OH/IR stars in the Magellanic Clouds

Wood, P. R.; Whiteoak, J. B.; Hughes, Shaun M. G.; Bessell, M. S.; Gardner, F. F.; Hyland, A. R.

doi:10.1086/171812

Cited by 182 publications

(293 citation statements)

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“…Evolutionary tracks from Bertelli et al (1994) are plotted and labelled by their Main Sequence progenitor mass. (Wood et al 1992;van Loon et al 2001a) exist, for which no optical spectrum has yet been possible to take.…”

Section: The Hertzsprung-russell Diagram Of Dust-enshrouded Agb Starsmentioning

confidence: 99%

“…Luminous, L AGB ∼ 10 4 L , and cool, T eff,AGB ∼ 2500−3500 K, stars on the upper slopes of the AGB experience intense mass loss, losing up to 80 per cent of their original mass at rates ofṀ AGB ∼ 10 −6 −10 −4 M yr −1 (Wood et al , 1992. Their luminosity is normally generated in a hydrogen-burning shell, isolated from the degenerate carbon-oxygen core and the overlying convective envelope, but episodically the temperature becomes sufficiently high to temporarily ignite a helium-burning shell (thermal pulses).…”

Section: Introductionmentioning

confidence: 99%

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An empirical formula for the mass-loss rates of dust-enshrouded red supergiants and oxygen-rich Asymptotic Giant Branch stars

Loon¹,

Cioni

Zijlstra

et al. 2005

A&A

384

359

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Abstract. We present an empirical determination of the mass-loss rate as a function of stellar luminosity and effective temperature, for oxygen-rich dust-enshrouded Asymptotic Giant Branch stars and red supergiants. To this aim we obtained optical spectra of a sample of dust-enshrouded red giants in the Large Magellanic Cloud, which we complemented with spectroscopic and infrared photometric data from the literature. Two of these turned out to be hot emission-line stars, of which one is a definite B[e] star. The mass-loss rates were measured through modelling of the spectral energy distributions. We thus obtain the massloss rate formula logṀ = −5.65 + 1.05 log(L/10 000 L ) − 6.3 log(T eff /3500 K), valid for dust-enshrouded red supergiants and oxygen-rich AGB stars. Despite the low metallicity of the LMC, both AGB stars and red supergiants are found at late spectral types. A comparison with galactic AGB stars and red supergiants shows excellent agreement between the mass-loss rate as predicted by our formula and that derived from the 60 µm flux density for dust-enshrouded objects, but not for optically bright objects. We discuss the possible implications of this for the mass-loss mechanism.

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Section: The Hertzsprung-russell Diagram Of Dust-enshrouded Agb Starsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

An empirical formula for the mass-loss rates of dust-enshrouded red supergiants and oxygen-rich Asymptotic Giant Branch stars

Loon¹,

Cioni

Zijlstra

et al. 2005

A&A

384

359

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“…Currently, the mechanism of mass loss of RSG stars and semi-regular or irregular AGBs is not known in detail. Nevertheless, in the case of Mira-variable AGB stars (mass-loss rates of 10 −6 M /yr -10 −4 M /yr, Wood et al 1983Wood et al , 1992, this mechanism is better understood. The theoretical models that explain the Mira massloss process are based on pulsations that extend the atmospheres to radii where dust can form, and subsequently on radiative pressure on dust grains that drives the wind (e.g., Bladh et al 2013).…”

Section: Introductionmentioning

confidence: 99%

What causes the large extensions of red supergiant atmospheres?

