The complex circumstellar environment of supernova 2023ixf

Zimmerman, Erez Arie and Irani, I. and Chen, Ping and Gal-Yam, Avishay and Schulze, Steve and Perley, D. A. and Sollerman, Jesper and Filippenko, Alexei and Shenar, Tomer and Yaron, O. and Shahaf, Sahar and Bruch, R. J. and Ofek, E. O. and Cia, A. De and Brink, Thomas G. and Yang, Yi and Vasylyev, S. S. and Ben-Ami, Sagi and Aubert, M. and Badash, Avshalom and Bloom, J. S. and Brown, P. J. and De, Kishalay and Dimitriadis, Georgios and Fransson, C. and Fremling, Christoffer and Hinds, K. and Horesh, Assaf and Johansson, J. P. and Kasliwal, Mansi and Kulkarni, S. R. and Kushnir, D. and Martin, C. and Matuszewski, Mateusz and McGurk, R. C. and Miller, Adam and Morag, J. and Neill, James and Nugent, P. E. and Post, R. S. and Prusinski, Nikolaus and Qin, Y. and Raichoor, A. and Riddle, Reed and Rowe, M. and Rusholme, Benjamin and Sfaradi, Itai and Sjoberg, Kane and Soumagnac, M. and Stein, R. D. and Strotjohann, N. L. and Terwel, J. H. and Wasserman, T. and Wise, Jacob and Wold, A. and Yan, L. and Zhang, Keming (2024) The complex circumstellar environment of supernova 2023ixf. Nature, 627. pp. 759-762. ISSN 0028-0836

Abstract

The early evolution of a supernova (SN) can reveal information about the environment and the progenitor star. When a star explodes in vacuum, the first photons to escape from its surface appear as a brief, hours-long shock-breakout flare1,2, followed by a cooling phase of emission. However, for stars exploding within a distribution of dense, optically thick circumstellar material (CSM), the first photons escape from the material beyond the stellar edge and the duration of the initial flare can extend to several days, during which the escaping emission indicates photospheric heating3. Early serendipitous observations2,4 that lacked ultraviolet (UV) data were unable to determine whether the early emission is heating or cooling and hence the nature of the early explosion event. Here we report UV spectra of the nearby SN 2023ixf in the galaxy Messier 101 (M101). Using the UV data as well as a comprehensive set of further multiwavelength observations, we temporally resolve the emergence of the explosion shock from a thick medium heated by the SN emission. We derive a reliable bolometric light curve that indicates that the shock breaks out from a dense layer with a radius substantially larger than typical supergiants.