Extended dust shell of the carbon star U Hydrae observed with AKARI

Izumiura, Hideyuki; Ueta, Toshiya; Yamamura, I.; Matsunaga, Noriyuki; Ita, Yoshifusa; Matsuura, M.; Nakada, Y.; Fukushi, H.; Mito, Hiroyuki; Tanabé, Toshihiko; Hashimoto, Osamu

doi:10.1051/0004-6361/201015163

Cited by 17 publications

(26 citation statements)

References 52 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…9. The CO data were subsequently complemented with images in dust-scattered light (González Delgado et al 2003a;Maercker et al 2010Maercker et al , 2014Olofsson et al 2010;Ramstedt et al 2011) and in thermal dust emission (Waters et al 1994;Izumiura et al 2011;Arimatsu et al 2011;Cox et al 2012a). Remarkably, one of the older shells, that of U Hya, has also been detected in the UV (Sanchez et al 2015).…”

Section: Brief Episodes Of Enhanced Mass Lossmentioning

confidence: 99%

Mass loss of stars on the asymptotic giant branch

Höfner

Olofsson

2018

Astron Astrophys Rev

475

376

View full text Add to dashboard Cite

As low-and intermediate-mass stars reach the asymptotic giant branch (AGB), they have developed into intriguing and complex objects that are major players in the cosmic gas/dust cycle. At this stage, their appearance and evolution are strongly affected by a range of dynamical processes. Large-scale convective flows bring newlyformed chemical elements to the stellar surface and, together with pulsations, they trigger shock waves in the extended stellar atmosphere. There, massive outflows of gas and dust have their origin, which enrich the interstellar medium and, eventually, lead to a transformation of the cool luminous giants into white dwarfs. Dust grains forming in the upper atmospheric layers play a critical role in the wind acceleration process, by scattering and absorbing stellar photons and transferring their outward-directed momentum to the surrounding gas through collisions. Recent progress in high-angularresolution instrumentation, from the visual to the radio regime, is leading to valuable new insights into the complex dynamical atmospheres of AGB stars and their windforming regions. Observations are revealing asymmetries and inhomogeneities in the photospheric and dust-forming layers which vary on time-scales of months, as well as more long-lived large-scale structures in the circumstellar envelopes. High-angularresolution observations indicate at what distances from the stars dust condensation occurs, and they give information on the chemical composition and sizes of dust grains in the close vicinity of cool giants. These are essential constraints for building B Susanne Höfner

show abstract

Section: Brief Episodes Of Enhanced Mass Lossmentioning

confidence: 99%

Mass loss of stars on the asymptotic giant branch

Höfner

Olofsson

2018

Astron Astrophys Rev

475

376

View full text Add to dashboard Cite

show abstract

“…The detached shell of U Hya is the largest in angular size observed to date. It was studied in detail by Izumiura et al (2011) using far-IR AKARI observations at 65 µm, 90 µm, 140 µm and 160 µm. They measure fluxes of the decomposed detached dust shell to be 45.5 ± 0.5 Jy at 65 µm and 23.0 ± 1.5 Jy at 160 µm, integrated over the total shell.…”

Section: U Hyamentioning

confidence: 99%

“…They measure fluxes of the decomposed detached dust shell to be 45.5 ± 0.5 Jy at 65 µm and 23.0 ± 1.5 Jy at 160 µm, integrated over the total shell. Izumiura et al (2011) utilised a detached dust shell model and derived a dust shell temperature of 40 -50 K and a shell β of 1.2.…”

Section: U Hyamentioning

confidence: 99%

Extended Dust Emission from Nearby Evolved Stars★

Dharmawardena

Kemper

Scicluna

et al. 2018

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

We present JCMT SCUBA-2 450µm and 850µm observations of 14 Asymptotic Giant Branch (AGB) stars (9 O-rich, 4 C-rich and 1 S-type) and one Red Supergiant (RSG) in the Solar Neighbourhood. We combine these observations with Herschel /PACS observations at 70µm and 160µm and obtain azimuthally-averaged surface-brightness profiles and their PSF subtracted residuals. The extent of the SCUBA-2 850 µm emission ranges from 0.01 to 0.16 pc with an average of ∼ 40% of the total flux being emitted from the extended component. By fitting a modified black-body to the four-point SED at each point along the radial profile we derive the temperature (T ), spectral index of dust emissivity (β) and dust column density (Σ) as a function of radius. For all the sources, the density profile deviates significantly from what is expected for a constant mass-loss rate, showing that all the sources have undergone variations in mass-loss during this evolutionary phase. In combination with results from CO line emission, we determined the dust-to-gas mass ratio for all the sources in our sample. We find that, when sources are grouped according to their chemistry, the resulting average dust-to-gas ratios are consistent with the respective canonical values. However we see a range of values with significant scatter which indicate the importance of including spatial information when deriving these numbers.

show abstract

“…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

View full text Add to dashboard Cite

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.

show abstract

Extended dust shell of the carbon star U Hydrae observed with AKARI

Cited by 17 publications

References 52 publications

Mass loss of stars on the asymptotic giant branch

Mass loss of stars on the asymptotic giant branch

Extended Dust Emission from Nearby Evolved Stars★

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

Contact Info

Product

Resources

About