Doppler imaging and differential rotation of σ 2 coronae borealis using song

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  • Yue Xiang, Chinese Academy of Sciences
  • ,
  • Shenghong Gu, Chinese Academy of Sciences, University of Chinese Academy of Sciences
  • ,
  • A. Collier Cameron, University of St Andrews
  • ,
  • J. R. Barnes, Open University Milton Keynes
  • ,
  • J. Christensen-Dalsgaard
  • F. Grundahl
  • V. Antoci
  • ,
  • M. F. Andersen
  • P. L. Pallé, Instituto Astrofisico de Canarias, University of La Laguna

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.

TidsskriftAstrophysical Journal
StatusUdgivet - apr. 2020

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