Paper

Late-time Hubble Space Telescope Ultraviolet Spectra of SN 2023ixf and SN 2024ggi Show Ongoing Interaction with Circumstellar Material

Filippenko, Alexei V, Janzen, Daryl, Meza Retamal, Nicolas E, Dessart, Luc, Pearson, Jeniveve, Kwok, Lindsey A, Andrews, Jennifer E, Griffin Hosseinzadeh, Terreran, Giacomo, Ravi, Aravind P, Hsu, Brian, Jacobson-Galan, W V, Franz, Noah, Howell, D Andrew, Subrayan, Bhagya M, Sand, David J, Dong, Yize, Gill, Kiranjyot, McCully, Curtis, Smith, Nathan, Farah, Joseph, Padilla-Gonzalez, Estefania, Collin, Christy, Martas, Aidan, Mehta, Darshana, Newsome, Megan, Jencson, Jacob E, Valenti, Stefano, Shrestha, Manisha, Jha, Saurabh W, Hoang, Emily T, Lundquist, Michael, Andrews, Moira, Bostroem, K Azalee

2025

Overview

We present far- and near-ultraviolet (UV) spectra of the Type II supernovae (SNe) SN~2023ixf from days 199 to 722 and SN~2024ggi at days 41 and 232. Both supernovae show broad, blueshifted, and asymmetric UV emission lines with an initial maximum velocity of \\(\\sim9000\\,km\\,s^{-1}\\) and narrow unresolved emission in CIV. We compare the optical and UV emission-line profiles, showing that they evolve from two distinct velocity profiles to a single profile tracing the UV emission. We interpret this as shock power from interaction with circumstellar material coming to dominate over the radioactive-decay power from the inner ejecta. Comparing our observations to radiative transfer models with injected shock power, we find SN~2024ggi is best matched by \\(P_{\\mathrm{shock, abs}}=1\\times10^{41}\\,erg\\,s^{-1}\\) at day 40, SN~2023ixf at day 300 and SN~2024ggi at day 200 are best matched by \\(P_{\\mathrm{shock,abs}}=1\\times10^{40}\\,erg\\,s^{-1}\\), and SN~2023ixf at day 600 is best matched by \\(P_{\\mathrm{shock,abs}}=5\\times10^{39}\\,erg\\,s^{-1}\\). From these models, we find the mass-loss rate of both supernovae increased just before explosion. For SN~2023ixf our mass-loss rates go from \\(4\\times10^{-5}\\,M_{\\odot}\\,yr^{-1}\\) at 600 yr before explosion to \\(2\\times10^{-2}\\,M_{\\odot}\\,yr^{-1}\\) at 15 yr prior to explosion. For SN~2024ggi, we find a mass-loss rate of \\(9\\times10^{-5}\\,M_{\\odot}\\,yr^{-1}\\) at 150 yr before explosion and \\(1\\times10^{-3}\\,M_{\\odot}\\,yr^{-1}\\) at 30 yr before explosion.

• Publisher: Cornell University Library, arXiv.org
• Subject: Ejecta / Explosions / Radiative transfer / Radioactive tracers / Space telescopes / Supernovae / Ultraviolet astronomy / Ultraviolet emission / Ultraviolet spectra / Velocity distribution