Revealing Ionization Conditions of Sz 102 with Spatially Resolved [Ne III] Microjets

Forbidden neon emission lines from small-scale microjets can probe high-energy processes in low-mass young stellar systems. We obtained spatially resolved [Ne iii] spectra in the microjets from the classical T Tauri Star Sz 102 using the Hubble Space Telescope Imaging Spectrograph at a spatial resolution of ∼0.″1. The blueshifted and redshifted [Ne iii] emission both peak in intensity within ∼0.″1 of the star and gradually decay along the flow outward to ∼0.″24. The spatial distribution and extent of the [Ne iii] microjet is consistent with a jet that is ionized close to the base and subsequently recombines on a longer timescale than the flow time. Ca ii H and K lines are also detected from the redshifted microjet with a line full-width at half-maximum of ∼170 km s-1, consistent with those of other forbidden emission lines, atop a 300 km s-1 wide stellar component. The launching radius of the Sz 102 jet, inferred from the observed line centroids and the range of inclination angles and stellar masses from the literature, is on the order of ∼0.03 au. The possible proximity of the launching region to the star allows immediate ionization without distance dilution from the circumstellar ionization sources, most likely keV X-ray flares generated by magnetic reconnection events in the star - disk system, to sustain the observed [Ne iii] flux.