The slow demise of the long-lived SN 2005ip

Abstract

The Type IIn supernova (SN) 2005ip is one of the most well-studied and long-lasting examples of a SN interacting with its circumstellar environment. The optical light curve plateaued at a nearly constant level for more than five years, suggesting ongoing shock interaction with an extended and clumpy circumstellar medium (CSM). Here we present continued observations of the SN from ∼1000 − 5000 days post-explosion at all wavelengths, including X-ray, ultraviolet, near-infrared, and mid-infrared. The UV spectra probe the pre-explosion mass loss and show evidence for CNO processing. From the bolometric light curve, we find that the total radiated energy is in excess of 1050 erg, the progenitor star’s pre-explosion mass-loss rate was $\gtrsim 1 \times 10^{-2}\, {\rm M_{\odot }~ yr}^{-1}$, and the total mass lost shortly before explosion was $\gtrsim 1\, {\rm M_\odot }$, though the mass lost could have been considerably larger depending on the efficiency for the conversion of kinetic energy to radiation. The ultraviolet through near-infrared spectrum is characterised by two high density components, one with narrow high-ionisation lines, and one with broader low-ionisation H I, He I, [O I], Mg II, and Fe II lines. The rich Fe II spectrum is strongly affected by Lyα fluorescence, consistent with spectral modeling. Both the Balmer and He I lines indicate a decreasing CSM density during the late interaction period. We find similarities to SN 1988Z, which shows a comparable change in spectrum at around the same time during its very slow decline. These results suggest that, at long last, the shock interaction in SN 2005ip may finally be on the decline.

Mid-InfraRed Outbursts in Nearby Galaxies (MIRONG). II. Optical Spectroscopic Follow-up

“…Only a subclass of SNe (Type IIn), which shows the signatures of the interaction between the SN ejecta and the circumstellar medium and exhibits obvious Balmer emissions, most notably Hα, with a weak or absent broad absorption component (Schlegel 1990;Filippenko 1997), bears some similarities with our sample. And some objects ,such as SN2010jl (Fransson et al 2014;Moriya et al 2020), SN2015da (Tartaglia et al 2020), SN2005ip (Stritzinger et al 2012;Fox et al 2020), and SN2006jd (Stritzinger et al 2012), displayed a long-lasting broad Hα with similar line luminosity to our sample and could be accompanied by coronal lines. However, their latetime spectra usually show prominent low-ionization emission lines such as near-infrared Ca II triplets and O Iλ8446, which are completely absent in our spectra.…”

Spitzer’s Last Look at Extragalactic Explosions: Long-term Evolution of Interacting Supernovae

“…Another group of SNe IIn (SNe 2005ip, 2006jd, and 2013L) seem to be a bit fainter during the first ∼2000 days (note, however, that in the first two cases there are no mid-IR data before ∼950 days and ∼1150 days, respectively), but decline more slowly thereafter. In these SNe, the most probable scenario is a large, pre-existing dust shell that is continuously heated by energetic photons generated by ongoing CSM interaction (see, e.g., Fox et al 2010Fox et al , 2011Fox et al , 2020Stritzinger et al 2012;Andrews et al 2017;Taddia et al 2020). Based on this picture, the decline rates of these SNe may hint that the level of CSM interaction continuously decreases in the last years (except in the case of SN 2010mc, which seems to be in a very long "plateau" phase even at ∼3000 days).…”

“…Another example is the Type IIn SN 2005ip, which has also been monitored for quite a long time (∼1000-5000 days; Fox et al 2020). The mid-IR and (soft) X-ray (Katsuda et al 2014;Smith et al 2017) LCs seem to follow similarly decreasing trends, in agreement with the scenario that the primary source of the observed mid-IR flux is warm dust radiatively heated by energetic photons emerging from CSM interaction, and that the shock may be finally reaching the outer extent of the dense CSM shell.…”

The morphology of the ejecta of SN 1987A at 31 years from 1150 to 10000 Å

“…This is supported by the general models of circumstellar interaction in Chevalier & Fransson (1994, 2017, where these lines dominate the cooling of the partially ionized regions in shocked ejecta. They have been observed throughout the evolution of interacting SNe (Fransson et al 2005(Fransson et al , 2014Fox et al 2020), albeit not as late or with the spatial resolution as is doable with SN 1987A. This doublet is indeed the strongest feature in our UV spectrum.…”