EP250827b/SN 2025wkm: An X-Ray Flash-supernova Powered by a Central Engine and Circumstellar Interaction

@article{srinivasaragavan2026ep250827bsn,
  title = {{EP250827b/SN 2025wkm: An X-Ray Flash-supernova Powered by a Central Engine and Circumstellar Interaction}},
  author = {Gokul P. Srinivasaragavan and Dongyue Li and Xander J. Hall and Ore Gottlieb and Genevieve Schroeder and He‐Yang Liu and Brendan O’Connor and Chichuan Jin and M. M. Kasliwal and Tomás Ahumada and Qinyu Wu and Chris L. Fryer and Annabelle E. Niblett and Dong Xu and Maria Edvige Ravasio and Grace Daja and Wenxiong Li and Shreya Anand and Anna Y. Q. Ho and Hui Sun and Daniel A. Perley and Yan Lin and Eric Burns and S. B. Cenko and J. Sollerman and Nikhil Sarin and Anthony L. Piro and Amar Aryan and M. Coleman Miller and Jie An and Tao An and Moira Andrews and Jule Augustin and Eric C. Bellm and Aleksandra Bochenek and Malte Busmann and Krittapas Chanchaiworawit and Huaqing Cheng and M. D. Caballero‐García and Alberto J. Castro-Tirado and Ali Esamdin and Jennifer Fabà-Moreno and Joseph Farah and Emilio Fernández-García and Shao-Yu Fu and J. P. U. Fynbo and Julius Gassert and Estefania Padilla Gonzalez and Ignacio Pérez-García and M. J. Graham and Maria I. Gritsevich and Daniel Gruen and Sergiy Guziy and He Lp and D. Andrew Howell and Jingwei Hu and Y. D. Hu and Abdusamatjan Iskandar and Joahan Castaneda Jaimes and Ji-an Jiang},
  journal = {The Astrophysical Journal Letters},
  year = {2026},
  month = jul,
  doi = {10.3847/2041-8213/ae7a68},
  url = {https://doi.org/10.3847/2041-8213/ae7a68},
  note = {CC BY},
}

TY  - JOUR
TI  - EP250827b/SN 2025wkm: An X-Ray Flash-supernova Powered by a Central Engine and Circumstellar Interaction
AU  - Gokul P. Srinivasaragavan
AU  - Dongyue Li
AU  - Xander J. Hall
AU  - Ore Gottlieb
AU  - Genevieve Schroeder
AU  - He‐Yang Liu
AU  - Brendan O’Connor
AU  - Chichuan Jin
AU  - M. M. Kasliwal
AU  - Tomás Ahumada
AU  - Qinyu Wu
AU  - Chris L. Fryer
AU  - Annabelle E. Niblett
AU  - Dong Xu
AU  - Maria Edvige Ravasio
AU  - Grace Daja
AU  - Wenxiong Li
AU  - Shreya Anand
AU  - Anna Y. Q. Ho
AU  - Hui Sun
AU  - Daniel A. Perley
AU  - Yan Lin
AU  - Eric Burns
AU  - S. B. Cenko
AU  - J. Sollerman
AU  - Nikhil Sarin
AU  - Anthony L. Piro
AU  - Amar Aryan
AU  - M. Coleman Miller
AU  - Jie An
AU  - Tao An
AU  - Moira Andrews
AU  - Jule Augustin
AU  - Eric C. Bellm
AU  - Aleksandra Bochenek
AU  - Malte Busmann
AU  - Krittapas Chanchaiworawit
AU  - Huaqing Cheng
AU  - M. D. Caballero‐García
AU  - Alberto J. Castro-Tirado
AU  - Ali Esamdin
AU  - Jennifer Fabà-Moreno
AU  - Joseph Farah
AU  - Emilio Fernández-García
AU  - Shao-Yu Fu
AU  - J. P. U. Fynbo
AU  - Julius Gassert
AU  - Estefania Padilla Gonzalez
AU  - Ignacio Pérez-García
AU  - M. J. Graham
AU  - Maria I. Gritsevich
AU  - Daniel Gruen
AU  - Sergiy Guziy
AU  - He Lp
AU  - D. Andrew Howell
AU  - Jingwei Hu
AU  - Y. D. Hu
AU  - Abdusamatjan Iskandar
AU  - Joahan Castaneda Jaimes
AU  - Ji-an Jiang
PY  - 2026
DA  - 2026/07/22
JO  - The Astrophysical Journal Letters
DO  - 10.3847/2041-8213/ae7a68
UR  - https://doi.org/10.3847/2041-8213/ae7a68
AB  - 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 45 erg s −1 , lasts over 1000 s, and has a peak energy E p < 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 50 erg assuming a typical LGRB circumburst constant density ( n ≈ 10 −3 –10 −1 cm −3 ) and microphysical parameters ( ϵ e = 0.1 and ϵ B = 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 ∼0.35 c and interact with an extended circumstellar medium with radius ∼10 13 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 56 Ni power the late-time emission. We end by discussing the landscape of XRF-SNe within the context of EP’s recent discoveries.
SN  - 2041-8205
SN  - 2041-8213
ER  -