Signatures of Intra-binary Shock Emission in the Black Widow Pulsar Binary PSR J2241−5236

We report on high-energy properties of the black widow pulsar PSR J2241−5236 in the X-ray and the Fermi-Large Area Telescope (LAT; GeV gamma-ray) bands. In the LAT band, the phase-averaged gamma-ray light curve shows orbital modulation below ∼1 GeV with a chance probability (p) monotonically decreasing with time to p ∼ 10−5. The peak of the light curve is near the superior conjunction of the pulsar (binary phase ϕB ≈ 0.25). We attribute the modulation to the intra-binary shock (IBS) emission and search for IBS signatures in the archival X-ray data. We find that the X-ray spectral fit requires a nonthermal component, which implies a possible IBS origin of the X-rays. We discuss our observations in the context of IBS scenarios.