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Differential rotation of EK Draconis remains unconstrained from ZDI/DI

Determine the surface differential rotation parameters of EK Draconis (equatorial rotation period and latitudinal shear) using Zeeman Doppler Imaging and Doppler Imaging analyses of the Stokes V and Stokes I Least-Squares Deconvolution (LSD) time series, as current attempts did not deliver conclusive results or a unique solution and solid-body rotation had to be assumed.

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Background

The paper uses Zeeman Doppler Imaging (ZDI) and Doppler Imaging (DI) to reconstruct the large-scale magnetic field and brightness maps of EK Draconis from a set of Stokes I and V LSD profiles collected in 2022. A search for differential rotation (DR) using the sheared image approach was attempted to characterize the latitudinal dependence of rotation.

However, the authors report that their DR search was inconclusive for Stokes V data and also failed to identify a unique solution with Stokes I, leading them to adopt a solid-body rotation model. This leaves the DR parameters of EK Draconis unresolved in their dataset, motivating future work to quantify the star’s rotational shear.

References

Contrary to , our search for surface differential rotation using the sheared image approach of did not deliver any conclusive results using Stokes V spectra, so solid body rotation was assumed in our model, leading to a reduced $\chi2$ equal to 1.15. We also searched again for the signature of differential rotation using the Stokes I time series, but failed to identify a unique solution.

— Multiwavelength Campaign Observations of a Young Solar-type Star, EK Draconis. II. Understanding Prominence Eruption through Data-Driven Modeling and Observed Magnetic Environment (2410.05523 - Namekata et al., 7 Oct 2024) in Section 2.1 (Doppler and Zeeman Doppler Imaging)