A very young, compact bipolar H2O maser outflow in the intermediate-mass star-forming LkHα 234 region

摘要: We report multi-epoch VLBI H$_2$O maser observations towards the compact cluster of YSOs close to Herbig Be star LkH$\alpha$ 234. This includes 234 and at least nine more that are formed within projected distances $\sim$10 arcsec ($\sim$9,000 au). detect emission four these YSOs. In particular, our (including proper motion measurements) reveal a remarkable very ($\sim$0.2 = $\sim$180 au), bipolar outflow emerging from embedded YSO VLA 2. estimate kinematic age $\sim$40 yr for this outflow, with expanding velocities $\sim$20 km s$^{-1}$ momentum rate $\dot M_w V_w$ $\simeq$ $10^{-4}-10^{-3}$ M$_{\odot}$ yr$^{-1}$ s$^{-1}$$\times (\Omega$/$4\pi)$, powered by few solar masses. propose is produced recurrent episodic jet ejections associated formation YSO. Short-lived ejection events have previously been found high-mass show now behaviour also present in intermediate-mass These short-lived probably related increases accretion rate, as observed low-mass predict presence an disk If detected, would represent one known examples stars disk-YSO-jet system scales hundred au.