Collier Cameron, A. and Davidson, V. A. and Hebb, L. and Skinner, G. and Anderson, D. R. and Christian, D. J. and Clarkson, W. I. and Enoch, B. and Irwin, J. and Joshi, Y. and Haswell, C. A. and Hellier, C. and Horne, K. D. and Kane, S. R. and Lister, T. A. and Maxted, P. F. L. and Norton, A. J. and Parley, N. and Pollacco, D. and Ryans, R. and Scholz, A. and Skillen, I. and Smalley, B. and Street, R. A. and West, R. G. and 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. ISSN 0035-8711 http://resolver.caltech.edu/CaltechAUTHORS:20100108-092958805
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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∝t^(0.56) , 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.
|Additional Information:||© 2009,RAS. Accepted 2009 July 30. Received 2009 July 30; in original form 2009 June 3. TheWASP Consortium consists of representatives from the Universities of Keele, Leicester, The Open University, Queens University Belfast and St Andrews, along with the Isaac Newton Group (La Palma) and the Instituto de Astrofisica de Canarias (Tenerife). The SuperWASP and WASP-S Cameras were constructed and operated with funds made available from Consortium Universities and PPARC/STFC. This publicationmakes use of data products from the 2MASS, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. This research has made use of the VizieR catalogue access tool, CDS, Strasbourg, France. We also thank the anonymous referee for insightful comments that led to substantial improvements in our methodology.|
|Subject Keywords:||methods: data analysis, techniques: photometric, stars: activity, stars: rotation, open clusters and associations: individual: Melotte 111|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||11 Jan 2010 22:59|
|Last Modified:||26 Dec 2012 11:40|
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