Gamma-ray Modes in a Transitional Pulsar
arXiv:2607.13019
The authors detect distinct gamma‑ray modes in the transitional millisecond pulsar PSR J1023+0038 and find that gamma‑ray flux is higher when the X‑ray flux is low, suggesting that jet emission, rather than pulsar‑wind interactions, dominates the GeV emission during these states.
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.
11 pages, 4 figures, 2 tables