A Millisecond Pulsar Binary Embedded in a Galactic Center Radio Filament

Abstract

The Galactic Center is host to a population of extraordinary radio filaments, thin linear structures that trace out magnetic field lines running perpendicular to the Galactic plane. Using Murriyang, the 64 m Parkes radio telescope, we conducted a search for pulsars centered on the position of a compact source in the filament G359.0$-$0.2. We discovered a millisecond pulsar (MSP), PSR J1744$-$2946, with a period $P = 8.4$ ms, that is bound in a 4.8 hr circular orbit around a $M_{\rm c} > 0.05\,M_{\odot}$ companion. The pulsar dispersion measure of $673.7 \pm 0.1$ pc cm$^{-3}$ and Faraday rotation measure of $3011 \pm 3$ rad m$^{-2}$ are the largest of any known MSP. Its radio pulses are moderately scattered due to multi-path propagation through the interstellar medium, with a scattering timescale of $0.87 \pm 0.08$ ms at 2.6 GHz. Using MeerKAT, we localized the pulsar to a point source embedded in a low-luminosity radio filament, the "Sunfish", that is unrelated to G359.0$-$0.2. Our discovery of the first MSP within 1$^{\circ}$ of the Galactic Center hints at a large population of these objects detectable via high frequency surveys. The association with a filament points to pulsars as the energy source responsible for illuminating the Galactic Center radio filaments.