Volume 569, September 2014
|Number of page(s)||22|
|Section||Interstellar and circumstellar matter|
|Published online||08 September 2014|
X-shooter spectroscopy of young stellar objects
1 INAF/Osservatorio Astrofisico of Arcetri, Largo E. Fermi, 5, 50125 Firenze, Italy
2 School of Cosmic Physics, Dublin Institute for Advanced Studies, 31 Fitzwilliams Place, 2 Dublin, Ireland
3 ESO/European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany
4 INAF/Osservatorio Astronomico di Capodimonte, Salita Moiariello, 16 80131 Napoli, Italy
5 Department of Planetary Science, Lunar and Planetary Lab, University of Arizona, 1629, E. University Blvd, 85719, Tucson, AZ, USA
6 INAF/Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy
7 ASI-Science Data Center, via del Politecnico snc, 00133 Rome, Italy
Received: 5 May 2014
Accepted: 13 June 2014
Disks around T Tauri stars are known to lose mass, as best shown by the profiles of the forbidden emission lines of low-ionization species. At least two separate kinematic components have been identified, one characterized by velocity shifts of tens to hundreds of km s-1 (HVC) and one with a much lower velocity of a few km s-1 (LVC). The HVC are convincingly associated to the emission of jets, but the origin of the LVC is still unknown. In this paper we analyze the forbidden line spectrum of a sample of 44 mostly low-mass young stars in Lupus and σ Ori observed with the X-shooter ESO spectrometer. We detect forbidden line emission of O i, O ii, S ii, N i, and N ii, and characterize the line profiles as LVC, blueshifted HVC, and redshifted HVC. We focus our study on the LVC. We show that there is a good correlation between line luminosity and both Lstar and the accretion luminosity (or the mass accretion rate) over a large interval of values (Lstar~ 10-2−1 L⊙; Lacc~ 10-5−10-1 L⊙; Ṁacc~ 10-11 − 10-7 M⊙/yr). The lines show the presence of a slow wind (Vpeak< 20 km s-1) that is dense (nH> 108 cm-3), warm (T ~ 5000−10 000 K), mostly neutral. We estimate the mass of the emitting gas and provide a value for the maximum volume it occupies. Both quantities increase steeply with the stellar mass, from ~ 10-12 M⊙ and ~0.01 AU3 for Mstar~ 0.1 M⊙, to ~ 3 × 10-10 M⊙ and ~1 AU3 for Mstar~ 1 M⊙, respectively. These results provide quite stringent constraints to wind models in low-mass young stars, that need to be explored further.
Key words: stars: low-mass / line: formation / ISM: jets and outflows / accretion, accretion disks
Based on observations collected at the European Souther Observatory at Paranal, under programs 084.C-0269(A), 085.C-0238(A), 086.C-0173(A), 087.C-0244(A) and 089.C-0143(A).
Appendices are available in electronic form at http://www.aanda.org
© ESO, 2014
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.