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

Abstract

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 Hα 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 6.5 m 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 ∼ − 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 Hα 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 ∼ 8.0 × 1037 erg s−1 for the Hα 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.