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

Bouvier, J.; Alencar, S. H. P.; Boutelier, T.; Dougados, C.; Balog, Z.; Grankin, K. N.; Hodgkin, S. T.; Ibrahimov, M.; Kun, M.; Magakian, T. Yu.; Pinte, C.

doi:10.1051/0004-6361:20066021

Cited by 241 publications

(321 citation statements)

References 42 publications

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“…The authors discussed the possibility of dusty clumps in the immediate vicinity of the central star, that could partially occult it and be responsible for the observed variability. Such fast variability has also been commonly observed around other young stars (e.g., AA Tau, Bouvier et al 2007). Based on CoRot photometric observations in NGC 2264, Alencar et al (2010) found that a high fraction of the 83 TTauri stars in their sample (30 to 40% of stars having inner dusty disks) exhibit photometric time variability comparable to the AA Tau phenomenon.…”

Section: Discussionsupporting

confidence: 63%

Sculpting the disk around T Chamaeleontis: an interferometric view

Olofsson

Benisty

Bouquin

et al. 2013

A&A

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Context. Circumstellar disks are believed to be the birthplace of planets and are expected to dissipate on a timescale of a few Myr. The processes responsible for the removal of the dust and gas will strongly modify the radial distribution of the circumstellar matter and consequently the spectral energy distribution. In particular, a young planet will open a gap, resulting in an inner disk dominating the near-IR emission and an outer disk emitting mostly in the far-infrared. Aims. We analyze a full set of data involving new near-infrared data obtained with the 4-telescope combiner (VLTI/PIONIER), new mid-infrared interferometric VLTI/MIDI data, literature photometric and archival data from VLT/NaCo/SAM to constrain the structure of the transition disk around T Cha. Methods. After a preliminary analysis with a simple geometric model, we used the MCFOST radiative transfer code to simultaneously model the SED and the interferometric observables from raytraced images in the H-, L -, and N-bands. Results. We find that the dust responsible for the strong emission in excess in the near-IR must have a narrow temperature distribution with a maximum close to the silicate sublimation temperature. This translates into a narrow inner dusty disk (0.07-0.11 AU), with a significant height (H/r ∼ 0.2) to increase the geometric surface illuminated by the central star. We find that the outer disk starts at about 12 AU and is partially resolved by the PIONIER, SAM, and MIDI instruments. We discuss the possibility of a self-shadowed inner disk, which can extend to distances of several AU. Finally, we show that the SAM closure phases, interpreted as the signature of a candidate companion, may actually trace the asymmetry generated by forward scattering by dust grains in the upper layers of the outer disk. These observations help constrain the inclination and position angle of the disk to about +58 • and −70 • , respectively. Conclusions. The circumstellar environment of T Cha appears to be best described by two disks spatially separated by a large gap. The presence of matter (dust or gas) inside the gap is, however, difficult to assess with present-day observations. Our model suggests the outer disk contaminates the interferometric signature of any potential companion that could be responsible for the gap opening, and such a companion still has to be unambiguously detected. We stress the difficulty to observe point sources in bright massive disks, and the consequent need to account for disk asymmetries (e.g. anisotropic scattering) in model-dependent search for companions.

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Section: Discussionsupporting

confidence: 63%

Sculpting the disk around T Chamaeleontis: an interferometric view

Olofsson

Benisty

Bouquin

et al. 2013

A&A

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“…The observed Hα and Hβ profiles of V2129 Oph cannot be easily decomposed with the simple Gaussian components typically used to represent the main accretion flow, the wind, and the accretion shock, in a similar way to the analyses of other stars, such as AA Tau (Bouvier et al 2007). To understand the observed emission-line variabilities, we therefore decided to try to reproduce the Balmer line profiles with radiative transfer calculations based on the 3D MHD structure of the accretion flow.…”

Section: Theoretical Line Profilesmentioning

confidence: 99%

“…They show an emission excess with respect to the photosphere at wavelengths from X-rays to the radio and are both spectroscopically and photometrically variable (Bouvier et al 2007). The CTTSs have strong permitted emission lines that vary on short timescales (days), a redshifted absorption component associated with the accreting material, and a blueshifted absorption component due to winds.…”

Section: Introductionmentioning

confidence: 99%

Accretion dynamics in the classical T Tauri star V2129 Ophiuchi

Alencar

Bouvier

Walter

et al. 2012

A&A

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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.

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“…Besides the emission associated with the protoplanets themselves and their associated circumplanetary discs, asymmetries can also be caused by dynamically-induced disc features such as spiral arms, disc warps (Alencar et al 2010;Muzerolle et al 2009), or disc physics-related processes such as gravitational instabilities, and density waves (Bouvier et al 2007). Additionally a highly inclined disc can induce strong asymmetries in an axial-symmetric disc owing to forward-scattered light from the illuminated inner rim of disc (Olofsson et al 2013;Cheetham et al 2015).…”

Section: Introductionmentioning

confidence: 99%

Sparse aperture masking interferometry survey of transitional discs

Willson

Kraus

Kluska

et al. 2016

A&A

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Context. Transitional discs are a class of circumstellar discs around young stars with extensive clearing of dusty material within their inner regions on 10s of au scales. One of the primary candidates for this kind of clearing is the formation of planet(s) within the disc that then accrete or clear their immediate area as they migrate through the disc. Aims. The goal of this survey was to search for asymmetries in the brightness distribution around a selection of transitional disc targets. We then aimed to determine whether these asymmetries trace dynamically-induced structures in the disc or the gap-opening planets themselves. Methods. Our sample included eight transitional discs. Using the Keck/NIRC2 instrument we utilised the Sparse Aperture Masking (SAM) interferometry technique to search for asymmetries indicative of ongoing planet formation. We searched for close-in companions using both model fitting and interferometric image reconstruction techniques. Using simulated data, we derived diagnostics that helped us to distinguish between point sources and extended asymmetric disc emission. In addition, we investigated the degeneracy between the contrast and separation that appear for marginally resolved companions. Results. We found FP Tau to contain a previously unseen disc wall, and DM Tau, LkHα330, and TW Hya to contain an asymmetric signal indicative of point source-like emission. We placed upper limits on the contrast of a companion in RXJ1842.9-3532 and V2246 Oph. We ruled the asymmetry signal in RXJ1615.3-3255 and V2062 Oph to be false positives. In the cases where our data indicated a potential companion we computed estimates for the value of M cṀc and found values in the range of 10 −5 − 10 −3 M 2 J yr −1 . Conclusions. We found significant asymmetries in four targets. Of these, three were consistent with companions. We resolved a previously unseen gap in the disc of FP Tau extending inwards from approximately 10 au.

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

Cited by 241 publications

References 42 publications

Sculpting the disk around T Chamaeleontis: an interferometric view

Sculpting the disk around T Chamaeleontis: an interferometric view

Accretion dynamics in the classical T Tauri star V2129 Ophiuchi

Sparse aperture masking interferometry survey of transitional discs

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