On the origin of continuum and line emission in CTTSs

TL;DR

This study uses 3D MHD simulations to model emission lines in CTTSs but finds significant discrepancies with observations, suggesting non-dipole magnetic fields play a crucial role.

Contribution

It demonstrates that dipole magnetic field assumptions are insufficient to explain observed emission line profiles and fluxes in CTTSs.

Findings

Simulated line profiles do not match observed spectra.

Predicted line fluxes are much higher than observed.

Non-dipole magnetic fields are likely important in CTTSs.

Abstract

We calculated profiles of CIV 1550, Si IV 1400, NV 1240 and OVI 1035 doublet lines using results of 3D MHD simulations of disc accretion onto young stars with dipole magnetic field. It appeared that our calculations can not reproduce profiles of these lines observed (HST/GHRS-STIS and FUSE) in CTTSs's spectra. We also found that the theory predicts much larger C IV 1550 line flux than observed (up to two orders of magnitude in some cases) and argue that the main portion of accretion energy in CTTSs is liberated outside accretion shock. We conclude that the reason of disagreement between the theory and observation is strongly non-dipole character of CTTS's magnetic field near its surface.