and the observed timescales suggest that the intermittency is regulated by processes beyond pure magnetospheric dynamics, such as crustal stress accumulation or the evolution of multipolar magnetic fields. The stability of the rotation measure over 2 yr disfavors environmental origins and supports an intrinsic origin for the observed intermittency.

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