X TrA through the eyes of MATISSE: More evidence of clumpy molecular layers around C-type asymptotic giant branch stars

Abstract

Aims. The goal of this study is to further the understanding of the wind formation mechanism in asymptotic giant branch (AGB) stars through the analysis of the close environment (within a few stellar radii) of the carbon star X TrA. Methods. X TrA was observed for the first time with the Mid-Infrared SpectroScopic Experiment instrument (MATISSE) in the L and N bands in low spectral resolution mode (R=30), and its close surroundings were mapped in specific wavelength ranges corresponding to specific molecules ($C_2{H}_2$ and HCN, at 3.1 and 3.8 $\mu$m) and dust (amorphous carbon and, for example, Sic at 11.3 $\mu$m), via image reconstruction techniques. Results. The angular diameter of the star ranges from 10 mas in the L band pseudo-continuum (3.5 $\mu$m) to 20 mas at 3.1 and 11.3 $\mu$m. The reconstructed images show some mild elongated features (along the east-west direction) and asymmetric protrusions, which are most evident around 3.1 $\mu$m. Imaging results highlight the clumpy nature of the circumstellar environment, starting from the photospheric region up to more distant layers. Conclusions. The angular diameters found for X TrA in the image data are in agreement with previous photospheric diameter estimates (following VLTI/MIDI 8-13 $\mu$m observations), and their wavelength dependence is similar to values found for other carbon stars observed with MATISSE (R Scl and V Hya). The 3.1 $\mu$m images presented here show highly asymmetric features, another case of a C-rich star with irregular morphologies close to the stellar disk; this supports the notion that the $C_2{H}_2+HCN$ abundance distribution usually originates from a clumpy layer around carbon stars.

References in corpus (23)

• A Catalog of Multiplicity among Bright Stellar Systems
• (Sub)stellar companions shape the winds of evolved stars
• The dust production rate of AGB stars in the Magellanic Clouds
• ALMA observations of the nearby AGB star L2 Puppis - I. Mass of the central star and detection of a candidate planet
• Distance estimates for AGB stars from parallax measurements
• A catalogue of stellar diameters and fluxes for mid-infrared interferometry
• Optical properties of silicon carbide for astrophysical applications I. New laboratory infrared reflectance spectra and optical constants
• Principles of image reconstruction in optical interferometry: tutorial
• The Keck Aperture Masking Experiment: Multi-Wavelength Observations of 6 Mira Variables
• Global 3D radiation-hydrodynamical models of AGB stars with dust-driven winds
• Characterisation of Galactic carbon stars and related stars from Gaia-EDR3
• The shock-heated atmosphere of an asymptotic giant branch star resolved by ALMA
• Temporal variations of the outer atmosphere and the dust shell of the carbon-rich Mira variable V Oph probed with VLTI/MIDI
• Rings and filaments: The remarkable detached CO shell of U Antliae
• The extended molecular envelope of the asymptotic giant branch star ${\pi }^1$ Gruis as seen by ALMA II. The spiral-outflow observed at high-angular resolution
• Atmospheric molecular blobs shape up circumstellar envelopes of AGB stars
• DEATHSTAR: Nearby AGB stars with the Atacama Compact Array II. CO envelope sizes and asymmetries: The S-type stars
• One month convection timescale on the surface of a giant evolved star
• Images of Betelgeuse with VLTI/MATISSE across the Great Dimming
• An accreting dwarf star orbiting the S-type giant star pi1 Gru
• An impressionist view of V Hydrae. When MATISSE paints Asymmetric Giant Blobs
• The K-band highest-resolution images of the Mira star R Car with GRAVITY-VLTI
• Locating dust and molecules in the inner circumstellar environment of R~Sculptoris with MATISSE

Cited by in corpus (1)

• The dusty envelopes of asymptotic giant branch stars with ultraviolet excesses