The first Doppler imaging of the active binary prototype RS Canum Venaticorum

Abstract

We present the first Doppler images of the prototypical active binarystar RS Canum Venaticorum, derived from high-resolution spectra observedin 2004, 2016 and 2017, using three different telescopes and observingsites. We apply the least-squares deconvolution technique to allobserved spectra to obtain high signal-to-noise line profiles, which areused to derive the surface images of the active K-type component. Ourimages show a complex spot pattern on the K star, distributed widely inlongitude. All star-spots revealed by our Doppler images are locatedbelow a latitude of about 70°. In accordance with previouslight-curve modelling studies, we find no indication of a polar spot onthe K star. Using Doppler images derived from two consecutive rotationalcycles, we estimate a surface differential rotation rate ofΔΩ = -0.039 ± 0.003 rad d-1 and α =ΔΩ/Ωeq = -0.030 ± 0.002 for the Kstar. Given the limited phase coverage during those two rotations, theuncertainty of our differential rotation estimate is presumably higher.