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        J-band variability of M dwarfs in the WFCAM Transit Survey

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        Author
        Goulding, N. T.
        Barnes, J. R.
        Pinfield, D.J.
        Kovacs, G.
        Birkby, J.
        Hodgkin, S.
        Catalan, S.
        Sipocz, B.
        Jones, H.R.A.
        del Burgo, C.
        Jeffers, S.V.
        Nefs, S.
        Galvez-Ortiz, M. -C.
        Martin, E. L.
        Attention
        2299/13882
        Abstract
        We present an analysis of the photometric variability of M dwarfs in the Wide Field Camera (WFCAM) Transit Survey. Although periodic light-curve variability in low mass stars is generally dominated by photospheric star spot activity, M dwarf variability in the J band has not been as thoroughly investigated as at visible wavelengths. Spectral type estimates for a sample of over 200 000 objects are made using spectral type-colour relations, and over 9600 dwarfs (J <17) with spectral types later than K7 were found. The light curves of the late-type sample are searched for periodicity using a Lomb-Scargle periodogram analysis. A total of 68 periodic variable M dwarfs are found in the sample with periods ranging from 0.16 to 90.33 d, with amplitudes in the range of similar to 0.009 to similar to 0.115 in the J band. We simulate active M dwarfs with a range of latitude-independent spot coverages and estimate a periodically variable fraction of 1-3 per cent for stars where spots cover more than 10 per cent of the star's surface. Our simulated spot distributions indicate that operating in the J band, where spot contrast ratios are minimized, enables variability in only the most active of stars to be detected. These findings affirm the benefits of using the J band for planetary transit searches compared to visible bands. We also serendipitously find a Delta J > 0.2 mag flaring event from an M4V star in our sample.
        Publication date
        2012-12
        Published in
        Monthly Notices of the Royal Astronomical Society
        Published version
        https://doi.org/10.1111/j.1365-2966.2012.21932.x
        Other links
        http://hdl.handle.net/2299/13882
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