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Article Dans Une Revue Monthly Notices of the Royal Astronomical Society Année : 2022

Linking chromospheric activity and magnetic field properties for late-type dwarf stars

Résumé

Spectropolarimetric data allow for simultaneous monitoring of stellar chromospheric logR′HK activity and the surface-averaged longitudinal magnetic field, , giving the opportunity to probe the relationship between large-scale stellar magnetic fields and chromospheric manifestations of magnetism. We present logR′HK and/or B_l measurements for 954 mid-F to mid-M stars derived from spectropolarimetric observations contained within the PolarBase database. Our magnetically active sample complements previous stellar activity surveys that focus on inactive planet-search targets. We find a positive correlation between mean logR′HK and mean log |B_l|, but for G stars the relationship may undergo a change between logR′HK∼−4.4 and −4.8. The mean logR′HK shows a similar change with respect to the logR′HK variability amplitude for intermediately active G stars. We also combine our results with archival chromospheric activity data and published observations of large-scale magnetic field geometries derived using Zeeman–Doppler Imaging. The chromospheric activity data indicate a slight under-density of late-F to early-K stars with −4.75≤logR′HK≤−4.5⁠. This is not as prominent as the original Vaughan–Preston gap, and we do not detect similar under-populated regions in the distributions of the mean |B_l|, or the B_l and logR′HK variability amplitudes. Chromospheric activity, activity variability, and toroidal field strength decrease on the main sequence as rotation slows. For G stars, the disappearance of dominant toroidal fields occurs at a similar chromospheric activity level as the change in the relationships between chromospheric activity, activity variability, and mean field strength.
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hal-03672902 , version 1 (17-03-2023)

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E.L. Brown, S.V. Jeffers, S.C. Marsden, J. Morin, S. Boro Saikia, et al.. Linking chromospheric activity and magnetic field properties for late-type dwarf stars. Monthly Notices of the Royal Astronomical Society, 2022, 514 (3), pp.4300-4319. ⟨10.1093/mnras/stac1291⟩. ⟨hal-03672902⟩
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