Anti-solar differential rotation and surface flow pattern on UZ Librae

TL;DR

This study analyzes Doppler images of UZ Librae from 1998 and 2000, revealing anti-solar differential rotation and complex surface flow patterns, with the shear magnitude varying between observations.

Contribution

It provides the first evidence of anti-solar differential rotation on UZ Librae using Doppler imaging and cross-correlation techniques.

Findings

Anti-solar differential rotation with shear alpha ~ -0.03 in 1998

Weaker anti-solar shear alpha ~ -0.004 in 2000

Complex surface flow patterns indicated by local correlation tracking

Abstract

We re-investigate UZ Librae spectra obtained at KPNO in 1998 and 2000. From the 1998 data we compose 11 consecutive Doppler images using the Ca I-6439, Fe I-6393 and Fe I-6411 lines. Applying the method of average cross-correlation of contiguous Doppler images we find anti-solar differential rotation with a surface shear of alpha ~ -0.03. The pilot application of the local correlation tracking technique for the same data qualitatively confirms this result and indicates complex flow pattern on the stellar surface. From the cross-correlation of the two available Doppler images in 2000 we also get anti-solar differential rotation but with a much weaker shear of alpha ~ -0.004.