Arcsecond-resolution $^\mathsf{{12}}$CO mapping of the yellow hypergiants IRC +10420 and AFGL 2343

Castro-Carrizo, A.; Quintana-Lacaci, G.; Bujarrabal, V.; Neri, R.; Alcolea, J.

doi:10.1051/0004-6361:20066169

Cited by 56 publications

(169 citation statements)

References 33 publications

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“…They also show that the model derived by Castro-Carrizo et al (2007) for low-J CO transitions was applicable, with minor changes, to higher excitation lines.…”

Section: Introductionmentioning

confidence: 60%

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Detection of circumstellar nitric oxide

Quintana-Lacaci

Agúndez

Cernicharo

et al. 2013

A&A

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Aims. During a full line survey towards IRC +10420 in the 3 and 1 mm bands, we detected the emission of circumstellar nitric oxide for the first time. We aim to study the formation of NO and to confirm the enrichment of nitrogen expected for the most massive, evolved stars predicted by the hot bottom burning process. Methods. We counted on a detailed model of the structure and kinematics of the molecular gas around IRC+10420. In addition, we used a chemical model to derive the NO abundance profile. We modified the initial nitrogen abundance in order to fit the observed NO profiles. These synthetic profiles were obtained using an LVG radiative transfer code. Results. We have detected NO in a circumstellar envelope for the first time, along with a variety of N-rich molecules, which in turn shows that IRC +10420 presents a N-rich chemistry. Furthermore, we have found that to reproduce the observed NO line profiles, the initial abundance of nitrogen in the chemical model has to be increased by a factor 20 with respect to the values of the standard O-rich stars.

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“…They also show that the model derived by Castro-Carrizo et al (2007) for low-J CO transitions was applicable, with minor changes, to higher excitation lines.…”

Section: Introductionmentioning

confidence: 60%

“…5. Quintana-Lacaci (2008) showed that the molecular material observed by Castro-Carrizo et al (2007) was only ejected during the YHG phase. No molecular gas expelled from the RSG phase was detected.…”

Section: Introductionmentioning

confidence: 99%

Detection of circumstellar nitric oxide

Quintana-Lacaci

Agúndez

Cernicharo

et al. 2013

A&A

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“…None of the YHGs in Wd 1 possess the old (∼4000 yr), massive (M > 1 M ) ejection nebulae seen in HD 179821 and IRC +10 420 (Oudmaijer et al 1996;Castro-Carrizo et al 2007). We suspect that in the extreme environment of Wd 1 such nebulae would quickly be ablated by the cluster wind arising from the OB stars -as appears to be the case for the RSGs W20 and W26 (see Sect.…”

Section: The Yellow Hypergiantsmentioning

confidence: 96%

“…For HD 33579 (A3Ia + ) in the LMC, Stahl et al (1991) (Lobel et al 2003). Castro-Carrizo et al (2007) measure outflow velocities of 35 km s −1 and 25−37 km s −1 for the ejecta associated with HD 179821 and IRC +10 420 (although a priori it is not clear if they were ejected in a RSG or YHG phase). For both these stars, variable mass-loss rates of 4−300 × 10 −5 M yr −1 and 1.2−3 × 10 −4 M yr −1 were found respectively during the nebulae formation events, with Blöcker et al (1999) also reporting a mass-loss rate in excess of 10 −3 M yr −1 for IRC +10 420 in the recent past.…”

Section: The Yellow Hypergiantsmentioning

confidence: 99%

Radio emission from the massive stars in the galactic super star cluster Westerlund 1

