Whelan, Emma and Alcalá, J.M. and Bacciotti, F. and Nisini, B. and Bonito, R. and Antoniucci, S. and Stelzer, B. and Biazzo, K. and D'Elia, V. and Ray, T.P. (2014) Accretion-ejection connection in the young brown dwarf candidate ISO-ChaI 217*. Astronomy and Astrophysics, 570 (A59). ISSN 0004-6361

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Abstract

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.

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: 089.C-0143(A).
Keywords:	accretion; accretion disks; stars: jets; brown dwarfs;
Academic Unit:	Faculty of Science and Engineering > Experimental Physics
Item ID:	9886
Depositing User:	Emma Whelan
Date Deposited:	07 Sep 2018 13:37
Journal or Publication Title:	Astronomy and Astrophysics
Publisher:	EDP Sciences
Refereed:	Yes
URI:	https://www.aanda.org
Use Licence:	This item is available under a Creative Commons Attribution Non Commercial Share Alike Licence (CC BY-NC-SA). Details of this licence are available here

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