The early discovery of SN 2017ahn: signatures of persistent interaction in a fast declining Type II supernova

Understand

We present high-cadence, comprehensive data on the nearby ($D\simeq33\,\rm{Mpc}$) Type II SN 2017ahn, discovered within $\sim$1 day of explosion, from the very early phases after explosion to the nebular phase.

• The observables of SN 2017ahn show a significant evolution over the $\simeq470\,\rm{d}$ of our follow-up campaign, first showing prominent, narrow Balmer lines and other high-ionization features purely in emission (i.e.
• flash spectroscopy features), which progressively fade and lead to a spectroscopic evolution similar to that of more canonical Type II supernovae.
• Over the same period, the decline of the light curves in all bands is fast, resembling the photometric evolution of linearly declining H-rich core-collapse supernovae.