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Description
Young stars interact with their accretion disk through their strong magnetosphere. We aim to investigate the magnetospheric accretion/ejection process in the young stellar system DoAr 44 (V2062 Oph). 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. We derive a rotational period of 2.96d 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 1.2M_{sun}_ star, moderately accreting from its disk (Macc=6.510^-9^M_{sun}_/yr), and seen at a low inclination (i~=30{deg}). Several optical and near-IR line profiles probing the accretion funnel flows (H{alpha}, H{beta}, HeI 1083nm, Pa{beta}) and the accretion shock (HeI 587.6nm) are modulated at the stellar rotation period. The most variable line profile is HeI 1083nm, 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{deg} onto the spin axis, with an intensity reaching about 800G at the photosphere, and up to 2+/-0.8kG 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 4.6R* (0.043au), which is consistent with the 5R* (0.047au) upper limit we derived for the size of the magnetosphere in our Paper I from long baseline interferometry. DoAr 44 is a pre-transitional disk system, exhibiting a 25-30au gap in its circumstellar disk, with the inner and outer disks being misaligned. On a scale of 0.1au 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.
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