OH/IR stars and their superwinds as observed by the<i>Herschel</i>Space Observatory

Justtanont, K.; Teyssier, D.; Barlow, M. J.; Matsuura, M.; Swinyard, Bruce; Waters, L. B. F. M.; Yates, J.

doi:10.1051/0004-6361/201321812

Cited by 30 publications

(48 citation statements)

References 60 publications

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“…11 (2013) conclusion of these stars being HBB AGB stars; the difference in the progenitor mass range (Justtanont et al 2013 assume masses above ∼ 5M ⊙ ) is just because the minimum mass to activate HBB is model dependent; e.g., it is ∼ 3.5 M ⊙ in the ATON models, while it is ∼ 4.5 M ⊙ in the D14-like models used by Justtanont et al (2013). We note, however, that these stars might be in a very advanced evolutionary stage, thus implying that their current mass could in principle be significantly smaller (down to ∼ 1 M ⊙ ) than the initial mass.…”

Section: Extreme O-rich Agb Stars Observed By Herschelmentioning

confidence: 98%

Studying the evolution of AGB stars in theGaiaepoch

Criscienzo¹,

Ventura²,

García-Hernández³

et al. 2016

Mon. Not. R. Astron. Soc.

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We present asymptotic giant branch (AGB) models of solar metallicity, to allow the interpretation of observations of Galactic AGB stars, whose distances should be soon available after the first release of the Gaia catalogue. We find an abrupt change in the AGB physical and chemical properties, occurring at the threshold mass to ignite hot bottom burning,i.e. 3.5 M ⊙ . Stars with mass below 3.5 M ⊙ reach the C-star stage and eject into the interstellar medium gas enriched in carbon , nitrogen and 17 O. The higher mass counterparts evolve at large luminosities, between 3 × 10 4 L ⊙ and 10 5 L ⊙ . The mass expelled from the massive AGB stars shows the imprinting of proton-capture nucleosynthesis, with considerable production of nitrogen and sodium and destruction of 12 C and 18 O. The comparison with the most recent results from other research groups are discussed, to evaluate the robustness of the present findings. Finally, we compare the models with recent observations of galactic AGB stars, outlining the possibility offered by Gaia to shed new light on the evolution properties of this class of objects.

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Section: Extreme O-rich Agb Stars Observed By Herschelmentioning

confidence: 98%

Studying the evolution of AGB stars in theGaiaepoch

Criscienzo¹,

Ventura²,

García-Hernández³

et al. 2016

Mon. Not. R. Astron. Soc.

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“…Indeed, extreme OH/IR stars were excluded from our sulphur survey sample due to the difficulty in finding a certain circumstellar model from CO emission lines that are often rife with interstellar contamination. Hashimoto & Izumiura (1997) suggest that V1300 Aql has recently become an OH/IR star in the superwind phase (Iben & Renzini 1983;Justtanont et al 2013;de Vries et al 2014), based on an analysis of the compact and thick circumstellar dust envelope. More recently, Cox et al (2012) studied the extended dust emission of a large sample of AGB stars and report V1300 Aql to have no extended emission that can be resolved at 70 or 160 µm by Herschel/PACS photometry, which supports the premise of a small dust envelope.…”

Section: Comparison With Chemical Modelsmentioning

confidence: 99%

Sulphur-bearing molecules in AGB stars

Danilovich

Sande

Beck

et al. 2017

A&A

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Context. Sulphur is a relatively abundant element in the local galaxy which is known to form a variety of molecules in the circumstellar envelopes of AGB stars. The abundances of these molecules vary based on the chemical types and mass-loss rates of AGB stars. Aims. Through a survey of (sub-)millimetre emission lines of various sulphur-bearing molecules, we aim to determine which molecules are the primary carriers of sulphur in different types of AGB stars. In this paper, the first in a series, we investigate the occurrence of H 2 S in AGB circumstellar envelopes and determine its abundance, where possible. Methods. We have surveyed 20 AGB stars with a range of mass-loss rates and of different chemical types using the APEX telescope to search for rotational transition lines of five key sulphur-bearing molecules: CS, SiS, SO, SO 2 and H 2 S. Here we present our results for H 2 S, including detections, non-detections and detailed radiative transfer modelling of the detected lines. We compare results based on different descriptions of the molecular excitation of H 2 S and different abundance distributions, including Gaussian abundances, where possible, and two different abundance distributions derived from chemical modelling results. Results. We detected H 2 S towards five AGB stars, all of which have high mass-loss rates ofṀ ≥ 5 × 10 −6 M yr −1 and are oxygenrich. H 2 S was not detected towards the carbon or S-type stars that fall in a similar mass-loss range. For the stars in our sample with detections, we find peak o-H 2 S abundances relative to H 2 between 4 × 10 −7 and 2.5 × 10 −5 . Conclusions. Overall, we conclude that H 2 S can play a significant role in oxygen-rich AGB stars with higher mass-loss rates, but is unlikely to play a key role in stars of other chemical types or the lower mass-loss rate oxygen-rich stars. For two sources, V1300 Aql and GX Mon, H 2 S is most likely the dominant sulphur-bearing molecule in the circumstellar envelope.

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“…No strong emission lines due to other molecules apart from H 2 O, OH, and CO have been reported from OH 127.8+0.0 (Lombaert et al 2013). Justtanont et al (2013) …”

Section: Observationsmentioning

confidence: 99%

“…For OH/IR stars with an optically thick circumstellar envelope, which prevents the direct determination of stellar abundance, other hot-bottom burning indicators must be used. Two such stars (AFGL 5379 and OH 26.5+0.6) have been observed with the Herschel Space Observatory (hereafter Herschel, Pilbratt et al 2010) (Justtanont et al 2013). An AGB evolutionary model for a 5 M star by Lattanzio & Wood (2003) shows that during hot-bottom burning, 18 O is preferentially destroyed with respect to the other two isotopes.…”

Section: Introductionmentioning

confidence: 99%

Herschelobservations of extreme OH/IR stars

Justtanont

Barlow

Blommaert

et al. 2015

A&A

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Aims. The late stages of stellar evolution are mainly governed by the mass of the stars. Low-and intermediate-mass stars lose copious amounts of mass during the asymptotic giant branch (AGB) which obscure the central star making it difficult to study the stellar spectra and determine the stellar mass. In this study, we present observational data that can be used to determine lower limits to the stellar mass. Methods. Spectra of nine heavily reddened AGB stars taken by the Herschel Space Observatory display numerous molecular emission lines. The strongest emission lines are due to H 2 O. We search for the presence of isotopologues of H 2 O in these objects. O. From stellar evolution calculations, this process is thought to occur when the stellar mass is above 5 M for solar metallicity. Hence, observations of different isotopologues of H 2 O can be used to help determine the lower limit to the initial stellar mass. Conclusions. From our observations, we deduce that these extreme OH/IR stars are intermediate-mass stars with masses of ≥5 M . Their high mass-loss rates of ∼10 −4 M yr −1 may affect the enrichment of the interstellar medium and the overall chemical evolution of our Galaxy.

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OH/IR stars and their superwinds as observed by theHerschelSpace Observatory

Cited by 30 publications

References 60 publications

Studying the evolution of AGB stars in theGaiaepoch

Studying the evolution of AGB stars in theGaiaepoch

Sulphur-bearing molecules in AGB stars

Herschelobservations of extreme OH/IR stars

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