* Astronomy

Title: Discovery of an outflow of the very low-mass star ISO 143
Authors: V. Joergens, T. Kopytova, A. Pohl

We discover that the very young very low-mass star ISO143 (M5) is driving an outflow based on spectro-astrometry of forbidden [SII] emission lines at 6716A and 6731A observed in UVES/VLT spectra. ISO143 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 very low masses. We have found the outflow of ISO143 to be intrinsically asymmetric and the accretion disk to not obscure the outflow, as solely the red outflow component is visible in the [SII] lines. ISO143 is only the third T Tauri object showing a stronger red outflow component in spectro-astrometry, after RW Aur (G5) and ISO217 (M6.25). We show here that including ISO143 two out of seven outflows confirmed in the very low-mass regime (M5-M8) are intrinsically asymmetric. We measure a spatial extension of the outflow in [SII] of up to 200-300 mas (about 30-50 AU) and velocities of up to 50-70 km/s. We detect furthermore line emission of ISO143 in CaII (8498), OI (8446), HeI (7065), and weakly in [FeII] (7155). We demonstrate based on a line profile analysis and decomposition that the CaII emission can be attributed to chromospheric activity, a variable wind, and the magnetospheric infall zone, the OI emission mainly to accretion-related processes but also a wind, and the HeI emission to chromospheric or coronal activity. We estimate the mass outflow rate to be of the order of 10^{-10} solar masses/yr and the mass accretion rate to be of the order of 10^{-8} to 10^{-9} solar masses/yer; these values are consistent with that of other brown dwarfs and very low-mass stars. The derived Mout/Macc ratio of 1-20% is not supporting previous findings of this number to be very large (>40%) for very low-mass objects.

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