We present the discovery and analysis of SN 2022oqm, a Type Ic supernova (SN) detected < 1 day after explosion. The SN rises to a blue and short-lived (2 days) initial peak. Early spectral observations of SN 2022oqm show a hot (40,000 K) continuum with high-ionization C and O absorption features at velocities of 4,000 km s −1 , while its photospheric radius expands at 20,000 km s −1 , indicating a pre-existing distribution of expanding C/O material, likely ejected ∼ 2 weeks before the explosion. After ∼ 2.5 days, both the spectrum and light curves evolve into those of a typical SN Ic, with line velocities of 10, 000 km s −1 , in agreement with the photospheric radius evolution. The optical light curves reach a second peak around t ∼ 15 days. By t = 60 days, the spectrum of SN 2022oqm becomes nearly nebular, displaying strong Ca II and [Ca II] emission with no detectable [O I] and marking this event as Ca-rich. The early behavior can be explained by 10 −3 M of optically thin circumstellar material (CSM) surrounding either (1) a massive compact progenitor such as a Wolf-Rayet star, (2) a massive stripped progenitor with an extended envelope, or (3) a binary system with a white dwarf. We propose that the early-time light curve is powered by a combination of interaction of the ejecta with the optically thin CSM and shock cooling (in the massive-star scenario), until the radioactive decay of 56 Ni becomes the dominant power source. The observations can be explained by CSM that is optically thick to X-ray photons which are down converted, is optically thick in the lines as seen in the spectra, and is optically thin to visible-light continuum photons that come either from down-converted X-rays or from the shock-heated ejecta. Calculations show that this scenario is self-consistent.
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