Volume 570, October 2014
|Number of page(s)||9|
|Section||Interstellar and circumstellar matter|
|Published online||16 October 2014|
Accretion-ejection connection in the young brown dwarf candidate ISO-ChaI 217⋆
1 Institut für Astronomie und Astrophysik, Kepler Center for Astro and Particle Physics, Eberhard Karls Universität, 72076 Tübingen, Germany
2 INAF-Osservatorio Astronomico di Capodimonte, via Moiariello, 16, 80131 Napoli, Italy
3 INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
4 INAF-Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monteporzio Catone, Italy
5 Dipartimento di Fisica e Chimica, Università di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy
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
8 Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2, Ireland
Received: 25 April 2014
Accepted: 19 August 2014
As the number of observed brown dwarf outflows is growing it is important to investigate how these outflows compare to the well-studied jets from young stellar objects. A key point of comparison is the relationship between outflow and accretion activity and in particular the ratio between the mass outflow and accretion rates (Ṁout/Ṁacc). The brown dwarf candidate ISO-ChaI 217 was discovered by our group, as part of a spectro-astrometric study of brown dwarfs, to be driving an asymmetric outflow with the blue-shifted lobe having a position angle of ~20°. The aim here is to further investigate the properties of ISO-ChaI 217, the morphology and kinematics of its outflow, and to better constrain Ṁout/Ṁacc. The outflow is spatially resolved in the [S ii] λλ6716,6731 lines and is detected out to ~1.̋6 in the blue-shifted lobe and 1′′ in the red-shifted lobe. The asymmetry between the two lobes is confirmed although the velocity asymmetry is less pronounced with respect to our previous study. Using thirteen different accretion tracers we measure log (Ṁacc) [M⊙/yr] = −10.6 ± 0.4. As it was not possible to measure the effect of extinction on the ISO-ChaI 217 outflow Ṁout was derived for a range of values of Av, up to a value of Av = 2.5 mag estimated for the source extinction. The logarithm of the mass outflow (Ṁout) was estimated in the range −11.7 to −11.1 for both jets combined. Thus Ṁout/Ṁacc [M⊙/yr] lies below the maximum value predicted by magneto-centrifugal jet launching models. Finally, both model fitting of the Balmer decrements and spectro-astrometric analysis of the Hα line show that the bulk of the H I emission comes from the accretion flow.
Key words: accretion, accretion disks / stars: jets / brown dwarfs
© ESO, 2014
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