Lithium enrichment on the single active K1-giant DI Piscium^⋆

Possible joint origin of differential rotation and Li enrichment

¹ Konkoly Observatory of the Hungarian Academy of Sciences, Konkoly Thegeút 15–17, 1121 Budapest, Hungary
e-mail: kriskovics@konkoly.hu
² Leibniz Institute for Astrophysics (AIP), An der Sternwarte 16, 14482 Potsdam, Germany

Received: 23 May 2014
Accepted: 14 August 2014

Abstract

Aims. We investigate the surface spot activity of the rapidly rotating, lithium-rich active single K-giant DI Psc to measure the surface differential rotation and understand the mechanisms behind the Li-enrichment.

Methods. Doppler imaging was applied to recover the surface temperature distribution of DI Psc in two subsequent rotational cycles using the individual mapping lines Ca  i 6439, Fe i 6430, Fe i 6421, and Li i 6708. Surface differential rotation was derived by cross-correlation of the subsequent maps. Difference maps are produced to study the uniformity of Li-enrichment on the surface. These maps are compared with the rotational modulation of the Li i 6708 line equivalent width.

Results. Doppler images obtained for the Ca and Fe mapping lines agree well and reveal strong polar spottedness, as well as cool features at lower latitudes. Cross-correlating the consecutive maps yields antisolar differential rotation with a shear coefficient α = −0.083 ± 0.021. The difference of the average and the Li maps indicates that the lithium abundance is non-activity related. There is also a significant rotational modulation of the Li equivalent width.