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I R O N AND T I T A N I U M A B U N D A N C E I N T H E A T M O S P H E R E S O F CHEMICALLY PECULIAR STARS

I. M. Kopylov Special Astrophysical Observatory Stavropolskij Kraj , 357147 Nizhnij Arkhyz, USSR.

ABSTRACT

From the equivalent widths ( ) of the selected Fell and Till lines the peculiarity indices P(FeII) and P(TiII) are determined for 70 normal B8-A8 stars of III-V luminosity classes and for 95 magnetic chemically peculiar (CP) B3-A8 stars. For normal stars all the P(FeII) and P(TiII) indices are within the limits of 0.5-1.7. A close correlation of P(FeII) and P (TiII) is found. The dependence character of P(FeII) and P(TiII) indices on the iron and titanium abundance [lg (Fe)] and [lg(Ti)], determined using the model atmosphere method, is ascertained, i.e. P indices can be used for promp determination of relative chemical abundance in the atmospheres of and A stars. Analysing the dependences of P(FeII) and P(TiII) on the spectral class (or Te ) peculiarity type and magnetic field for CP-stars it follows: a) . P(FeII) and P (TiII) indices increase rapidly with the temperature increase from the "normal" values P= 0.5-1.7 for the latest (Sr, C r , Eu) stars (Sp A3-A8, 8700 7500 K) . They approach the values from >2 to 10-13 for the hot (He-weak), Si 4200 and Hg, Mn stars (Sp B3-B8, 18000 12000 K) , b) . Fe and Ti overabundances in the atmospheres (on the surface on the average) of CP-stars of He-weak, Si , Si 4200 and, perhaps, Hg, Mn types can approach 2.7 dex., c) . He-weak, Si , Si 4200 stars with the substantionally strengthened Fe , Ti , Cr etc. metal lines with P(FeII) +P(TiII)/2>4 have two times larger than CP stars of the other peculiarity types within the same interval of spectral classes, B3-B8: for them =2000 Gs, for the other (Si, He-weak) stars = 1 0 0 0 G s, for Hg, Mn stars < B e > = 4 2 0 G s.

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