An RGB composite image of G289.6+5.8 showing the large-scale radio structure of the remnant. The image combines the ASKAP–EMU 944 MHz total intensity map (red and blue) with WISE 12 µm emission (green). To emphasise the structure of the source, the radio image is displayed in two different scalings: the red layer uses a linear stretch to highlight the bright filaments and central region, and the blue layer a logarithmic stretch to enhance the low surface brightness emission. From Lazarevic et al. 2026.

In a search for low surface brightness radio nebulae using the ASKAP–EMU survey, Lazarević et al. discovered a faint radio shell, G289.6+5.8, which has a central point-like radio source at the position of the soft gamma-ray source IGR J11187–5438. The central radio source is spatially coincident with a previously known low-mass X-ray binary (LMXB) with an M-type donor star. However, the recently determined Gaia DR3 distance of 267 pc and correspondingly low X-ray luminosity cast doubt on the LMXB classification. Neither radio nor X-ray pulsations are detected. Chance-alignments between radio shell, central radio source, optical star, gamma-ray, and X-ray sources appear unlikely. By combining all currently available evidence, we conclude that G289.6+5.8 is a remnant of a low-energy core-collapse explosion of an intermediate mass star (∼8 solar masses) in a binary system with an M-type secondary, which remained bound after the explosion. In this scenario, G289.6+5.8 is a supernova remnant, while the central gamma- and X-ray source is associated with a young neutron star driving a pulsar wind interacting with its M-type stellar companion, making IGR J11187–5438 a nascent spider-type X-ray binary. Spiders are a class of millisecond pulsars (MSPs) in compact binaries with low-mass companions. In these systems, a relativistic pulsar wind collides with and blows away the outer layers of the optical star, producing high-energy emission from an intra-binary shock rather than from accretion.

The image above is a RGB composite image of G289.6+5.8 showing thelarge-scale radio structure of the remnant. The image combines the ASKAP–EMU 944 MHz total intensity map (red and blue) with WISE 12 µm emission (green). To emphasise the structure of the source, the radio image is displayed in two different scalings: the red layer uses a linear stretch to highlight the bright filaments and central region, and the blue layer a logarithmic stretch to enhance the low surface brightness emission. The 15 arcsecond synthesised circular beam is shown in the lower-left corner. The gamma-ray source IGR J11187–5438 lies within the compact nebula at the centre.