Mass loss from evolved stars. I - Observations of 17 stars in the CO/2-1/ line

Knapp, G. R.; Phillips, T. G.; Leighton, Robert B.; Lo, K. Y.; Wannier, P. G.; Wootten, Alwyn; Huggins, P. J.

doi:10.1086/159589

Cited by 104 publications

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“…A.1. References or remarks are (1) Knapp & Morris (1985), (2) Margulis et al (1990), (3) Nyman et al (1992), (4) Sopka et al (1989), (5) Knapp et al (1982), (6) Olofsson et al (1993), (7) Neri et al (1998), (8) archive data, (9) Teyssier et al (2006), (10) Groenewegen et al (1998), (11) Huggins et al (1988), (12) Wang et al (1994), (13) Wannier & Sahai (1986), (14) Bieging & Latter (1994), (-) this study. Since the effective temperatures of late-type stars are welldetermined by the intrinsic V−K colour (Sect.…”

Section: Discussionmentioning

confidence: 99%

“…The most important species for such investigations is carbon monoxide, CO. More specifically, observations of lines resulting from transitions from states with angular momentum quantum number J to J−1 can be used to derive density, velocity and kinetic temperature in the envelope. Previous surveys have focussed on the analysis of only a few low-excitation rotational transitions of CO (J = 1−0, 2−1, 3−2), or have used simple analytical expressions to derive the mass-loss rate from the parameters of these transitions (Knapp et al 1982;Knapp & Morris 1985;Olofsson et al 1993;Loup et al 1993;Neri et al 1998;Ramstedt et al 2008). Since we have access to an extensive data set covering both low and high-J molecular lines, we want to provide mass-loss estimators based on multiple CO lines, including those of high excitation levels.…”

Section: Introductionmentioning

confidence: 99%

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

Beck

Decin

Koter

et al. 2010

A&A

236

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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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

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

236

281

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“…Its radius grows from ∼1R to a few 10 2 R (Haniff, Scholz, & Tuthill 1995). The star begins to lose matter, and an extensive gas-dust circumstellar envelope forms (Knapp et al 1982). The red giant stage is very short as compared to the main sequence stage; it takes no more than a few hundred thousand years.…”

Section: Circumstellar Molecular Masersmentioning

confidence: 99%

“…-probably excited by shock waves (Wood 1979;Gillet, Maurice, & Baade 1983;Fox, Wood, & Dopita 1984). The stars lose matter at a rateṀ ∼ 10 −7 -10 −5 M yr −1 (Knapp et al 1982). The lost matter forms a circumstellar envelope, containing molecules and dust.…”

Section: Circumstellar Molecular Masersmentioning

confidence: 99%

Molecular Masers in Variable Stars

Rudnitskij¹

2002

Publ. – Astron. Soc. Aust

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When a star with a mass of one to a few solar masses enters the red giant stage of its evolution, the radius of its atmosphere reaches several astronomical units. Pulsational instability is typical for this stage. Most stars become Mira-type or semiregular variables with light cycles of a few hundred days. Red giants lose mass at a rate M = 10−7−10−5M⊙ yr−1. Extensive gas–dust circumstellar envelopes form. These envelopes contain various molecular species. Some of these molecules (OH, H2O, SiO, HCN) manifest themselves in maser radio emission. Data on the H2O maser variability and its connection with the stellar brightness variations are discussed. In the H2O line circumstellar masers can be divided into ‘stable’ (showing persistent emission — R Aql, U Her, S CrB, X Hya) and ‘transient’ (appearing in the H2O line once per 10–15 stellar light cycles — R Leo, R Cas, U Aur). Physical mechanisms of the maser variability are discussed. The most probable process explaining the observed visual–H2O correlation is the influence of shock waves on the masing region. Usually it is assumed that shocks in Mira atmospheres are driven by stellar pulsations. Here an alternative explanation is proposed. If a star during its main sequence life possessed a planetary system, similar to the solar system, the planets will be embedded in a rather dense and hot medium. Effects of a planet revolving around a red giant at a short distance (inside its circumstellar envelope) are discussed. A shock produced by the supersonic motion of a planet can account for the correlated variability of the Hα line emission and H2O maser. If the planetary orbit is highly eccentric, then the connected Hα–H2O flare episodes may be explained by the periastron passage of the planet. New tasks for the upgraded ATCA are discussed.

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“…However, in 1975, Mufson et al detected the J = 1 -0 rotational transition of CO in NGC 7027. The angular extent of the CO emission is about 40" (Knapp et al 1982), several times larger than the size of the optical object. At least in this case, we had a planetary nebula with an important molecular component.…”

Section: Introductionmentioning

confidence: 94%

Molecules and Neutral Hydrogen in Planetary Nebulae

Rodrı́guez¹

1989

Symp. - Int. Astron. Union

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ABSTRACT. Molecules and/or neutral hydrogen have been detected in a modest number of planetary nebulae. However, when detected, these indicators of a significant neutral component can provide fundamental information on the total mass of the envelope, its chemistry and kinematics, and on the morphology and evolutionary status of the planetary nebula. A review of recent results is presented, giving emphasis to CO (carbon monoxide), H2 (molecular hydrogen), OH (hydroxil), and HI (neutral hydrogen). A major development of the last few years has been the capability to map with considerable angular resolution these species in planetary nebulae. In the best studied cases, the neutral component appears to be located surrounding the "waist" of a bipolar planetary nebulae. These is evidence suggesting that molecules and neutral hydrogen are not as uncommon in planetary nebula as the present statistics suggest. Indeed, the outer parts of a considerable fraction of the known planetary nebulae could be neutral. It is possible that a combination of good selection criteria and long integrations with the best telescopes could increase largely the number of known cases.

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Mass loss from evolved stars. I - Observations of 17 stars in the CO/2-1/ line

Cited by 104 publications

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

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

Molecular Masers in Variable Stars

Molecules and Neutral Hydrogen in Planetary Nebulae

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