Formation of current helicity and emerging magnetic flux in solar active regions |
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| Authors: | Hongqi Zhang |
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| Institution: | School of Physics, University College UNSW, Australian Defence Force Academy, Canberra ACT 2600, Australia;Department of Astronomy, University of Cape Town, Private Bag, Rondebosch 7700, South Africa;Steward Observatory, University of Arizona, 933 N. Cherry Avenue, Tuscon, AZ 85721, USA;Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802, USA |
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| Abstract: | We present the results of a photometric study of X-ray-active weak-lined T Tauri (WTT) stars in the η Chamaeleontis star cluster. Multi-epoch V -band photometric monitoring during 1999 and 2000 of the 10 X-ray-active WTT stars found that all were variable in one or both years, with periods ascribed to rotational modulation of starspots. Comparison between the rotational and X-ray properties of these objects indicates the saturation level,  observed in other studies of X-ray-active pre-main-sequence stars, persists in the η Cha stars from the slow- to the fast-rotator regimes. Cousins VRI photometry of the WTT stars has enabled us to investigate further the photometric properties of these stars. The stars appear sufficiently coeval to distinguish near-equal-mass binaries within the sample. A new Hertzsprung–Russell diagram for these objects suggests ages of 4–9 Myr for M-type RECX primaries using the tracks of D'Antona & Mazzitelli. |
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| Keywords: | stars: activity stars: pre-main-sequence stars: rotation open clusters and associations: individual: η Chamaeleontis X-rays: stars |
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