SN 2019zrk, a bright SN 2009ip analog with a precursor

We present photometric and spectroscopic observations of the Type IIn supernova SN 2019zrk (also known as ZTF 20aacbyec). The SN shows a > 100 day precursor, with a slow rise, followed by a rapid rise to M ≈ -19.2 in the r and g bands. The post-peak light-curve decline is well fit with an exponential decay with a timescale of ~39 days, but it shows prominent undulations, with an amplitude of ~1 mag. Both the light curve and spectra are dominated by an interaction with a dense circumstellar medium (CSM), probably from previous mass ejections. The spectra evolve from a scattering-dominated Type IIn spectrum to a spectrum with strong P-Cygni absorptions. The expansion velocity is high, ~16000 km s^-1, even in the last spectra. The last spectrum ~110 days after the main eruption reveals no evidence for advanced nucleosynthesis. From analysis of the spectra and light curves, we estimate the mass-loss rate to be ~4×10^-2M_⊙ yr^-1 for a CSM velocity of 100 km s^-1, and a CSM mass of 1M_⊙. We find strong similarities for both the precursor, general light curve, and spectral evolution with SN 2009ip and similar SNe, although SN 2019zrk displays a brighter peak magnitude. Different scenarios for the nature of the 09ip-class of SNe, based on pulsational pair instability eruptions, wave heating, and mergers, are discussed.