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| Paper: |
Properties of Candidate Magnetic Grand Minimum Stars |
| Volume: |
448, 16th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun |
| Page: |
1239 |
| Authors: |
Saar, S. H. |
| Abstract: |
Using a large database of Ca II HK measurements from exoplanet
search candidates, I explore properties of stars with the lowest
activity levels. The minimum R′HK level (using the
traditional calibration) seen in bona-fide dwarfs (as determined
spectroscopically) is a strong function of metallicity: log RHK(min) ≈ -5.1 – 0.2 log M/H. Dwarf stars with a small Δ
R′HK above this boundary uniformly show fractional rms Ca II HK index
SHK variation of σS /〈SHK〉 ≤ 2%. I propose stars which show this low-variability, low RHK
behavior on timescales of several years (longer than a
typical solar minimum) are candidates for being in
magnetic grand minima (MM). These candidate MM stars span a wide
range in M/H and Teff, but show a sharp cutoff at higher masses.
Their v sin i distribution is consistent with their being drawn
from a mostly older (≥ 2 Gyr) stellar population. |
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