Accretion dynamics in the classical T Tauri star V2129 Oph

TL;DR

This study combines photometric, spectroscopic, and 3D MHD simulations to analyze accretion processes and magnetic field configurations in the classical T Tauri star V2129 Oph, confirming complex magnetospheric accretion models.

Contribution

It provides the first detailed comparison of observed variability with 3D MHD models incorporating multipolar magnetic fields in V2129 Oph.

Findings

Photometric and spectroscopic variability explained by rotational modulation of hot and cold spots.

Theoretical line profiles qualitatively match observed line profile modulation.

Complex, non-axisymmetric magnetic fields are supported by variability data.

Abstract

We analyze the photometric and spectroscopic variability of the classical T Tauri star V2129 Oph over several rotational cycles to test the dynamical predictions of magnetospheric accretion models. The photometric variability and the radial velocity variations in the photospheric lines can be explained by rotational modulation due to cold spots, while the radial velocity variations of the He I (5876 \AA) line and the veiling variability are due to hot spot rotational modulation. The hot and cold spots are located at high latitudes and about the same phase, but the hot spot is expected to sit at the chromospheric level, while the cold spot is at the photospheric level. Using the dipole+octupole magnetic-field configuration previously proposed in the literature for the system, we compute 3D MHD magnetospheric simulations of the star-disk system. We use the simulation's density, velocity and scaled temperature structures as input to a radiative transfer code, from which we calculate theoretical line profiles at all rotational phases. The theoretical profiles tend to be narrower than the observed ones, but the qualitative behavior and the observed rotational modulation of the H\alpha and H\beta emission lines are well reproduced by the theoretical profiles. The spectroscopic and photometric variability observed in V2129 Oph support the general predictions of complex magnetospheric accretion models with non-axisymmetric, multipolar fields.