Cut-off Characterisation of Energy Spectra of Bright Fermi Sources: Current instrument limits and future possibilities

TL;DR

This study analyzes the spectral cut-offs of bright Fermi sources like blazars and pulsars, demonstrating current limitations and future improvements possible with next-generation Cherenkov telescopes such as CTA.

Contribution

It provides the first detailed constraints on spectral cut-offs of bright Fermi sources and assesses how future CTA observations can significantly improve these constraints.

Findings

Current Fermi-LAT data constrain spectral cut-offs effectively for bright sources.

CTA observations can substantially enhance the precision of cut-off parameter measurements.

Future ground-based telescopes will outperform current satellite capabilities in spectral analysis.

Abstract

In this paper some of the brightest GeV sources observed by the Fermi-LAT were analysed, focusing on their spectral cut-off region. The sources chosen for this investigation were the brightest blazar flares of 3C~454.3 and 3C~279 and the Vela pulsar with a reanalysis with the latest Fermi-LAT software. For the study of the spectral cut-off we first explored the Vela pulsar spectrum, whose statistics in the time interval of the 3FGL catalog allowed strong constraints to be obtained on the parameters. We subsequently performed a new analysis of the flaring blazar SEDs. For these sources we obtained constraints on the cut-off parameters under the assumption that their underlying spectral distribution is described by a power-law with a stretched exponential cut-off. We then highlighted the significant potential improvements on such constraints by observations with next generation ground based Cherenkov telescopes, represented in our study by the Cherenkov Telescope Array (CTA). Adopting currently available simulations for this future observatory, we demonstrate the considerable improvement in cut-off constraints achievable by observations with this new instrument when compared with that achievable by satellite observations.