Discovery of a Variable Yellow Supergiant Progenitor for the Type IIb SN 2024abfo

<jats:title>Abstract</jats:title>
<jats:p>We report the discovery of a progenitor candidate for the Type IIb SN 2024abfo using multiepoch pre-explosion images from the Hubble Space Telescope and the Dark Energy Camera Legacy Survey. The progenitor exhibited a ∼0.7 mag decline in F814W from 2001 to 2013, followed by significant brightening and color fluctuations in the <jats:italic>g</jats:italic>, <jats:italic>r</jats:italic>, and <jats:italic>z</jats:italic> bands. This is the first time that substantial photometric variability has been found for the progenitor of a SN IIb. We suggest that the variability is caused by intrinsic changes in the progenitor star instead of varying obscuration by circumstellar dust. Our results show that the progenitor of SN 2024abfo was likely a yellow supergiant star with an initial mass of 12–18 <jats:italic>M</jats:italic>
<jats:sub>⊙</jats:sub> for circumstellar reddening of <jats:italic>E</jats:italic>(<jats:italic>B</jats:italic> − <jats:italic>V</jats:italic>)<jats:sub>CSM</jats:sub> < 0.2 mag. Our study underscores the critical role of multiepoch imaging surveys in revealing the final stages of core-collapse supernovae progenitors.</jats:p>