SN 2024iss: A Multiwavelength Exposé of a Type IIb Supernova with an Early-time Ultraviolet Spectrum and Shock-breakout Constraints
Abstract
Abstract We present multiwavelength observations and analysis of SN 2024iss, a Type IIb supernova (SN IIb) located at ∼14 Mpc. The first Zwicky Transient Facility detection of SN 2024iss is ∼40 minutes after first light (one of the earliest detections of a SN IIb to date) and a Hubble Space Telescope (HST) UV spectrum was obtained at 7 days (the earliest HST UV SN IIb spectrum to date). We estimate an ejecta mass range of 1.1–3.3 M ⊙ and a 56 Ni mass of 0.11 ± 0.01 M ⊙ from bolometric light-curve modeling and He-star model comparisons. We fit shock-cooling emission models to estimate a progenitor radius of 100–320 R ⊙ and an envelope mass of 0.07–0.46 M ⊙ . We compare optical/UV spectra to binary progenitor models, which indicate a stripped H-rich envelope mass of 0.19–0.28 M ⊙ . We use early-time X-ray detections to calculate circumstellar material (CSM) densities that are consistent with a progenitor mass-loss rate of 5 × 10 −4 M ⊙ yr −1 ( v w = 100 km s −1 ), corresponding to 2–5 yr preexplosion. In the UV, we observe strong Mg ii emission extending to 15,000 km s −1 as well as weak P Cygni profiles of iron-group elements (e.g., Fe, Ti, Al, Ni) present in outer SN ejecta. The overall spectroscopic evolution of SN 2024iss is comparable to that of SNe IIb, but its increased brightness at peak is influenced by SN ejecta–CSM interaction. Nebular spectroscopy of SN 2024iss at ∼260–412 days reveals multipeaked forbidden-line profiles of O i and Mg i ] indicative of inner ejecta asymmetry and/or clumping. We demonstrate the utility of a rich, multiwavelength data set for constraining the progenitor systems and explosion dynamics of SNe IIb.
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Authors: Rujula Yete, Wynn Jacobson-Galan, Ferdinand Ferdinand, Luc Dessart, Mansi Kasliwal, Kyle Davis, Anthony Piro, Victoria Villar, Igor Andreoni, Katie Auchettl, Kenneth Chambers, Ryan Chornock, Michael Coughlin, David Coulter, Richard Dekany, Ryan J. Foley, Ori D. Fox, Lluís Galbany, Christa Gall, Anjasha Gangopadhyay, Jared A. Goldberg, Gowri Govindaraj, Xinze Guo, Mark Huber, Joahan Castaneda Jaimes, Jenna Karcheski, Ravjit Kaur, Charles D. Kilpatrick, Russ Laher 良主嶺, Natalie LeBaron, Chien-Cheng Lin, Raffaella Margutti, Y. C. Pan, Kishore Patra, Haille Perkins, Pessi PJ, Oleksandra Pyshna, Armin Rest, S. Romagnoli, Steve Schulze, Huei Sears, Aidan Sedgewick, Matthew Siebert, Avinash Singh, Jesper Sollerman, Niharika Sravan, Samaporn Tinyanont, Richard Wainscoat, Qinan Wang, Daniel Warshofsky, Yuhan Yao, Yossef Zenati
Institutions: Johns Hopkins University, The University of Melbourne, University of North Carolina at Chapel Hill, Drexel University, University of Copenhagen, University of Minnesota, Michigan State University, Sorbonne Université, Centre National de la Recherche Scientifique, University of Illinois Urbana-Champaign, Massachusetts Institute of Technology, Rutgers, The State University of New Jersey, National Central University, Weizmann Institute of Science, Stockholm University, University of California System, California Institute of Technology, University of Minnesota System, Institut d'Estudis Espacials de Catalunya, Carnegie Observatories, The Open University, University of Hawaii System, Institute of Space Science - INFLPR Subsidiary, National Astronomical Research Institute of Thailand, Institute of Space Sciences, Space Telescope Science Institute, Miller College, Center for Astrophysics Harvard & Smithsonian, Geophysical Survey, Astrophysics Division