Multiple components in the molecular outflow of the red supergiant NML Cyg

Andrews, H.; Beck, E. De; Hirvonen, Per

doi:10.1093/mnras/stab3244

Cited by 6 publications

(5 citation statements)

References 61 publications

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“…(Asplund et al 2009). In contrast, Andrews et al (2022) found the following ratios for NML Cyg, based on SiO: 28 Si/ 29 Si ≈ 10.9 ± 0.9, 28 Si/ 30 Si ≈ 9.5 ± 0.7, and 29 Si/ 30 Si ≈ 0.9 ± 0.4. However, these ratios were based solely on line intensities for SiO, which very likely has high opacities in the main isotopologue, resulting in artificially low numbers.…”

Section: Isotopic Ratios In Nml Cygmentioning

confidence: 77%

“…For NML Cyg, the survey suggests 32 S/ 34 S = 50 ± 25, as derived from SiS, also consistent with the solar value of 25, within the errors (see Table 4). Andrews et al (2022) did not derive any sulfur isotope ratios, but values of 32 S/ 34 S ∼ 10-15 were estimated for the envelope of IK Tau (Velilla Prieto et al 2017) and 32 in R Dor (Danilovich et al 2016); both are O-rich AGB stars.…”

Section: Isotopic Ratios In Nml Cygmentioning

confidence: 99%

“…Similar asymmetric winds were found for VY CMa, making NML Cyg a close "twin." Andrews et al (2022) also have conducted a 68-116 GHz spectral survey of the envelope of NML Cyg, using the Onsala 20 m telescope. They observed fewer molecules than in the ARO 1 mm survey (CO, SO, SO 2 , HCN, SiO, and SiS), but modeled multiple CO and SiO lines from other measurements (Herschel Space Observatory, James Clerk Maxwell Telescope).…”

Section: Introductionmentioning

confidence: 99%

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The Arizona Radio Observatory 1 mm Spectral Survey of the Hypergiant Star NML Cygni (215–285 GHz)

Singh

Edwards

Ziurys

2022

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A sensitive (1σ rms ≤ 3 mK; 2 MHz resolution) 1 mm spectral survey (214.5–285.5 GHz) of the envelope of the oxygen-rich supergiant star NML Cygni (NML Cyg) has been conducted using the 10 m Submillimeter Telescope of the Arizona Radio Observatory. These data represent the first spectral line survey of NML Cyg and are complementary to a previous 1 mm survey of the envelope of a similar hypergiant, VY Canis Majoris (VY CMa). The complete NML Cyg data set is presented here. In the survey, 104 emission lines were observed, arising from 17 different molecules and 4 unidentified features. Many of the observed features have complex line profiles, arising from asymmetric outflows characteristic of hypergiant stars. While most of the lines in the survey arise from SiO, SO, SO2, and SiS, CO had the strongest emission. Five other C-bearing species are identified in the survey (HCN, CN, HCO+, CS, and HNC), demonstrating an active carbon chemistry despite the O-rich environment. Moreover, NS was observed, but not NO, although favorable transitions of both molecules lie in the surveyed region. Sulfur chemistry appears to be prominent in NML Cyg and plays an important role in the collimated outflows. The refractory species observed, NaCl and AlO, have narrow emission lines, indicating that these molecules do not reach the terminal expansion velocity. NaCl and AlO likely condense into dust grains at r < 50 R *. From NaCl, the chlorine isotope ratio was determined to be 35Cl/37Cl = 3.85 ± 0.30.

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Section: Isotopic Ratios In Nml Cygmentioning

confidence: 77%

Section: Isotopic Ratios In Nml Cygmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The Arizona Radio Observatory 1 mm Spectral Survey of the Hypergiant Star NML Cygni (215–285 GHz)

Singh

Edwards

Ziurys

2022

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“…There are additionally three tentative detections of SO 2 towards AH Sco in the 2 = 2 state and four tentative detections towards VX Sgr in the 1 = 1 state. Previous studies of the more massive and highly evolved red supergiants VY CMa and NML Cyg (Adande et al 2013;Andrews et al 2022) report asymmetric and localised emission for both stars, including multiple components of SO and SO 2 . In contrast, when considering only the lowerenergy ground vibrational state SO and SO 2 emission observed by ATOMIUM, we do not see directed outflows for VX Sgr or AH Sco.…”

