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The main-sequence rotation-colour relation in the Coma Berenices open cluster

Collier Cameron, A.; Davidson, V. A.; Hebb, L.; Skinner, G.; Anderson, D. R.; Christian, D. J.; Clarkson, W. I.; Enoch, B.; Irwin, J.; Joshi, Y.; Haswell, C. A.; Hellier, C.; Horne, K. D.; Kane, S. R.; Lister, T. A.; Maxted, P. F. L.; Norton, A. J.; Parley, N.; Pollacco, D.; Ryans, R.; Scholz, A.; Skillen, I.; Smalley, B.; Street, R. A.; West, R. G.; Wilson, D. M. and Wheatley, P. J. (2009). The main-sequence rotation-colour relation in the Coma Berenices open cluster. Monthly Notices of the Royal Astronomical Society, 400(1) pp. 451–462.

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We present the results of a photometric survey of rotation rates in the Coma Berenices (Melotte 111) open cluster, using data obtained as part of the SuperWASP exoplanetary transit-search programme. The goal of the Coma survey was to measure precise rotation periods for main-sequence F, G and K dwarfs in this intermediate-age (∼600 Myr) cluster, and to determine the extent to which magnetic braking has caused the stellar spin periods to converge. We find a tight, almost linear relationship between rotation period and J−K colour with an rms scatter of only 2 per cent. The relation is similar to that seen among F, G and K stars in the Hyades. Such strong convergence can only be explained if angular momentum is not at present being transferred from a reservoir in the deep stellar interiors to the surface layers. We conclude that the coupling time-scale for angular momentum transport from a rapidly spinning radiative core to the outer convective zone must be substantially shorter than the cluster age, and that from the age of Coma onwards stars rotate effectively as solid bodies. The existence of a tight relationship between stellar mass and rotation period at a given age supports the use of stellar rotation period as an age indicator in F, G and K stars of Hyades age and older. We demonstrate that individual stellar ages can be determined within the Coma population with an internal precision of the order of 9 per cent (rms), using a standard magnetic braking law in which rotation period increases with the square root of stellar age. We find that a slight modification to the magnetic-braking power law, P∝t0.56 , yields rotational and asteroseismological ages in good agreement for the Sun and other stars of solar age for which p-mode studies and photometric rotation periods have been published

Item Type: Journal Item
Copyright Holders: 2009 The Authors, 2009 Journal compilation RAS
ISSN: 1365-2966
Keywords: photometric; activity of stars; rotation of stars; open clusters and associations; Melotte 111
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Physical Sciences
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Item ID: 18566
Depositing User: Andrew Norton
Date Deposited: 15 Oct 2009 08:10
Last Modified: 07 Dec 2018 19:21
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