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arXiv · 2512.09223

An extragalactic gamma-ray binary formed in supernova 2022jli

Pengfei Zhang·Zhongxiang Wang·Shunhao Ji
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Abstract

On May 5 2022, a type Ic supernova (SN) explosion SN~2022jli was discovered. This SN showed additional optical emissions, which were found to exhibit 12.4-day periodic undulations and concordant periodic velocity shifts. These key features likely indicate a compact object in a binary system was formed. A faint $γ$-ray source was also detected at the position of the SN and upon checking the $γ$-ray photons' arrival times, it was revealed that the same 12.4-day periodicity was likely present. Here we report our detailed analysis results for the $γ$-ray source. Not only was the $γ$-ray emission detectable for $\sim$1.5\,years since the discovery time, but a strong modulation at period 12.5\,day was also clearly determined. Considering the newly formed compact object to be a neutron star or a stellar-mass black hole, the putative binary, having an orbital period of 12.5\,day, is likely the first extragalactic high-energy system detected. The system may serve as a valuable example for the formation of many such binaries observed in the Milky Way and nearby galaxies.

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Pengfei Zhang, Zhongxiang Wang, Shunhao Ji. 2025-12-10. An extragalactic gamma-ray binary formed in supernova 2022jli. https://arxiv.org/abs/2512.09223

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