The detached dust shells around the carbon AGB stars R Scl and V644 Sco

Abstract

Detached shells are believed to be created during a thermal pulse, and constrain the time scales and physical properties of one of the main drivers of late stellar evolution. We aim at determining the morphology of the detached dust shells around the carbon AGB stars R Scl and V644 Sco, and compare this to observations of the detached gas shells. We observe the polarised, dust-scattered stellar light around these stars using the PolCor instrument mounted on the ESO 3.6m telescope. Observations were done with a coronographic mask to block out the direct stellar light. The polarised images clearly show the detached shells. Using a dust radiative transfer code to model the dust-scattered polarised light, we constrain the radii and widths of the shells to 19.5 arcsec and 9.4 arcsec for the detached dust shells around R Scl and V644 Sco, respectively. Both shells have an overall spherical symmetry and widths of approx. 2 arcsec. For R Scl we can compare the observed dust emission directly with high spatial-resolution maps of CO(3-2) emission from the shell observed with ALMA. We find that the dust and gas coincide almost exactly, indicating a common evolution. The data presented here for R Scl are the most detailed observations of the entire dusty detached shell to date. For V644 Sco these are the first direct measurements of the detached shell. Also here we find that the dust most likely coincides with the gas shell. The observations are consistent with a scenario where the detached shells are created during a thermal pulse. The determined radii and widths will constrain hydrodynamical models describing the pre-pulse mass loss, the thermal pulse, and post-pulse evolution of the star.

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Cited by in corpus (14)

• Pulsation-triggered dust production by asymptotic giant branch stars
• A detailed view of the gas shell around R Sculptoris with ALMA
• Simplified models of stellar wind anatomy for interpreting high-resolution data: Analytical approach to embedded spiral geometries
• ALMA observations of the "fresh" carbon-rich AGB star TX Piscium. The discovery of an elliptical detached shell
• Morphology and kinematics of the gas envelope of Mira Ceti
• Properties of dust in the detached shells around U Ant, DR Ser, and V644 Sco
• H12CN and H13CN excitation analysis in the circumstellar outflow of R Scl
• Detection of CI line emission from the detached CO shell of the AGB star R Sculptoris
• PACS and SPIRE range spectroscopy of cool, evolved stars
• Detection of the S(1) Rotational Line of H2 toward IRC+10216: A Simultaneous Measurement of Mass-Loss Rate and CO Abundance
• An independent distance estimate to the AGB star R Sculptoris
• An Infrared Study of the Circumstellar Material Associated with the Carbon Star R Sculptoris
• Probing the dynamical and kinematical structures of detached shells around AGB stars
• Extended view on the dust shells around two carbon stars