New observations of the beat Cepheid variable AX Velorum

The light variation of the beat Cepheid variable AX Velorum is of a double mode nature, in which the fundamental mode maintains a coherent and stable frequency oscillation, while the first overtone mode undergoes small period changes which can lead to phase displacements of at least 0.07 over a five-year interval. The last thirty years of data on AX Vel suggest that the first overtone energy has increased with respect to that in the fundamental mode.