PTF11rka: an interacting supernova at the crossroads of stripped-envelope and H-poor super-luminous stellar core collapses

TL;DR

PTF11rka is a hydrogen-poor supernova with characteristics bridging stripped-envelope and super-luminous core-collapse supernovae, showing evidence of ejecta interaction with dense circumstellar material and similarities to GRB-associated supernovae.

Contribution

This study presents detailed observations and analysis of PTF11rka, revealing its unique properties and its position at the intersection of different supernova classes, with implications for explosion mechanisms and progenitor environments.

Findings

Ejected ~8 Msun of material with KE ~4 x 10^{51} erg.

Spectra show narrow lines indicating dense circumstellar interaction.

Light curve similar to superluminous SN 2007bi but less luminous and faster.

Abstract

The hydrogen-poor supernova PTF11rka (z = 0.0744), reported by the Palomar Transient Factory, was observed with various telescopes starting a few days after the estimated explosion time of 2011 Dec. 5 UT and up to 432 rest-frame days thereafter. The rising part of the light curve was monitored only in the R_PTF filter band, and maximum in this band was reached ~30 rest-frame days after the estimated explosion time. The light curve and spectra of PTF11rka are consistent with the core-collapse explosion of a ~10 Msun carbon-oxygen core evolved from a progenitor of main-sequence mass 25--40 Msun, that liberated a kinetic energy (KE) ~ 4 x 10^{51} erg, expelled ~8 Msun of ejecta (Mej), and synthesised ~0.5 Msun of 56Nichel. The photospheric spectra of PTF11rka are characterised by narrow absorption lines that point to suppression of the highest ejecta velocities ~>15,000 km/s. This would be expected if the ejecta impacted a dense, clumpy circumstellar medium. This in turn caused them to lose a fraction of their energy (~5 x 10^50 erg), less than 2% of which was converted into radiation that sustained the light curve before maximum brightness. This is reminiscent of the superluminous SN 2007bi, the light-curve shape and spectra of which are very similar to those of PTF11rka, although the latter is a factor of 10 less luminous and evolves faster in time. PTF11rka is in fact more similar to gamma-ray burst supernovae (GRB-SNe) in luminosity, although it has a lower energy and a lower KE/Mej ratio.