Journal article
EP250827b/SN 2025wkm: An X-Ray Flash-supernova Powered by a Central Engine and Circumstellar Interaction
Astrophysical journal. Letters, v 1006(2), pL36
01 Aug 2026
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Abstract
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 ∼1045 erg s−1, lasts over 1000 s, and has a peak energy Ep < 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 ≳1050 erg assuming a typical LGRB circumburst constant density (n ≈ 10−3–10−1 cm−3) and microphysical parameters (ϵe = 0.1 and ϵB = 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 ∼1013 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 56Ni power the late-time emission. We end by discussing the landscape of XRF-SNe within the context of EP’s recent discoveries.
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- Title
- EP250827b/SN 2025wkm: An X-Ray Flash-supernova Powered by a Central Engine and Circumstellar Interaction
- Creators
- Gokul P Srinivasaragavan - University of Maryland, College ParkDongyue Li - Chinese Academy of SciencesXander J Hall - Carnegie Mellon UniversityOre Gottlieb - Kavli Institute for Particle Astrophysics and CosmologyGenevieve Schroeder - Cornell UniversityHeyang LiuBrendan O’Connor - Carnegie Mellon UniversityChichuan Jin - Chinese Academy of SciencesMansi Kasliwal - California Institute of TechnologyTomás Ahumada - Cerro Tololo Inter-American ObservatoryQinyu Wu - Chinese Academy of SciencesChristopher L FryerAnnabelle E NiblettDong Xu - Chinese Academy of SciencesMaria Edvige Ravasio - Radboud University NijmegenGrace Daja - Carnegie Mellon UniversityWenxiong Li - Chinese Academy of SciencesShreya Anand - California Institute of TechnologyAnna Y. Q Ho - Cornell UniversityHui Sun - Chinese Academy of SciencesDaniel A Perley - Liverpool John Moores UniversityLin YanEric Burns - Louisiana State UniversityS. Bradley Cenko - Goddard Space Flight CenterJesper Sollerman - Stockholm UniversityNikhil Sarin - University of CambridgeAnthony L Piro - Carnegie Institution for ScienceAmar Aryan - National Central UniversityM. Coleman Miller - University of Maryland, College ParkJie An - Chinese Academy of SciencesTao An - Chinese Academy of SciencesMoira Andrews - Las Cumbres Observatory Global Telescope NetworkJule AugustinEric C Bellm - University of WashingtonAleksandra Bochenek - Liverpool John Moores UniversityMalte Busmann - Excellence Cluster OriginsKrittapas Chanchaiworawit - National Astronomical Research Institute of ThailandHuaqing ChengMaria D Caballero-García - Instituto de Astrofísica de AndalucíaAlberto J Castro-Tirado - Instituto de Astrofísica de AndalucíaAli Esamdin - Chinese Academy of SciencesJennifer Fabá-MorenoJoseph Farah - Las Cumbres Observatory Global Telescope NetworkEmilio Fernández-García - Instituto de Astrofísica de AndalucíaShaoyu FuJohan P. U Fynbo - University of CopenhagenJulius GassertEstefania Padilla GonzalezIgnacio Pérez-García - Instituto de Astrofísica de AndalucíaMatthew Graham - California Institute of TechnologyMaria Gritsevich - University of HelsinkiDaniel Gruen - Excellence Cluster OriginsSergiy Guziy - Instituto de Astrofísica de AndalucíaLinbo HeD. Andrew Howell - Las Cumbres Observatory Global Telescope NetworkJingwei Hu - Chinese Academy of SciencesYou-Dong HuAbdusamatjan Iskandar - Chinese Academy of SciencesJoahan Castaneda JaimesJi-An Jiang - University of Science and Technology of ChinaNing Jiang - University of Science and Technology of ChinaShuaiqing Jiang - Chinese Academy of SciencesRunduo Liang - Chinese Academy of SciencesZhixing Ling - Chinese Academy of SciencesJialian Liu - Tsinghua UniversityXing Liu - Chinese Academy of SciencesYuan Liu - Chinese Academy of SciencesFrank J Masci - California Institute of TechnologyCurtis McCully - Las Cumbres Observatory Global Telescope NetworkMegan Newsome - Las Cumbres Observatory Global Telescope NetworkKanthanakorn Noysena - National Astronomical Research Institute of ThailandShashi B. PandeyKangrui Ni - Central China Normal UniversityAntonella Palmese - Carnegie Mellon UniversityHan-Long Peng - Nanjing Normal UniversityJosiah Purdum - California Institute of TechnologyYu-Jing Qin - California Institute of TechnologySam Rose - California Institute of TechnologyBen Rusholme - California Institute of TechnologyRubén Sánchez-Ramírez - Instituto de Astrofísica de AndalucíaCassie SevillaRoger Smith - California Institute of TechnologyYujia Song - Chinese Academy of SciencesNiharika Sravan - Drexel UniversityRobert Stein - Goddard Space Flight CenterConstantin TaborGiacomo Terreran - Adler PlanetariumSamaporn Tinyanont - National Astronomical Research Institute of ThailandPablo VegaLetian Wang - Chinese Academy of SciencesTinggui WaingXiaofeng Wang - Tsinghua UniversitySiyu Wu - Instituto de Astrofísica de AndalucíaXuefeng WuKathryn Wynn - Las Cumbres Observatory Global Telescope NetworkYunfei Xu - Chinese Academy of SciencesShengyu Yan - Tsinghua UniversityWeimin Yuan - Chinese Academy of SciencesBinbin ZhangChen Zhang - Chinese Academy of SciencesZipei Zhu - Chinese Academy of SciencesXiaoxiong Zuo - Chinese Academy of SciencesGursimran Bhullar
- Publication Details
- Astrophysical journal. Letters, v 1006(2), pL36
- Publisher
- IOP Publishing
- Number of pages
- 30
- Grant note
- MOE divided by (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic) divided by Program for Changjiang Scholars and Innovative Research Team in University ((sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)): 11-YSFMS-0008-001- P1 Deutsche Forschungsgemeinschaft (DFG): EXC-2094 390783311 Chinese Academy of Sciences (CAS): XDB0550200) MOST divided by National Natural Science Foundation of China (NSFC): 12473016 Tianshan Talent Training Program: 2023TSYCLJ0053 EC divided by European Research Council (ERC): 101095973 National Science Foundation (NSF): AST- 2308113 NASA divided by GSFC divided by Astrophysics Science Division (ASD): 80GSFC24M0006 MOST divided by National Key Research and Development Program of China (NKPs): 2022YFA1602902 National Astronomical Research Institute of Thailand (NARIT): TRTC12C 001 National Science and Technology Council (NSTC): 114-2112-M-008-021-MY3 (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic) divided by Natural Science Foundation of Xinjiang Uygur Autonomous Region (Xinjiang Natural Science Foundation): 2024D01D32
G.P.S. acknowledges Kaustav K. Das for useful conversations about understanding CSM interaction in stripped-envelope SNe, and Jillian Rastinejad for compiling the LCs presented in Figure 15. G.P.S. thanks the ZTF and EP publication boards for their useful comments on the manuscript prior to submission, along with the anonymous referee for their comments and suggestions. G.P.S. acknowledges Simi Bhullar for her moral support through the paper writing process and through G.P.S's postdoc application season. Though she is an attorney and not a scientist in the field, she is on the author list for bringing to life the artistic depiction shown in Figure 16. G.P.S. acknowledges the players on the Caltech Men's Basketball team - Josh Balami, Finnegan Fancher, Stuart Florescu, Ido Geffen, Dagemawi Getachew, Dorian Glogovac, Pranit Gunjal, Noah Hicks, Robert Jackson, Andrew Koclanes, Ryan Rodrigue, Chase Williamson, and coaches Dr. Oliver Eslinger and Seamus McKiernan. Their energy and commitment during the beginning of the 2025-2026 season made practices a welcome outlet for assistant coach G.P.S. to recharge after long days and nights of paper writing and postdoc applications.
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- Physics
- Web of Science ID
- WOS:001827839300001
- Other Identifier
- 991022197369104721