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 $M_{\mathrm{c}}>0.05M_{\odot }$ 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.

6 pages, 4 figures, 1 table. Accepted for publication in ApJ Letters