Search for Ultra-high-energy Photons from Gravitational Wave Sources with the Pierre Auger Observatory

A search for time-directional coincidences of ultra-high-energy (UHE) photons above 10 EeV with gravitational wave (GW) events from the LIGO/Virgo runs O1 to O3 is conducted Pierre Auger Observatory. Due distinctive properties photon interactions and background expected hadronic showers, a subset most interesting GW selected based on their localization quality distance. Time periods 1000 s around 1 day after are analyzed. No observed. Upper limits UHE fluence event derived that typically at $\sim$7 MeV cm$^{-2}$ (time period 1000~s) $\sim$35 day). proximity binary neutron star merger GW170817, energy source transferred into 40 constrained be less than 20% its total energy. These first sources.