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    The first X-shooter observations of jets from young stars*


    Bacciotti, F. and Whelan, Emma and Alcalá, J.M. and Nisini, B. and Podio, L. and Randich, S. and Stelzer, B. and Cupani, G. (2011) The first X-shooter observations of jets from young stars*. Astrophysical Journal Letters, 737 (L26). ISSN 0004-637X

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    Abstract

    We present the first pilot study of jets from young stars conducted with X-shooter, on the ESO/Very Large Telescope. As it offers simultaneous, high-quality spectra in the range 300-2500 nm, X-shooter is uniquely important for spectral diagnostics in jet studies. We chose to probe the accretion/ejection mechanisms at low stellar masses examining two targets with well-resolved continuous jets lying on the plane of the sky: ESO-HA 574 in Chameleon I and Par-Lup3-4 in Lupus III. The mass of the latter is close to the sub-stellar boundary (M sstarf = 0.13 M ☉). A large number of emission lines probing regions of different excitation are identified, position-velocity diagrams are presented, and mass outflow/accretion rates are estimated. Comparison between the two objects is striking. ESO-HA 574 is a weakly accreting star for which we estimate a mass accretion rate of $\log (\dot{M}_{{\rm acc}}) = -10.8 \pm 0.5$ (in M ☉ yr–1), yet it drives a powerful jet with $\dot{M}_{{\rm out}}$ ~ 1.5-2.7 × 10–9 M ☉ yr–1. These values can be reconciled with a magneto-centrifugal jet acceleration mechanism assuming that the presence of the edge-on disk severely depresses the luminosity of the accretion tracers. In comparison, Par-Lup3-4, with stronger mass accretion ($\log (\dot{M}_{{\rm acc}}) = -9.1 \pm 0.4$ M ☉ yr–1), drives a low-excitation jet with about $\dot{M}_{{\rm out}}$ ~ 3.2 × 10–10 M ☉ yr–1 in both lobes. Despite the low stellar mass, $\dot{M}_{{\rm out}}$/$\dot{M}_{{\rm acc}}$ for Par-Lup3-4 is at the upper limit of the range usually measured for young objects, but still compatible with a steady magneto-centrifugal wind scenario if all uncertainties are considered.

    Item Type: Article
    Additional Information: *Based on Observations collected with X-shooter at the Very Large Telescope on Cerro Paranal (Chile), operated by the European Southern Observatory (ESO). Program ID: 085.C-0238(A). Citation: F. Bacciotti et al 2011 ApJL 737 L26
    Keywords: ISM: jets and outflows; stars: formation;
    Academic Unit: Faculty of Science and Engineering > Experimental Physics
    Item ID: 9894
    Identification Number: https://doi.org/10.1088/2041-8205/737/2/L26
    Depositing User: Emma Whelan
    Date Deposited: 10 Sep 2018 14:44
    Journal or Publication Title: Astrophysical Journal Letters
    Publisher: IOP Publishing
    Refereed: Yes
    URI:

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