Velocity-Resolved [Ne III] from X-Ray Irradiated Sz 102 Microjets

Neon emission lines are good indicators of high-excitation regions close to a young stellar system because of their high ionization potentials and large critical densities. We have discovered [Ne III]λ3869 emission from the microjets of Sz 102, a low-mass young star in Lupus III. Spectroastrometric analyses of two-dimensional [Ne III] spectra obtained from archival high-dispersion ($R\approx 33,000$) Very Large Telescope/UVES data suggest that the emission consists of two velocity components spatially separated by ~ 0."3, or a projected distance of ~ 60 AU. The stronger redshifted component is centered at ~ +21 km/s with a line width of ~ 140 km/s, and the weaker blueshifted component at ~ -90 km/s with a line width of ~ 190 km/s. The two components trace velocity centroids of the known microjets and show large line widths that extend across the systemic velocity, suggesting their potential origins in wide-angle winds that may eventually collimate into jets. Optical line ratios indicate that the microjets are hot ($T\lesssim1.6\times10^4$ K) and ionized ($n_e\gtrsim5.7\times10^4$ cm$^{-3}$). The blueshifted component has ~ 13% higher temperature and ~ 46% higher electron density than the redshifted counterpart, forming a system of asymmetric pair of jets. The detection of the [Ne III]λ3869 line with the distinct velocity profile suggests that the emission originates in flows that may have been strongly ionized by deeply embedded hard X-ray sources, most likely generated by magnetic processes. The discovery of [Ne III]λ3869 emission along with other optical forbidden lines from Sz 102 support the picture of wide-angle winds surrounding magnetic loops in the close vicinity of the young star. Future high sensitivity X-ray imaging and high angular-resolution optical spectroscopy may help confirm the picture proposed.

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