Metallicism and pulsation: the discovery of δ Scuti variability in a classical Am star, HD 1097
Open Access
- 1 June 1989
- journal article
- Published by Oxford University Press (OUP) in Monthly Notices of the Royal Astronomical Society
- Vol. 238 (4) , 1077-1084
- https://doi.org/10.1093/mnras/238.4.1077
Abstract
HD 1097 is classified A3/5mF0–F5 which makes it an extreme example of a classical Am star. The weakness of the Ca IIK-line argues that it is an Am and not an Ap star. This paper presents the discovery of light variability in HD 1097 with a period of 81.17 ± 0.05 min with a semi-amplitude through a Johnson B filter of 4.52 ± 0.16 mmag. For the Teff and presumed luminosity of HD 1097 this period is consistent with fundamental or first overtone pulsation. HD 1097 is thus both a classical Am star and a δ Scuti variable. If diffusion is the correct explanation for the abundance anomalies in the Am stars, then there must be sufficient residual helium left in the He II ionization zone to drive small-amplitude pulsation. That pulsation must not generate turbulence with velocities greater than a very small fraction of a cm s−1. The expected pulsation velocity at the surface of HD 1097 is a few hundred m s−1.Keywords
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