2021MNRAS.500.1844K -
Mon. Not. R. Astron. Soc., 500, 1844-1850 (2021/January-2)
The large-scale magnetic field of Proxima Centauri near activity maximum.
KLEIN B., DONATI J.-F., HEBRARD E.M., ZAIRE B., FOLSOM C.P., MORIN J., DELFOSSE X. and BONFILS X.
Abstract (from CDS):
We report the detection of a large-scale magnetic field at the surface of the slowly rotating fully convective (FC) M dwarf Proxima Centauri. 10 circular polarization spectra, collected from 2017 April to July with the HARPS-Pol spectropolarimeter, exhibit rotationally modulated Zeeman signatures suggesting a stellar rotation period of 89.8 ± 4.0 d. Using Zeeman-Doppler Imaging, we invert the circular polarization spectra into a surface distribution of the large-scale magnetic field. We find that Proxima Cen hosts a large-scale magnetic field of typical strength 200 G, whose topology is mainly poloidal, and moderately axisymmetric, featuring, in particular, a dipole component of 135 G tilted at 51° to the rotation axis. The large-scale magnetic flux is roughly 3x smaller than the flux measured from the Zeeman broadening of unpolarized lines, which suggests that the underlying dynamo is efficient at generating a magnetic field at the largest spatial scales. Our observations occur ∼1 yr after the maximum of the reported 7 yr-activity cycle of Proxima Cen, which opens the door for the first long-term study of how the large-scale field evolves with the magnetic cycle in an FC very low mass star. Finally, we find that Proxima Cen's habitable zone planet, Proxima-b, is likely orbiting outside the Alfven surface, where no direct magnetic star-planet interactions occur.
Abstract Copyright:
© 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
Journal keyword(s):
techniques: polarimetric - stars: individual: Proxima Centauri - stars: low-mass - stars: magnetic field - stars: rotation
Simbad objects:
2
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