A post-perihelion constraint on the CO${}_2$/H${}_2$O ratio of interstellar comet 3I/ATLAS from [O I] forbidden lines

Yoshiharu Shinnaka, Ko Tsujimoto, Hideyo Kawakita +3

We present high-resolution optical spectroscopy of interstellar comet 3I/ATLAS (C/2025 N1) obtained with the High Dispersion Spectrograph mounted on the Subaru Telescope on UT 2026…