Periodicity and pulsational mode of five bright yellow supergiants

Five yellow supergiant variables with long semi-periodic variation (P≳40 day) have been studied. UBVRI photometry and radial velocities were obtained during the same observing seasons. These observations together with previous data in the literature were used to determine the characteristic time of the variation. Empirical masses, radii and pulsation constants Q were determined. A discussion of the expected values of Q for fundamental radial pulsation in large and massive stars allows a discussion on the pulsation mode of the stars in our sample. ε Aur, V509 Cas and ϱ Cas are likely non-radial pulsators, massive $$(15\lt{M}/{M}_{\odot}\,\lt30)\,\text{and}\,\text{large}\,(250\lt{R}/{R}_{\odot}\lt800)$$ . For 89 Her, arguments are offered in favour of a non-pure radial pulsational behaviour. For HD161796 a new periodic switch from 43 days in early 1981 to 62 days in 1982 was found. High luminosity $$({M}_{V}=-8\,\text{to}\,-9)\,\text{and}\,\text{mass}\,(M =14\,\text{to}\,24\,{M}_{\odot})$$ are consistent with radial pulsation as suggested by the period switches observed in 19797–80 and 1981–82.