Abundances in Magnetic Ap Stars

Abstract

AbstractThe spatial inhomogeneities, Zeeman broadening, and extreme abundance anomalies have thus far prevented definitive analyses of magnetic CP stars. Nevertheless, the abundance anomalies are so large that many of them have been known for decades. Abundance excesses of iron-peak elements of factors of 10 to 100 are common. Relative abundances on the iron peak are not constant. The lines of vanadium and nickel are often weak, and these elements may even be deficient in some stars. In spitè of the large variations, the odd-even effect persists; there is only minor evidence that chemical separation has perturbed the nuclear pattern. The lanthanide rare earths can have excesses of 100 to 1000 or even more in extreme cases. For these elements there is some evidence of fractionation. The actinide rare earth elements uranium and thorium are weakly (but surely!) present in a few of the magnetic CP stars: the best case is HR 465.