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Accretion dynamics in the classical T Tauri star V2129 Ophiuchi

Abstract : Context. Classical T Tauri stars are variable objects on several timescales, but just a few of them have been studied in detail, with different observational techniques and over many rotational cycles to enable the analysis of the stellar and circumstellar variations on rotational timescales.
Aims: We test the dynamical predictions of the magnetospheric accretion model with synoptic data of the classical T Tauri star V2129 Oph obtained over several rotational cycles.
Methods: We analyze high resolution observations obtained with the HARPS, ESPaDOnS, and SMARTS spectrographs and simultaneous photometric measurements, clearly sampling four rotational cycles, and fit them with cold/hot spot models and radiative transfer models of emission lines.
Results: The photometric variability and the radial velocity variations in the photospheric lines can be explained by the rotational modulation due to cold spots, while the radial velocity variations of the He i (5876 Å) line and the veiling variability are due to hot spot rotational modulation. The hot and cold spots are located at high latitudes and about the same phase, but the hot spot is expected to sit at the chromospheric level, while the cold spot is at the photospheric level. The mass-accretion rate of the system is stable overall around (1.5 ± 0.6) × 10-9 M yr-1, but can increase by three times this value in a rotational cycle, during an accretion burst. The Hα and Hβ emission-line profiles vary substantially and are well-reproduced by radiative transfer models calculated from the funnel flow structure of three-dimensional magnetohydrodynamic simulations, using the dipole+octupole magnetic-field configuration previously proposed for the system. Our diskwind models do not provide a significant contribution to the emission or absorption Hα line profile of V2129 Oph.
Conclusions: The global scenario proposed by magnetospheric accretion for classical T Tauri stars is able to reproduce the spectroscopic and photometric variability observed in V2129 Oph.

This work uses observations made with the HARPS instrument at the 3.6-m ESO telescope (La Silla, Chile) in the framework of the LP182.D-0356.

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S. H. P. Alencar, J. Bouvier, F. M. Walter, C. Dougados, J. -F. Donati, et al.. Accretion dynamics in the classical T Tauri star V2129 Ophiuchi. Astronomy and Astrophysics - A&A, EDP Sciences, 2012, 541, ⟨10.1051/0004-6361/201118395⟩. ⟨insu-03612437⟩

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