Kinematics and H_2 morphology of the multipolar Post-AGB star IRAS 16594-4656

• Published in: arXiv.org 2008-01
• Main Authors: G C Van de Steene, Ueta, T, P A M van Hoof, Reyniers, M, Ginsburg, A G
• Format: Article
• Language: English
• Subjects: Asymptotic giant branch stars; Ejecta; Emission; Equatorial regions; Kinematics; Lobes; Morphology; Near infrared radiation; Physical properties; Stellar winds
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.0801.0674

context: The spectrum of IRAS 16594-4656 shows shock excited H_2 emission and collisionally excited emission lines such as[O I],[C I],and [Fe II]. aim: The goal is to determine the location of the H_2 and [Fe II] shock emission, to determine the shock velocities,and constrain the physical properties in the shock. methods: High resolution spectra of the H_2 1-0 S(1),H_2 2-1 S(1), [Fe II], and Pa\(\beta\) emission lines were obtained with the near infrared spectrograph Phoenix on Gemini South. results: The position-velocity diagrams of H_2 1-0 S(1), H_2 2-1 S(1), and [Fe II] are presented. The H_2 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 H_2 profile and appear to be produced in the same shock. They all indicate an expansion velocity of ~8 km/s and the presence of a neutral, very high density region with \(n_{\rm e}\) about 3 x 10^6 to 5 x10^7 cm\(^{-3}\). The [Fe II] emission however is single peaked. It has a gaussian FWHM of 30 km/s and a total width of 62 km/s at 1% of the peak. The Pa\(\beta\) profile is even wider with a gaussian FWHM of 48 km/s and a total width of 75 km/s at 1% of the peak. conclusions: The H\(_2\) emission is excited in a slow 5 to 20 km/s 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 H_2 data shows a hollow structure with less H_2 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 Pa\(\beta\) emission also appears to originate close to the star.