Nature 531, 70–73 (2016); doi:10.1038/nature16976

In this Letter, we omitted to cite preliminary results from the low-energy extension of the Pierre Auger Observatory, as presented at the International Cosmic Ray Conference 2015 (ref. 1). Figure 1 of this Corrigendum shows measurements of the average value of Xmax for the Low Frequency Array (LOFAR), and earlier experiments using different techniques, now including the data from the Pierre Auger Observatory1, specifically the contribution of A. Porcelli. Our values are in agreement with those of ref. 1 within systematic uncertainties.

Figure 1
figure 1

This is an updated version of Fig. 2 of the original Letter, including the new data from ref. 1. Measurements of Xmax. Error bars indicate 1σ statistical uncertainties and the shaded area represents the systematic uncertainty of the LOFAR results. The systematic uncertainties for Auger are indicated by the small horizontal lines above and below their data points.

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