Zs. K\Hovári, H. Korhonen, L. Kriskovics, K. Vida, J. -F. Donati, H. Le Coroller, J. D. Monnier E. Pedretti, P. Petit
We investigate the temporal spot evolution of the K-giant component in the RS
CVn-type binary system $\zeta$\,Andromedae to establish its surface
differential rotation. Doppler imaging is used to study three slightly
overlapping spectroscopic datasets, obtained independently at three different
observing sites. Each dataset covers one full stellar rotation with good phase
coverage, and in total, results in a continuous coverage of almost three
stellar rotations ($P_{\rm rot}=$17.8\,d). Therefore, these data are well
suited for reconstructing surface temperature maps and studying temporal
evolution in spot configurations. Surface differential rotation is measured by
the means of cross-correlation of all the possible image pairs. The individual
Doppler reconstructions well agree in the revealed spot pattern, recovering
numerous low latitude spots with temperature contrasts of up to
$\approx$1000\,K with respect to the unspotted photosphere, and also an
asymmetric polar cap which is diminishing with time. Our detailed
cross-correlation study consistently indicate solar-type differential rotation
with an average surface shear $\alpha\approx0.055$, in agreement with former
results.
View original:
http://arxiv.org/abs/1201.2921
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