2005A&A...430L..17R

We have derived the mean broadening profile of the star V102 in the region of the open cluster IC 4665 from high resolution spectroscopy. At a projected equatorial rotation velocity of vsini=(105±12)km/s we find strong deviation from classical rotation. We discuss several scenarios, the most plausible being strong differential rotation in latitudinal direction. For this scenario we find a difference in angular velocity of ΔΩ=3.6±0.8rad/d (ΔΩ/Ω=0.42±0.09). From the Hα line we derive a spectral type of A9 and support photometric measurements classifying IC 4665 V102 as a non-member of IC 4665. At such early spectral type this is the strongest case of differential rotation observed so far. Together with three similar stars, IC 4665 V102 seems to form a new class of objects that exhibit extreme latitudinal shear in a very shallow convective envelope.