Ultrahigh-Energy Photons as a Probe of Nearby Transient Ultrahigh-Energy Cosmic-Ray Sources and Possible Lorentz-Invariance Violation

Understand

Detecting neutrinos and photons is crucial to identifying the sources of ultrahigh-energy cosmic rays (UHECRs), especially for transient sources.

• We focus on ultrahigh-energy gamma-ray emission from transient sources such as gamma-ray bursts, since >EeV gamma rays can be more direct evidence of UHECRs than PeV neutrinos and GeV-TeV gamma rays.
• We demonstrate that coincident detections of about 1-100 events can be expected by current and future UHECR detectors such as Auger and JEM-EUSO, and the detection probability can be higher than that of neutrinos for nearby transient sources at <50-100 Mpc.
• They may be useful for constraining the uncertain cosmic radio background as well as knowing the source properties and maximum energy of UHECRs.