The He I λ10830 Å line as a probe of winds and accretion in young stars in Lupus and Upper Scorpius☆

Context. The He I lambda 0830 angstrom line is a high excitation line which allows us to probe the material in the innermost regions of protostellar disks, and to trace both accreting and outflowing material simultaneously. Aims. We use X-shooter observations of a sample of 107 young stars in the Lupus (1-3 Myr) and Upper Scorpius (5-10 Myr) star-forming regions to search for correlations between the line properties, as well as the disk inclination and accretion luminosity. Methods. We identified eight distinct profile types in the sample. We fitted Gaussian curves to the absorption and/or emission features in the line to measure the maximum velocities traced in absorption, the full-width half-maximum (FWHM) of the line features, and the Gaussian area of the features. Results. We compare the proportion of each profile type in our sample to previous studies in Taurus. We find significant variations between Taurus and Lupus in the proportion of P Cygni and inverse P Cygni profiles, and between Lupus and Upper Scorpius in the number of emission-only and combination profile types. We examine the emission-only profiles in our sample individually and find that most sources (nine out of 12) with emission-only profiles are associated with known jets. When examining the absorption features, we find that the blue-shifted absorption features appear less blue-shifted at disk inclinations close to edge-on, which is in line with past works, but no such trend with inclination is observed in the sources with only red-shifted features. Additionally, we do not see a strong correlation between the FWHM and inclination. Higher accretion rates were observed in sources with strong blue-shifted features which, along with the changes in the proportions of each profile type observed in the two regions, indicates that younger sources may drive stronger jets or winds. Conclusions. Overall, we observe variations in the proportion of each He I lambda 10830 angstrom profile type and in the line properties which indicates an evolution of accretion and ejection signatures over time, and with source properties. These results confirm past works and models of the He I lambda 10830 angstrom line, but for a larger sample and for multiple star-forming regions. This work highlights the power of the He I lambda 0830 angstrom line as a probe of the gas in the innermost regions of the disk.

Automated summary

The study used the He I λ0830 angstrom line to probe the material in the inner regions of protostellar disks in young stars from Lupus and Upper Scorpius, finding variations in profile types and line properties, indicating changes in accretion and outflow signatures over time and with source properties.