Metallicity, pulsation and mass loss in globular cluster low-mass AGB stars

2009 ◽  
Author(s):  
Iain McDonald ◽  
Jacco Th. van Loon ◽  
Martha L. Boyer ◽  
Eric Stempels
Keyword(s):  
Mass Loss ◽  
Globular Cluster ◽  
Agb Stars ◽  
Low Mass

scholarly journals The Production of Low Mass Carbon Stars; Carbon-rich Dredge Up or Oxygen-rich Mass Loss?

1989 ◽  
Vol 106 ◽  
pp. 229-231
Author(s):  
R.E. Stencel ◽  
J.E. Pesce ◽  
K.M. MacGregor
Keyword(s):  
Mass Loss ◽  
Selective Removal ◽  
Secondary Effect ◽  
Agb Stars ◽  
Radiative Force ◽  
Conventional Theory ◽  
Carbon Stars ◽  
Solar Mass ◽  
Low Mass ◽  
Momentum Coupling

AbstractConventional theory explains the origin of carbon stars as due to dredge up of carbon enriched material from the stellar core during helium flash events late in the life of solar mass AGB stars (e.g. Boothroyd and Sackmann 1988). This relatively efficient process however, seems to produce a larger C/O ratio than observed (Lambert et al. 1987). A secondary effect which could contribute to the appearance of carbon stars, is the selective removal of oxygen from the atmosphere by radiative force expulsion of oxygen rich dust grains (e.g. silicates like [Mg, Fe2SiO4]). We present calculations for this scenario which evaluate the degree of momentum coupling between the grains and gas under the thermodynamical conditions of AGB star atmospheres.

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

1999 ◽  
Vol 191 ◽  
pp. 561-566
Author(s):  
C. Loup ◽  
E. Josselin ◽  
M.-R. Cioni ◽  
H.J. Habing ◽  
J.A.D.L. Blommaert ◽  
...  
Keyword(s):  
Mass Loss ◽  
High Mass ◽  
Evolutionary Models ◽  
Agb Stars ◽  
Complete Sample ◽  
High Mass Loss ◽  
Low Mass ◽  
The One ◽  
Good Agreement ◽  
Loss Rates

We surveyed 0.5 square degrees in the Bar of the LMC with ISOCAM at 4.5 and 12 μm, 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 2 500 to 14 000 L⊙, 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, as well as the percentage of obscured stars among TP-AGB stars, is in very good agreement with the evolutionary models of Vassiliadis & Wood (1993) if most of the TP-AGB stars that we find have initial masses smaller than 1.5 to 2 M⊙.

scholarly journals EVOLUTION OF THERMALLY PULSING ASYMPTOTIC GIANT BRANCH STARS. IV. CONSTRAINING MASS LOSS AND LIFETIMES OF LOW MASS, LOW METALLICITY AGB STARS

2014 ◽  
Vol 790 (1) ◽  
pp. 22 ◽  
Author(s):  
Philip Rosenfield ◽  
Paola Marigo ◽  
Léo Girardi ◽  
Julianne J. Dalcanton ◽  
Alessandro Bressan ◽  
...  
Keyword(s):  
Mass Loss ◽  
Asymptotic Giant Branch ◽  
Asymptotic Giant Branch Stars ◽  
Agb Stars ◽  
Low Metallicity ◽  
Low Mass ◽  
Giant Branch Stars

Evolutionary Calculations for Planetary Nebula Nuclei with Continuing Mass Loss and Realistic Starting Conditions

1984 ◽  
Vol 5 (4) ◽  
pp. 543-546 ◽  
Author(s):  
D. J. Faulkner ◽  
P. R. Wood
Keyword(s):  
Mass Loss ◽  
White Dwarf ◽  
Planetary Nebula ◽  
Asymptotic Giant Branch ◽  
Agb Stars ◽  
Considerable Uncertainty ◽  
Starting Conditions ◽  
Low Mass ◽  
Rich Material

The mechanism by which planetary nebula (PN) shells are ejected is still subject to considerable uncertainty. It is generally assumed that the precursors of these objects are low mass (M< 5 M⊙) asymptotic giant branch (AGB) stars, and that the nucleus of a planetary nebula (NPN) is undergoing a final gravitational contraction to the white dwarf state. The shell consists of some or all of the remaining unburnt (though not necessarily uncontaminated), hydrogen-rich material out of which the star was originally formed.

