Investigating the magnetospheric accretion process in the young pre-transitional disk system DoAr 44 (V2062 Oph): A multiwavelength interferometric, spectropolarimetric, and photometric observing campaign

Context. Young stars interact with their accretion disk through their strong magnetosphere. Aims. We aim to investigate the magnetospheric accretion/ejection process in the young stellar system DoAr 44 (V2062 Oph). Methods. We monitored the system over several rotational cycles, combining high-resol...

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Published in:Astronomy and astrophysics (Berlin) 2020-11, Vol.643, p.A99
Main Authors: Bouvier, J., Alecian, E., Alencar, S. H. P., Sousa, A., Donati, J.-F., Perraut, K., Bayo, A., Rebull, L. M., Dougados, C., Duvert, G., Berger, J.-P., Benisty, M., Pouilly, K., Folsom, C., Moutou, C.
Format: Article
Language:English
Subjects:
Astrophysics
Physics
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Summary:Context. Young stars interact with their accretion disk through their strong magnetosphere. Aims. We aim to investigate the magnetospheric accretion/ejection process in the young stellar system DoAr 44 (V2062 Oph). Methods. We monitored the system over several rotational cycles, combining high-resolution spectropolarimetry at both optical and near-IR wavelengths with long-baseline near-IR inteferometry and multicolor photometry. Results. We derive a rotational period of 2.96 d from the system’s light curve, which is dominated by stellar spots. We fully characterize the central star’s properties from the high signal-to-noise, high-resolution optical spectra we obtained during the campaign. DoAr 44 is a young 1.2 M ⊙ star, moderately accreting from its disk ( Ṁ acc = 6.5 10 −9 M ⊙  yr −1 ), and seen at a low inclination ( i  ≃ 30°). Several optical and near-IR line profiles probing the accretion funnel flows (H α , H β , HeI 1083 nm, Pa β ) and the accretion shock (HeI 587.6 nm) are modulated at the stellar rotation period. The most variable line profile is HeI 1083 nm, which exhibits modulated redshifted wings that are a signature of accretion funnel flows, as well as deep blueshifted absorptions indicative of transient outflows. The Zeeman-Doppler analysis suggests the star hosts a mainly dipolar magnetic field, inclined by about 20° onto the spin axis, with an intensity reaching about 800 G at the photosphere, and up to 2 ± 0.8 kG close to the accretion shock. The magnetic field appears strong enough to disrupt the inner disk close to the corotation radius, at a distance of about 4.6 R ⋆ (0.043 au), which is consistent with the 5 R ⋆ (0.047 au) upper limit we derived for the size of the magnetosphere in our Paper I from long baseline interferometry. Conclusions. DoAr 44 is a pre-transitional disk system, exhibiting a 25–30 au gap in its circumstellar disk, with the inner and outer disks being misaligned. On a scale of 0.1 au or less, our results indicate that the system is steadily accreting from its inner disk through its tilted dipolar magnetosphere. We conclude that in spite of a highly structured disk on the large scale, perhaps the signature of ongoing planetary formation, the magnetospheric accretion process proceeds unimpeded at the star-disk interaction level.
ISSN:0004-6361
1432-0746
1432-0756
DOI:10.1051/0004-6361/202038892