Analysis of variability of TW Hya as observed by MOST and ASAS in 2009

Author： Siwak Michal Rucinski Slavek M. Matthews Jaymie M. Pojmański Grzegorz Kuschnig Rainer Guenther David B. Moffat Anthony F. J. Sasselov Dimitar Weiss Werner W.

Publisher： Oxford University Press

ISSN： 0035-8711

Source： Monthly Notices of the Royal Astronomical Society, Vol.410, Iss.4, 2011-02, pp. : 2725-2729

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Abstract

ABSTRACTAs a continuation of our previous studies in 2007 and 2008, new photometric observations of the T Tauri star TW Hya obtained by the MOST satellite and the All Sky Automated Survey (ASAS) project over 40 d in 2009 with temporal resolution of 0.2 d are presented. A wavelet analysis of the combined MOST–ASAS data provides a rich picture of coherent, intermittent, variable-period oscillations, similarly as discovered in the 2008 data. The periods (1.3–10 d) and systematic period shortening on time-scales of weeks can be interpreted within the model of magnetorotationally controlled accretion processes in the inner accretion disc around the star. Within this model and depending on the assumed visibility of plasma parcels causing the oscillations, the observed shortest oscillation period may indicate the stellar rotation period of 1.3 or 2.6 d, synchronized with the disc at 4.5 or 7.1 R_⊙ , respectively.