Joint analysis of TeV blazar light curves with FACT and HAWC

TL;DR

This study combines long-term, high-energy light curves from FACT and HAWC to analyze blazar variability, offering enhanced temporal coverage and cross-validation of flux variations in Mrk 421 and Mrk 501.

Contribution

It introduces a joint analysis method leveraging two observatories to improve monitoring of blazar variability over hours to days.

Findings

Largely correlated flux variations between FACT and HAWC.

Detected deviations explained by rapid variability within hours.

Extended observational coverage enhances understanding of blazar emission processes.

Abstract

Probing the high energy emission processes of blazars through their variability relies crucially on long-term monitoring. We present unprecedented light curves from unbiased observations of very high energy fluxes from the blazars Mrk 421 and Mrk 501 based on a joint analysis of data from the First G-APD Cherenkov Telescope (FACT) and the High Altitude Water Cherenkov (HAWC) Observatory. Thanks to an offset of 5.3 hours of the geographic locations, a complementary coverage of up to 12 hours of observation per day allows us to track variability on time scales of hours to days in more detail than with single-instrument analyses. Complementary features, such as better sensitivity thanks to a lower energy threshold with FACT and more regular coverage throughout the year with HAWC, provide valuable cross checks and extensions to the individual analyses. Daily flux comparisons for both Mrk 421 and Mrk 501 show largely correlated variations with a few significant exceptions. These deviations between measurements can be explained through fast variability within a few hours and will be discussed in detail.