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We present six epochs of optical spectropolarimetry of the Type II supernova(SN) 2023ixf ranging from $\sim$ 2 to 15 days after the explosion. Polarimetrywas obtained with the Kast double spectrograph on the Shane 3 m telescope atLick Observatory, representing the earliest such observations ever captured foran SN. We observe a high continuum polarization $p_{\text{cont}} \approx 1$ %on days +1.4 and +2.5 before dropping to 0.5 % on day +3.5, persisting at thatlevel up to day +14.5. Remarkably, this change coincides temporally with thedisappearance of highly ionized "flash" features. The decrease of the continuumpolarization is accompanied by a $\sim 70^\circ$ rotation of the polarizationposition angle ($PA$) as seen across the continuum. The early evolution of thepolarization may indicate different geometric configurations of theelectron-scattering atmosphere as seen before and after the disappearance ofthe emission lines associated with highly-ionized species (e.g., He II, C IV, NIII), which are likely produced by elevated mass loss shortly prior to the SNexplosion. We interpret the rapid change of polarization and $PA$ from days+2.5 to +4.5 as the time when the SN ejecta emerge from the dense asymmetriccircumstellar material (CSM). The temporal evolution of the continuumpolarization and the $PA$ is consistent with an aspherical SN explosion thatexhibits a distinct geometry compared to the CSM. The rapid follow-upspectropolarimetry of SN 2023ixf during the shock ionization phase reveals anexceptionally asymmetric mass-loss process leading up to the explosion.

Early-time Spectropolarimetry of the Aspherical Type II Supernova SN 2023ixf