Unveiling the progenitor of SN 2023ixf: Circumstellar dust and its implications for the red supergiant problem

The nearby Type II supernova SN 2023ixf offers a critical test of the long-standing ‘red supergiant problem’ – the apparent absence of high-mass red-supergiant progenitors in pre-explosion imaging. We present new late-time observations of SN 2023ixf: SiFAP2 photometry (714–772 d) with a custom supernova calibration, Swift -UVOT detections (788–801 d), and the one of the latest spectroscopic observations beyond 100 days (DOLoRES at 772 d). Combining these with archival data, we obtain two discrepant progenitor-mass estimates: light-curve modelling yields 5.5–14 M ⊙ , while nebular oxygen mass (∼2.3 M ⊙ ) and other spectroscopic diagnostics point to 17–19 M ⊙ . We reconcile this tension with a Bayesian Monte-Carlo framework that includes anisotropic circumstellar dust. Our analysis demonstrates that even a modest, clumpy circumstellar medium can produce sufficient extinction to bias luminosity-based masses downwards by ∼9 M ⊙ . Late-time photometry and spectroscopy further reveal clear signatures of shock interaction with circumstellar material (CSM) shells ejected centuries before explosion. SN 2023ixf thus provides direct evidence that circumstellar obscuration is a major contributor to the apparent lack of massive red-supergiant progenitors, underscoring the need for multi-method, multi-epoch observations for robust progenitor-mass determination.