We have studied over 1600 Am stars at a photometric precision of 1mmag with SuperWASP photometric data. Contrary to previous belief, we find that around 200 Am stars are pulsating delta Sct and gamma Dor stars, with low amplitudes that have been missed in previous, less extensive studies. While the amplitudes are generally low, the presence of pulsation in Am stars places a strong constraint on atmospheric convection, and may require the pulsation to be laminar. While some pulsating Am stars have been previously found to be delta Sct stars, the vast majority of Am stars known to pulsate are presented in this paper. They will form the basis of future statistical studies of pulsation in the presence of atomic diffusion.
Results of 131 stars from Renson's (1991, Cat. <III/162>) catalogue of Ap and Am stars observed with the {Delta}-a system are presented. With few exceptions the probability division of Renson for membership in the CP2 group of peculiar stars is nicely reflected by peculiar values of {Delta}-a. Comparison with already available {Delta}-a values yields slightly larger values due to a minor shift in the g_1_ filter sampling the depression. For a description of the {Delta}-a and Stroemgren photometric system, see e.g. <GCPD/75> and <GCPD/04>, respectively.
Differential Stroemgren uvby observations from the Four College Automated Photoelectric Telescope (FCAPT) are presented for the metallic-lined stars 60 Tau and HR 1528 and the magnetic Chemically Peculiar stars HR 8216 and HR 8770. The first star, which is a {delta} Scuti variable, was found not to change its mean magnitudes. HR 1528 is best described as constant. A decade of photometry of HR 8216 shows that its b and y values have changed by -0.016 and -0.010mag, respectively, over this time and now can be considered a photometric variable. For HR 8770 a period of 5.3923 days is derived with the photometric variability being generally in phase. The light curves also suggest possible surface abundance inhomogeneities.
Accurate physical properties of eclipsing stars provide important constraints on models of stellar structure and evolution, especially when combined with spectroscopic information on their chemical composition. Empirical calibrations of the data also lead to accurate mass and radius estimates for exoplanet host stars. Finally, accurate data for unusual stellar subtypes, such as Am stars, also help to unravel the cause(s) of their peculiarities. We aim to determine the masses, radii, effective temperatures, detailed chemical composition and rotational speeds for the Am-type eclipsing binaries SWCMa (A4-5m) and HWCMa (A6m) and compare them with similar normal stars.
