Magnetar Flare-driven Bumpy Declining Light Curves in Hydrogen-poor Superluminous Supernovae

Abstract

Recent observations indicate that hydrogen-poor superluminous supernovae (SLSNe-I) often display bumpy declining light curves. However, the cause of these undulations remains unclear. In this paper, we have improved the magnetar model, which includes flare activities. We present a systematic analysis of a well-observed SLSN-I sample with bumpy light curves in their late phase. These SLSNe-I were identified from multiple transient surveys, such as the Pan-STARRS1 Medium Deep Survey and the Zwicky Transient Facility. Our study provides a set of magnetar-powered model light curve fits for five SLSNe-I, which accurately reproduce the observed light curves using reasonable physical parameters. By extracting the essential characteristics of both the explosions and central engines, these fits provide valuable insights into investigating their potential association with gamma-ray burst engines. We found that the SLSN flares tend to be the dim and long extension of GRB flares in the peak luminosity versus peak time plane. Conducting large-scale, high-cadence surveys in the near future could enhance our comprehension of both SLSN undulating light curve properties and their potential relationship with GRBs by modeling their light curve characteristics.

A Swift Fix for Nuclear Outbursts

“…A non-negligible fraction of SLSNe-I show signs of bumps or undulations in their light curves (Nicholl et al 2016;Lunnan et al 2020;Hosseinzadeh et al 2022;West et al 2023). This behavior is not typical of a basic magnetar spin-down model, although some recent work has attempted to extend magnetar models to describe bumpy light curves (Dong et al 2023). Furthermore, some studies have suggested that ∼ 25% of SLSNe-I, particularly those with light curve undulations, can be better described with a H-poor CSM interaction model (Chen et al 2022b).…”

“…A growing number of SLSNe-I exhibit bumps or undulations in their light curves, further confusing the problem. Such light curves are difficult to explain with a magnetar central engine (e.g., Nicholl et al 2017c), although some efforts have been made to extend the magnetar model (Dong et al 2023). Instead, the light curve undulations may be more naturally explained by unstable accretion onto a BH or CSM interactions, although spectral predictions for such models are lacking (e.g., Gal-Yam 2019a).…”

Bumpy Superluminous Supernovae Powered by a Magnetar–Star Binary Engine

“…Alternatively, in the magnetar engine model, the lightcurve bumps can, in principle, be attributed to the intermittent violent energy releases from the magnetar Dong et al 2023) or the variable thermalization efficiency of the injected energy (Vurm & Metzger 2021;Moriya et al 2022), while the general shape of the SLSN lightcurves can usually be successfully modeled by the magnetar spin-down whose temporal behavior scales as L ∝ t −2 (e.g., Inserra et al 2013;Liu et al 2017;Nicholl et al 2017;Blanchard et al 2020). However, the specific mechanism that would cause the significant variation in the energy released by the magnetar is uncertain, though it would presumably be related to the progenitor star and magnetar formation physics.…”