SN 2022jli: A Type Ic Supernova with Periodic Modulation of Its Light Curve and an Unusually Long Rise

We present multiwavelength photometry and spectroscopy of SN 2022jli, an unprecedented Type Ic supernovadiscovered in the galaxy NGC 157 at a distance of ≈ 23 Mpc. The multiband light curves reveal many remarkablecharacteristics. Peaking at a magnitude of g = 15.11 ± 0.02, the high-cadence photometry reveals periodicundulations of 12.5 ± 0.2 days superimposed on the 200-day supernova decline. This periodicity is observed in thelight curves from nine separate filter and instrument configurations with peak-to-peak amplitudes of ; 0.1 mag.This is the first time that repeated periodic oscillations, over many cycles, have been detected in a supernova lightcurve. SN 2022jli also displays an extreme early excess that fades over ≈25 days, followed by a rise to a peakluminosity of Lopt = 1042.1 erg s−1. Although the exact explosion epoch is not constrained by data, the time fromexplosion to maximum light is  59 days. The luminosity can be explained by a large ejecta mass (Mej ≈ 12 ±6 Me) powered by 56Ni, but we find it difficult to quantitatively model the early excess with circumstellarinteraction and cooling. Collision between the supernova ejecta and a binary companion is a possible source of thisemission. We discuss the origin of the periodic variability in the light curve, including interaction of the SN ejectawith nested shells of circumstellar matter and neutron stars colliding with binary companions.