scholarly journals CO in OH/IR-Stars - on Excitation and Mass Loss

1989 ◽  
Vol 106 ◽  
pp. 368-368
Author(s):  
A. Heske ◽  
H.J. Habing ◽  
W.E.C.J. van der Veen ◽  
A. Omont ◽  
T. Forveille
Keyword(s):  
Mass Loss ◽  
Agb Stars ◽  
Line Formation ◽  
Circumstellar Envelopes ◽  
Simple Method ◽  
Long Period ◽  
Ir Stars ◽  
Low Mass ◽  
The Impact ◽  
Loss Rates

Observations of CO in long period variables have been widely used to determine mass loss rates by applying models for CO line formation (e.g. Knapp and Morris, 1985) which use a simple method to take the impact from infrared radiation into account. Recent 00(2-1) and (1-0) observations of some more evolved OH/IR stars yielded much too low mass loss rates using these simple models, thus indicating that they cannot be extrapolated to far evolved AGB stars with optically thick circumstellar envelopes.

scholarly journals Evolutionary effects of mass loss in low-mass stars

1981 ◽  
Vol 59 ◽  
pp. 319-338
Author(s):  
Alvio Renzini
Keyword(s):  
Mass Loss ◽  
Globular Cluster ◽  
Planetary Nebula ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Central Star ◽  
Red Giants ◽  
Low Mass Stars ◽  
Low Mass ◽  
Actual Mass

AbstractThe effects of mass loss on the evolution of low-mass stars (actual mass smaller than 1.4 Mʘ) are reviewed. The case of globular cluster stars is discussed in some detail, and it is shown that evolutionary theory sets quite precise limits to the mass-loss rate in population II red giants. The effects of mass loss on the final evolutionary stages of stars producing white dwarfs is also discussed. In particular, the interaction of the wind from the hot central star with the surrounding planetary nebula is considered. Finally, the problem of the origin of hydrogen-deficient stars is briefly discussed.

scholarly journals Evolution and Mixing on the Agb

1989 ◽  
Vol 106 ◽  
pp. 161-175 ◽  
Author(s):  
John C. Lattanzio
Keyword(s):  
Mass Loss ◽  
Stellar Surface ◽  
Evolutionary Models ◽  
Agb Stars ◽  
Carbon Stars ◽  
Convective Core ◽  
Nuclear Burning ◽  
Low Mass ◽  
Stellar Models

AbstractIt is now well known that Nature can make Carbon stars at lower luminosities than can (human) theorists. A number of workers, stimulated by this challenge, have been attracted to the problem. In this paper I review recent evolutionary models of relatively low mass AGB stars, with emphasis placed on the mixing of carbon to the stellar surface. In particular I discuss some recent improvements in the physics used to construct stellar models. These topics include: breathing pulses of the convective core found during core helium exhaustion; the effects of carbon recombination; the occurrence of semiconvection in the region between the two nuclear burning shells; and the importance of mass loss. Recent calculations have successfully produced models of low luminosity Carbon stars. The strengths and weaknesses of these models will be contrasted.

scholarly journals On Low Mass AGB Stars

1991 ◽  
Vol 145 ◽  
pp. 275-285 ◽  
Author(s):  
I.-Juliana Sackmann ◽  
Arnold I. Boothroyd
Keyword(s):  
Mass Loss ◽  
Narrow Range ◽  
Carbon Star ◽  
Theoretical Models ◽  
Initial Mass ◽  
Mixing Length ◽  
Agb Stars ◽  
Low Mass Stars ◽  
Low Mass ◽  
Thermal Pulses

Recent results on low mass AGB stars are presented. Observed amounts of AGB mass loss imply that thermal pulses will only be encountered for stars of initial mass less than about 4M⊙ for Pop I and 3 M⊙ for Pop II. Mc – L, Me – τif, and Mc – Tb relations are summarized. Carbon dredge-up has been found in low mass stars of both Pop I and Pop II; the mixing length parameter α is crucial to dredge-up, and its value must be normalized according to each author's opacities and mixing length treatment (e.g., via the Sun's Te and L). The “carbon star mystery” is nearing a solution, but a new “s-process mystery” has appeared: only in a narrow range of mass and metallicity have theoretical models been found that encounter the semiconvective 13C s-process mechanism.

scholarly journals The hydrodynamical structure of circumstellar envelopes around low mass-loss rate, low outflow velocity AGB stars

2002 ◽  
Vol 388 (2) ◽  
pp. 609-614 ◽  
Author(s):  
J. M. Winters ◽  
T. Le Bertre ◽  
L.-Å. Nyman ◽  
A. Omont ◽  
K. S. Jeong
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Agb Stars ◽  
Circumstellar Envelopes ◽  
Outflow Velocity ◽  
Low Mass
Sign in / Sign up

Export Citation Format

Share Document