Section: Rsg Starsmentioning

confidence: 87%

ATOMIUM: Molecular inventory of 17 oxygen-rich evolved stars observed with ALMA

Wallström,

Danilovich,

Müller

et al. 2024

A&A

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The dusty winds of cool evolved stars are a major contributor of the newly synthesised material enriching the Galaxy and future generations of stars. However, the details of the physics and chemistry behind dust formation and wind launching have yet to be pinpointed. Recent spatially resolved observations show the importance of gaining a more comprehensive view of the circumstellar chemistry, but a comparative study of the intricate interplay between chemistry and physics is still difficult because observational details such as frequencies and angular resolutions are rarely comparable. Aiming to overcome these deficiencies, ATOMIUM is an ALMA Large Programme to study the physics and chemistry of the circumstellar envelopes of a diverse set of oxygen-rich evolved stars under homogeneous observing conditions at three angular resolutions between sim 0.02$ Here we summarize the molecular inventory of these sources, and the correlations between stellar parameters and molecular content. Seventeen oxygen-rich or S-type asymptotic giant branch (AGB) and red supergiant (RSG) stars have been observed in several tunings with ALMA Band 6, targeting a range of molecules to probe the circumstellar envelope and especially the chemistry of dust formation close to the star. We systematically assigned the molecular carriers of the spectral lines and measured their spectroscopic parameters and the angular extent of the emission of each line from integrated intensity maps. Across the ATOMIUM sample, we detect 291 transitions of 24 different molecules and their isotopologues. This includes several first detections in oxygen-rich AGB/RSG stars: PO $ and $ and several high energy H$_2$O transitions. We also find several first detections in S-type AGB stars: vibrationally excited HCN $ and SiS $ as well as first detections of the molecules SiC, AlCl, and AlF in W Aql. Overall, we find strong correlations between the following molecular pairs: CS and SiS, CS and AlF, NaCl and KCl, AlO and SO and SO, and and H$_2$O; meaning both molecules tend to have more detected emission lines in the same sources. The measured isotopic ratios of Si and S are found to be consistent with previous measurements, except for an anomalously high 29Si/30Si ratio of $4 1$ in the RSG VX Sgr. This paper presents the overall molecular inventory and an initial analysis of the large ATOMIUM dataset, laying the groundwork for future work deriving molecular abundances and abundance profiles using radiative transfer modeling which will provide more rigorous tests for chemical models.

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“…On the other hand, we do not know the effect that the dust could make where T > 800 K; although, we expect it to be small. Moreover, localised gaseous ejections, related to magnetic fields and surface activity were recently suggested as a major contributor to mass loss from RSGs (Humphreys & Jones 2022;Andrews et al 2022;López Ariste et al 2022). To explore this effect in detail, we would need to use 3D models, which is out of the scope of this paper.…”

Section: Discussionmentioning

confidence: 99%

The effect of winds on atmospheric layers of red supergiants

González-Torà

Wittkowski

Davies

et al. 2023

A&A

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Context. Red supergiants (RSGs) are evolved massive stars in a stage preceding core-collapse supernova. The physical processes that trigger mass loss in their atmospheres are still not fully understood, and they remain one of the key questions in stellar astrophysics. Based on observations of α Ori, a new semi-empirical method to add a wind to hydrostatic model atmospheres of RSGs was recently developed. This method can reproduce many of the static molecular shell (or 'MOLsphere') spectral features. Aims. We used this method of adding a semi-empirical wind to a MARCS model atmosphere to compute synthetic observables, comparing the model to spatially resolved interferometric observations. We present a case study to model published interferometric data of HD 95687 and V602 Car obtained with the AMBER instrument at the Very Large Telescope Interferometer (VLTI). Methods. We computed model intensities with respect to the line-of-sight angle (µ) for different mass-loss rates, spectra, and visibilities using the radiative transfer code Turbospectrum. We were able to convolve the models to match the different spectral resolutions of the VLTI instruments, studying a wavelength range of 1.8 − 5 µm corresponding to the K, L, and M bands for GRAVITY and MATISSE data. The model spectra and squared visibility amplitudes were compared with the published VLTI/AMBER data. Results. The synthetic visibilities reproduce observed drops in the CO, SiO, and water layers that are not shown in visibilities based on MARCS models alone. For the case studies, we find that adding a wind onto the MARCS model with simple radiative equilibrium dramatically improves the agreement with the squared visibility amplitudes as well as the spectra, with the fit being even better when applying a steeper density profile than predicted from previous studies. Our results reproduce observed extended atmospheres up to several stellar radii. Conclusions. This paper shows the potential of our model to describe extended atmospheres in RSGs. It can reproduce the shapes of the spectra and visibilities with a better accuracy in the CO and water lines than previous models. The method can be extended to other wavelength bands for both spectroscopic and interferometric observations. We provide temperature and density stratifications that succeed, for the first time, in reproducing observed interferometric properties of RSG atmospheres.

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Multiple components in the molecular outflow of the red supergiant NML Cyg

Cited by 6 publications

References 61 publications

The Arizona Radio Observatory 1 mm Spectral Survey of the Hypergiant Star NML Cygni (215–285 GHz)

The Arizona Radio Observatory 1 mm Spectral Survey of the Hypergiant Star NML Cygni (215–285 GHz)

ATOMIUM: Molecular inventory of 17 oxygen-rich evolved stars observed with ALMA

The effect of winds on atmospheric layers of red supergiants

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