Volume 565, May 2014
|Number of page(s)||22|
|Published online||14 May 2014|
Institut für Astronomie und Astrophysik, Kepler Center for Astro and
Particle Physics, Eberhard Karls Universität,
2 Università di Palermo, P.zza del Parlamento 1, 90134 Palermo, Italy
3 INAF – Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy
4 INAF – Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monte Porzio, Italy
5 INAF – Osservatorio Astronomico di Capodimonte, via Moiariello, 16, 80131 Napoli, Italy
6 INAF – Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
7 UJF-Grenoble 1/CNRS-INSU, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG) UMR 5274, 38041 Grenoble, France
8 ESO, Alonso de Córdova 3107, Castilla 19001, Santiago 19, Chile
Accepted: 6 March 2014
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 (0.13 M⊙) 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 Ṁout/Ṁacc. 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. Ṁacc 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 Ṁacc. It is found that log(Ṁacc) = −9.15 ± 0.45M⊙ yr-1 and −9.30 ± 0.27M⊙ yr-1 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 Ṁout through a calculation of the gas emissivity based on a 5-level atom model. As this method for deriving Ṁout 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 Ṁout are far more accurate. Overall the accuracy of earlier measurements of Ṁout/Ṁacc is refined and Ṁout/Ṁacc = 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) Ṁout/Ṁacc 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 Ṁacc, 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 Ṁout/Ṁacc 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 Ṁout/Ṁacc and, thus, jet launching mechanisms for the lowest mass jet drivingsources, compare to the case of the well-studied low mass stars.
Key words: stars: formation / ISM: jets and outflows / accretion, accretion disks / line: identification
Based on Observations collected with X-Shooter and UVES at the Very Large Telescope on Cerro Paranal (Chile), operated by the European Southern Observatory (ESO). Program ID’s: 085.C-0238(A) and 078.C-0429(A).
Appendix A is available in electronic form at http://www.aanda.org
© ESO, 2014
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