Cross Calibration of Imaging Air Cherenkov Telescopes with Fermi

TL;DR

This paper presents a method to cross calibrate Fermi gamma-ray observations with ground-based air Cherenkov telescopes using a synchrotron and inverse Compton emission model of the Crab Nebula, improving energy measurement consistency.

Contribution

It introduces a model-based approach to calibrate Fermi and ground-based telescopes by comparing predicted and observed inverse Compton emission from the Crab Nebula.

Findings

Derived energy calibration factors for Fermi and ground-based measurements.

Validated the model against spectral energy distribution data.

Enhanced cross-instrument calibration accuracy.

Abstract

An updated model for the synchrotron and inverse Compton emission from a population of high energy electrons of the Crab Nebula is used to reproduce the measured spectral energy distribution from radio to high energy gamma-rays. By comparing the predicted inverse Compton component with recent Fermi measurements of the nebula's emission, it is possible to determine the average magnetic field in the nebula and to derive the underlying electron energy distribution. The model calculation can then be used to cross calibrate the Fermi observations with ground based air shower measurements. The resulting energy calibration factors are derived and can be used for combining broad energy measurements taken with Fermi in conjunction with ground based measurements.