Issue |
A&A
Volume 421, Number 3, July III 2004
|
|
---|---|---|
Page(s) | 1159 - 1168 | |
Section | Stellar atmospheres | |
DOI | https://doi.org/10.1051/0004-6361:20034502 | |
Published online | 29 June 2004 |
The close T Tauri binary V 4046 Sagittarii*
1
Department of Astronomy and Space Physics, Box 515, 751 20 Uppsala, Sweden
2
Stockholm Observatory, AlbaNova University Center, 106 91 Stockholm, Sweden
Corresponding author: H. C. Stempels, Eric.Stempels@not.iac.es
Received:
13
October
2003
Accepted:
1
April
2004
We have collected high-resolution () VLT-UVES spectrograms of the close T Tauri binary V 4046 Sgr from 3500–6750 Å at different phases of its 2.4 day orbital period. The high quality of these spectra allows us to present an
improved ephemeris of the system. To model the photospheric
absorption line spectrum we calculate synthetic spectra for the observed
phases of the system. These synthetic spectra are used to determine veiling
levels, and to extract emission line profiles that are undistorted by
photospheric absorption lines. We find that the shapes of the strong emission
lines of H and Ca ii H & K all vary periodically with phase. A weak
veiling continuum is superimposed on the stellar absorption line spectra. The
Ca ii H & K emission lines are composed of two narrow emission
components that closely follow the stellar orbital motion, and we speculate
that these lines are formed in global chromospheric networks on the stars. Also
the Balmer lines have similar narrow “stellar" components, possibly also
chromospheric. However, in addition there are extended wings on each side of
the line centers of all H lines, which change dramatically in shape with the
orbital phase. We find that the shape and velocity changes of the wing
components are consistent with two concentrations of gas moving at high velocity
but co-rotating with the stars. These concentrations move with a projected
velocity of 80 km s-1 around the center of mass. They are located well inside
the edge of the circumbinary disk, and also inside the co-linear Lagrangian
points of this binary. With this concept we obtain a very good agreement
between calculated and observed line profiles of H8, H9 and H10 as a function
of phase. In some recent calculations of mass transfer from circumbinary disks
to close binaries in circular motion, accumulations of gas in
co-rotation with the stars develop, resulting in structures which are similar
to what we have found from our observations. We also investigate the cause of
periodic photometric variations observed by others.
Key words: stars: pre-main sequence / stars: binaries (including multiple): close / accretion, accretion disks
© ESO, 2004
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