Gamma-Ray and Hard X-Ray Emission from Pulsar-Aided Supernovae as a Probe of Particle Acceleration in Embryonic Pulsar Wind Nebulae

TL;DR

This paper proposes that early gamma-ray and X-ray emissions from embryonic pulsar wind nebulae in supernovae can serve as effective probes of particle acceleration and the mechanisms behind luminous supernovae and gamma-ray bursts, with potential detectability by current telescopes.

Contribution

It introduces detailed models of early PWN emissions considering electromagnetic cascades, Klein-Nishina effects, and two-photon processes, highlighting observational strategies for detecting these signals.

Findings

Early PWN emissions can be observed in X-ray and gamma-ray bands.

NuSTAR and Fermi can detect signals from nearby supernovae.

High-energy observations can reveal particle acceleration and dissipation mechanisms.

Abstract

It has been suggested that some classes of luminous supernovae (SNe) and gamma-ray bursts (GRBs) are driven by newborn magnetars. Fast-rotating proto-neutron stars have also been of interest as potential sources of gravitational waves (GWs). We show that for a range of rotation periods and magnetic fields, hard X rays and GeV gamma rays provide us with a promising probe of pulsar-aided SNe. It is observationally known that young pulsar wind nebulae (PWNe) in the Milky Way are very efficient lepton accelerators. We argue that, if embryonic PWNe satisfy similar conditions at early stages of SNe (in ~1-10 months after the explosion), external inverse-Compton emission via upscatterings of SN photons is naturally expected in the GeV range as well as broadband synchrotron emission. To fully take into account the Klein-Nishina effect and two-photon annihilation process that are important at early times, we perform detailed calculations including electromagnetic cascades. Our results suggest that hard X-ray telescopes such as NuSTAR can observe such early PWN emission by followup observations in months-to-years. GeV gamma rays may also be detected by Fermi for nearby SNe, which serve as counterparts of these GW sources. Detecting the signals will give us an interesting probe of particle acceleration at early times of PWNe, as well as clues to driving mechanisms of luminous SNe and GRBs. Since the Bethe-Heitler cross section is lower than the Thomson cross section, gamma rays would allow us to study subphotospheric dissipation. We encourage searches for high-energy emission from nearby SNe, especially Type Ibc SNe including super-luminous objects.