Far-Ultraviolet to Near-Infrared Observations of SN 2023ixf: A high energy explosion engulfed in complex circumstellar material

Abstract: We present early-phase panchromatic photometric and spectroscopic coverage spanning far-ultraviolet (FUV) to the near-infrared (NIR) regime of the nearest hydrogen-rich core-collapse supernova in the last 25 years, SN 2023ixf. We observe early 'flash' features in the optical spectra due to a confined dense circumstellar material (CSM). We observe high-ionization absorption lines (FeII, MgII) in the ultraviolet spectra from very early on. We also observe a multi-peaked emission profile of H-alpha in the spectrum beginning ~16 d, which indicates ongoing interaction of the SN ejecta with a pre-existing shell-shaped CSM having an inner radius of ~75 AU and an outer radius of ~140 AU. The shell-shaped CSM is likely a result of enhanced mass loss ~35-65 years before the explosion assuming a standard Red-Supergiant wind. The UV spectra are dominated by multiple highly ionized narrow absorption features and broad emission features from elements such as C, N, O, Si, Fe, and Ni. Based on early light curve models of Type II SNe, we infer that the nearby dense CSM confined to (7+-3)e14cm (~45 AU) is a result of enhanced mass loss (10^{-3.0+-0.5} Msol/yr) two decades before the explosion.