Issue |
A&A
Volume 409, Number 2, October II 2003
|
|
---|---|---|
Page(s) | 573 - 580 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20030981 | |
Published online | 17 November 2003 |
Detection of an orbiting gas disk in the Red Rectangle *
1
Observatorio Astronómico Nacional, Apartado 1143, 28800 Alcalá de Henares, Spain
2
IRAM, 300 rue de la Piscine, 38406 St Martin d'Hères, France e-mail: neri@iram.fr
3
Observatorio Astronómico Nacional, C/Alfonso XII, 3, 28014 Madrid, Spain e-mail: j.alcolea@oan.es
4
Laboratoire d'Astrophysique de Grenoble, BP 53, 38041 Grenoble Cedex 9, France e-mail: Claudine.Kahane@obs.ujf-grenoble.fr
Corresponding author: V. Bujarrabal, v.bujarrabal@oan.es
Received:
9
April
2003
Accepted:
19
June
2003
We present interferometric maps of CO emission in the Red Rectangle, a
well known protoplanetary nebula. The CO emission is found to arise from a
relatively thin equatorial disk, extending about 5´´ in the direction
perpendicular to the symmetry axis of the optical nebula.
The velocity dispersion of the emission clearly increases towards
the center, in a pattern significantly coincident with that
expected for a Keplerian velocity field.
Modeling of the CO maps confirms that the emitting
gas is probably rotating around the central star(s), with a
Kepler-like velocity distribution (at least in the central regions)
that would correspond to a central mass ~0.9 .
Other possible explanations to the observations are discussed, but
are found to be unlikely. Our models also suggest that the density
and temperature increase towards the center roughly
proportionally to the inverse radius. The asymmetry observed in the
line profile and intensity distribution (the red part being stronger)
can be explained by self-absorption if, superimposed to the rotation
velocity, there is a low radial expansion at a velocity of about
0.4 km s-1, at least in the outer disk regions.
This is the first probable detection of a gas disk
in Kepler-like rotation around a post-AGB star.
Key words: stars: AGB and post-AGB / stars: circumstellar matter / radio-lines: stars / planetary nebulae: individual: Red Rectangle
© ESO, 2003
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