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Title:
Kinematics and H{2} morphology of the multipolar post-AGB star IRAS 16594-4656
Authors:
van de Steene, G. C.; Ueta, T.; van Hoof, P. A. M.; Reyniers, M.; Ginsburg, A. G.
Affiliation:
AA(Royal Observatory of Belgium, Ringlaan 3, 1180 Brussels, Belgium ), AB(Royal Observatory of Belgium, Ringlaan 3, 1180 Brussels, Belgium; Department of Physics and Astronomy, University of Denver, 2112 E. Wesley, Denver, CO 80208, USA ), AC(Royal Observatory of Belgium, Ringlaan 3, 1180 Brussels, Belgium ), AD(Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium ), AE(Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80309, USA)
Publication:
Astronomy and Astrophysics, Volume 480, Issue 3, 2008, pp.775-783 (A&A Homepage)
Publication Date:
03/2008
Origin:
EDP Sciences
Keywords:
shock waves, stars: AGB and post-AGB, stars: winds, outflows, stars: individual : IRAS 16594-4656, ISM: molecules
DOI:
10.1051/0004-6361:20078880
Bibliographic Code:
2008A&A...480..775V

Abstract

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 3 × 106 to 5 × 107 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.

Based on observations collected at the Gemini-South with the Phoenix instrument under GS-2003A-Q-41, and VLT under 65.L-0615(A).

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