UBVRI & ugriz photometry of supernova SN 2017gmr

SN 2017gmr does not show signs of narrow, high-ionization emission lines in the early optical spectra, yet the optical light-curve evolution suggests that an extra energy source from circumstellar medium (CSM) interaction must be present for at least 2 days after explosion.

Modeling of the early light curve indicates a ~500R{sun} progenitor radius, consistent with a rather compact red supergiant, and late-time luminosities indicate that up to 0.130{+/-}0.026M{sun} of 56Ni are present, if the light curve is solely powered by radioactive decay, although the 56Ni mass may be lower if CSM interaction contributes to the post-plateau luminosity. Prominent multipeaked emission lines of H{alpha} and [O^I^] emerge after day 154, as a result of either an asymmetric explosion or asymmetries in the CSM.