Testing a stochastic acceleration model of pulsar wind nebulae: Early evolution of a wind nebula associated with SN 1986J

TL;DR

This study models the early evolution of a pulsar wind nebula in SN 1986J, showing that stochastic acceleration explains its rising radio flux and providing insights into the properties of very young pulsars.

Contribution

It introduces a stochastic acceleration model for young PWNe and applies it to SN 1986J, linking flux evolution to acceleration and turbulence decay timescales.

Findings

The 5 GHz flux of PWN 1986J is consistent with stochastic acceleration.

Electron acceleration timescale is about 10 years.

Turbulence decay timescale is about 70 years.

Abstract

Over three thousand pulsars have been discovered, but none have been confirmed to be younger than a few hundred years. Observing a pulsar after a supernova explosion will help us understand the properties of newborn ones, including their capability to produce gamma-ray bursts and fast radio bursts. Here, the possible youngest pulsar wind nebula (PWN) at the center of the SN 1986J remnant is studied. We demonstrate that the 5 GHz flux of 'PWN 1986J', increasing with time, is consistent with a stochastic acceleration model of PWNe developed to explain the flat radio spectrum of the Crab Nebula. We obtain an acceleration time-scale of electrons/positrons and a decay time-scale of the turbulence responsible for the stochastic acceleration as about 10 and 70 years, respectively. Our findings suggest that efficient stochastic acceleration and rising radio/submm light curves are characteristic signatures of the youngest PWNe. Follow-up ${\it ALMA}$ observations of decades-old supernovae within a few tens of Mpc, including SN 1986J, are encouraged to reveal the origin of the flat radio spectrum of PWNe.