The effects of a magnetar engine on the gamma-ray burst-associated supernovae: Application to double-peaked SN 2006aj

TL;DR

This study models how a magnetar engine influences supernova emissions associated with long gamma-ray bursts, successfully explaining the double-peaked light curves of SN 2006aj and supporting the magnetar's role in GRB phenomena.

Contribution

The paper presents a detailed model linking magnetar engine effects to supernova light curves, especially explaining the double peaks in SN 2006aj, and constrains the magnetar's magnetic field strength.

Findings

The first light curve peak is due to shock breakout from the magnetar wind.

Magnetar energy injection partly powers the supernova emission.

Late UV excess may be caused by pulsar wind nebula emission leakage.

Abstract

A millisecond magnetar engine has been widely suggested to exist in gamma-ray burst (GRB) phenomena, in view of its substantial influences on the GRB afterglow emission. In this paper, we investigate the effects of the magnetar engine on the supernova (SN) emission which is associated with long GRBs and, specifically, confront the model with the observational data of SN 2006aj/GRB 060218. SN 2006aj is featured by its remarkable double-peaked ultraviolet-optical (UV-opt) light curves. By fitting these light curves, we demonstrate that the first peak can be well accounted for by the breakout emission of the shock driven by the magnetar wind, while the primary supernova emission is also partly powered by the energy injection from the magnetar. The magnetic field strength of the magnetar is constrained to be $\sim 10^{15}$ G, which is in good agreement with the common results inferred from the afterglow emission of long GRBs. In more detail, it is further suggested that the UV excess in the late emission of the supernova could also be due to the leakage of the non-thermal emission of the pulsar wind nebula (PWN), if some special conditions can be satisfied. The consistency between the model and the SN 2006aj observation indicates that the magnetar engine is likely to be ubiquitous in the GRB phenomena and even further intensify their connection with the phenomena of superluminous supernovae.