# Millisecond Magnetar Birth Connects FRB 121102 to Superluminous Supernovae and Long Duration Gamma-ray Bursts

## TL;DR

This paper proposes that the repeating FRB 121102 originates from a young millisecond magnetar formed in a recent superluminous supernova or gamma-ray burst, linking these phenomena through observational and theoretical evidence.

## Contribution

It introduces a magnetar-based model connecting FRB 121102 with SLSNe-I and LGRBs, supported by host galaxy properties and supernova remnant evolution constraints.

## Key findings

- FRB 121102's host galaxy resembles those of SLSNe-I and LGRBs.
- The age of the magnetar is estimated to be less than a century.
- The quiescent radio source is consistent with supernova remnant shock emission.

## Abstract

Sub-arcsecond localization of the repeating fast radio burst FRB 121102 revealed its coincidence with a dwarf host galaxy and a steady (`quiescent') non-thermal radio source. We show that the properties of the host galaxy are consistent with those of long-duration gamma-ray bursts (LGRB) and hydrogen-poor superluminous supernovae (SLSNe-I). Both LGRBs and SLSNe-I were previously hypothesized to be powered by the electromagnetic spin-down of newly-formed, strongly-magnetized neutron stars with millisecond birth rotation periods (`millisecond magnetars'). This motivates considering a scenario whereby the repeated bursts from FRB 121102 originate from a young magnetar remnant embedded within a young hydrogen-poor supernova remnant. Requirements on the GHz free-free optical depth through the expanding supernova ejecta (accounting for photo-ionization by the rotationally-powered magnetar nebula), energetic constraints on the bursts, and constraints on the size of the quiescent source all point to an age of less than a few decades to a century. The quiescent radio source can be attributed to synchrotron emission from the shock interaction between the fast outer layer of the supernova ejecta with the surrounding wind of the progenitor star, or from deeper within the magnetar wind nebula. Alternatively, the radio emission could be an orphan afterglow from an initially off-axis LGRB jet, though this might require the source to be too young. The young age of the source can be tested by searching for a time derivative of the dispersion measure and predicted fading of the quiescent radio source. We propose future tests of the SLSNe-I/LGRB/FRB connection, such as searches for FRBs from nearby SLSNe-I/LGRB on timescales of decades after their explosions.