Constraining Parameters in Pulsar Models of Repeating FRB 121102 with High-Energy Follow-up Observations

TL;DR

This paper investigates high-energy emissions from a pulsar model of FRB 121102, constraining pulsar parameters and explaining the lack of observed high-energy counterparts through efficiency limits.

Contribution

It introduces a new method to constrain pulsar parameters in FRB models using high-energy observational limits, explaining non-detections.

Findings

High-energy emission efficiency is very low, explaining non-detections.

Constraints on pulsar spin period and magnetic field are derived.

The method can be applied to other FRB sources.

Abstract

Recently, a precise (sub-arcsecond) localization of the repeating fast radio burst (FRB) 121102 has led to the discovery of persistent radio and optical counterparts, the identification of a host dwarf galaxy at a redshift of $z=0.193$, and several campaigns of searches for higher-frequency counterparts, which gave only upper limits on the emission flux. Although the origin of FRBs remains unknown, most of the existing theoretical models are associated with pulsars, or more specifically, magnetars. In this paper, we explore persistent high-energy emission from a rapidly rotating highly magnetized pulsar associated with FRB 121102 if internal gradual magnetic dissipation occurs in the pulsar wind. We find that the efficiency of converting the spin-down luminosity to the high-energy (e.g., X-ray) luminosity is generally much smaller than unity, even for a millisecond magnetar. This provides an explanation for the non-detection of high-energy counterparts to FRB 121102. We further constrain the spin period and surface magnetic field strength of the pulsar with the current high-energy observations. In addition, we compare our results with the constraints given by the other methods in previous works and would expect to apply our new method to some other open issues in the future.