Discovery of an outflow of the very low-mass star ISO 143

We discover that the very young very low-mass star ISO143 (M5) is driving an outflow based on spectro-astrometry of forbidden [S II] emission lines at 6716 angstrom and 6731 angstrom observed in UVES/VLT spectra. This adds another object to the handful of brown dwarfs and very low-mass stars (M5-M8) for which an outflow has been confirmed and which show that the T Tauri phase continues at very low masses. We find the outflow of ISO143 to be intrinsically asymmetric and the accretion disk to not obscure the outflow, as only the red outflow component is visible in the [S II] 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 [S II] of up to 200-300 mas (about 30-50 AU) and velocities of up to 50-70 km s(-1). We furthermore detect line emission of ISO143 in Ca II (8498 angstrom), OI (8446 angstrom), He I (7065 angstrom), and weakly in [Fe II] (7155 angstrom). Based on a line profile analysis and decomposition we demonstrate that (i) the Ca II emission can be attributed to chromospheric activity, a variable wind, and the magnetospheric infall zone, (ii) the OI emission mainly to accretion-related processes but also a wind, and (iii) the He I emission to chromospheric or coronal activity. We estimate a mass outflow rate of ISO143 of similar to 10(-10) M-circle dot yr(-1) and a mass accretion rate in the range of similar to 10(-8) to similar to 10(-9) M-circle dot yr(-1). These values are consistent with those of other brown dwarfs and very low-mass stars. The derived (M)over dot(out)/(M)over dot(acc) ratio of 1-20% does not support previous findings of this number being very large (>40%) for very low-mass objects.