PSR J1311–3430

PSR J1311–3430 is a pulsar with a spin period of 2.5 milliseconds. It is the first millisecond pulsar found via gamma-ray pulsations. The source was originally identified by the Energetic Gamma Ray Experiment Telescope as a bright gamma ray source, but was not recognized as a pulsar until observations with the Fermi Gamma-ray Space Telescope discovered pulsed gamma ray emission. The pulsar has a helium-dominated companion much less massive than itself, and the two are in an orbit with a period of 93.8 minutes. The system is explained by a model where mass from the low mass companion was transferred on to the pulsar, increasing the mass of the pulsar and decreasing its period. These systems are known as Black Widow Pulsars, named after the original such system discovered, PSR B1957+20, and may eventually lead to the companion being completely vaporized. Among systems like these, the orbital period of PSR J1311–3430 is the shortest ever found. Spectroscopic observations of the companion suggest that the mass of the pulsar is 2.7 ${\displaystyle M_{\odot }}$ (solar masses). Though there is considerable uncertainty in this estimate, the minimum mass for the pulsar that the authors find adequately fits the data is 2.15 ${\displaystyle M_{\odot }}$, which is still more massive than PSR J1614−2230, the previous record holder for most massive known pulsar.