Star-disk interactions in the strongly accreting T Tauri star S CrA N
Context. Classical T Tauri stars are thought to accrete material from their surrounding protoplanetary disks through funnel flows along their magnetic field lines. The classical T Tauri stars with high accretion rates (∼10−7 M⊙ yr−1) are ideal targets for testing this magnetospheric accretion scenar...
| Autores: | , , , , , , , , , , , , , |
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| Tipo de recurso: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 2023 |
| País: | Brasil |
| Institución: | Universidade Federal de Minas Gerais (UFMG) |
| Repositorio: | Repositório Institucional da UFMG |
| Idioma: | inglés |
| OAI Identifier: | oai:repositorio.ufmg.br:1843/79457 |
| Acceso en línea: | https://doi.org/10.1051/0004-6361/202347145 http://hdl.handle.net/1843/79457 https://orcid.org/0000-0002-5762-0249 https://orcid.org/0000-0001-5260-7179 https://orcid.org/0000-0003-3099-757X https://orcid.org/0000-0002-9328-9530 https://orcid.org/0000-0002-9023-7890 https://orcid.org/0000-0002-9628-2959 https://orcid.org/0000-0002-7450-6712 https://orcid.org/0000-0001-7633-7038 https://orcid.org/0000-0001-7788-3727 https://orcid.org/0000-0001-7397-8972 https://orcid.org/0000-0001-6660-936X https://orcid.org/0000-0003-3547-3783 https://orcid.org/0000-0002-0493-4674 |
| Access Level: | acceso abierto |
| Palabra clave: | Stars: variables: T Tauri Stars: individual: S CrA N Herbig Ae/Be Stars: magnetic field Techniques: spectroscopic Techniques: polarimetric Accretion Accretion disks Estrelas - Campos magnéticos Estrelas T Tauri Astronomia |
| Sumario: | Context. Classical T Tauri stars are thought to accrete material from their surrounding protoplanetary disks through funnel flows along their magnetic field lines. The classical T Tauri stars with high accretion rates (∼10−7 M⊙ yr−1) are ideal targets for testing this magnetospheric accretion scenario in a sustained regime. Aims. We constrained the accretion-ejection phenomena around the strongly accreting northern component of the S CrA young binary system (S CrA N) by deriving its magnetic field topology and its magnetospheric properties, and by detecting ejection signatures, if any. Methods. We led a two-week observing campaign on S CrA N with the ESPaDOnS optical spectropolarimeter at the Canada-France-Hawaii Telescope. We recorded 12 Stokes I and V spectra over 14 nights. We computed the corresponding least-squares deconvolution (LSD) profiles of the photospheric lines and performed Zeeman-Doppler imaging (ZDI). We analyzed the kinematics of noticeable emission lines, namely He I λ5876 and the first four lines of the Balmer series, which are known to trace the accretion process. Results. We found that S CrA N is a low-mass (0.8 M⊙) young (∼1 Myr) and fully convective object exhibiting strong and variable veiling (with a mean value of 7 ± 2), which suggests that the star is in a strong accretion regime. These findings could indicate a stellar evolutionary stage between Class I and Class II for S CrA N. We reconstructed an axisymmetric large-scale magnetic field (∼70% of the total energy) that is primarily located in the dipolar component, but has significant higher poloidal orders. From the narrow emission component radial velocity curve of He I λ5876, we derived a stellar rotation period of P* = 7.3 ± 0.2 days. We found a magnetic truncation radius of ∼2 R* which is significantly closer to the star than the corotation radius of ∼6 R*, suggesting that S CrA N is in an unstable accretion regime. That the truncation radius is quite smaller than the size of the Brγ line emitting region, as measured with the GRAVITY interferometer (∼8 R*), supports the presence of outflows, which is nicely corroborated by the line profiles presented in this work. Conclusions. The findings from spectropolarimetry are complementary to those provided by optical long-baseline interferometry, allowing us to construct a coherent view of the innermost regions of a young, strongly accreting star. The strong and complex magnetic field reconstructed for S CrA N is inconsistent with the observed magnetic signatures of the emission lines associated with the postshock region, however. We recommend a multitechnique synchronized campaign of several days to place more constrains on a system that varies on a timescale of about one day. |
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