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SN 2023ixf in Messier 101: A Variable Red Supergiant as the Progenitor Candidate to a Type II Supernova

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We present preexplosion optical and infrared (IR) imaging at the site of the type II supernova (SN II) 2023ixf in Messier 101 at 6.9 Mpc. We astrometrically registered a ground-based image of SN 2023ixf to archival Hubble Space Telescope (HST), Spitzer Space Telescope (Spitzer), and ground-based near-IR images. A single point source is detected at a position consistent with the SN at wavelengths ranging from HST R band to Spitzer 4.5 μm. Fitting with blackbody and red supergiant (RSG) spectral energy distributions (SEDs), we find that the source is anomalously cool with a significant mid-IR excess. We interpret this SED as reprocessed emission in a 8600 R⊙ circumstellar shell of dusty material with a mass ∼5 × 10−5M⊙ surrounding a log(L/L)=4.74±0.07 and Teff=3920−160+200 K RSG. This luminosity is consistent with RSG models of initial mass 11 M⊙, depending on assumptions of rotation and overshooting. In addition, the counterpart was significantly variable in preexplosion Spitzer 3.6 and 4.5 μm imaging, exhibiting ∼70% variability in both bands correlated across 9 yr and 29 epochs of imaging. The variations appear to have a timescale of 2.8 yr, which is consistent with κ-mechanism pulsations observed in RSGs, albeit with a much larger amplitude than RSGs such as α Orionis (Betelgeuse).



5109 Space Sciences, 51 Physical Sciences

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Astrophysical Journal Letters

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IOP Publishing
European Commission Horizon 2020 (H2020) ERC (101002652)
European Commission Horizon 2020 (H2020) Marie Sk?odowska-Curie actions (873089)