Circumstellar environment of the M-type AGB star R Dor. APEX spectral scan at $159.0-368.5$ GHz

Abstract

Our current insights into the circumstellar chemistry of asymptotic giant branch (AGB) stars are largely based on studies of carbon-rich stars and stars with high mass-loss rates. In order to expand the current molecular inventory of evolved stars we present a spectral scan of the nearby, oxygen-rich star R Dor, a star with a low mass-loss rate ($\sim 2\times 10^{-7}{M}_{\odot }$/yr). We carried out a spectral scan in the frequency ranges 159.0-321.5GHz and 338.5-368.5 GHz (wavelength range 0.8-1.9mm) using the SEPIA/Band-5 and SHeFI instruments on the APEX telescope and we compare it to previous surveys, including one of the oxygen-rich AGB star IK Tau, which has a high mass-loss rate ($\sim 5\times 10^{-6}{M}_{\odot }$/yr). The spectrum of R Dor is dominated by emission lines of SO${}_2$ and the different isotopologues of SiO. We also detect CO, H${}_2$O, HCN, CN, PO, PN, SO, and tentatively TiO${}_2$, AlO, and NaCl. Sixteen out of approximately 320 spectral features remain unidentified. Among these is a strong but previously unknown maser at 354.2 GHz, which we suggest could pertain to H${}_2$SiO, silanone. With the exception of one, none of these unidentified lines are found in a similarly sensitive survey of IK Tau performed with the IRAM 30m telescope. We present radiative transfer models for five isotopologues of SiO (${}^{28}$SiO, ${}^{29}$SiO, ${}^{30}$SiO, Si${}^{17}$O, Si${}^{18}$O), providing constraints on their fractional abundance and radial extent. We derive isotopic ratios for C, O, Si, and S and estimate that R Dor likely had an initial mass in the range 1.3-1.6$M_{\odot }$, in agreement with earlier findings based on models of H${}_2$O line emission. From the presence of spectral features recurring in many of the measured thermal and maser emission lines we tentatively identify up to five kinematical components in the outflow of R Dor, indicating deviations from a smooth, spherical wind.

66 pages, 25 figures, Accepted for publication in Astronomy & Astrophysics. Fully reduced FITS spectrum made available through CDS

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• Search for aluminium monoxide in the winds of oxygen-rich AGB stars
• SiO masers from AGB stars in the vibrationally excited v=1,v=2, and v=3 states
• A molecular line survey of the extreme carbon star CRL 3068 at millimeter wavelengths
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Cited by in corpus (25)

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• Rotation of the asymptotic giant branch star R Doradus
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• An ALMA view of CS and SiS around oxygen-rich AGB stars
• Radio Stars: from kHz to THz
• Rotational spectra of vibrationally excited AlO and TiO in oxygen rich stars
• ATOMIUM: Molecular inventory of 17 oxygen-rich evolved stars observed with ALMA
• ATOMIUM: Halide molecules around the S-type AGB star W Aquilae
• HD101584: Circumstellar characteristics and evolutionary status
• The surprisingly carbon-rich environment of the S-type star W Aql
• SiO, 29SiO, and 30SiO emission from 67 oxygen-rich stars. A survey of 61 maser lines from 7 to 1 mm
• Chemical modelling of dust-gas chemistry within AGB outflows -- II. Effect of the dust-grain size distribution
• Morpho-kinematics of the circumstellar envelope of the AGB star R Dor: a global view
• Multiple components in the molecular outflow of the red supergiant NML Cyg
• A large bubble around the AGB star R Dor detected in the UV
• Molecules, shocks, and disk in the axi-symmetric wind of the MS-type AGB star RS Cancri
• Maser emission from the CO envelope of the asymptotic giant branch star W Hydrae
• Contemporaneous high-angular-resolution imaging of the AGB star W Hya in vibrationally excited H2O lines and visible polarized light with ALMA and VLT/SPHERE-ZIMPOL
• The nascent wind of AGB star R Doradus: evidence for a recent episode of enhanced mass loss
• Evidence for episodic and patchy mass ejection in the circumstellar envelope of AGB star R Leonis
• [C I] and [C II] emission in the circumstellar envelope of IRC +10216 I. Observational data and NLTE modeling of the [C I] emission
• Juice-SWI during the Lunar-Earth-Gravity-Assist (LEGA) - Part 2: Instrument operations
• Millimetre observations of the S-type AGB star $\chi$ Cygni: variability of the emission of the inner envelope
• High-angular-resolution ALMA imaging of the inhomogeneous dynamical atmosphere of the asymptotic giant branch star W Hya
• Molecular line polarisation from the circumstellar envelopes of Asymptotic Giant Branch stars