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On the relation between activity and rotation in main‐sequence stars
Author(s) -
Teplitskaya R. B.
Publication year - 1989
Publication title -
astronomische nachrichten
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.394
H-Index - 63
eISSN - 1521-3994
pISSN - 0004-6337
DOI - 10.1002/asna.2113100312
Subject(s) - physics , rossby number , stars , astrophysics , main sequence , stellar rotation , convection , rotation (mathematics) , saturation (graph theory) , sequence (biology) , astronomy , mathematics , geometry , thermodynamics , combinatorics , turbulence , chemistry , biochemistry
A modified index of the level of stellar chromospheric activity, A ' Call , is proposed. It is calculated from the measured emission flux density in cores of Ca II H and K lines; however, unlike the other known indices, it is free from the influence of the colour of a star. Application of the new index leads to amodified activityrotation relationship in lower main‐sequence stars. It is shown that in the coordinate system log A' Call , log Ro ( Ro being Rossby number) F‐M stars obey a common relationship corresponding to the parameter α = 1.6. The obtained curve shows no evidence for activity saturation for stars with small Rossby numbers, but in slowly rotating stars with thin convection zones the activity level tends to a constant value.