LSQ14bdq: A Type Ic super-luminous supernova with a double-peaked light curve

TL;DR

This paper analyzes the unique double-peaked light curve of the super-luminous Type Ic supernova LSQ14bdq, proposing a model involving shock cooling and central engine re-energization to explain its features.

Contribution

It introduces a detailed interpretation of the double-peaked light curve of LSQ14bdq, suggesting a combined shock cooling and central engine model, which is novel for this supernova type.

Findings

Initial peak likely from post-shock cooling of extended stellar material.

Main peak possibly powered by a central engine such as a magnetar or black hole.

Progenitor likely a large star, not a compact Wolf-Rayet star.

Abstract

We present data for LSQ14bdq, a hydrogen-poor super-luminous supernova (SLSN) discovered by the La Silla QUEST survey and classified by the Public ESO Spectroscopic Survey of Transient Objects. The spectrum and light curve are very similar to slow-declining SLSNe such as PTF12dam. However, detections within ~1 day after explosion show a bright and relatively fast initial peak, lasting for ~15 days, prior to the usual slow rise to maximum light. The broader, main peak can be fit with either central engine or circumstellar interaction models. We discuss the implications of the precursor peak in the context of these models. It is too bright and narrow to be explained as a normal 56Ni-powered SN, and we suggest that interaction models may struggle to fit the two peaks simultaneously. We propose that the initial peak may arise from the post-shock cooling of extended stellar material, and reheating by a central engine drives the second peak. In this picture, we show that an explosion energy of ~2x10^{52} erg and a progenitor radius of a few hundred solar radii would be required to power the early emission. The competing engine models involve rapidly spinning magnetars (neutron stars) or fall-back accretion onto a central black hole. The prompt energy required may favour the black hole scenario. The bright initial peak effectively rules out a compact Wolf-Rayet star as a progenitor, since the inferred energies and ejected masses become unphysical.