Dougherty

Clark

Negueruela

et al. 2010

A&A

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Aims. Current mass-loss rate estimates imply that main sequence line-driven winds are not sufficient to strip away the H-rich envelope to yield Wolf-Rayet (WR) stars. The rich transitional population of the young massive cluster Westerlund 1 (Wd 1) provides an ideal laboratory to observe and constrain mass-loss processes throughout the transitional phase of stellar evolution. Methods. We present an analysis of deep radio continuum observations of Wd 1 obtained with the Australia Telescope Compact Array at four frequency bands that permit investigation of the intrinsic characteristics of the radio emission. Results. We detect 18 cluster members, a sample dominated by the cool hypergiants, with additional detections amongst the hotter OB supergiants and WR stars. The radio properties of the sample are diverse, with thermal, non-thermal and composite thermal/nonthermal sources present. Mass-loss rates determined for stars with partially optically thick stellar winds are ∼10 −5 M yr −1 across all spectral types, insufficient to enable the formation of WRs during a massive star lifetime, and the stars must undergo a period of greatly enhanced mass loss. The sgB[e] star W9, the brightest radio source in Wd 1, may provide an example, with a current mass-loss rate an order of magnitude higher than the other cluster members, and an extended nebula interpreted as a wind from an earlier epoch with a density ∼3× the current wind. Such an envelope structure in W9 is reminiscent of luminous blue variables, and one that shows evidence of two eras of high, possibly eruptive mass loss. Surprisingly, three of the OB supergiants are detected, implying unusually dense winds, though they are embedded in more extended emission regions that may influence the derived parameters. They also may have composite spectra, suggesting binarity, which can lead to a higher flux than expected from a stellar wind. Spatially resolved nebulae are associated with three of the four RSGs and three of the six YHGs in the cluster, which are due to quiescent mass loss rather than outbursts. The extended nebulae of W20 and W26 have a cometary morphology, implying significant interaction with either the intracluster medium or cluster wind. For some of the cool star winds, the ionizing source may be a companion star though the cluster radiation density is sufficiently high to provide the necessary ionizing radiation. Five WR stars are detected with composite spectra, interpreted as arising in colliding-wind binaries.

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“…Castro-Carrizo et al (2007) mention variations in the mass-loss rate for both hypergiants on time scales of ∼1000 years. In this study, where we only consider CO emission lines measured with single-dish telescopes, we lack sensitivity for the rapid density fluctuations.…”

Section: Variabilitymentioning

confidence: 99%

Probing the mass-loss history of AGB and red supergiant stars from CO rotational line profiles

Beck

Decin

Koter

et al. 2010

A&A

240

281

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Context. The evolution of intermediate and low-mass stars on the asymptotic giant branch is dominated by their strong dust-driven winds. More massive stars evolve into red supergiants with a similar envelope structure and strong wind. These stellar winds are a prime source for the chemical enrichment of the interstellar medium. Aims. We aim to (1) set up simple and general analytical expressions to estimate mass-loss rates of evolved stars, and (2) from those calculate estimates for the mass-loss rates of the asymptotic giant branch, red supergiant, and yellow hypergiant stars in our galactic sample. Methods. The rotationally excited lines of carbon monoxide (CO) are a classic and very robust diagnostic in the study of circumstellar envelopes. When sampling different layers of the circumstellar envelope, observations of these molecular lines lead to detailed profiles of kinetic temperature, expansion velocity, and density. A state-of-the-art, nonlocal thermal equilibrium, and co-moving frame radiative transfer code that predicts CO line intensities in the circumstellar envelopes of late-type stars is used in deriving relations between stellar and molecular-line parameters, on the one hand, and mass-loss rate, on the other. These expressions are applied to our extensive CO data set to estimate the mass-loss rates of 47 sample stars. Results. We present analytical expressions for estimating the mass-loss rates of evolved stellar objects for 8 rotational transitions of the CO molecule and thencompare our results to those of previous studies. Our expressions account for line saturation and resolving of the envelope, thereby allowing accurate determination of very high mass-loss rates. We argue that, for estimates based on a single rotational line, the CO(2-1) transition provides the most reliable mass-loss rate. The mass-loss rates calculated for the asympotic giant branch stars range from 4 × 10 −8 M yr −1 up to 8 × 10 −5 M yr −1 . For red supergiants they reach values between 2 × 10 −7 M yr −1 and 3 × 10 −4 M yr −1 . The estimates for the set of CO transitions allow time variability to be identified in the mass-loss rate. Possible mass-loss-rate variability is traced for 7 of the sample stars. We find a clear relation between the pulsation periods of the asympotic giant branch stars and their derived mass-loss rates, with a levelling off at ∼3 × 10 −5 M yr −1 for periods exceeding 850 days. Conclusions.

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Arcsecond-resolution $^\mathsf{{12}}$CO mapping of the yellow hypergiants IRC +10420 and AFGL 2343

Cited by 56 publications

References 33 publications

Detection of circumstellar nitric oxide

Detection of circumstellar nitric oxide

Radio emission from the massive stars in the galactic super star cluster Westerlund 1

Probing the mass-loss history of AGB and red supergiant stars from CO rotational line profiles

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