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Keywords:

  • supergiants;
  • stars: variables: Cepheids

ABSTRACT

To identify the pulsation mode of three low-amplitude classical Cepheids, namely V1334 Cyg, V440 Per and V636 Cas, we use absolute magnitudes which are based upon Mv–Fe ii/Fe i line depth relations. We determine that V1334 Cyg is pulsating in the first overtone, and that V440 Per and V636 Cas are fundamental mode pulsators. Their low amplitudes are due to their position close to the edge of the instability strip.