ugriBV phot. & spectra of type II-P SN2019mhm

Based on optical spectroscopy and photometry, we show that SN 2019mhm exhibits broad lines of hydrogen with a velocity of -8500R+/-200km/s and a 111+/-2d extended plateau in its luminosity, typical of the Type II-P subclass. We also fit its late-time bolometric light curve and infer that it initially produced a ^56^Ni mass of 1.3x10^-2^+/-5.5x10^-4^M_{sun}_.

Using imaging from the Wide Field Planetary Camera 2 on the Hubble Space Telescope obtained 19yr before explosion, we aligned to a postexplosion Wide Field Camera 3 image and demonstrate that there is no detected counterpart to the SN to a limit of >24.53mag in F814W, corresponding to an absolute magnitude limit of M_F814W_{<}-7.7mag. Comparing to massive-star evolutionary tracks, we determine that the progenitor star had a maximum zero-age main-sequence mass <17.5M_{sun}_, consistent with other SN II-P progenitor stars.