Query : 2012A&A...543A.151J

2012A&A...543A.151J - Astronomy and Astrophysics, volume 543A, 151-151 (2012/7-1)

The bipolar outflow and disk of the brown dwarf ISO 217.


Abstract (from CDS):

We show that the very young brown dwarf candidate ISO217 (M6.25) is driving an intrinsically asymmetric bipolar outflow with a stronger and slightly faster red-shifted component based on spectro-astrometry of forbidden [SII] emission lines at 6716Å and 6731Å observed in UVES/VLT spectra taken in 2009. ISO217 is only one of a handful of brown dwarfs and very low-mass stars (M5-M8) for which an outflow has been detected and that show that the T Tauri phase continues at the substellar limit. We measure a spatial extension of the outflow in [SII] of up to ±190mas (about ±30AU) and velocities of up to ±40-50km/s. We find that the basic outflow properties (spatial extension, velocities, and outflow position angle) are of similar order as those determined in the discovery spectra from May 2007 of Whelan and coworkers. We show that the velocity asymmetry between both lobes is variable on timescales of a few years and that the strong asymmetry of a factor of two found in 2007 might be smaller than originally anticipated when using a more realistic stellar rest-velocity. We also detect forbidden line emission of [FeII]λ7155Å, for which we propose as a potential origin the hot inner regions of the outflow. To comprehensively understand the ISO217 system, we determine the properties of its accretion disk based on radiative transfer modeling of the SED from 0.66 to 24µm. This disk model agrees very well with Herschel/PACS data at 70µm. We find that the disk is flared and intermediately inclined (i∼45°). The total disk mass of the best-fit model is 4x10–6M, which is low compared to the accretion and outflow rate of ISO217 from the literature (∼10–10M/yr). We propose that this discrepancy can be explained by either a higher disk mass than inferred from the model because of strong undetected grain growth and/or by an on average lower accretion rate and outflow rate than the determined values. We show that a disk inclination significantly exceeding 45°, as suggested from Hα modeling and from both lobes of the outflow being visible, is inconsistent with the SED data. Thus, despite its intermediate inclination angle, the disk of this brown dwarf does not appear to obscure the red outflow component in [SII], which is very rarely seen for T Tauri objects (only one other case).

Abstract Copyright:

Journal keyword(s): brown dwarfs - stars: pre-main sequence - circumstellar matter - stars: formation - ISM: jets and outflows - stars: individual: ISO217

Simbad objects: 9

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Number of rows : 9
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
1 V* DG Tau Or* 04 27 04.6921275888 +26 06 16.060169268 13.57 13.97 10.50 12.28   K6Ve 1007 1
2 V* RW Aur TT* 05 07 49.5662483 +30 24 05.177426   10.86 9.60 9.95   K1/5e+K5e 769 0
3 NAME Cha 1 MoC 11 06 48 -77 18.0           ~ 1099 1
4 ISO-ChaI 217 Y*O 11 09 52.1372780448 -76 39 12.876642648         16.63 ~ 44 0
5 TWA 27 LM* 12 07 33.4675524840 -39 32 54.016625184     19.95 17.99 15.88 M8IVe 330 0
6 V* V1192 Sco Or* 16 08 51.4348063536 -39 05 30.460358652     21.9 18.97 18.18 M5 69 0
7 [GY92] 3 Y*O 16 26 21.9078410496 -24 44 39.697627344       17.95 15.62 M6.5 53 0
8 [GY92] 204 TT* 16 27 06.5924837856 -24 41 48.871282992       17.57 15.43 M5 93 0
9 2MASS J19013357-3700304 Y*O 19 01 33.5761986624 -37 00 30.453110028           M6.5 45 0

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