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

TL;DR

This study analyzes the variability of TW Hya using MOST and ASAS data from 2009, revealing intermittent oscillations and potential links to stellar rotation and accretion processes.

Contribution

It provides new photometric observations and wavelet analysis of TW Hya, extending previous studies and offering insights into its variable-period oscillations and underlying accretion mechanisms.

Findings

Detected coherent, intermittent oscillations with periods of 1.3 - 10 days.

Observed systematic period shortening over weeks.

Suggested possible stellar rotation periods of 1.3 or 2.6 days.

Abstract

As 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 ASAS project over 40 days in 2009 with temporal resolution of 0.2 days 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 days) and systematic period shortening on time scales of weeks can be interpreted within the model of magneto-rotationally controlled accretion processes in the inner accretion disk around the star. Within this model and depending on the assumed visibility of plasma parcels causing the oscillations, the observed shortest-period oscillation period may indicate the stellar rotation period of 1.3 or 2.6 d, synchronized with the disk at 4.5 or 7.1 solar radii, respectively.