Fermi LAT observations of cosmic-ray electrons from 7 GeV to 1 TeV

TL;DR

This paper reports on Fermi LAT measurements of cosmic-ray electrons between 7 GeV and 1 TeV, extending previous spectra and analyzing spectral features with high precision.

Contribution

It provides a detailed analysis of the cosmic-ray electron spectrum over a broad energy range using Fermi LAT data, including validation and cross-checks for improved accuracy.

Findings

Electron spectrum follows a power law with index -3.08 ± 0.05.

No prominent spectral features detected within uncertainties.

Possible slight spectral hardening around 100 GeV and softening above 500 GeV.

Abstract

We present the results of our analysis of cosmic-ray electrons using about 8 million electron candidates detected in the first 12 months on-orbit by the Fermi Large Area Telescope. This work extends our previously-published cosmic-ray electron spectrum down to 7 GeV, giving a spectral range of approximately 2.5 decades up to 1 TeV. We describe in detail the analysis and its validation using beam-test and on-orbit data. In addition, we describe the spectrum measured via a subset of events selected for the best energy resolution as a cross-check on the measurement using the full event sample. Our electron spectrum can be described with a power law $\propto {\rm E}^{-3.08 \pm 0.05}$ with no prominent spectral features within systematic uncertainties. Within the limits of our uncertainties, we can accommodate a slight spectral hardening at around 100 GeV and a slight softening above 500 GeV.