Extreme Stellar Death and Galaxy Feedback at z = 2: A Rest-frame Ultraviolet Characterization of the Strongly Lensed Superluminous Supernova 2025wny

Willem B. Hoogendam; David O. Jones; Christopher J. Storfer; Luca Izzo; Kyle W. Davis; Miranda Y. Kong; Katie Auchettl; Aadya Agrawal; David R. Aguilera-Dena; Kenneth C. Chambers; Siyuan Chen; Thomas de Boer; Ryan J. Foley; Matthew Grayling; Jason T. Hinkle; Jens Hjorth; Mark E. Huber; Chien-Cheng Lin; Thomas B. Lowe; Eugene A. Magnier; Kaisey S. Mandel; C. Tanner Murphey; Gautham Narayan; Gregory S. H. Paek; Kishore C. Patra; Haille M. L. Perkins; Armin Rest; Benjamin J. Shappee; Richard J. Wainscoat

arXiv · 2610.08903

Extreme Stellar Death and Galaxy Feedback at z = 2: A Rest-frame Ultraviolet Characterization of the Strongly Lensed Superluminous Supernova 2025wny

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Abstract

We present photometric and spectroscopic follow-up observations of the strongly-lensed H-poor superluminous supernova (SLSN) 2025wny at $z = 2.0155$. We use integral-field Keck-II/KCWI spectroscopy to obtain rest-frame ultraviolet spectra spanning $11$ to $61$ days after maximum light. We use Pan-STARRS photometry to constrain the brightest image's magnification, finding $μ_A=19.4\pm1.6$, a factor of $\sim$2-4 higher than mass-modeling estimates. We fit the Pan-STARRS photometry with a magnetar energy-injection model including $^{56}$Ni decay using the Modular Open Source Fitter for Transients (MOSFiT); the model can reproduce the near-maximum light curve with parameters typical of local universe SLSNe-I, including a magnetar spin period $P_{\rm spin}=4.1^{+0.7}_{-1.0}\,\mathrm{ms}$ and magnetic field $B_{\perp}=2.4^{+1.1}_{-0.8}\times10^{14}\,\mathrm{G}$; however, the late-time plateau suggests an additional power source. Spectroscopically, iron-group element line blanketing is virtually absent in the rest-frame UV spectra, and the absorption features match previously identified SLSN-I features from abundance tomography. Based on narrow ISM line metallicity estimates, SN 2025wny exploded in a sub-solar-metallicity galaxy. From host-galaxy lines in our rest-frame UV-to-optical spectrum we estimate high-velocity outflows of $\sim$575 km s$^{-1}$ and an exceptionally high Ly$α$ escape fraction of $f_{esc}^{Lyα}=0.23\pm0.03$. SN 2025wny matches lower-redshift SLSNe reasonably well. Upcoming surveys like LSST and Roman will discover additional high-redshift SLSNe, further testing whether SLSNe-I explosions remain consistent at the population level in the early universe.

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Willem B. Hoogendam, David O. Jones, Christopher J. Storfer, Luca Izzo, Kyle W. Davis, Miranda Y. Kong, Katie Auchettl, Aadya Agrawal, David R. Aguilera-Dena, Kenneth C. Chambers, Siyuan Chen, Thomas de Boer, Ryan J. Foley, Matthew Grayling, Jason T. Hinkle, Jens Hjorth, Mark E. Huber, Chien-Cheng Lin, Thomas B. Lowe, Eugene A. Magnier, Kaisey S. Mandel, C. Tanner Murphey, Gautham Narayan, Gregory S. H. Paek, Kishore C. Patra, Haille M. L. Perkins, Armin Rest, Benjamin J. Shappee, Richard J. Wainscoat. 2026-10-06. Extreme Stellar Death and Galaxy Feedback at z = 2: A Rest-frame Ultraviolet Characterization of the Strongly Lensed Superluminous Supernova 2025wny. https://arxiv.org/abs/2610.08903

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