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Abstract Classical T Tauri stars (CTTSs) are young, low-mass stars that accrete material from their surrounding protoplanetary disk. To better understand accretion variability, we conducted a multiepoch, multiwavelength photometric monitoring campaign of four CTTSs, TW Hya, RU Lup, BP Tau, and GM Aur, in 2021 and 2022, contemporaneous with Hubble Space Telescope UV and optical spectra. We find that all four targets display significant variability in their light curves, generally on days-long timescales (but in some cases year-to-year), often due to periodicity associated with stellar rotation and to stochastic accretion variability. There is a strong connection between mass accretion and photometric variability in all bands, but the relationship varies per target and epoch. Thus, photometry should be used with caution as a direct measure of accretion in CTTSs.
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Unstable accretion in TW Hya: 3D simulations and comparisons with observations
ABSTRACT We investigate the origin of photometric variability in the classical T Tauri star TW Hya by comparing light curves obtained by Transiting Exoplanet Survey Satellite (TESS) and ground-based telescopes with light curves created using three-dimensional (3D) magnetohydrodynamic (MHD) simulations. TW Hya is modelled as a rotating star with a dipole magnetic moment, which is slightly tilted about the rotational axis. We observed that for various model parameters, matter accretes in the unstable regime and produces multiple hotspots on the star’s surface, which leads to stochastic-looking light curves similar to the observed ones. Wavelet and Fourier spectra of observed and modelled light curves show multiple quasi-periodic oscillations (QPOs) with quasi-periods from less than 0.1 to 9 d. Models show that variation in the strength and tilt of the dipole magnetosphere leads to different periodograms, where the period of the star may dominate or be hidden. The amplitude of QPOs associated with the stellar period can be smaller than that of other QPOs if the tilt of the dipole magnetosphere is small and when the unstable regime is stronger. In models with small magnetospheres, the short-period QPOs associated with rotation of the inner disc dominate and can be mistaken for a stellar period. We show that longer period (5–9 d) QPOs can be caused by waves forming beyond the corotation radius.
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- Award ID(s):
- 2009820
- PAR ID:
- 10575432
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 538
- Issue:
- 1
- ISSN:
- 0035-8711
- Format(s):
- Medium: X Size: p. 480-502
- Size(s):
- p. 480-502
- Sponsoring Org:
- National Science Foundation
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