Paper detail

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

We present the first Doppler images of the prototypical active binary star RS CVn, derived from high-resolution spectra observed in 2004, 2016 and 2017, using three different telescopes and observing sites. We apply the least-squares deconvolution technique to all observed spectra to obtain high signal-to-noise line profiles, which are used to derive the surface images of the active K-type component. Our images show a complex spot pattern on the K star, distributed widely in longitude. All starspots revealed by our Doppler images are located below a latitude of about 70$^{\circ}$. In accordance with previous light-curve modeling studies, we find no indication of a polar spot on the K star. Using Doppler images derived from two consecutive rotational cycles, we estimate a surface differential rotation rate of $ΔΩ= -0.039 \pm 0.003 ~rad~d^{-1}$ and $α= ΔΩ/Ω_{eq} = -0.030 \pm 0.002$ for the K star. Given the limited phase coverage during those two rotations, the uncertainty of our differential rotation estimate is presumably higher.