A Burst in a Wind Bubble and the Impact on Baryonic Ejecta: High-Energy Gamma-Ray Flashes and Afterglows from Fast Radio Bursts and Pulsar-Driven Supernova Remnants

TL;DR

This paper investigates high-energy signatures of wind bubbles formed by compact remnants, exploring their potential to produce detectable gamma-ray flashes and afterglows associated with fast radio bursts and supernova remnants.

Contribution

It introduces a detailed model of high-energy emissions from wind bubbles around magnetars and neutron stars, highlighting their observational signatures and implications for FRBs and supernovae.

Findings

High-energy gamma-ray escape is possible for nebulae older than 10-100 years.

Bright sub-mm radio emission from nebulae may serve as FRB counterparts.

Relativistic shocks in nebulae can produce short gamma-ray flashes and afterglows.

Abstract

Tenuous wind bubbles, which are formed by the spin-down activity of central compact remnants, are relevant in some models of fast radio bursts (FRBs) and super-luminous supernovae. We study their high-energy signatures, focusing on the role of pair-enriched bubbles produced by young magnetars, rapidly-rotating neutron stars, and magnetized white dwarfs. (i) First, we study the nebular properties and the conditions allowing for escape of high-energy gamma-rays and radio waves, showing that their escape is possible for nebulae with ages of >10-100 yr. In the rapidly-rotating neutron star scenario, we find that radio emission from the quasi-steady nebula itself may be bright enough to be detected especially at sub-mm frequencies, which is relevant as a possible counterpart of pulsar-driven SNe and FRBs. (ii) Second, we consider the fate of bursting emission in the nebulae. We suggest that an impulsive burst may lead to a highly relativistic flow, which would interact with the nebula. If the shocked nebula is still relativistic, pre-existing non-thermal particles in the nebula can be significantly boosted by the forward shock, leading to short-duration (maybe millisecond or longer) high-energy gamma-ray flashes. Possible dissipation at the reverse shock may also lead to gamma-ray emission. (iii) After such flares, interactions with the baryonic ejecta may lead to afterglow emission with a duration of days to weeks. In the magnetar scenario, this burst-in-bubble model leads to the expectation that nearby (<10-100 Mpc) high-energy gamma-ray flashes may be detected by HAWC and CTA, and the subsequent afterglow emission may be seen by radio telescopes such as VLA. (iv) Finally, we discuss several implications specific to FRBs, including constraints on the emission regions and limits on soft gamma-ray counterparts.