Monitoring the radio galaxy M87 with HAWC

TL;DR

This paper reports on four years of daily TeV gamma-ray monitoring of the radio galaxy M87 with HAWC, revealing mostly low activity consistent with other instruments but hints of increased activity after September 2017.

Contribution

First continuous TeV gamma-ray monitoring of M87 with HAWC, providing new insights into its variability and activity states over several years.

Findings

HAWC observations align with low activity states reported by other telescopes.

Hints of increased activity in M87 after September 2017.

Demonstrates HAWC's capability for long-term monitoring of variable radio galaxies.

Abstract

Studies of radio galaxies at TeV energies are fascinating because their jets are misaligned concerning our sightline. Thus, it provides us with a unique opportunity to study the structure of their jets, the radiative processes, and the acceleration mechanisms involved in them. In addition, some radio galaxies have presented variability in their emission, like the giant radio galaxy M87, which has reported several activity periods. Due to its duty cycle >95% and instantaneous field of view of 2 sr, HAWC provides daily monitoring of variable sources visible from the Northern Hemisphere. In this work, we show the results of monitoring M87 between January 2015 and December 2018. HAWC's observations are consistent with the low activity state reported by other instruments (like H.E.S.S and MAGIC). However, after September 2017 (~MJD 58000), the HAWC measurements of M87 show hints of higher activity.