A Natural ≳100× Telescope: Discovery of the Strongly Lensed Type II SN 2025mkn at z = 1.37

Lemon, C; Goobar, A; Johansson, J; Mörtsell, E; Schulze, S; Andreoni, I; Bochenek, A; Brennan, SJ; Busmann, M; Coughlin, M; Das, KK; Dhawan, S; Fremling, C; Gangopadhyay, A; Gruen, D; Hall, XJ; Ho, AYQ; Kasliwal, MM; Perley, DA; Rigault, M; Schroeder, G; Smith, M; Sollerman, J; Somalwar, JJ; Stein, R; Thorp, S; Townsend, A; Wise, JL; Yan, L; Arendse, N; Bellm, EC; Chen, TX; Drake, A; Masci, FJ; Purdum, J; Smith, R; Hinkle, JT; Rivera-Thorsen, TE; Shappee, BJ; Tucker, MA; Aguilar, J; Ahlen, S; Aldering, G; BenZvi, S; Bianchi, D; Brooks, D; Claybaugh, T; de la Macorra, A; Della Costa, J; Dey, A; Doel, P; Flaugher, B; Font-Ribera, A; Forero-Romero, JE; Gaztañaga, E; Gontcho A. Gontcho, S; Gutierrez, G; Huterer, D; Ishak, M; Jimenez, J; Joyce, D; Juneau, S; Kehoe, R; Kim, AG; Kirkby, D; Kisner, T; Kremin, A; Lahav, O; Landriau, M; Le Guillou, L; Levi, ME; Manera, M; Meisner, A; Miquel, R; Moustakas, J; Nadathur, S; O’Connor, B; Palanque-Delabrouille, N; Palmese, A; Percival, WJ; Pérez-Ràfols, I; Poppett, C; Prada, F; Rossi, G; Sanchez, E; Schlegel, D; Schubnell, M; Shafieloo, A; Silber, J; Sprayberry, D; Tarlé, G; Weaver, BA; Zou, H

A Natural ≳100× Telescope: Discovery of the Strongly Lensed Type II SN 2025mkn at z = 1.37

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Lemon, C ORCID: 0000-0003-2456-9317, Goobar, A ORCID: 0000-0002-4163-4996, Johansson, J ORCID: 0000-0001-5975-290X, Mörtsell, E ORCID: 0000-0002-8380-6143, Schulze, S ORCID: 0000-0001-6797-1889, Andreoni, I ORCID: 0000-0002-8977-1498, Bochenek, A ORCID: 0009-0008-2714-2507, Brennan, SJ ORCID: 0000-0003-1325-6235, Busmann, M ORCID: 0009-0001-0574-2332, Coughlin, M ORCID: 0000-0002-8262-2924, Das, KK ORCID: 0000-0001-8372-997X, Dhawan, S ORCID: 0000-0002-2376-6979, Fremling, C ORCID: 0000-0002-4223-103X, Gangopadhyay, A ORCID: 0000-0002-3884-5637, Gruen, D ORCID: 0000-0003-3270-7644, Hall, XJ ORCID: 0000-0002-9364-5419, Ho, AYQ ORCID: 0000-0002-9017-3567, Kasliwal, MM ORCID: 0000-0002-5619-4938, Perley, DA ORCID: 0000-0001-8472-1996, Rigault, M ORCID: 0000-0002-8121-2560 et al (2026) A Natural ≳100× Telescope: Discovery of the Strongly Lensed Type II SN 2025mkn at z = 1.37. The Astrophysical Journal Letters, 1003 (2). L47-L47. ISSN 2041-8205

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Publisher URL: https://doi.org/10.3847/2041-8213/ae6780

Abstract

We present the discovery of SN2025mkn, a gravitationally lensed Type II supernova. First detected as a blue transient in Zwicky Transient Facility (ZTF), 0". 83 from a z = 0.42 elliptical galaxy, the follow-up SNIFS/ UH2.2m and LRIS/Keck spectra revealed absorption lines at z = 1.371. Later JWST NIRCam imaging shows that the bright transient is a close pair of point sources separated by ~0".07 , and a 30 times fainter counterimage opposite the lens, for which NIRSpec reveals strong Hα emission also at z = 1.371. The lightcurves and spectra are consistent with the Type II supernova source being magnified ≳100 times, with ∼250 required to reconcile its luminosity with that of nearby events such as SN2023ixf. Lens models are consistent with such high magnifications, and always show that the faint image arrived first (undetected in earlier ZTF imaging), consistent with the later spectral phase of this fainter image. A fourth image is also predicted and possibly detected in the NIRSpec data. Lightcurve-based time-delay measurements are not possible due to the first image being the faintest; however, the resolved NIRSpec spectra offer a future opportunity for time-delay cosmography through supernova phase measurements.

Item Type:	Article
Uncontrolled Keywords:	5101 Astronomical Sciences; 51 Physical Sciences; 0201 Astronomical and Space Sciences; Astronomy & Astrophysics; 5101 Astronomical sciences; 5109 Space sciences
Subjects:	Q Science > QB Astronomy
Divisions:	Astrophysics Research Institute
Publisher:	American Astronomical Society
Date of acceptance:	20 April 2026
Date of first compliant Open Access:	10 June 2026
Date Deposited:	10 Jun 2026 08:33
Last Modified:	10 Jun 2026 08:33
DOI or ID number:	10.3847/2041-8213/ae6780
URI:	https://researchonline.ljmu.ac.uk/id/eprint/28792

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