Lazarevic et al. report the discovery of a bow-shock pulsar wind nebula (PWN), dubbed Thunder, powered by the radio pulsar PSR J1631−4722 and projected within the Galactic supernova remnant (SNR) G336.7+0.5 (Nimbus). The system was first identified ASKAP observations for the Evolutionary Map of the Universe (EMU) survey and further characterised using MeerKAT Galactic Plane Survey data and follow-up ATCA observations at 5.5 and 9 GHz.

Assuming a distance of 7 kpc, the radio images resolve an elongated ∼80 arcsecond (2.7 parsec) cometary nebula, indicative of a high-velocity pulsar. An X-ray counterpart extending ∼50 arcseconds (1.7 pc) is detected in archival XMM-Newton data. The flat radio spectrum and hard X-ray photon index indicate synchrotron emission from relativistic particles injected in the pulsar wind. Polarisation analysis reveals a highly ordered magnetic field aligned with the nebular flow, with fractional polarisation reaching up to 30% in the tail. An equipartition estimate gives a PWN magnetic-field strength of 54~140 micro-gauss. Pulsar timing over a 2.2 year baseline reveals strong timing noise and a small spin glitch. The SNR shows no clear diffuse X-ray counterpart. The morphology and multiwavelength properties of the Nimbus–Thunder system, together with evolutionary models, constrain the system age to 30,000~45,000 years.

The image above is a composite image of ASKAP 1367 MHz radio emission (orange-red) and WISE 12 µm infrared emission (cyan) of the SNR G336.7+0.5 (Nimbus) region. Thunder, PWN J1631−4721, is marked by the white dashed box. The radio synthesised beam size of 8.8 × 7.4 arcseconds is shown in the lower-left corner. The dashed line indicates a line parallel to the Galactic plane, offset by 0.35 degrees.