2014A&A...565A..80W

In this paper a comprehensive analysis of VLT/X-Shooter observations of two jet systems, namely ESO-Hα 574 a K8 classical T Tauri star and Par-Lup 3-4 a very low mass (0.13M_☉) M5 star, is presented. Both stars are known to have near-edge on accretion disks. A summary of these first X-shooter observations of jets was given in a 2011 letter. The new results outlined here include flux tables of identified emission lines, information on the morphology, kinematics and physical conditions of both jets and, updated estimates of {dot}(M)_out/{dot}(M)_acc. Asymmetries in the ESO-Hα 574 flow are investigated while the Par-Lup 3-4 jet is much more symmetric. The density, temperature, and therefore origin of the gas traced by the Balmer lines are investigated from the Balmer decrements and results suggest an origin in a jet for ESO-Hα 574 while for Par-Lup 3-4 the temperature and density are consistent with an accretion flow. {dot}(M)_acc is estimated from the luminosity of various accretion tracers. For both targets, new luminosity relationships and a re-evaluation of the effect of reddening and grey extinction (due to the edge-on disks) allows for substantial improvements on previous estimates of {dot}(M)_acc. It is found that log({dot}(M)_acc)=-9.15 ±0.45M_☉/yr and -9.30 ±0.27M_☉/yr for ESO-Hα 574 and Par-Lup 3-4 respectively. Additionally, the physical conditions in the jets (electron density, electron temperature, and ionisation) are probed using various line ratios and compared with previous determinations from iron lines. The results are combined with the luminosity of the [SII]λ6731 line to derive {dot}(M)_out through a calculation of the gas emissivity based on a 5-level atom model. As this method for deriving {dot}(M)_out comes from an exact calculation based on the jet parameters (measured directly from the spectra) rather than as was done previously from an approximate formula based on the value of the critical density at an assumed unknown temperature, values of {dot}(M)_out are far more accurate. Overall the accuracy of earlier measurements of {dot}(M)_out/{dot}(M)_acc is refined and {dot}(M)_out/{dot}(M)_acc=0.5(+1.0)(-0.2) and 0.3(+0.6)(-0.1) for the ESO-Hα 574 red and blue jets, respectively, and 0.05(+0.10)(-0.02) for both the Par-Lup 3-4 red and blue jets. While the value for the total (two-sided) {dot}(M)_out/{dot}(M)_acc in ESO-Hα 574 lies outside the range predicted by magneto-centrifugal jet launching models, the errors are large and the effects of veiling and scattering on extinction measurements, and therefore the estimate of {dot}(M)_acc, should also be considered. ESO-Hα 574 is an excellent case study for understanding the impact of an edge-on accretion disk on the observed stellar emission. The improvements in the derivation of {dot}(M)_out/{dot}(M)_acc means that this ratio for Par-Lup 3-4 now lies within the range predicted by leading models, as compared to earlier measurements for very low mass stars. Par-Lup 3-4 is one of a small number of brown dwarfs and very low mass stars which launch jets. Therefore, this result is important in the context of understanding how {dot}(M)_out/{dot}(M)_acc and, thus, jet launching mechanisms for the lowest mass jet driving sources, compare to the case of the well-studied low mass stars.