Linking chromospheric activity and magnetic field properties for late-type dwarf stars. Issue 3 (10th May 2022)

• Record Type: Journal Article
• Authors: Brown, E L; Jeffers, S V; Marsden, S C; Morin, J; Boro Saikia, S; Petit, P; Jardine, M M; See, V; Vidotto, A A; Mengel, M W; Dahlkemper, M N; the BCool Collaboration,
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 514:Issue 3(2022)
• Page Start: 4300
• Page End: 4319
• Publication Date: 2022-05-10
• Subjects: stars: activity -- stars: late-type -- stars: magnetic field; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stac1291
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: Spectropolarimetric data allow for simultaneous monitoring of stellar chromospheric $\log {R^{\prime }_{\rm {HK}}}$ activity and the surface-averaged longitudinal magnetic field, Bl, giving the opportunity to probe the relationship between large-scale stellar magnetic fields and chromospheric manifestations of magnetism. We present $\log {R^{\prime }_{\rm {HK}}}$ and/or Bl 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 $\log {R^{\prime }_{\rm {HK}}}$ and mean log | Bl |, but for G stars the relationship may undergo a change between $\log {R^{\prime }_{\rm {HK}}}\sim -4.4$ and −4.8. The mean $\log {R^{\prime }_{\rm {HK}}}$ shows a similar change with respect to the $\log {R^{\prime }_{\rm {HK}}}$ 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 $-4.75\le \log {R^{\prime }_{\rm HK}}\le -4.5$ . 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 | Bl |, or the Bl and $\log {R^{\prime }_{\rm HK}}$ 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.