宇宙爆発の新型を発見(New Type of Cosmic Explosion Linked to Supernovae Detected by China’s EP Satellite)

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2025-07-01 中国科学院(CAS)

中国の「アインシュタイン・プローブ(EP)」衛星が、これまで知られていなかった新種の宇宙爆発を発見しました。これは、大質量星の死に伴って発生する、非常に短時間かつ微弱なX線の閃光(トランジェント)で、名称は「EP240414a」。この閃光は約40億光年先から発せられ、続く観測で超新星「SN 2024gsa」と関連があることが判明しました。従来のガンマ線バーストに似た、しかしより遅くエネルギーの小さい相対論的ジェットも観測され、爆発の物理過程やジェット形成の解明に貴重な手がかりを提供しました。EPの高感度「ロブスターアイ」技術により、これまでの観測機では捉えられなかったこのような現象の検出が可能となり、今後の新発見が期待されています。

<関連情報>

Ic-BL型超新星に伴う弱い相対論的ジェットからの高速X線過渡現象 A fast X-ray transient from a weak relativistic jet associated with a type Ic-BL supernova

H. Sun,W.-X. Li,L.-D. Liu,H. Gao,X.-F. Wang,W. Yuan,B. Zhang,A. V. Filippenko,D. Xu,T. An,S. Ai,T. G. Brink,Y. Liu,Y.-Q. Liu,C.-Y. Wang,Q.-Y. Wu,X.-F. Wu,Y. Yang,B.-B. Zhang,W.-K. Zheng,T. Ahumada,Z.-G. Dai,J. Delaunay,N. Elias-Rosa,… H. Zou
Nature Astronomy  Published:26 June 2025
DOI:https://doi.org/10.1038/s41550-025-02571-1

宇宙爆発の新型を発見(New Type of Cosmic Explosion Linked to Supernovae Detected by China’s EP Satellite)

Abstract

Massive stars end their lives as core-collapse supernovae, among which some extremes are broad-lined type Ic supernovae from Wolf–Rayet stars associated with long-duration gamma-ray bursts (LGRBs) with powerful relativistic jets. Their less-extreme brethren make unsuccessful jets that are choked inside the stars, appearing as X-ray flashes or low-luminosity GRBs. However, there exists a population of extragalactic fast X-ray transients with timescales ranging from seconds to thousands of seconds, whose origins remain obscure. Here we report the discovery of the bright X-ray transient EP240414a detected by the Einstein Probe, which is associated with the type Ic supernova SN 2024gsa at a redshift of 0.401. The X-ray emission evolution is characterized by a very soft energy spectrum peaking at <1.3 keV, which makes it different from known LGRBs, X-ray flashes or low-luminosity GRBs. Follow-up observations at optical and radio bands revealed the existence of a weak relativistic jet that interacts with an extended shell surrounding the progenitor star. Located on the outskirts of a massive galaxy, this event reveals a population of explosions of Wolf–Rayet stars characterized by a less powerful engine that drives a successful but weak jet, possibly owing to a progenitor star with a smaller core angular momentum than in traditional LGRB progenitors.

1701物理及び化学
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