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

E L Brown*, S V Jeffers, S C Marsden, J Morin, S Boro Saikia, P Petit, M M Jardine, V See, A A Vidotto, M W Mengel, M N Dahlkemper, The BCool Collaboration

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

14 Citations (Scopus)
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Spectropolarimetric data allow for simultaneous monitoring of stellar chromospheric logR′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 logR′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 logR′HK and mean log |Bl|, 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 |Bl|, or the Bl 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.
Original languageEnglish
Article numberstac1291
Number of pages21
JournalMonthly Notices of the Royal Astronomical Society
Publication statusAccepted/In press - 10 May 2022


  • Stars: late-type
  • Stars: activity
  • Stars:magnetic field


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