Abstract
Context. High-resolution studies of microjets in T Tauri stars (cTTs) reveal key information on the jet collimation and launching mechanism, but only a handful of systems have been mapped so far. Aims. We wish to perform a detailed study of the microjet from the 2 Myoung star RY Tau, to investigate the influence of its higher stellar mass and claimed close binarity on jet properties. Methods. Spectro-imaging observations of RY Tau were obtained in (O i)λ6300 with resolutions of 0. 4 and 135 km s −1 ,u sing the integral field spectrograph OASIS at the Canada-France-Hawaii Telescope. Deconvolved images reach a resolution of 0. 2. Results. The blueshifted jet is detected within 2 �� of the central star. We determine its PA, collimation, 2D kinematics, mass-flux rate, ejection to accretion ratio, and transverse velocity shifts taking accurately into account errors due to finite signal to noise ratio. The RY Tau system is shown to provide important constraints to several models of steady MHD ejection. Conclusions. The remarkably similar properties of the RY Tau microjet compared to jets from lower mass cTTs gives support to the common belief that the jet launching mechanism is universal over a broad range of stellar masses. The proximity between the jet PA and the PA of the photocenter variations observed by Hipparcos calls into question the interpretation of the latter in terms of binarity of RY Tau. Partial occultation events of the photosphere may offer an alternative explanation.
Highlights
One of the main open problems in star formation is to understand the physical mechanism by which mass in young stars is ejected from the accreting system and collimated into jets
The remarkably similar properties of the RY Tau microjet compared to jets from lower mass cTTs gives support to the common belief that the jet launching mechanism is universal over a broad range of stellar masses
We present in this paper sub-arcsecond optical spectroimaging observations of the RY Tau microjet in [O i] obtained with the OASIS integral field spectrograph coupled with adaptive optics correction at the Canada France Hawaii telescope
Summary
One of the main open problems in star formation is to understand the physical mechanism by which mass in young stars is ejected from the accreting system and collimated into jets. Microjets from T Tauri stars offer a unique opportunity to probe the inner 100 AUs of the outflow where the acceleration and collimation processes occur, and to place strong observational constraints on the ejection mechanism in young. That the jet phenomenon is very robust over orders of magnitude of central stellar mass is testified by the fact that both brown dwarfs and Herbig Ae/Be stars are known to drive collimated outflows (Whelan et al 2005; Corcoran & Ray 1997). It is important to extend the sample of microjets studied at high angular resolution to central sources of differing mass and binary status
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