| Issue |
A&A
Volume 674, June 2023
|
|
|---|---|---|
| Article Number | A118 | |
| Number of page(s) | 9 | |
| Section | Stellar atmospheres | |
| DOI | https://doi.org/10.1051/0004-6361/202245664 | |
| Published online | 12 June 2023 | |
Zeeman Doppler imaging of ξ Boo A and B★
Leibniz-Institute for Astrophysics Potsdam (AIP),
An der Sternwarte 16,
14482
Potsdam, Germany
e-mail: kstrassmeier@aip.de, tcarroll@aip.de, ilyin@aip.de
Received:
11
December
2022
Accepted:
27
April
2023
Aims. We present a magnetic-field surface map for both stellar components of the young visual binary ξ Boo AB (A: G8V, B: K5V).
Methods. We employed high-resolution Stokes-V spectra obtained with the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope (LBT). We inverted Stokes V line profiles with our iMAP software and compared them with previous inversions. We employed an iterative regularization scheme without the need for a penalty function and incorporated a three-component description of the surface magnetic-field vector. The spectral resolution of our data is 130 000 (0.040–0.055 Å) and we obtain a signal-to-noise ratio (S/N) of up to 3000 per pixel depending on wavelength. We used a singular-value decomposition (SVD) of a total of 1811 spectral lines to average Stokes-V profiles. Our mapping is accompanied by a residual bootstrap error analysis.
Results. We constructed magnetic flux densities of the radial field component for ξ Boo A and ξ Boo B of up to plus or −115±5 G and 55±3 G, respectively. The magnetic morphology of ξ Boo A is characterized by a very high latitude, nearly polar spot of negative polarity and three low-to-mid-latitude spots of positive polarity, while that of ξ Boo B is characterized by four low-to-mid-latitude spots of mixed polarity. No polar magnetic field is reconstructed for the cooler ξ Boo B star. Both our maps are dominated by the radial field component, containing 86% and 89% of the magnetic energy of ξ Boo A and B, respectively. We find only weak azimuthal and meridional field densities on both stars (plus or −15–30 G), about a factor two weaker than what was seen previously for ξ Boo A. The phase averaged longitudinal field component and dispersion is +4.5±1.5 G for ξ Boo A and −5.0±3.0 G for ξ Boo B.
Key words: stars: imaging / stars: activity / stars: magnetic field / starspots / stars: individual: ξ Boo
© The Authors 2023
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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