In:
Astronomy & Astrophysics, EDP Sciences, Vol. 674 ( 2023-6), p. A203-
Kurzfassung:
Context. T Tauri stars are known to be the cradle of planet formation. Most exoplanets discovered to date lie at the very inner part of the circumstellar disk ( 〈 1 au). The innermost scale of young stellar objects is therefore a compelling region to be addressed, and long-baseline interferometry is a key technique to unveil their mysteries. Aims. We aim to spatially and spectrally resolve the innermost scale (≤1 au) of the young stellar system CI Tau to constrain the inner disk properties and better understand the magnetospheric accretion phenomenon. Methods. The high sensitivity offered by the combination of the four 8-m class telescopes of the Very Large Telescope Interferometer (VLTI) allied with the high spectral resolution (R ~ 4000) of the K -band beam combiner GRAVITY offers a unique capability to probe the sub-au scale of the CI Tau system, tracing both dust (continuum) and gas (Br γ line) emission regions. We developed a physically motivated geometrical model to fit the interferometric observables – visibilities and closure phases (CP) – and constrained the physical properties of the inner dusty disk. The continuum-corrected pure line visibilities have been used to estimate the size of the Hydrogen I Br γ emitting region. Results. From the K -band continuum study, we report a highly inclined ( i ~ 70°) resolved inner dusty disk, with an inner edge located at a distance of 21 ± 2 R ★ from the central star, which is significantly larger than the dust sublimation radius ( R sub = 4.3 to 8.6 R ★ ). The inner disk appears misaligned compared to the outer disk observed by ALMA and the non-zero closure phase indicates the presence of an asymmetry that could be reproduced with an azimuthally modulated ring with a brighter south-west side. From the differential visibilities across the Br γ line, we resolved the line-emitting region, and measured a size of 4.8 - 1.0 + 0.8 R ★ . Conclusions. The extended inner disk edge compared to the dust sublimation radius is consistent with the claim of an inner planet, CI Tau b, orbiting close in. The inner-outer disk misalignment may be induced by gravitational torques or magnetic warping. The size of the Br γ emitting region is consistent with the magnetospheric accretion process. Assuming it corresponds to the magnetospheric radius, it is significantly smaller than the co-rotation radius ( R cor = 8.8 ± 1.3 R ★ ), which suggests an unstable accretion regime that is consistent with CI Tau being a burster.
Materialart:
Online-Ressource
ISSN:
0004-6361
,
1432-0746
DOI:
10.1051/0004-6361/202346446
Sprache:
Englisch
Verlag:
EDP Sciences
Publikationsdatum:
2023
ZDB Id:
1458466-9
SSG:
16,12
