Very late-time spectroscopy of SN 2009ip: Constraints on the ongoing H emission

Context. The peculiar supernova (SN) 2009ip was an ambiguous event that placed many questions on its true origin. Here, we present very late-time spectroscopic and photometric observations of SN 2009ip, obtained 9 years (3274 days) after the 2012B outburst. Aims. We analyze the Hff emission still present in the very late-time spectrum of SN 2009ip. We also obtain photometric measurements in r, g and i bands. Methods. We obtain observations of SN 2009ip on 2021 September 10 with the IMACS instrument at the 6.5m Magellan Baade Telescope, located at the Las Campanas Observatory. Results. SN 2009ip was detected in r, g and i bands, with an absolute magnitude in r band of similar to-8:66 mag. We show that the source faded significantly since the last observations in these bands. We further show that the very late-time spectrum contains a persistent Hff emission, although no other emission lines were detected. We measure a full width at half maximum of 930 +/- 40 km s(-1) and luminosity of similar to 8:0 +/- 1037 erg s(-1) for the H alpha emission. The luminosity decreased relatively slowly in comparison to the last observations and its fading rate is very similar to other long-living interacting transients, such as SN 2005ip. Finally, we conclude that although these properties could be consistent with a non-regular core-collapse SN, they could also be explained by non-terminal explosion scenarios.