Follow-up Search for UHE Photons from Gravitational Wave Sources with the Pierre Auger Observatory

PIERRE AUGER COLLABORATION; A. MARIAZZI

Berlin

Conferencia; 37th International Cosmic Ray Conference (ICRC2021); 2021

Multimessenger astronomy has become increasingly important during the past decade. Someastronomical objects have already been successfully observed in the light of multiple messengersignals, allowing for a much deeper understanding of their physical properties. The PierreAuger Observatory has taken part in multimessenger astronomy with an exhaustive explorationof the ultra-high-energy sky. In this contribution, for the first time, a search for UHE photonsfrom the sources of gravitational waves is presented. Interactions with the cosmic backgroundradiation fields are expected to attenuate any possible flux of ultra-high-energy photons fromdistant sources and a non-negligible background of air shower events with hadronic origin makesan unambiguous identification of primary photons a challenging task. In the analysis presentedhere, a selection strategy is applied to both GW sources and air shower events aiming to providemaximum sensitivity to a possible photon signal. At the same time, a window is kept open forhypothetical new-physics processes, which might allow for much larger interaction lengths ofphotons in the extragalactic medium. Preliminary results on the UHE photon fluence from aselection of GW sources, including the binary neutron star merger GW170817 are presented.