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Abstract We present and analyze the extensive optical broadband photometry of the Type II SN 2023ixf up to 1 yr after explosion. We find that, when compared to two preexisting model grids, the bolometric light curve is consistent with drastically different combinations of progenitor and explosion properties. This may be an effect of known degeneracies in Type IIP light-curve models. We independently compute a large grid ofMESA+STELLAsingle-star progenitor and light-curve models with various zero-age main-sequence masses, mass-loss efficiencies, and convective efficiencies. Using the observed progenitor variability as an additional constraint, we select stellar models consistent with the pulsation period and explode them according to previously established scaling laws to match plateau properties. Our hydrodynamic modeling indicates that SN 2023ixf is most consistent with a moderate-energy ( $E_{\exp }\approx 7\times 10^{50}$erg) explosion of an initially high-mass red supergiant progenitor (≳16.5M_⊙) that lost a significant amount of mass in its prior evolution, leaving a low-mass hydrogen envelope (≲3M_⊙) at the time of explosion, with a radius ≳950R_⊙and a synthesized⁵⁶Ni mass of ≈0.068M_⊙. We posit that previous mass transfer in a binary system may have stripped the envelope of SN 2023ixf’s progenitor. The analysis method with pulsation period presented in this work offers a way to break degeneracies in light-curve modeling in the future, particularly with the upcoming Vera C. Rubin Observatory Legacy Survey of Space and Time, when a record of progenitor variability will be more common. 

Abstract We present the discovery of an exceptional dimming event in a cool supergiant star in the Local Volume spiral M51. The star, dubbed M51-DS1, was found as part of a Hubble Space Telescope (HST) search for failed supernovae (SNe). The supergiant, which is plausibly associated with a very young (≲6 Myr) stellar population, showed clear variability (amplitude ΔF814W≈ 0.7 mag) in numerous HST images obtained between 1995 and 2016, before suddenly dimming by >2 mag inF814Wsometime between late 2017 and mid-2019. In follow-up data from 2021, the star rebrightened, ruling out a failed supernova. Prior to its near-disappearance, the star was luminous and red (M_F814W≲ − 7.6 mag,F606W−F814W= 1.9–2.2 mag). Modeling of the pre-dimming spectral energy distribution of the star favors a highly reddened, very luminous ( $\log \left[L/L_{\odot }\right]=5.4$–5.7) star withT_eff≈ 3700–4700 K, indicative of a cool yellow or post-red supergiant (RSG) with an initial mass of ≈26–40M_⊙. However, the local interstellar extinction and circumstellar extinction are uncertain, and could be lower: the near-IR colors are consistent with an RSG, which would be cooler (T_eff≲ 3700 K) and slightly less luminous ( $\log \left[L/L_{\odot }\right]=5.2$–5.3), giving an inferred initial mass of ≈19–22M_⊙. In either case, the dimming may be explained by a rare episode of enhanced mass loss that temporarily obscures the star, potentially a more extreme counterpart to the 2019–2020 “Great Dimming” of Betelgeuse. Given the emerging evidence that massive evolved stars commonly exhibit variability that can mimic a disappearing star, our work highlights a substantial challenge in identifying true failed SNe. 

Abstract We analyze pre-explosion near- and mid-infrared (IR) imaging of the site of SN 2023ixf in the nearby spiral galaxy M101 and characterize the candidate progenitor star. The star displays compelling evidence of variability with a possible period of ≈1000 days and an amplitude of Δm≈ 0.6 mag in extensive monitoring with the Spitzer Space Telescope since 2004, likely indicative of radial pulsations. Variability consistent with this period is also seen in the near-IRJandK_sbands between 2010 and 2023, up to just 10 days before the explosion. Beyond the periodic variability, we do not find evidence for any IR-bright pre-supernova outbursts in this time period. The IR brightness ( $M_{K_s}=-10.7$mag) and color (J−K_s= 1.6 mag) of the star suggest a luminous and dusty red supergiant. Modeling of the phase-averaged spectral energy distribution (SED) yields constraints on the stellar temperature ( $T_{\mathrm{eff}}={3500}_{-1400}^{+800}$K) and luminosity ( $\log L/L_{\odot }=5.1\pm 0.2$). This places the candidate among the most luminous Type II supernova progenitors with direct imaging constraints, with the caveat that many of these rely only on optical measurements. Comparison with stellar evolution models gives an initial mass ofM_init= 17 ± 4M_⊙. We estimate the pre-supernova mass-loss rate of the star between 3 and 19 yr before explosion from the SED modeling at $\dot{M}\approx 3\times {10}^{-5}$to 3 × 10⁻⁴M_⊙yr⁻¹for an assumed wind velocity ofv_w= 10 km s⁻¹, perhaps pointing to enhanced mass loss in a pulsation-driven wind.