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We analyse continuum and molecular emission, observed with Atacama Large Millimetre/submillimetre Array, from the dust-enshrouded intermediate-mass asymptotic giant branch (AGB) star OH 30.1−0.7. We find a secondary peak in the continuum maps, 'feature B', separated by 4.6 arcsec from the AGB star, which corresponds to a projected separation of |$1.8\times 10^{4}$| au, placing a lower limit on the physical separation. This feature is most likely composed of cold dust and is likely to be ejecta associated with the AGB star, though we cannot rule out that it is a background object. The molecular emission we detect includes lines of CO, SiS, CS, |$\mathrm{SO}_2$|⁠ , NS, NaCl, and KCl. We find that the NS emission is off centre and arranged along an axis perpendicular to the direction of feature B, indicative of a UV-emitting binary companion (e.g. a G-type main sequence star or hotter), perhaps on an eccentric orbit, contributing to its formation. However, the NaCl and KCl emission constrain the nature of that companion to not be hotter than a late B-type main-sequence star. We find relatively warm emission arising from the inner wind and detect several vibrationally excited lines of SiS (⁠|$\upsilon =1$|⁠), NaCl (up to |$\upsilon =4$|⁠), and KCl (up to |$\upsilon =2$|⁠), and emission from low-energy levels in the mid to outer envelope, as traced by |$\mathrm{SO}_2$|⁠. The CO emission is abruptly truncated around 3.5 arcsec or 14 000 au from the continuum peak, suggesting that mass loss at a high rate may have commenced as little as 2800 yr ago. [ABSTRACT FROM AUTHOR]

We present JWST images of the well-known planetary nebula NGC 6720 (the Ring Nebula), covering wavelengths from 1.6 to 25  |$\, \mu$| m. The bright shell is strongly fragmented with some 20 000 dense globules, bright in H2, with a characteristic diameter of 0.2 arcsec and density nH ∼ 105–106 cm−3. The shell contains a narrow ring of polycyclic aromatic hydrocarbon (PAH) emission. H2 is found throughout the shell and also in the halo. H2 in the halo may be located on the swept-up walls of a biconal polar flow. The central cavity is filled with high-ionization gas and shows two linear structures which we suggest are the edges of a biconal flow, seen in projection against the cavity. The central star is located 2 arcsec from the emission centroid of the cavity and shell. Linear features ('spikes') extend outward from the ring, pointing away from the central star. Hydrodynamical simulations reproduce the clumping and possibly the spikes. Around 10 low-contrast, regularly spaced concentric arc-like features are present; they suggest orbital modulation by a low-mass companion with a period of about 280 yr. A previously known much wider companion is located at a projected separation of about 15 000 au; we show that it is an M2–M4 dwarf. NGC 6720 is therefore a triple star system. These features, including the multiplicity, are similar to those seen in the Southern Ring Nebula (NGC 3132) and may be a common aspect of such nebulae. [ABSTRACT FROM AUTHOR]

We report on the successful search for CO (2–1) and (3–2) emission associated with OH/IR stars in the Galactic bulge. We observed a sample of eight extremely red asymptotic giant branch stars with the Atacama Pathfinder EXperiment telescope and detected seven. The sources were selected at a sufficiently high galactic latitude to avoid interference by interstellar CO, which hampered previous studies of inner galaxy stars. To study the nature of our sample and the mass-loss, we constructed the spectral energy distribution (SEDs) from photometric data and Spitzer IRS spectroscopy. In a first step, we apply radiative transfer modelling to fit the SEDs and obtain luminosities and dust mass-loss rates (MLRs). Through dynamical modelling, we then retrieve the total MLR and the gas-to-dust ratios. We derived variability periods of our stars. The luminosities range between approximately 4000 and 5500 L⊙ and periods are shorter than 700 d. The total MLR ranges between 10−5 and 10−4 M⊙ yr−1. Comparison with evolutionary models shows that the progenitor mass ≈1.5 M⊙, similar to the bulge Miras of intermediate age (3 Gyr). The gas-to-dust ratios are between 100 and 400 and are similar to what is found for OH/IR stars in the galactic disc. One star, IRAS 17347−2319, has a very short period of approximately 300 d that may be decreasing further. It may belong to a class of Mira variables with a sudden change in period as observed in some Galactic objects. It would be the first example of an OH/IR star in this class and deserves further follow-up observations. [ABSTRACT FROM AUTHOR]

Atacama Large Millimetre Array observations show a non-detection of carbon monoxide around the four most luminous asymptotic giant branch (AGB) stars in the globular cluster 47 Tucanae. Stellar evolution models and star counts show that the mass-loss rates from these stars should be ~1.2-3.5 × 10-7 M⊙ yr-1. We would naïvely expect such stars to be detectable at this distance (4.5 kpc). By modelling the ultraviolet radiation field from post-AGB stars and white dwarfs in 47 Tuc, we conclude that CO should be dissociated abnormally close to the stars. We estimate that the CO envelopes will be truncated at a few hundred stellar radii from their host stars and that the line intensities are about two orders of magnitude below our current detection limits. The truncation of CO envelopes should be important for AGB stars in dense clusters. Observing the CO (3-2) and higher transitions and targeting stars far from the centres of clusters should result in the detections needed to measure the outflow velocities from these stars. [ABSTRACT FROM AUTHOR]

Presents the observations of IRC+10216 in the J=9-8 and 12-11 rotational lines on ground vibrational state of carbon monoxide. Use of Kuiper Airborne Observatory; Presence of low temperature distribution; Lack of evidence on changes in mass-loss rate.