Journal Article

Photometric variability of the T Tauri star TW Hya on time-scales of hours to years*

Slavek M. Rucinski, Jaymie M. Matthews, Rainer Kuschnig, Grzegorz Pojmański, Jason Rowe, David B. Guenther, Anthony F. J. Moffat, Dimitar Sasselov, Gordon A. H. Walker and Werner W. Weiss

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 391, issue 4, pages 1913-1924
Published in print December 2008 | ISSN: 0035-8711
Published online December 2008 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2008.14014.x
Photometric variability of the T Tauri star TW Hya on time-scales of hours to years*

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Microvariability & Oscillations of STars (MOST) and All Sky Automated Survey (ASAS) observations have been used to characterize photometric variability of TW Hya on time-scales from a fraction of a day to 7.5 weeks and from a few days to 8 yr, respectively. The two data sets have very different uncertainties and temporal coverage properties and cannot be directly combined, nevertheless, they suggest a global variability spectrum with ‘flicker-noise’ properties, that is with amplitudes , over >4 decades in frequency, in the range f= 0.0003–10 c d−1. A 3.7 d period is clearly present in the continuous 11 d, 0.07 d time resolution, observations by MOST in 2007. Brightness extrema coincide with zero-velocity crossings in periodic (3.56 d) radial-velocity variability detected in contemporaneous spectroscopic observations of Setiawan et al. and interpreted as caused by a planet. The 3.56/3.7 d periodicity was entirely absent in the second, 4 times longer MOST run in 2008, casting doubt on the planetary explanation. Instead, a spectrum of unstable single periods within the range of 2–9 d was observed; the tendency of the periods to progressively shorten was well traced using the wavelet analysis. The evolving periodicities and the overall flicker-noise characteristics of the TW Hya variability suggest a combination of several mechanisms, with the dominant ones probably related to the accretion processes from the disc around the star.

Keywords: stars: pre-main-sequence; stars: variables: other

Journal Article.  9623 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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