Monitoring the Variable Gamma-Ray Sky with HAWC

TL;DR

The HAWC observatory continuously monitors the TeV gamma-ray sky, providing extensive data on blazar activity, which aids in detecting gamma-ray flares and correlating with neutrino observations, enhancing multi-messenger astronomy.

Contribution

This work presents the first large-scale, unbiased daily gamma-ray light curves from HAWC, enabling real-time flare detection and multi-wavelength, multi-messenger studies of high-energy astrophysical sources.

Findings

Detection of blazar flaring activity

First real-time gamma-ray flare alerts

Correlation with neutrino observations

Abstract

The High Altitude Water Cherenkov (HAWC) observatory monitors the gamma-ray sky at energies between 100 GeV and 100 TeV with a wide field of view of $\sim 2$ steradians. A duty cycle of $\sim 90$% allows HAWC to scan two thirds of the sky every day and has resulted in an unprecedented data set of unbiased and evenly sampled daily TeV light curves, collected over more than one year of operation since the completion of the array. These measurements highlight the flaring activity of the blazars Markarian 421 and Markarian 501 and allow us to discuss the frequency of high flux states and correlations with observations at other wavelengths. We will present a first look at how we are using the HAWC data to search for gamma-ray signals and variability from the directions of possible TeV gamma-ray sources and the locations of high-energy neutrinos observed by IceCube. For a selected list of objects, we perform a search for flares in real time during data taking in order to quickly alert other observatories when increased activity is detected. We include here the first results from these flare trigger efforts, focused on monitoring blazars.