Magnetospheric accretion-ejection processes in the classical T Tauri star AA Tauri

By J. Bouvier, S. Alencar, T. Boutelier, C. Dougados, Z. Balog, K. Grankin, S. Hodgkin, M. Ibrahimov, M. Kun, T. Magakian and 1 more. 2006

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Context. Accretion and ejection are complex and related processes that vary on various timescales in young stars. Aims. We intend to investigate the accretion and outflow dynamics and their interaction from observations of the classical T Tauri star AA Tau. Methods. From a long time series of high resolution (R = 115 000) HARPS spectra and simultaneous broad-band photometry, we report new evidence for magnetospheric accretion as well as ejection processes in the nearly edge-on classical T Tauri star AA Tau. Results. AA Tau’s light curve is modulated with a period of 8.22 d. The recurrent luminosity dips are due to the periodic occultation of the central star by the magnetically-warped inner disk edge located at about 9 R� . Balmer line profiles exhibit a clear rotational modulation of high-velocity redshifted absorption components with a period of 8.22 days as well, with a maximum strength when the main accretion funnel flow passes through the line of sight. At the same time, the luminosity of the system decreases by about 1 mag, indicative of circumstellar absorption of the stellar photosphere by the magnetically-warped, corotating inner disk edge. The photospheric and He I radial velocities also exhibit periodic variations, and the veiling is modulated by the appearance of the accretion shock at the bottom of the accretion funnel. Diagnostics of hot winds and their temporal behaviour are also presented. Conclusions. The peculiar geometry of the young AA Tau system (nearly edge-on) allows us to uniquely probe the acretion-ejection region close to the star. We find that most spectral and photometric diagnostics vary as expected from models of magneticallychannelled accretion in young stars, with a large scale magnetosphere tilted by 20 ◦ onto the star’s spin axis. We also find evidence for time variability of the magnetospheric accretion flow on a timescale of a few rotational periods.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/542a50625605bf176e7c8c8b1727e58290fc6530

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Citations in the corpus

CSI 2264: SIMULTANEOUS OPTICAL AND INFRARED LIGHT CURVES OF YOUNG DISK-BEARING STARS IN NGC 2264 WITH CoRoT and SPITZER—EVIDENCE FOR MULTIPLE ORIGINS OF VARIABILITY (2014, background): “…surface (Koldoba et al. 2008), unsteady accretion and hot spot evolution (e.g., Fernandez & Eiroa 1996, Stassun & Wood 1999, Carpenter et al. 2002, Scholz et al. 2009, van Boekel et al. 2010), and instabilities in the accretion disk (e.g., Bertout et al. 1988, Bertout 1989, Bouvier et al. 2007).”
Launching of conical winds and axial jets from the disc–magnetosphere boundary: axisymmetric and 3D simulations (2009, background): “Bouvier et al. (2007) have shown that magnetospheric expansion in the CTTS AA Tau may occur with a period of a few weeks.”
UV Excess Measures of Accretion onto Young Very Low Mass Stars and Brown Dwarfs (2008, background): “Variability of 0.1–0.2 dex is also commonly seen in repeated veiling measurements of DF Tau, TW Hya, and AA Tau (Johns-Krull & Basri 1997; Batalha et al. 2002; Bouvier et al. 2007).”