SN 2023ixf in Messier 101: Photo-ionization of Dense, Close-in Circumstellar Material in a Nearby Type II Supernova

We present UV/optical observations and models of supernova (SN) 2023ixf, a type II SN located in Messier 101 at 6.9 Mpc. Early-time ("flash") spectroscopy of SN 2023ixf, obtained primarily at Lick Observatory, reveals emission lines of H I, He I/II, C IV, and N III/IV/V with a narrow core and broad, symmetric wings arising from the photo-ionization of dense, close-in circumstellar material (CSM) located around the progenitor star prior to shock breakout. These electron-scattering broadened line profiles persist for $\sim$8 days with respect to first light, at which time Doppler broadened features from the fastest SN ejecta form, suggesting a reduction in CSM density at $r \gtrsim 10^{15}$ cm. The early-time light curve of SN2023ixf shows peak absolute magnitudes (e.g., $M_{u} = -18.6$ mag, $M_{g} = -18.4$ mag) that are $\gtrsim 2$ mag brighter than typical type II supernovae, this photometric boost also being consistent with the shock power supplied from CSM interaction. Comparison of SN 2023ixf to a grid of light curve and multi-epoch spectral models from the non-LTE radiative transfer code CMFGEN and the radiation-hydrodynamics code HERACLES suggests dense, solar-metallicity, CSM confined to $r = (0.5-1) \times 10^{15}$ cm and a progenitor mass-loss rate of $\dot{M} = 10^{-2}$ M$_{\odot}$yr$^{-1}$. For the assumed progenitor wind velocity of $v_w = 50$ km s$^{-1}$, this corresponds to enhanced mass-loss (i.e., ``super-wind'' phase) during the last $\sim$3-6 years before explosion.Comment: 18 pages, 8 figures. Submitted to ApJ

SN 2023ixf in Messier 101: Photo-ionization of Dense, Close-in Circumstellar Material in a Nearby Type II Supernova

International audienceAbstract We present UV and/or optical observations and models of SN 2023ixf, a type II supernova (SN) located in Messier 101 at 6.9 Mpc. Early time ( flash ) spectroscopy of SN 2023ixf, obtained primarily at Lick Observatory, reveals emission lines of H i , He i/ii , C iv , and N iii/iv/v with a narrow core and broad, symmetric wings arising from the photoionization of dense, close-in circumstellar material (CSM) located around the progenitor star prior to shock breakout. These electron-scattering broadened line profiles persist for ∼8 days with respect to first light, at which time Doppler broadened the features from the fastest SN ejecta form, suggesting a reduction in CSM density at r ≳ 10 15 cm. The early time light curve of SN 2023ixf shows peak absolute magnitudes (e.g., M u = −18.6 mag, M g = −18.4 mag) that are ≳2 mag brighter than typical type II SNe, this photometric boost also being consistent with the shock power supplied from CSM interaction. Comparison of SN 2023ixf to a grid of light-curve and multiepoch spectral models from the non-LTE radiative transfer code CMFGEN and the radiation-hydrodynamics code HERACLES suggests dense, solar-metallicity CSM confined to r = (0.5–1) × 10 15 cm, and a progenitor mass-loss rate of M ̇ = 10 − 2 M ⊙ yr −1 . For the assumed progenitor wind velocity of v w = 50 km s −1 , this corresponds to enhanced mass loss (i.e., superwind phase) during the last ∼3–6 yr before explosion