Resolving the Inner Arcsecond of the RY Tau Jet with HST
Abstract
Faint X-ray emission from hot plasma (T x > 106 K) has been detected extending outward a few arcseconds along the optically delineated jets of some classical T Tauri stars including RY Tau. The mechanism and location where the jets are heated to X-ray temperatures are unknown. We present high spatial resolution Hubble Space Telescope (HST) far-ultraviolet long-slit observations of RY Tau with the slit aligned along the jet. The primary objective was to search for C IV emission from warm plasma at T C IV ∼ 105 K within the inner jet (<1″) that cannot be fully resolved by X-ray telescopes. Spatially resolved C IV emission is detected in the blueshifted jet extending outward from the star to 1″ and in the redshifted jet out to 0.″5. C IV line centroid shifts give a radial velocity in the blueshifted jet of -136 ± 10 km s-1 at an offset of 0.″29 (39 au) and deceleration outward is detected. The deprojected jet speed is subject to uncertainties in the jet inclination, but values ≳200 km s-1 are likely. The mass-loss rate in the blueshifted jet is at least {\dot{M}}jet,{blue}}=2.3× {10}-9 M ⊙ yr-1, consistent with optical determinations. We use the HST data along with optically determined jet morphology to place meaningful constraints on candidate jet-heating models including a hot-launch model in which the jet is heated near the base to X-ray temperatures by an unspecified (but probably magnetic) process, and downstream heating from shocks or a putative jet magnetic field.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 2018
- DOI:
- 10.3847/1538-4357/aaab58
- arXiv:
- arXiv:1801.08568
- Bibcode:
- 2018ApJ...855..143S
- Keywords:
-
- ISM: jets and outflows;
- stars: individual: RY Tau;
- stars: mass-loss;
- stars: pre-main sequence;
- ultraviolet: stars;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 21 pages, 4 tables, 7 figures