Doppler imaging and differential rotation of σ 2 Coronae Borealis using SONG

Yue Xiang, Shenghong Gu, A. Collier Cameron, J. R. Barnes, J. Christensen-Dalsgaard, F. Grundahl, V. Antoci, M. F. Andersen, P. L. Pallé

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5 Citations (Scopus)


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.
Original languageEnglish
Article number164
JournalAstrophysical Journal
Issue number2
Publication statusPublished - 28 Apr 2020


  • Stellar activity (1580)
  • Close binary stars (254)
  • Doppler imaging (400)
  • Starspots (1572)


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