Spectroscopic and interferometric signatures of magnetospheric accretion in young stars

Abstract

Methods. We use the code MCFOST to solve the non-LTE problem of line formation in non-axisymmetric accreting magnetospheres. We compute the Brγ line profile originating from accretion columns for models with different magnetic obliquities. We also derive monochromatic synthetic images of the Brγ line emitting region across the line profile. This spectral line is a prime diagnostics of magnetospheric accretion in young stars and is accessible with the long baseline near-infrared interferometer GRAVITY installed at the ESO Very Large Telescope Interferometer. Results. We derive Brγ line profiles as a function of rotational phase and compute interferometric observables, visibilities and phases, from synthetic images. The line profile shape is modulated along the rotational cycle, exhibiting inverse P Cygni profiles at the time the accretion shock faces the observer. The size of the line's emission region decreases as the magnetic obliquity increases, which is reflected in a lower line flux. We apply interferometric models to the synthetic visibilities in order to derive the size of the line-emitting region. We find the derived interferometric size to be more compact than the actual size of the magnetosphere, ranging from 50 to 90\% of the truncation radius. Additionally, we show that the rotation of the non-axisymmetric magnetosphere is recovered from the rotational modulation of the Brγ-to-continuum photo-centre shifts, as measured by the differential phase of interferometric visibilities.

References in corpus (11)

• Monte Carlo radiative transfer in protoplanetary disks
• On the formation of H-alpha line emission around classical T Tauri stars
• Magnetospheric accretion on the T Tauri star BP Tauri
• Non-equilibrium hydrogen ionization in 2D simulations of the solar atmosphere
• The origin of hydrogen line emission for five Herbig Ae/Be stars spatially resolved by VLTI/AMBER spectro-interferometry
• The magnetic field and accretion regime of CI Tau
• A measure of the size of the magnetospheric accretion region in TW Hydrae
• The magnetic obliquity of accreting T Tauri stars
• Star-disk interaction in the T Tauri star V2129 Oph: An evolving accretion-ejection structure
• Line and continuum radiative transfer modelling of AA Tau
• Atomic line radiative transfer with MCFOST I. Code description and benchmarking

Cited by in corpus (4)

• The GRAVITY young stellar object survey -- XI. Probing the inner disk and magnetospheric accretion region of CI Tau
• Stable accretion and episodic outflows in the young transition disk system GM Aurigae
• The GRAVITY young stellar object survey XIV : Investigating the magnetospheric accretion-ejection processes in S CrA N
• Three-dimensional, Time-dependent MHD Simulation of Disk-Magnetosphere-Stellar Wind Interaction in a T Tauri, Protoplanetary System