Winds and Accretion in Young Stars

TL;DR

This paper explores how accretion-powered winds in young stars are launched and influence stellar spin-down, using the He I 10830 line as a diagnostic to understand star-disk magnetic interactions and wind geometry.

Contribution

It introduces the He I 10830 line as a new diagnostic tool for studying magnetically controlled winds and star-disk interactions in accreting young stars.

Findings

He I 10830 line effectively probes wind geometry and magnetic interactions.

Wind launching is sensitive to disk accretion rate.

Accretion-powered winds contribute to stellar spin-down.

Abstract

Establishing the origin of accretion powered winds from forming stars is critical for understanding angular momentum evolution in the star-disk interaction region. Here, the high velocity component of accretion powered winds is launched and accreting stars are spun down, in defiance of the expected spin-up during magnetospheric accretion. T Tauri stars in the final stage of disk accretion offer a unique opportunity to study the connection between accretion and winds and their relation to stellar spindown. Although spectroscopic indicators of high velocity T Tauri winds have been known for decades, the line of He I 10830 offers a promising new diagnostic to probe the magnetically controlled star-disk interaction and wind-launching region. The high opacity and resonance scattering properties of this line offer a powerful probe of the geometry of both the funnel flow and the inner wind that, together with other atomic and molecular spectral lines covering a wide range of excitation and ionization states, suggests that the magnetic interaction between the star and disk, and the subsequent launching of the inner high velocity wind, is sensitive to the disk accretion rate.