Evidence for GeV emission of the superluminous supernova SN 2017egm

TL;DR

This study reports the detection of a GeV gamma-ray transient associated with superluminous supernova SN 2017egm, supporting the hypothesis that a young magnetar acts as the central engine powering such luminous explosions.

Contribution

First evidence of GeV emission from a superluminous supernova, linking gamma-ray signals to the magnetar model for the explosion's energy source.

Findings

Detected a gamma-ray transient 2 months after SN 2017egm

Gamma-ray signal has at least 4σ significance

Emission properties match magnetar model predictions

Abstract

Superluminous supernovae (SLSNe) are a new class of transients with luminosities $\sim10 -100$ times larger than the usual core-collapse supernovae (SNe). Their origin is still unclear and one widely discussed scenario involves a millisecond magnetar central engine. The GeV-TeV emission of SLSNe has been predicted in the literature but has not been convincingly detected yet. Here we report the results of the search for $\gamma$-ray emission in the direction of SN 2017egm, one of the closest SLSNe detected so far, using 15 years of {\it Fermi}-LAT Pass 8 data. There is a transient $\gamma$-ray source appearing about 2 months after this event and lasting a few months. Monte Carlo simulations show that the $\gamma$-ray signal has a global significance of {\it at least} 4$\sigma$. Both the peak time and the luminosity of the GeV emission are consistent with the magnetar model prediction, suggesting that such a GeV transient is the high-energy counterpart of SN 2017egm and the central engine of this SLSNe is a young magnetar.