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Brown Dwarf Activity Down to the Planetary Border

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Brown Dwarf Activity Down to the Planetary Border Viki Joergens Max-Planck-Institut für Astronomie Heidelberg, Zentrum für Astronomie der Universität Heidelberg Disks, accretion and outflows of brown dwarfs Brown dwarf activity down to the planetary border Chamaeleon I star forming cloud credit ESO The exploration of disks, accretion and outflows of Do BDs form via the same path as stars? The launch of jets and outflows is a key process in young brown dwarfs (BD) plays an important role Can planets form around BDs? the formation phase. Simulations suggest that out- in developing our understanding of BD formation, How do disks develop in a low-gravity, -tempera- flows are a natural by-product of isolated BD for- planet formation, and the physics of circumstellar ture, and -radiation environment? mation and a potential path to overcome the disks and outflows in general. It is related to fun- Down to which minimum mass can we detect Jeans-mass problem (Machida, Inutsuka+ 2009). damental open questions in stellar astronomy, disks, accretion and outflows? We detect and explore disks, accretion and out- such as: flows of BDs down to the planetary border, as pre- sented in the following. The bipolar outflow and disk of the brown dwarf ISO 217 Joergens, Pohl, Sicilia-Aguilar, Henning 2012, A&A, 543, A151 Spectro-astrometry of forbidden [SII] emission Spectral energy distribution and disk model of ISO217 ISO217 - [SII] 6731 near-IR (JHK) We show that ISO 217 (M6.25) is driving an intrinsically asymmetric bipolar outflow with a stronger and slightly fas- Spitzer / IRAC+MIPS+IRS ter red-shifted component based on spectro-astrometry with (mid-IR 3-24μm) 30 mas precision of forbidden [S II] emission lines in UVES / ) VLT spectra. -1 s -2 We show that the velocity asymmetry between both lobes is Herschel / PACS variable on timescales of a few years and that the suggested (erg cm (erg (far-IR 70-160μm) strong asymmetry of a factor of two (Whelan et al. 2009) λ [SII]: F might be smaller than originally anticipated. λ 80 mas photosphere M6, Teff~3000K We determine the disk properties based on SED modeling spatial position of continuum, i.e. -6 RADMC disk model and find a flared disk with mass ≥ 4x10 MSun , grain growth central source (Dullemond & Dominik) and an inclination of i ≤ 45 deg. wavelength (μm) 175 mas Discovery of an outflow of the very low-mass star ISO 143 Joergens, Kopytova, Pohl 2012, A&A, 548, A124 Spectro-astrometry of forbidden [SII] emission ISO143 - [SII] 6716 Oxygen emission line O I 8446 of ISO143 200 We discover that the very low-mass star ISO 143 (M5) is dri- as accretion tracer 150 ving an outflow based on spectro-astrometry of forbidden [S II] emission lines at 6716 Å and 6731 Å observed in UVES/ VLT / UVES 100 mass accretion rate spectrum -8 -9 VLT spectra. This adds another object to the handful of ~ 10 - 10 MSun/yr 50 brown dwarfs and very low-mass stars (M5-M8) for which an 0 outflow has been confirmed and which show that the T Tauri counts [arbitrary units] phase continues at very low masses. -50 -100 0.30-400 -300 -200 -100 0 100 200 300 400 We find the outflow of ISO 143 to be intrinsically asymmetric. 0.25 velocity [km/s] spatial 0.20 offset [SII] We estimate a mass outflow rate of ISO 143 of ∼10−10 M⊙/yr line: 0.15 and a mass accretion rate in the range of ∼10−8 to ∼10−9 M⊙/ 0.10 170 mas ~ 28 AU 0.05 spatial position yr. The derived Mout/Macc ratio of 1–20% does not support -0.00 of continuum, i.e. previous findings of this number being very large (>40%) for -0.05 central source -0.10 very low-mass objects. offset [arcseconds] -0.15 -0.20 -0.25 -0.30 -400 -300 -200 -100 0 100 200 300 400 velocity [km/s] OTS 44: Disk and accretion at the planetary border Joergens, Bonnefoy, Liu, Bayo, Wolf, Rojo 2013, A&A, submitted OTS 44 is a very low-mass brown dwarf (M9.5), which has a Strong Hydrogen emission lines of OTS44 Spectral energy distribution and disk model mass around the Deuterium burning limit of 6-17 MJup (Luh- of OTS44 man et al. 2004; Luhman 2007; Bonnefoy et al. 2013). The de- tection of mid-IR excess emission with Spitzer indicates the presence of a disk (Luhman et al. 2005). VLT / SINFONI SED model by Y. Liu, S. Wolf We explore the properties of OTS 44 and its disk based on the detection of cold dust at far-IR wavelengths with Her- spectrum credit: schel and on the discovery of broad and strong Hydrogen e- K. Luhman mission lines in optical and IR spectra, e.g. VLT / SINFONI. We perform a detailed modeling of the spectral energy dis- tribution of OTS 44 using a radiative transfer code (Wolf 2003) and Herschel data (Harvey et al. 2012). We can de- monstrate that OTS44 has a substantial disk and determine its mass and geometry. We discover broad and strong Halpha and Paschen beta emission of OTS 44 giving direct evidence of active accretion of an object at the planetary border. A detailed analysis will be presented in Joergens, Bonnefoy, Liu et al. (2013)..
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