TESS observations of Am stars

The metallic-line (Am) stars are chemically peculiar A and early F stars that show weak spectral lines of Ca K and Sc and strong iron-group features compared to their hydrogen-line spectral type. The abundance peculiarities of Am stars can be explained by chemical separation due to radiative diffusion and gravitational settling. In a normal A star this separation is destroyed by fast rotation, however Am stars rotate slowly enough to prevent this mechanism. The metallic-line stars are located in the classical instability zone, where pulsating Delta Scuti stars lie. The Delta Scuti pulsations are driven by the kappa-mechanism operating in the He II ionisation zone. For many years it was assumed that classical Am stars cannot pulsate due to the gravitational settling of helium. However, over time it appeared that many Am stars pulsate. We analyse high-precision photometric data gathered by the TESS satellite to check (1) if pulsation characteristics (e.g. number of frequencies, amplitudes) are different for Am and chemically normal stars, and (2) if the incidence of pulsations in Am stars decreases with increasing degree of chemical peculiarity.