Amplitude variability of the cepheid V473 Lyr

The star V473 Lyr is a short-period cepheid (P = 1.49d) with a very strong modulation of the amplitude on a time scale near 1200d. Previously unpublished photometry is presented. This includes good coverage near the maximum amplitude. The available photometry and radial-velocity measurements going back to 1966 are analyzed with PERIOD04 to examine whether the amplitude variability is caused by beating between close frequencies. In particular, we have looked for the existence of a close frequency triplet with equidistant frequency spacing. This is required by the Combination Mode Hypothesis, which explains equidistant frequency triplets by a combination of two frequencies. The frequency triplet determined by us for V473 Lyr misses equidistancy by 0.00005 ± 0.00001 cd−1.