A very luminous magnetar-powered supernova associated with an ultra-long gamma-ray burst

TL;DR

This paper reports the discovery of a super-luminous supernova, 2011kl, associated with an ultra-long gamma-ray burst, explained by energy injection from a magnetar, revealing a new link between magnetars and luminous supernovae.

Contribution

It provides the first clear association of a supernova with an ultra-long gamma-ray burst and introduces a magnetar-powered model to explain its extreme luminosity.

Findings

Supernova 2011kl is over 3 times more luminous than typical GRB-associated supernovae.

The supernova's spectrum indicates low metal content and a rapid evolution.

Magnetar energy injection explains the supernova's high luminosity and spectral features.

Abstract

A new class of ultra-long duration (>10,000 s) gamma-ray bursts has recently been suggested. They may originate in the explosion of stars with much larger radii than normal long gamma-ray bursts or in the tidal disruptions of a star. No clear supernova had yet been associated with an ultra-long gamma-ray burst. Here we report that a supernova (2011kl) was associated with the ultra-long duration burst 111209A, at z=0.677. This supernova is more than 3 times more luminous than type Ic supernovae associated with long gamma-ray bursts, and its spectrum is distinctly different. The continuum slope resembles those of super-luminous supernovae, but extends farther down into the rest-frame ultra-violet implying a low metal content. The light curve evolves much more rapidly than super-luminous supernovae. The combination of high luminosity and low metal-line opacity cannot be reconciled with typical type Ic supernovae, but can be reproduced by a model where extra energy is injected by a strongly magnetized neutron star (a magnetar), which has also been proposed as the explanation for super-luminous supernovae.