The Likely Cause of the EGRET GeV Anomaly and its Implications

TL;DR

This paper investigates the EGRET GeV anomaly, suggesting it was likely caused by systematic errors in detector sensitivity estimation rather than new physics like dark matter annihilation, with implications for future gamma-ray missions.

Contribution

The study reanalyzes the EGRET anomaly, identifies potential systematic errors, and challenges the dark matter interpretation, providing a revised understanding of the gamma-ray background.

Findings

The anomaly is likely due to sensitivity estimation errors.

Systematic errors can mimic signals attributed to dark matter.

Results support the original EGRET background spectrum findings.

Abstract

Analysis of data from the EGRET gamma-ray detector on the Compton Gamma Ray Observatory indicated an anomaly in the form of an excess diffuse galactic flux at GeV energies over that which was theoretically predicted. Various explanations for this anomaly have been put forth, including the invocation of supersymmetric dark matter annihilation. We reexamine these explanations here, including a new discussion of the possible systematic errors in the sensitivity determination of the EGRET detector. We conclude that the most likely explanation of the EGRET ``GeV anomaly'' was an error in the estimation of the of the EGRET sensitivity at energies above ~1 GeV. We give reasons why such a situation could have occurred. We find evidence from our new all-sky analysis which is inconsistent with the assumption that the anomaly can be a signal of supersymmetric dark matter annihilation. We also reconfirm the original results of the EGRET team on the extragalactic gamma-ray background spectrum. There are important implications of our analysis for the upcoming Gamma Ray Large Area Telescope (GLAST) mission.