A1 Refereed original research article in a scientific journal
EP250108a/SN 2025kg: A Jet-driven Stellar Explosion Interacting with Circumstellar Material
Authors: Srinivasaragavan, Gokul P.; Hamidani, Hamid; Schroeder, Genevieve; Sarin, Nikhil; Ho, Anna Y. Q.; Piro, Anthony L.; Cenko, S. Bradley; Anand, Shreya; Sollerman, Jesper; Perley, Daniel A.; Maeda, Keiichi; O'Connor, Brendan; Kuncarayakti, Hanindyo; Miller, M. Coleman; Ahumada, Tomas; Vail, Jada L.; Duffell, Paul; Dastidar, Ranadeep; Andreoni, Igor; Bochenek, Aleksandra; Brennan, Sean. J.; Carney, Jonathan; Chen, Ping; Freeburn, James; Gal-Yam, Avishay; Jacobson-Galan, Wynn; Kasliwal, Mansi M.; Li, Jiaxuan; Li, Maggie L.; Sravan, Niharika; Warshofsky, Daniel E.
Publisher: American Astronomical Society
Publishing place: BRISTOL
Publication year: 2025
Journal: Astrophysical Journal Letters
Journal name in source: The Astrophysical Journal Letters
Journal acronym: ASTROPHYS J LETT
Article number: L60
Volume: 988
Issue: 2
Number of pages: 26
ISSN: 2041-8205
eISSN: 2041-8213
DOI: https://doi.org/10.3847/2041-8213/ade870
Web address : https://doi.org/10.3847/2041-8213/ade870
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/499747338
We present optical, radio, and X-ray observations of EP250108a/SN 2025kg, a broad-line Type Ic supernova (SN Ic-BL) accompanying an Einstein Probe (EP) fast X-ray transient at z = 0.176. EP250108a/SN 2025kg possesses a double-peaked optical light curve, and its spectrum transitions from a blue underlying continuum to a typical SN Ic-BL spectrum over time. We fit a radioactive decay model to the second peak of the optical light curve and find SN parameters that are consistent with the SN Ic-BL population, while its X-ray and radio properties are consistent with those of low-luminosity GRB (LLGRB) 060218/SN 2006aj. We explore three scenarios to understand the system's multiwavelength emission: (a) SN ejecta interacting with an extended circumstellar medium (CSM), (b) the shocked cocoon of a collapsar-driven jet choked in its stellar envelope, and (c) the shocked cocoon of a collapsar-driven jet choked in an extended CSM. Models (b) and (c) can explain the optical light curve and are also consistent with the radio and X-ray observations. We favor model (c) because it can self-consistently explain both the X-ray prompt emission and first optical peak, but we do not rule out model (b). From the properties of the first peak in model (c), we find evidence that EP250108a/SN 2025kg interacts with an extended CSM and infer an envelope mass M-e similar to 0.1 M-circle dot and radius R-e similar to 4 x 10(13) cm. EP250108a/SN 2025kg's multiwavelength properties make it a close analog to LLGRB 060218/SN 2006aj and highlight the power of early follow-up observations in mapping the environments of massive stars prior to core collapse
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Funding information in the publication:
G.P.S. thanks Jillian Rastinejad and Rob Eyles-Ferris for useful discussions about the nature of this source. G.P.S. thanks Kaustav K. Das for useful insight about the relationship between the peaks in double-peaked SNe. G.P.S. thanks Simi Bhullar for her moral support during the paper writing process. B.O. is supported by the McWilliams Fellowship at Carnegie Mellon University. K.M. acknowledges support from JSPS KAKENHI grants JP24KK0070 and JP24H01810 and the JSPS Bilateral Joint Research Project (JPJSBP120229923). H.K. was funded by the Research Council of Finland projects 324504, 328898, and 353019. G.P.S. thanks Ehud Nakar for useful discussions regarding the interpretaion of this source.
