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arXiv · 2607.13019

Gamma-ray Modes in a Transitional Pulsar

Maksat Satybaldiev·Manuel Linares
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Abstract

Transitional millisecond pulsars (tMSPs) exhibit a unique sub-luminous disk state, at the cross-roads between accretion and rotation power, where they switch between two distinct X-ray modes. We present the discovery of gamma-ray modes in PSR J1023+0038, the first confirmed tMSP, from stacking Fermi-LAT data during the modes (which we identify using simultaneous X-ray observations). Surprisingly, we find that gamma-rays and X-rays are anti-correlated during this mode switching: the gamma-ray flux is higher in the X-ray low mode, and vice versa. This contradicts the state-of-the-art model, which predicts bright gamma-rays from the interaction between the pulsar wind and surrounding disk via synchrotron and inverse Compton processes. Because the pulsar wind is likely absent in the gamma-ray high (X-ray low) mode, which is also brighter in the radio band, we suggest that jet emission is dominant in GeV gamma-rays.

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Maksat Satybaldiev, Manuel Linares. 2026-07-14. Gamma-ray Modes in a Transitional Pulsar. https://arxiv.org/abs/2607.13019

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