The Slow Demise of the Long-Lived SN 2005ip

TL;DR

This study provides extensive multi-wavelength observations of supernova SN 2005ip over several years, revealing details about its prolonged shock interaction with circumstellar material and signs of its decline.

Contribution

It offers new insights into the late-time evolution of SN 2005ip, including detailed spectral analysis and estimates of pre-explosion mass loss, highlighting the transition phase of the supernova.

Findings

Total radiated energy exceeds 10^50 erg

Progenitor's pre-explosion mass-loss rate was > 0.01 M_sun/yr

Spectral features indicate decreasing CSM density over time

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 $\sim 1000-5000$ 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 $10^{50}$ 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 Ly$\alpha$ 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.