Speaker
Description
The Auger Engineering Radio Array (AERA), consisting of 153 stations over 17 km$^2$, was the largest radio detector for cosmic rays until the deployment of the Auger Radio Detector in 2024. Over the years it has helped to advance the understanding of air-shower radio emission and methods for its detection, and has thereby paved the way to the successful commissioning of its successor. In this contribution, we will discuss highlights from 15 years of AERA operation and cosmic ray measurements: Accurate absolute calibration of AERA was achieved using galactic background emission as a standard candle, also demonstrating the long-time stability of the detector. Knowing the calibration of the detector, the absolute energy scale of cosmic ray measurements has recently been calibrated with AERA data and first-principles radio-emission simulations, confirming (within systematics) the cosmic-ray energy scale set by the fluorescence detector of the Observatory. The depth of the shower maximum was measured using the radio-emission footprint with a resolution competitive with the fluorescence detector. It could also be demonstrated that this quantity can be determined using the interferometric technique. Lastly, the muon content of inclined air showers (60$^\circ$ to 80$^\circ$) was investigated in a hybrid detection mode, utilising events measured by the water-Cherenkov detector array as well as AERA, confirming the expected muon-deficit in current generation hadronic interaction models.