Abnormal lithium abundance in several Ap-Bp stars

Abstract

Using observations of rapidly rotating roAp star HD 12098, obtained with 6m telescope of SAO RAS in 2005 in nine rotational phases (0.001-0.817), and code V. Tsymbal ROTATE we identified 3 lithium spots on the surface of star, one of them coincided with the position of one magnetic pole and two others are located near the other pole, symmetrically with respect to it. Perhaps magnetic field of the star has a more complex structure than the dipole [17]. Lithium abundance in the spots is greater than cosmic one. It can be explained by diffusion of lithium in the presence of a magnetic field or by production of lithium in the reactions of "spallation" on the surface of star near the magnetic poles (see, for example, [4]). Enhanced lithium abundances was also determined for other two slowly rotating Ap stars HR 465 and HD 965. The analysis is performed using a synthetic spectrum method taking into account magnetic splitting of lines by the SYNTHM code of S. Khan [5].