SN 2023ixf in Messier 101: Photo-ionization of Dense, Close-in Circumstellar Material in a Nearby Type II Supernova
W. V. Jacobson-Galán, Luc Dessart, R. Margutti, R. Chornock, R. J. Foley, C. D. Kilpatrick, D. O. Jones, K. Taggart, C. R. Angus, Snehasish Bhattacharjee, Lila Braff, Daniel Brethauer, Adam J. Burgasser, F. Cao, Colin Carlile, K. C. Chambers, D. A. Coulter, E. Dominguez-Ruiz, C. B. Dickinson, Thomas de Boer, Alexander Gagliano, C. Gall, Hua Gao, E. L. Gates, Sebastián Gómez, Muryel Guolo, Melissa Halford, J. Hjorth, M. E. Huber, M. N. Johnson, Preethi R. Karpoor, T. Laskar, Natalie LeBaron, Zhexing Li, Y. Lin, S. D. Loch, P. Lynam, E. A. Magnier, Philip R. Maloney, David Matthews, M. McDonald, Hao-Yu Miao, D. Milisavljević, Y. C. Pan, S. Pradyumna, C. L. Ransome, Jon M. Rees, A. Rest, C. Rojas-Bravo, Nathan R. Sandford, Loraine Sandoval Ascencio, S. Sanjaripour, Alessandro Savino, Huei Sears, N. Sharei, S. J. Smartt, Emma Softich, Christopher A. Theissen, Samaporn Tinyanont, Hurum Maksora Tohfa, V. Ashley Villar, Qinan Wang, R. J. Wainscoat, A. L. Westerling, Eli Wiston, M. A. Wozniak, S. K. Yadavalli, Yossef Zenati
Abstract
Abstract 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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover accent="true"> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>̇</mml:mo> </mml:mrow> </mml:mover> <mml:mo>=</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> <mml:mspace width="0.25em"/> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> </mml:math> 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.