Strong Constraints on Millisecond Pulsar Injection Spectra from Fermi-LAT Observations of the Galactic Center

Abstract

Millisecond pulsars (MSPs) are a leading explanation of the Galactic Center excess (GCE) observed in Fermi-LAT data. We constrain this scenario by jointly modeling prompt and inverse-Compton $γ$ rays from MSP-injected $e^\pm$ on the Galactic bulge, using recent Fermi-LAT GCE spectra from state-of-the-art interstellar emission models and data analysis. Current data place strong upper limits on the efficiency ratio $η_e/η_γ$ across broad $e^\pm$ injection scenarios, surpassing those from globular-cluster observations with MAGIC and competitive with projected CTAO sensitivities toward the Galactic bulge.