SN 2023rve: A Type II Supernova with No Nebular Oxygen

We report on multiband photometric and spectroscopic observations of SN 2023rve, a nearby Type II supernova (SN II) discovered in galaxy NGC 1097 (D= 15.4 plus or minus 3.2 Mpc). Nearby SNe II provide constraints on late-stage evolution and progenitor mass loss, particularly the role of circumstellar material (CSM) in shaping SN II observables. SN 2023rve peaks with an absolute V-band magnitude of-17.1 and declines at a rate of 0.90 plus or minus 0.02 mag/50 days during the plateau. The bolometric light curve implies a 56 Ni mass of 0.0064 M. Using hydrodynamic light-curve modeling, we infer an intermediate-mass progenitor (14-18 M), a low explosion energy of 0.27 times 10 51 ergs, and a dense CSM component with radial extent of 2900 R and density of 10 18 g cm-1. This supports growing evidence that enhanced pre-SN mass loss influences the diversity of SNe II. The nebular spectra of SN 2023rve show narrow He I lines and an absence of [O I] lines unprecedented among Type II SNe. Comparison with other SNe II shows that only two other known objects, both with higher velocities, lack oxygen signatures at similar epochs, <10% of the sample. The lack of oxygen emission combined with low explosion energy, a long plateau, and a small synthesized nickel mass may be consistent with partial fallback of material onto the compact remnant. We also discuss alternative explanations for the suppressed oxygen emission, including dust formation, oxygen-calcium mixing, and ongoing CSM interaction.