# HAWC Observations Strongly Favor Pulsar Interpretations of the Cosmic-Ray Positron Excess

## TL;DR

This study uses HAWC gamma-ray observations of pulsars Geminga and B0656+14 to demonstrate that pulsars likely dominate the cosmic-ray positron excess observed by experiments like PAMELA and AMS-02.

## Contribution

The paper provides the first detailed gamma-ray based constraints on pulsar contributions to the local cosmic-ray positron flux, strongly supporting pulsars as the primary source.

## Key findings

- Pulsars produce high-energy positrons consistent with observed excess.
- Gamma-ray data constrains pulsar contributions to cosmic-ray positrons.
- Pulsars are likely the main source of the cosmic-ray positron excess.

## Abstract

Recent measurements of the Geminga and B0656+14 pulsars by the gamma-ray telescope HAWC (along with earlier measurements by Milagro) indicate that these objects generate significant fluxes of very high-energy electrons. In this paper, we use the very high-energy gamma-ray intensity and spectrum of these pulsars to calculate and constrain their expected contributions to the local cosmic-ray positron spectrum. Among models that are capable of reproducing the observed characteristics of the gamma-ray emission, we find that pulsars invariably produce a flux of high-energy positrons that is similar in spectrum and magnitude to the positron fraction measured by PAMELA and AMS-02. In light of this result, we conclude that it is very likely that pulsars provide the dominant contribution to the long perplexing cosmic-ray positron excess.