Dusty shells surrounding the carbon variables S Scuti and RT Capricorni

Mečina, M.; Kerschbaum, F.; Groenewegen, M. A. T.; Ottensamer, R.; Blommaert, J. A. D. L.; Mayer, Andreas; Decin, L.; Luntzer, A.; Vandenbussche, B.; Posch, Th.; Waelkens, Christoffel

doi:10.1051/0004-6361/201321117

Cited by 13 publications

(21 citation statements)

References 51 publications

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“…The shapes and composition of the grains are also large uncertainties, and they have to be constrained by spectral observations. For some detached shell objects, far-infrared observations exist (Kerschbaum et al 2010;Izumiura et al 2011;Mečina et al 2014). R Scl has been observed with the Large Bolometer Camera (LABOCA) on the Atacama Pathfinder Experiment (APEX) at 850 µm, and we are currently performing observations with LABOCA of three additional detached shell sources (V644 Sco, U Ant, and DR Ser) to probe the contribution of large dust grains to the total mass.…”

Section: The Importance Of Constraining the Shellsmentioning

confidence: 99%

The detached dust shells around the carbon AGB stars R Sculptoris and V644 Scorpii

Maercker

Ramstedt

Leal-Ferreira

et al. 2014

A&A

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Context. The morphology of the circumstellar envelopes (CSE) around asymptotic giant branch (AGB) stars gives information on the mass-loss process from the star, its evolution and wind, and on the effect of binary interaction. However, determining the distribution of dust in the circumstellar envelopes is difficult. Observations of polarised, dust-scattered stellar light in the optical have produced images with high-spatial resolution of the envelopes around evolved stars. For sources with detached shells in particular, this method has proven extremely successful. Detached shells are believed to be created during a thermal pulse, and studying them can constrain the time scales and physical properties of one of the main drivers of late stellar evolution. Aims. We aim at determining the morphology of the detached shells around the carbon AGB stars R Scl and V644 Sco. In particular, we attempt to constrain the radii and widths of the detached dust shells around the stars and compare them to observations of the detached gas shells. Methods. We observed the polarised, dust-scattered stellar light around the carbon AGB stars R Scl and V644 Sco using the PolCor instrument mounted on the ESO 3.6 m telescope. Observations were done with a coronographic mask to block out the direct stellar light. The polarised images clearly show the detached shells around R Scl and V644 Sco. Using a dust radiative transfer code to model the dust-scattered polarised light, we constrained the radii and widths of the shells. Results. We determine radii of 19. 5 and 9. 4 for the detached dust shells around R Scl and V644 Sco, respectively. Both shells have an overall spherical symmetry and widths of ≈2 . For R Scl, we can compare the observed dust emission directly with high spatialresolution 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. Conclusions. 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 postpulse evolution of the star.

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Section: The Importance Of Constraining the Shellsmentioning

confidence: 99%

The detached dust shells around the carbon AGB stars R Sculptoris and V644 Scorpii

Maercker

Ramstedt

Leal-Ferreira

et al. 2014

A&A

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“…An overview of the MESS objects is given by Cox et al (2012) and detailed studies of individual objects are presented in Ladjal et al (2010a), Kerschbaum et al (2010), Jorissen et al (2011, 2013, Decin et al (2011Decin et al ( , 2012, van Hoof et al (2013), and Mečina et al (2014 Sacuto et al (2008) and Paladini et al (in prep.). The MIDI observations do not deviate from spherical symmetry.…”

Section: Herschel/pacsmentioning

confidence: 99%

Large-scale environments of binary AGB stars probed byHerschel

Mayer

Jorissen

Paladini

et al. 2014

A&A

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Context. The Mass loss of Evolved StarS (MESS) sample observed with PACS on board the Herschel Space Observatory revealed that several asymptotic giant branch (AGB) stars are surrounded by an asymmetric circumstellar envelope (CSE) whose morphology is most likely caused by the interaction with a stellar companion. The evolution of AGB stars in binary systems plays a crucial role in understanding the formation of asymmetries in planetary nebulae (PNe), but at present, only a handful of cases are known where the interaction of a companion with the stellar AGB wind is observed. Aims. We probe the environment of the very evolved AGB star π 1 Gruis on large and small scales to identify the triggers of the observed asymmetries. Methods. Observations made with Herschel/PACS at 70 μm and 160 μm picture the large-scale environment of π 1 Gru. The close surroundings of the star are probed by interferometric observations from the VLTI/AMBER archive. An analysis of the proper motion data of Hipparcos and Tycho-2 together with the Hipparcos Intermediate Astrometric Data help identify the possible cause for the observed asymmetry. Results. The Herschel/PACS images of π 1 Gru show an elliptical CSE whose properties agree with those derived from a CO map published in the literature. In addition, an arc east of the star is visible at a distance of 38 from the primary. This arc is most likely part of an Archimedean spiral caused by an already known G0V companion that is orbiting the primary at a projected distance of 460 au with a period of more than 6200 yr. However, the presence of the elliptical CSE, proper motion variations, and geometric modelling of the VLTI/AMBER observations point towards a third component in the system, with an orbital period shorter than 10 yr, orbiting much closer to the primary than the G0V star.

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“…Most notable are the geometrically thin, detached CO and dust shells around carbon-rich AGB stars. Presently there are published data on seven CO shells (Schöier et al 2005) and 17 dust shells of this type (Ramstedt et al 2011;Cox et al 2012;Maercker et al 2014;Mečina et al 2014, and references therein) (not all of the dust shells are clearly of the geometrically thin type). We note here that some stars with prominent dust shells, e.g.…”

Section: Introductionmentioning

confidence: 99%

Detection of CI line emission from the detached CO shell of the AGB star R Sculptoris

Olofsson

Bergman

Lindqvist

2015

A&A

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Context. Stars on the asymptotic giant branch (AGB) lose substantial amounts of matter, to the extent that they are important for the chemical evolution of, and dust production in, the Universe. The mass loss is believed to increase gradually with age on the AGB, but it may also occur in the form of bursts, possibly related to the thermal pulsing phenomenon. Detached, geometrically thin, CO shells around carbon stars are good signposts of brief and intense mass ejection. Aims. We aim to put further constraints on the physical properties of detached CO shells around AGB stars. Methods. The photodissociation of CO and other carbon-bearing species in the shells leads to the possibility of detecting lines from neutral carbon. We have therefore searched for the CI( 3 P 1 − 3 P 0 ) line at 492 GHz towards two carbon stars, S Sct and R Scl, with detached CO shells of different ages, ≈8000 and 2300 years, respectively. Results. The CI( 3 P 1 − 3 P 0 ) line was detected towards R Scl. The line intensity is dominated by emission from the detached shell. The detection is at a level consistent with the neutral carbon coming from the full photodissociation of all species except CO, and with only limited photoionisation of carbon. The best fit to the observed 12 CO and 13 CO line intensities, assuming a homogeneous shell, is obtained for a shell mass of ≈0.002 M , a temperature of ≈100 K, and a CO abundance with respect to H 2 of 10 −3 . The estimated CI/CO abundance ratio is ≈0.3 for the best-fit model. However, a number of arguments point in the direction of a clumpy medium, and a viable interpretation of the data within such a context is provided.

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Dusty shells surrounding the carbon variables S Scuti and RT Capricorni

Cited by 13 publications

References 51 publications

The detached dust shells around the carbon AGB stars R Sculptoris and V644 Scorpii

The detached dust shells around the carbon AGB stars R Sculptoris and V644 Scorpii

Large-scale environments of binary AGB stars probed byHerschel

Detection of CI line emission from the detached CO shell of the AGB star R Sculptoris

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