ﻻ يوجد ملخص باللغة العربية
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 ($dot{M}_{out}$/$dot{M}_{acc}$). 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 $sim$ 20$^{circ}$. The aim here is to further investigate the properties of ISO-ChaI 217, the morphology and kinematics of its outflow, and to better constrain ($dot{M}_{out}$/$dot{M}_{acc}$). The outflow is spatially resolved in the $[SII]lambda lambda 6716,6731$ lines and is detected out to $sim$ 1farcs6 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($dot{M}_{acc}$) [M$_{sun}$/yr]= -10.6 $pm$ 0.4. As it was not possible to measure the effect of extinction on the ISO-ChaI 217 outflow $dot{M}_{out}$ was derived for a range of values of A$_{v}$, up to a value of A$_{v}$ = 2.5 mag estimated for the source extinction. The logarithm of the mass outflow ($dot{M}_{out}$) was estimated in the range -11.7 to -11.1 for both jets combined. Thus $dot{M}_{out}$/$dot{M}_{acc}$ [Msun/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 H$alpha$ line show that the bulk of the H I emission comes from the accretion flow.
Studying the accretion process in very low-mass objects has important implications for understanding their formation mechanism. Many nearby late-M dwarfs that have previously been identified in the field are in fact young brown dwarf members of nearb
We present new XSHOOTER spectra of NLTT5306, a 0.44 $pm$ 0.04msun white dwarf in a short period (101,min) binary system with a brown dwarf companion that is likely to have previously undergone common envelope evolution. We have confirmed the presence
Brown dwarfs are important objects because they may provide a missing link between stars and planets, two populations that have dramatically different formation history. In this paper, we present the candidate binaries with brown dwarf companions tha
We present a study of the radial distribution of dust species in young brown dwarf disks. Our work is based on a compositional analysis of the 10 and 20 micron silicate emission features for brown dwarfs in the Taurus-Auriga star-forming region. A fu
We report the discovery of the youngest brown dwarf with a disk at 102 pc from the Sun, WISEA~J120037.79-784508.3 (W1200-7845), via the Disk Detective citizen science project. We establish that W1200-7845 is located in the 3.7$substack{+4.6 -1.4}$ M