Arroyo-Torres

Wittkowski²,

Chiavassa

et al. 2015

A&A

Self Cite

108

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Aims. This research has two main goals. First, we present the atmospheric structure and the fundamental parameters of three red supergiants (RSGs), increasing the sample of RSGs observed by near-infrared spectro-interferometry. Additionally, we test possible mechanisms that may explain the large observed atmospheric extensions of RSGs. Methods. We carried out spectro-interferometric observations of the RSGs V602 Car, HD 95687, and HD 183589 in the near-infrared K-band (1.92−2.47 μm) with the VLTI/AMBER instrument at medium spectral resolution (R ∼ 1500). To categorize and comprehend the extended atmospheres, we compared our observational results to predictions by available hydrostatic PHOENIX, available 3D convection, and new 1D self-excited pulsation models of RSGs. Results. Our near-infrared flux spectra of V602 Car, HD 95687, and HD 183589 are well reproduced by the PHOENIX model atmospheres. The continuum visibility values are consistent with a limb-darkened disk as predicted by the PHOENIX models, allowing us to determine the angular diameter and the fundamental parameters of our sources. Nonetheless, in the case of V602 Car and HD 95686, the PHOENIX model visibilities do not predict the large observed extensions of molecular layers, most remarkably in the CO bands. Likewise, the 3D convection models and the 1D pulsation models with typical parameters of RSGs lead to compact atmospheric structures as well, which are similar to the structure of the hydrostatic PHOENIX models. They can also not explain the observed decreases in the visibilities and thus the large atmospheric molecular extensions. The full sample of our RSGs indicates increasing observed atmospheric extensions with increasing luminosity and decreasing surface gravity, and no correlation with effective temperature or variability amplitude. Conclusions. The location of our RSG sources in the Hertzsprung-Russell diagram is confirmed to be consistent with the red limits of recent evolutionary tracks. The observed extensions of the atmospheric layers of our sample of RSGs are comparable to those of Mira stars. This phenomenon is not predicted by any of the considered model atmospheres including available 3D convection and new 1D pulsation models of RSGs. This confirms that neither convection nor pulsation alone can levitate the molecular atmospheres of RSGs. Our observed correlation of atmospheric extension with luminosity supports a scenario of radiative acceleration on Doppler-shifted molecular lines.

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“…Among these TP-AGB stars, 28 are obscured, with (Ks-LW10)o up to 7.3. Finally, among these 28 obscured AGB stars, only 9 were detected in the IRAS pointed observations (Schwering & Israel 1990), and only 1 was previously identified by Wood et al (1992). Among the 9 IRAS sources, one finds some of the reddest objects, but not all of them.…”

mentioning

confidence: 88%

“…The maximum of their emission is in the infrared, typically between 2 and 20 usn, The first search for obscured AGB stars in the Large Magellanic Cloud (LMC) has been done by Frogel & Richer (1983), with a moderate success due to their magnitude limit of 11 in the K band, and to the small area surveyed. Later, searches based on the IRAS data have been much more successful, leading to the discovery of more than 50 obscured AGB stars in the whole LMC (Reid et al 1990;Reid 1991;Wood et al 1992;Zijlstra et al 1996;van Loon et al 1997van Loon et al , 1998. However, due to the sensitivity limit of IRAS (even using the Faint Star Catalogue and the pointed observations), only the brightest or land reddest sources could be detected by IRAS (Loup et al 1997).…”

Section: Introductionmentioning

confidence: 99%

ISOCAM and DENIS Survey of 0.5 square degrees in the Bar of the LMC. Detection of the whole TP-AGB Star Population

Loup

Josselin

Cioni

et al. 1999

Symp. - Int. Astron. Union

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Abstract. We surveyed 0.5 square degrees in the Bar of the LMC with ISOCAM at 4.5 and 12 j-tm, and with DENIS in the I, J, and Ks bands. Our goal was to build a complete sample of Thermally-Pulsing AGB stars. Here we present the first analysis of 0.14 square degrees. In total we find about 300 TP-AGB stars. Among these TP-AGB stars, 9% are obscured AGB stars (high mass-loss rates); 9 of them were detected by IRAS, and only 1 was previously identified. Their luminosities range from 2500 to 14000 L 0 , with a distribution very similar to the one of optical TP-AGB stars [i.e, those with low mass-loss rates). Such a luminosity distribution, 561 of use, available at https://www.cambridge.org/core/terms. https://doi

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OH/IR stars in the Magellanic Clouds

Cited by 182 publications

References 0 publications

An empirical formula for the mass-loss rates of dust-enshrouded red supergiants and oxygen-rich Asymptotic Giant Branch stars

An empirical formula for the mass-loss rates of dust-enshrouded red supergiants and oxygen-rich Asymptotic Giant Branch stars

What causes the large extensions of red supergiant atmospheres?

ISOCAM and DENIS Survey of 0.5 square degrees in the Bar of the LMC. Detection of the whole TP-AGB Star Population

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