Late-Onset Energy Injection in Type Ic SNe and W-Shaped O II Absorption in SLSNe-I

TL;DR

This paper presents a model where late energy injection from a quark star formation event explains the luminosity, spectral features, and evolution of hydrogen-poor superluminous supernovae, linking them to neutron star phase transitions.

Contribution

It introduces a novel model involving a neutron star phase transition to quark matter that accounts for the delayed energy injection and spectral features of SLSNe-I, supported by observational data.

Findings

Reproduces light curves and spectra of SLSNe-I

Predicts a systematic age offset between spectroscopic and photometric measurements

Suggests double-peaked SLSNe-I can probe quark-matter microphysics

Abstract

We show that delayed (weeks-months) energy injection into expanding Type Ic supernova (SN) ejecta can reproduce the luminosity and spectral evolution of hydrogen-poor superluminous SNe (SLSNe-I). Late-time reheating sets the radiation temperature and density needed for the W-shaped OII absorption near peak, explaining its disappearance as the ejecta cools without extra excitation mechanisms. In our model, the neutron star (NS) undergoes a core phase transition to deconfined quark matter at time t_QN, triggering rapid magnetic field amplification and forming a hybrid star (HS; a QCD-magnetar). This Quark-Nova (QN) resets the central engine, weeks to months after the SN, by converting the NS rotational energy into renewed energy injection, producing two powering epochs separated by a delay determined by hadron-to-quark microphysics. The model reproduces photometric and spectroscopic evolution of SLSNe-I such as iPTF13ajg, SN2010gx, PTF09cnd, and PTF09atu. We predict a systematic offset between spectroscopic and photometric ages when pre-QN emission is below detection limits, and discuss observational signatures distinguishing QCD-magnetars from standard magnetars. Double-peaked SLSNe-I may probe the hadron-quark transition, constraining quark-matter parameters like deconfinement density and surface tension.