高能暂现源 · 每日文献综述

We present the discovery of EP250827b/SN 2025wkm, an X-ray flash (XRF) discovered by the Einstein Probe (EP), accompanied by a broad-line Type Ic supernova (SN Ic-BL) at z = 0.1194. EP250827b possesses a prompt X-ray luminosity of ∼10<SUP>45</SUP> erg s<SUP>−1</SUP>, lasts over 1000 s, and has a peak energy E<SUB>p</SUB> &lt; 1.5 keV at 90% confidence. SN 2025wkm possesses a double-peaked optical light curve (LC), though its bolometric luminosity plateaus after its initial peak for ∼20 days, consistent with a central engine injecting additional energy into the explosion. Its spectrum transitions from a blue to red continuum with clear blueshifted broad absorption features consistent with a SN Ic-BL classification. We do not detect any transient radio emission and rule out the existence of an on-axis, energetic jet ≳10<SUP>50</SUP> erg assuming a typical LGRB circumburst constant density (n ≍ 10<SUP>−3</SUP>─10<SUP>−1</SUP> cm<SUP>−3</SUP>) and microphysical parameters (ϵ<SUB>e</SUB> = 0.1 and ϵ<SUB>B</SUB> = 0.01). In the model we invoke, the collapse gives rise to a long-lived magnetar, potentially surrounded by an accretion disk. Magnetically driven winds from the magnetar and the disk mix together and break out with a velocity ∼0.35c and interact with an extended circumstellar medium with radius ∼10<SUP>13</SUP> cm, generating X-ray breakout emission through nonthermal free─free processes. The disk outflows and magnetar winds power blackbody photospheric emission as they cool adiabatically and thermalize, producing the first SN peak. The spin-down luminosity of the magnetar and radioactive decay of <SUP>56</SUP>Ni power the late-time emission. We end by discussing the landscape of XRF-SNe within the context of EP's recent discoveries.