3 The Am stars

The sample of Am stars is from Abt & Morrell (1995) supplemented by stars that I found were hot Am stars by performing abundance analyses using spectrograms taken at the Dominion Astrophysical Observatory (see Adelman 1994; Caliskan & Adelman 1997 and references therein). Am stars which were $\delta$ Scuti stars or which were in systems with variable companions were excluded. In the sample which remained, there were some variable stars. Most are eclipsing binaries: GW Eri (= HD 26591), RR Lyn (= HD 44691), WW Aur (= HD 46052), S Ant (= HD 46810), CO Cam (= HD 106112), V624 Her (= HD 86809), KO Aql (= HD 92117), DV Aql (= HD 199603), and AN And (= HD 219815) while IW Per (= HD 21912) is an ellipsoidal variable. These stars were moved to the bottom of Table 2 and their values were not plotted in the diagrams. Figure 3 shows the standard error vs. mean magnitude plot of the remaining stars and Fig. 4 the standard error vs. amplitude relation. In the former plot HD 201671 was excluded and HD 133408 in the later. The later star's position in the last plot may be due to one discrepant value.

  

Figure 3: The standard error vs. mean Hipparcos magnitude diagram for the Am stars

  

Figure 4: The amplitude vs. standard error diagram for Am stars

Comparing Figs. 1 and 3, which were plotted with similarly scaled axes, shows generally similar distributions and lower bounds at each magnitude. Four stars are possible variables HD 27628 (= 60 Tau), HD 30453 (= HR 1528), HD 124915 (= HR 5341), and HD 223991 (= HR 9044). For the Am stars, as there are known eclipsing binaries, we must keep this possibility in mind. Corbally (1987) believes contrary to Abt & Morrell (1995) that HR 9044 is a composite between A5 IVn and A2 Vn stars which on the aggregate looks like an Am star. The only remaining star with a period in Table 2 HD 16769 is a spectroscopic binary.