Variability of Late-time Radio Emission in SLSN PTF10hgi

TL;DR

This study reports the first observed significant variability in late-time radio emission of a superluminous supernova, PTF10hgi, over several years, and explores possible origins including AGN, jet afterglow, or magnetar wind nebula.

Contribution

It provides the first evidence of late-time radio variability in a SLSN and constrains the light curve, offering insights into potential physical mechanisms behind the emission.

Findings

Detected ~40% decrease in radio flux over 2 years.

Radio emission peaks 8-9 years post-explosion.

Models suggest afterglow or magnetar wind nebula as plausible explanations.

Abstract

We report the time variability of the late-time radio emission in a Type-I superluminous supernova (SLSN), PTF10hgi, at z = 0.0987. The Karl G. Jansky Very Large Array 3 GHz observations at 8.6 and 10 years after the explosion both detected radio emission with a ~40% decrease in flux density in the second epoch. This is the first report of a significant variability of the late-time radio light curve in a SLSN. Through combination with previous measurements in two other epochs, we constrained both the rise and decay phases of the radio light curve over three years, peaking at approximately 8-9 years after the explosion with a peak luminosity of L(3GHz) = 2 x 10^21 W/Hz. Possible scenarios for the origin of the variability are an active galactic nucleus (AGN) in the host galaxy, an afterglow caused by the interaction between an off-axis jet and circumstellar medium, and a wind nebula powered by a newly-born magnetar. Comparisons with models show that the radio light curve can be reproduced by both the afterglow model and magnetar wind nebula model. Considering the flat radio spectrum at 1-15 GHz and an upper limit at 0.6 GHz obtained in previous studies, plausible scenarios are a low-luminosity flat-spectrum AGN or a magnetar wind nebula with a shallow injection spectral index.