# Monitoring the Extragalactic High Energy Sky

## TL;DR

This paper discusses the importance of monitoring blazars in the high-energy extragalactic sky using Fermi-LAT data, highlighting tools like FLaapLUC for triggering follow-up observations to study their flaring activity.

## Contribution

It introduces and describes the FLaapLUC tool used within the H.E.S.S. collaboration for monitoring and triggering follow-up observations of blazar flares.

## Key findings

- FLaapLUC effectively identifies blazar flares in real-time.
- Monitoring enables timely multi-wavelength follow-up observations.
- Data products and pipelines enhance blazar variability studies.

## Abstract

Blazars are jetted active galactic nuclei with a jet pointing close to the line of sight, hence enhancing their intrinsic luminosity and variability. Monitoring these sources is essential in order to catch them flaring and promptly organize follow-up multi-wavelength observations, which are key to providing rich data sets used to derive e.g., the emission mechanisms at work, and the size and location of the flaring zone. In this context, the Fermi-LAT has proven to be an invaluable instrument, whose data are used to trigger many follow-up observations at high and very high energies. A few examples are illustrated here, as well as a description of different data products and pipelines, with a focus given on FLaapLUC, a tool in use within the H.E.S.S. collaboration.