A spectro-astrometric study of southern pre-main sequence stars. Binaries, outflows, and disc structure down to AU scales
Abstract
We present spectro-astrometric observations for 28 southern pre-main sequence (PMS) stars and investigate their circumstellar environment down to AU scales. The structures detected in the ``position spectra'' include: (1) almost all the known binary companions in our sample (Sz 68, Sz 41, HO Lup, VW Cha, S CrA, AS 205), (2) companion candidates which have not been detected by infrared speckle techniques (T CrA, MWC 300), (3) monopolar and bipolar jets (AS 353A, CS Cha), (4) a combination of jets and a bow shock (VV CrA), and (5) a combination of a jet and stellar companion (R CrA). Results in known binaries show that this technique is capable of detecting binaries with separations down to ~ 10 milliarcsec. Both components in each binary appear to have strikingly similar profiles in Hα emission, indicating a similarity of circumstellar activity (mass accretion and/or a wind), and supporting the scenario of core fragmentation for the mechanism of binary formation. The bipolar Hα jet in CS Cha has a spatial scale of ~ 1.5 AU, similar to that previously observed in RU Lup, and likely be heated by a mechanism other than shocks. From the spatial scale, velocity, and Hα luminosity, we estimate the mean hydrogen density in the AU-scale bipolar flows to be ga 107 cm-3. The bipolar geometry in these jets can be explained by the presence of a disc gap/hole at AU scales, which could be induced by a gas-giant planet at the ice condensation radius.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- January 2003
- DOI:
- 10.1051/0004-6361:20021544
- arXiv:
- arXiv:astro-ph/0210559
- Bibcode:
- 2003A&A...397..675T
- Keywords:
-
- accretion;
- accretion discs;
- line: formation;
- line: profiles;
- stars: activity;
- stars: evolution;
- stars: pre-main-sequence;
- Astrophysics
- E-Print:
- 18 pages including 10 figures, accepted for publication in Astronomy and Astrophysics