| Issue |
A&A
Volume 480, Number 3, March IV 2008
|
|
|---|---|---|
| Page(s) | 775 - 783 | |
| Section | Interstellar and circumstellar matter | |
| DOI | https://doi.org/10.1051/0004-6361:20078880 | |
| Published online | 09 January 2008 | |
Kinematics and H
morphology of the multipolar post-AGB star
IRAS 16594-4656*
1
Royal Observatory of Belgium, Ringlaan 3, 1180 Brussels, Belgium e-mail: [gsteene;pvh@oma.be]
2
Department of Physics and Astronomy, University of Denver, 2112 E. Wesley, Denver, CO 80208, USA e-mail: tueta@du.edu
3
Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium e-mail: maarten@ster.kuleuven.ac.be
4
Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80309, USA
Received:
19
October
2007
Accepted:
21
December
2007
Context. The spectrum of IRAS 16594-4656 shows shock-excited H2 emission and collisionally excited emission lines such as [O i], [C i], and [Fe ii].
Aims.The goal is to determine the location of the H2 and [Fe ii] shock emission, to determine the shock velocities, and to constrain the physical properties in the shock.
Methods.High resolution spectra of the H2 1–0 S(1), H2 2–1 S(1), [Fe ii], and Paβ emission lines were obtained with the near infrared spectrograph Phoenix on Gemini South.
Results.The position-velocity diagrams of H2 1–0 S(1), H2 2–1 S(1),
and [Fe ii] are presented. The H2 and [Fe ii]
emission is spatially extended.
The collisionally excited [O i] and [C i]
optical emission lines have a similar double-peaked profile compared to the extracted H2
profile and appear to be produced in the same shock. They all
indicate an expansion velocity of ~8 km s-1 and the presence
of a neutral, very high-density region with ne about
to 
cm-3.
However, the [Fe ii] emission is single-peaked. It has a Gaussian FWHM of
30 km s-1 and a total width of 62 km s-1 at 1% of the peak.
The Paβ profile is even wider with a Gaussian FWHM of 48 km s-1
and a total width of 75 km s-1 at 1% of the peak.
Conclusions.The H2 emission is excited in a slow 5 to 20 km s-1 shock into dense material at the edge of the lobes, caused by the interaction of the AGB ejecta and the post-AGB wind. The 3D representation of the H2 data shows a hollow structure with less H2 emission in the equatorial region. The [Fe ii] emission is not present in the lobes, but originates close to the central star in fast shocks in the post-AGB wind or in a disk. The Paβ emission also appears to originate close to the star.
Key words: shock waves / stars: AGB and post-AGB / stars: winds, outflows / stars: individual : IRAS 16594-4656 / ISM: molecules
© ESO, 2008
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