Resurrection of Type IIL Supernova 2018ivc: Implications for a Binary Evolution Sequence Connecting Hydrogen-rich and Hydrogen-poor Progenitors

Long-term observations of synchrotron emission from supernovae (SNe), covering more than a year after the explosion, provide unique opportunity to study poorly-understood evolution massive stars in final millennium their lives via changes mass-loss rate. Here, we present result our long-term monitoring peculiar type IIL SN 2018ivc, using Atacama Large Millimeter/submillimeter Array (ALMA). Following initial decay, it showed unprecedented rebrightening starting at ~ explosion. This is one rare examples showing such emission, and first case millimeter wavelengths. We find be optically-thin regime unlike optically-thick centimeter emission. As such, can robustly reconstruct distribution circumstellar matter (CSM) thus history ~1,000 years. that progenitor 2018ivc had experienced very high rate >~10^{-3} Msun/yr ~1,500 years before which was followed by moderately (>~10^{-4} Msun/yr) up until From this behavior, suggest represents an extreme version binary toward SNe IIb, bridges hydrogen-poor (toward Ib/c, without hydrogen envelope) hydrogen-rich (SNe IIP, with envelope).