Doppler imaging and differential rotation of σ 2 Coronae Borealis using SONG
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We present new Doppler images of both components of the double-lined binary σ 2 CrB, based on the high-resolution spectroscopic data collected during 11 nights in 2015 March–April. The observed spectra form two independent data sets with sufficient phase coverage. We apply the least-squares deconvolution to all observed spectra to obtain high signal-to-noise mean profiles, from which we derive the Doppler images of both components of σ 2 CrB simultaneously. The surfaces of both F9 and G0 components are dominated by pronounced polar spots. The F9 component exhibits a weak spot at latitude 30° and its mid-to-low latitudes are relatively featureless. The G0 star shows an extended spot structure at latitude 30°, and its surface spot coverage is larger than that of the F9 star, which suggests a higher level of magnetic activity. With the cross-correlation method, we derive a solar-like surface differential rotation on the G0 star of σ 2 CrB for the first time, and the surface shear rate is ΔΩ = 0.180 ± 0.004 rad days−1 and α = ΔΩ/Ωeq = 0.032 ± 0.001. We do not obtain a clear surface shear law for the F9 star due to the lack of mid-to-low latitude features, but detect a systematic longitude shift of high-latitude spots, which indicates a slower rotation with respect to the corotating frame.
Xiang , Y , Gu , S , Cameron , A C , Barnes , J R , Christensen-Dalsgaard , J , Grundahl , F , Antoci , V , Andersen , M F & Pallé , P L 2020 , ' Doppler imaging and differential rotation of σ 2 Coronae Borealis using SONG ' , Astrophysical Journal , vol. 893 , no. 2 , 164 . https://doi.org/10.3847/1538-4357/ab8229
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DescriptionThis work is supported by National Natural Science Foundation of China (grant Nos. 10373023, 10773027, 11333006, 11603068, and U1531121) and Chinese Academy of Sciences project (No. KJCX2-YW-T24). Funding for the Stellar Astrophysics Centre is provided by The Danish National Research Foundation (Grant DNRF106).
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